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Research shows climate change is having a significant impact on the UK’s birds

RSPB report says climate change is having an impact on migration patterns, breeding habits, and the distribution of species

Climate change is also thought to be one of the main causes of seabird declines

January 10th 2018

The RSPB has published a report on the state of the UK’s birds which features a particular focus on the impact of climate change. [1] The report was produced jointly by the RSPB, the British Trust for Ornithology, the Wildfowl & Wetlands Trust, and the UK’s statutory bodies for nature conservation in England, Wales, Scotland and Northern Ireland. Much of the data on particular species, showing increases or decreases in bird populations over recent decades, was released by the UK Government last November via the Department for the Environment, Food & Rural Affairs (Defra) and discussed in last month’s article – see ‘Defra releases latest statistics on the UK’s wild bird populations’.

The RSPB report however includes a special feature on the impact of climate change on the UK’s birds, which brings together the results of various research studies. The report summarises recent trends as regards climate change and highlights the ways in which these trends are already having an impact on the UK’s bird populations. Looking ahead, it also discusses the potential impacts of climate change if recent trends continue as predicted, including a number of case studies. It then makes an argument for building ecological resistance to those impacts and presents ways of helping species to adapt. In summary, the report says that climate change will provide some species with opportunities, while others could be threatened with extinction as a breeding bird in the UK.

Climate Change: Recent Trends

The report says that climate change has been assessed as the second-largest driver in the UK of observed changes in wildlife populations, second only to the intensification of agriculture which has been the main cause of wildlife decline. As regards recent trends, the report cites research by the Met Office and evidence from the last climate change risk assessment produced by the Adaptation Sub-Committee of the UK Government’s Committee on Climate Change. The figures show that 8 of the 10 warmest years on record in the UK have occurred since 1990, with average UK temperatures increasing by almost 1°C since the 1980s. Sea surface temperatures have also increased, with 9 of the 10 warmest years for UK seas having occurred since 1989. Heavy rainfall events during winter have contributed to a slight increase in rainfall across the UK, with Scotland’s average rainfall 11% higher in the ten-year period from 2007 to 2016 than in the twenty-year period from 1961 to 1990. UK sea levels rose by 14cm in the last century and the rate is increasing.

These trend are expected to continue. Current projections are for rising temperatures, wetter winters, drier summers, and an increase in the frequency and intensity of extreme weather events, such as heatwaves, droughts, heavy rain and floods. Scientists have forecast that mean summer temperatures could rise by 5°C in many parts of the UK by 2050, while mean winter rainfall could increase by 10% or more, possibly by as much as 50%. In short, we can expect winters to be wetter while summers will be drier and warmer.

The UK’s resident birds have benefited from milder winters

The changes in climate that have already taken place have had a noticeable impact on the UK’s bird populations. The report cites research which shows that trends in temperature and rainfall over the past 30 years have had an impact on the increase or decrease in numbers of specific species, on the distribution of species, and on the timing of natural events such as migration and breeding. The authors state: “Since the early 1990s, birds in the UK, and Europe as a whole, have shown changes in numbers and distribution consistent with a warming climate.”

In last month’s article, we looked in some detail at bird population increases and decreases. To what extent are these changes an effect of climate change? The report says that many resident species have shown long-term increases in abundance which have been linked to increases in winter and spring temperatures, with milder winters boosting the chances of survival. Research cited in the report has found that fluctuations in the population trends of one of the UK’s largest breeding birds, the grey heron, and one of the smallest, the wren, are closely related to annual variations in mean winter temperatures. Another study has found that long periods of cold days with continuous frost reduce wren survival rates, which can be halved by more than 10 consecutive days of frost. [2]

However, the report’s authors go on to say that both the grey heron and the wren have shown increasing trends due to less severe winters. This is not entirely accurate, as Defra’s statistics show that the grey heron has in fact suffered a long-term decline of 17% over a 40-year period (1975 to 2015), whilst the figures produced in the RSPB report show a 5% decline in the long-term and a 17% decline in the short-term. Elsewhere in the report, the great tit, robin, nuthatch, treecreeper and dunnock are also cited as examples of species whose numbers have increased in the long-term due to increases in winter and spring temperatures. This is not entirely accurate either as Defra’s statistics, reproduced in the RSPB report, show long-term declines for the treecreeper and dunnock. [3]

The wren, great tit, robin and nuthatch do however show long-term increases, together with a number of other resident species which appear to be benefiting from milder winters. [4] These increases vary across the UK. The report says: “Country-specific trends for great tits and wrens show that increases have been greatest in Northern Ireland, followed by Scotland, with no significant difference between England and Wales. These patterns are likely to be caused by overall population increases and improving climatic conditions in the north and west.” The report says a number of summer migrants are also faring better in Scotland compared to the rest of the UK, such as the willow warbler, tree pipit, house martin and cuckoo – the cuckoo has seen a 33% increase in Scotland in the 1995 to 2015 period but has declined elsewhere in the UK.

“Go forth and multiply”

As well as regional variations in species increases, research has shown that the overall distributions of bird populations have changed, with climate change being the most likely cause. In short, species have expanded their territories northwards and westwards, and also to higher altitudes where suitable habitats can be found. A comparison of population distributions over a twenty-year period, comparing a bird atlas of 1991 with a bird atlas of 2011, shows an average shift of about 13km to the north and west for some species more generally found in the south, including the goldfinch and the nuthatch, and also summer migrants such as the chiffchaff and blackcap. The report says “both blackcaps and chiffchaffs are expanding their breeding range northwards and into higher altitudes as the climatic conditions become more favourable.” Milder winters in the UK and in Europe have helped to boost their chances of survival, and the report says that increasing numbers of both species now stay in the UK for the winter, though the report also says that other drivers (such as the availability of food and habitat) may also be playing a part in these changes.

Previously scarce species have expanded their range

Changes in distribution have been noted not only for common and widespread species, residents and visitors alike, but for some species that used to be scarce in the UK, such as the Cetti’s warbler, which takes its name from the eighteenth-century Italian zoologist Francesco Cetti. The RSPB says that the Cetti’s warbler bred initially in Kent in 1972, and its preferred habitat is damp areas close to wetlands. The Cetti’s warbler colonised the south-east of the UK in the 1970s, but the report says that the Cetti’s warbler has subsequently expanded its range and now has the core of its distribution in the south-west. Although its numbers were dramatically reduced by the cold winters of 2009/2010 and 2010/2011, the species has since recovered and it continues to increase in numbers and expand its range. The report says that “the arrival and subsequent population expansion of Cetti’s warblers breeding in the UK since 1973 is seen as an example of the northward shift in distribution of some species as a result of climate change.”

The report includes a case study of the Dartford warbler, which used to be the UK’s only resident warbler and was found only in small numbers in the south of England. The authors say that the Dartford warbler is vulnerable to severe winter weather, and its numbers in the UK “may have declined to a low of 11 pairs in 1963 following two very cold winters.” Milder winters have subsequently produced a population increase, with research recording more than 2,500 pairs in 2006. Milder winters are also thought to be the cause of a wider distribution. The Dartford warbler has expanded its range by moving into suitable habitat at higher altitudes and by spreading into more northerly areas including Derbyshire and Suffolk, compared to its southern base in Dorset and Hampshire. Like the Cetti’s warbler however, its numbers have fluctuated due to its vulnerability to cold winters. The report says that the UK’s population of Dartford warblers could become increasingly important in a European context as its numbers are declining severely in France and Spain, and much of its territory in southern Europe may become unsuitable given the projected impact of climate change.

Changes in distribution are having an impact on bird communities

Some of the UK’s birds are generally more prevalent in the south (such as the two warblers mentioned above), while some are generally more prevalent in the north of the UK. Thus some species have a northern margin to their range while some have a southern margin. With this northward expansion and rising numbers, does this mean that some species are now generally more widespread, or are they simply moving further north and leaving their former territories behind?

The research cited in the report suggests that what is happening is in fact a northern shift, but the loss of territory on the southern margin is happening at a slower rate than the gain of territory in the north, which has resulted in a more widespread distribution. The report says that for a number of resident species, “expansion at the northern edges of their ranges, where suitability is increasing, has been more rapid than the rate of loss at the southern range margins, where suitability is declining.” This has produced an overall expansion of the ranges of some species at a rate in excess of 1km per year. One piece of research has found that “southerly-distributed species, resident species and habitat generalists are increasing relative to northern or upland species, long-distance migrants and habitat specialists,” while another study has found that, across Europe, “warm-associated species are becoming more common relative to cold-associated species”. Looking ahead to the future impact of climate change, research suggests that “there are more southern species with potential for northward expansion in the UK than there are northern species predicted to contract, and observations suggest this is already happening.”

These changes in distribution have led to changes in the composition of bird communities, with research showing that bird communities are becoming more similar to each other. The regional variations in populations trends, and the timing of important events such as breeding and migration, have also led to these changes in the composition of bird communities. The report says that this can affect species interactions, “such as predator-prey relationships and competition,” which in turn can drive further population change.

Research has also investigated the potential impact of climate change on the UK’s rare breeding birds, with the trend for a northern shift in distribution meaning that some rare species could disappear completely. The report says that these birds often occur at the edge of their breeding ranges: “Species currently only found to the south of the UK are projected to shift north and east, and to higher elevations as the climate there becomes more suitable. Conversely, those birds which have their southern, ‘trailing’ range edge within the UK are likely to decline as that edge moves north, or even moves out of the UK altogether.” Because of the impact of climate change, the report says most of these species have been assessed as having a high potential for extinction as a breeding bird in the UK, “as the projected shifts in suitable climatic conditions mean that the UK will become less suitable.” In the case of the purple sandpiper, whimbrel, dotterel, common scoter, capercaillie, Arctic skua and Slavonian grebe, “the effect is likely to be more detrimental as their UK populations are already in decline.”

The early bird catches the worm?

Climate change is not only having an impact on the numbers and the locations of the UK’s birds, but is also having an impact on the timing of natural events such as migration and breeding. The report cites research which has found that a number of common migrants are now arriving in the UK earlier than they used to, and also laying eggs earlier, “with the result that swallows, for example, are arriving in the UK 15 days earlier and breeding 11 days earlier than they did in the 1960s.” Some species are also delaying their departure, including blackcaps, chiffchaffs and garden warblers, which means that some migratory species are now staying longer in the UK as a result of their earlier arrival and later departure. The report says that sand martins and whitethroats, for instance, now spend around two weeks longer in the UK than in the 1960s, while garden warblers spend four weeks longer.

Research has found that “species that have extended their stay in the UK show more positive trends in abundance over the period studied (1960 to 2010), compared to species that have not altered their timing of migration, for example cuckoos and turtle doves.” However, the report also says that “timings vary annually in relation to spring temperatures and conditions on migration.” For instance, surveys published by the British Trust for Ornithology found that blackcaps and chiffchaffs bred significantly later in 2016 than they have in recent years, which is thought to be the result of lower April temperatures.

The report says that the great tit is one of a number of species, “including swallows, chiffchaffs and willow warblers,” that now breed earlier compared to the past, with great tits now laying their eggs on average 11 days earlier than they did in 1968. With these advances in egg-laying however, there is the potential for a mismatch between the timings of the peak food demands of breeding birds and peak food availability, as the timings of events vary between birds, plants and insects. Research has found that “across a wide range of species of plants and insects, timing has advanced on average by about four days for a 1°C increase in temperature, compared to birds which have advanced by an average of two days.”

Food availability and breeding success: Winners and losers?

Is this mismatch having an impact on breeding success? The report says that the mismatch between breeding and food availability has been studied in detail only for a few species, and has not been directly linked to reductions in breeding success or large-scale population decline in the UK. The authors say that changes in the abundance of insect prey populations may be more important.

However, one study has concluded that the impact of climate change on bird populations is most severe for long-distance migrants because of this mismatch during the breeding season, leading to a potential reduction in breeding success and subsequent population decline, as in the case of the pied flycatcher in the Netherlands. Another study suggests that climate change may explain the decline of the UK’s ring ouzels, as “long-distance migrants may suffer negative consequences from warmer, drier conditions during the spring and summer potentially influencing food availability and abundance”. The report says that the tree pipit (another long-distance migrant) may also be vulnerable to changes in the timing of insect availability. This negative outlook for long-distance migrants is counterbalanced however by the research mentioned above, which has found that migrants who stay longer in the UK are more successful at breeding.

Warmer and drier conditions during spring and summer may have negative consequences for some bird species, but these conditions can also have positive consequences for others. The report says that warmer temperatures during the breeding season have been shown to have a positive effect on breeding success for a range of species:

“For example, birds that feed insects to their young, such as great tits and chaffinches, have improved productivity in warm, dry springs, probably mediated by increased prey abundance and good foraging conditions. Further evidence comes from numerous studies which show positive effects of temperature on chick growth and productivity in waders and other ground-nesting species with mobile young (for example, golden plover, common sandpiper and corncrake).”

Despite these positive effects however, all three species (golden plover, common sandpiper and corncrake) have declined in the long term, along with several of the UK’s breeding waders and farmland birds. [5]

The impact of extreme weather

As mentioned above, research has shown that trends in temperature and rainfall over the past 30 years have had an impact on bird population fluctuations. The RSPB report says that “changes to patterns of rainfall and temperature can have diverse effects on a population’s breeding success.” Can we conclude therefore that it is climate change that is causing a bird population to rise or fall? This is a challenge for researchers, as the report states:

“Identifying whether observed changes are caused by climate change remains a challenge, and the subject of a range of studies, analyses and modelling approaches. Conversely, there remains much to understand about the importance of extreme weather events in driving population change, and the impact of increasing severity and frequency of such events on species survival and breeding success.”

Current projections on climate change predict an increase in the frequency and intensity of extreme weather events, as mentioned above. These projections also predict milder and wetter winters, and warmer and drier summers. In the last decade however, the UK has experienced extreme weather events at various times throughout the year, which means that winters can also be extremely cold (such as the long cold spell of 2010/2011), while spring and summer can also be extremely wet. The RSPB report says that “over the last decade, wetter June weather has become more frequent, in line with expected climate change.” This can have an impact on the breeding success of the UK’s birds.

For instance, the Met Office reported that the spring of 2012 was the wettest April to June period on record. Grahame Madge, a press officer for the RSPB and also the Met Office, said this was having an impact on ground-nesting waders. “Flooding at several key sites has seen hundreds of wader nests washed out,” he said, “including 600 at the RSPB’s Ouse Washes reserve in Cambridgeshire.” [6] A report by the British Trust for Ornithology on the 2011 Breeding Bird Survey suggested that unfavourable weather conditions was exacerbating the long-term decline of the UK’s breeding waders, such as the lapwing and curlew. [7]

On the other hand, a period of drought can also have an impact on the breeding success of the UK’s waders. The RSPB report says that the drying of soils on their breeding grounds, “which is already a problem due to the drainage of lowland meadows and upland bogs, may be exacerbated by climate change. Wetter areas are important sources of insects which breeding waders, such as curlews and golden plovers, feed to their young.” The report includes a case study of the golden plover, whose numbers were down by 20% in 2015 compared to 1970. The authors of the study warn that golden plover populations could decline further as warmer, drier summers and periods of drought have an impact on cranefly populations, which are essential food in the breeding season. The report states:

“Golden plovers breeding in the UK uplands are among the most southerly populations in their global range. Golden plovers rely on cranefly larvae (also known as leatherjackets) for food, which are highly sensitive to drought, and high temperatures in August reduce the abundance of craneflies the following year. This means that climate change could limit the birds’ food supply, reducing chick survival and overall breeding success.”

The report says that, overall, golden plovers have been assessed as having a high risk of climate-related decline. A study of golden plover populations in the Peak District has concluded that improvements in winter survival are likely to be outweighed by the reductions in breeding success as cranefly populations decline. As for the curlew, its population is projected to fall by 50% over the period 1997 to 2080 under a medium climate change scenario. And, as mentioned above, other waders that breed in upland areas, such as dotterels, purple sandpipers and whimbrels, are considered to be at a high risk of extinction as a breeding bird in the UK due to habitat changes and reduced food availability.

However, the report says that habitat management could help upland birds such as the golden plover to be more resilient to climate change. It cites research on how to maintain peatland ecosystems in a changing climate:

“Throughout the 20th century, many UK upland peatlands were drained to improve agriculture, but this exacerbates cranefly declines and has further impacts on ecosystem functioning. Experimental examination of three drained peatlands has shown that blocking drains as part of restoration programmes leads to wetter peat and higher cranefly abundances. Blocking drainage ditches therefore provides more food for golden plovers in drained peatlands, aiding populations in a climate that is changing to drier summers.”

Another study has found that “re-wetting” peatlands can achieve similar benefits for ecosystems, which include not only an increase in cranefly abundances, but also improvements in water quality and carbon storage together with reductions in flood risk. The RSPB report says that such benefits are already being realised through landscape-scale restoration projects; for instance, the Sustainable Catchment Management Programme, which is a partnership between United Utilities, the RSPB, local farmers, “and a wide range of other stakeholders.” The programme was designed to ensure the sustainable environmental management of 20,000 hectares of a water catchment area owned by United Utilities and situated in the Peak District and the Forest of Bowland. [8] Other studies have identified further actions that would help golden plovers. These land management measures, not related to climate change, include “the legal control of generalist predators, the removal of conifer plantations in inappropriate areas, the re-profiling of forest edges around protected areas, and the provision of suitable feeding conditions through vegetation management.”

As a further example of the impact of temperature and rainfall, the report cites research on the Slavonian grebe. In this case, it is rainfall rather than drought that is known to cause problems. A study has found that “Slavonian grebes in Scotland had higher breeding success when temperatures were higher during chick rearing, but periods of particularly heavy rainfall during the breeding season led to smaller populations.” Another study concludes that the breeding success of some raptors and grouse species can also be very sensitive to rainfall during chick rearing. The report says that cold and wet weather conditions over a number of breeding seasons may be a factor in the decline of the hen harrier population, which is on the brink of extinction as a breeding bird in the UK. However, a national survey of the hen harrier in 2016 identified the main factor limiting its numbers as “the illegal killing of birds associated with driven grouse moor management in northern England and parts of mainland Scotland.”

The report also cites a national survey of the capercaillie carried out in 2015/2016. The authors say that the breeding success of the capercaillie is “known to be adversely affected by high rainfall in June when the chicks hatch, and by delayed warming in spring. Understanding how rainfall affects breeding success, and how patterns of rainfall might change in the future, will be important in assessing the vulnerability of the population to climate change and the relative importance of other drivers.”

Climate change and seabird decline

As we have seen, changes in the timing of migration and breeding, as well as changes in distribution, have been linked to rising temperatures, and indicate how the UK’s birds are changing their habits in response to a changing climate. The RSPB report says that, as the climate changes, the ability to adapt to a changing environment will be essential in enabling bird populations to persist. However, it points out that the ability to adapt varies between species. This is apparent in the case of the UK’s seabird populations, with some coping better than others.

Three seabird species have suffered a marked decline since the beginning of the seabird index in 1986: Arctic skua by 80%, black-legged kittiwake by 62%, and the European shag by 48%. [9] These declines, and those of other seabirds, are partly the result of reduced breeding success, which has been associated with warming seas and changes to food abundance and availability. During the breeding season, kittiwakes and shags are heavily reliant on sandeels, and declines in sandeel abundance are thought to be having an impact on their productivity. Declines in sandeels may also be a factor in the decline of the Arctic skua. The report says that the overall decline of the UK’s breeding seabirds is a particular cause for concern, with climate change being a major contributory factor:

“Climate change is considered to be one of the primary causes of seabird declines, through indirect effects via changes in prey availability and abundance, and through direct effects such as increased mortality from the increasing frequency and intensity of extreme weather events. These processes will interact with current drivers such as unsustainable fisheries, pollutants, marine renewables and disease. Overall negative relationships between temperature and the productivity of seabirds have been shown for kittiwakes, fulmars and puffins, as well as common, Arctic and little terns.”

The report includes a case study of the UK’s kittiwake population, which has declined as a result of “both falling breeding success and adult survival.” Kittiwakes tend to feed off the sea surface, and research has shown that their reliance on sandeels during the breeding season means that they could be affected in two ways: firstly, through a reduction in the availability of sandeels caused by industrial fishing in the North Sea; and secondly, through changing ocean conditions caused by rising sea temperatures. [10] Pulling together research on this subject, the report explains:

“Rising sea surface temperature has changed the plankton community on which sandeels rely. In addition, rising temperature is also changing the process of stratification – the relationship between sea temperature and salinity, which creates density differences between deep and shallow waters. Earlier or stronger stratification can ultimately reduce food availability for kittiwakes and the species’ breeding success has been found to be lower in areas where this has occurred. Based on these relationships, projections for the late twenty-first century suggest that the breeding success of the 11 northern UK colonies studied could fall by up to 43%.”

The decline of the shag population has also been linked to reduced breeding success and the availability of sandeels, but the report also says changes in weather patterns may be having an impact as a shag’s plumage is only partially waterproof, “perhaps making them more susceptible to mortality during prolonged periods of wet and windy weather.” The report states:

“Stormy weather may also lead to shag starvation through reduced foraging success, probably due to increased water turbidity. Such weather patterns are predicted to increase with climate change. Severe events in the winters of 1993/94, 2004/05 and 2012/13 caused large numbers of birds to die (known as a “wreck”) and affected the population considerably. Breeding numbers were not fully recovered following the wreck of 1993/94 when the storms of 2004/05 hit and no recovery was apparent before 2012/13. The population was at its lowest yet recorded in 2013, and by 2015 had only improved marginally.”

In our article on the wild bird statistics released by Defra, we reported that five of the thirteen species in the seabird index have increased since the beginning of the index in 1986: razorbill by 58%; common guillemot by 57%; Arctic tern by 39%; sandwich tern by 5%; and great black-backed gull by 7%. The black-headed gull population (included in the ‘other’ index) has also increased by 16%. Figures produced in the RSPB report from the Seabird Monitoring Programme include figures for the gannet and the great skua, which also show a long-term increase in the 1986 to 2015 period, and figures for the roseate tern, which show a long-term decline but a short-term increase (2015 compared to 2000). [11] This raises the question: why are several seabird species in decline in the UK, while a number of other species show long-term increases?

The report says the reason for these long-term increases is that these species are more flexible in their food sources, foraging strategy, and breeding habits, “which may be allowing these species to thrive while others are failing”:

“A trait that many of these species share is a lack of specialisation in their preferred food types. When sandeel abundance is low, guillemots can switch from their preferred sandeel diet to sprat, young gadids (species in the cod family), pipefish or even squid when feeding chicks. Both black-headed gulls and gannets have a varied diet, with the former feeding on multiple species of crustaceans and molluscs, and the latter on varying species and sizes of fish. As these species are increasing when more specialised feeders are in decline, it appears that being flexible with food may mitigate the effects of climate change.

However, the report says that fulmars appear to be an exception to this apparent pattern. Although fulmars “have long foraging ranges and are not particularly specialised in their feeding habits,” the species has seen a long-term decline in numbers since 1986 (a fall of 22% according to Defra’s statistics, and 33% according to the RSPB’s figures). [12] The report says that, although correlations have been observed between North Atlantic climate variation and both fulmar adult survival and breeding success, the specific driver for this decline is unclear.

Looking ahead, the report says that habitat suitability for seabirds around the UK is projected to shift northward over the next century, and the distribution of species may shift with changing conditions. In the case of the Arctic skua, models of the likely impact of climate change predict that this bird could become extinct in the UK by 2100.

Climate change and the UK’s wintering waterbirds

According to Defra’s statistics, the number of waterbirds that migrate to the UK for the winter has seen a 92% increase overall when 2014/15 figures are compared to 1975/76, as we reported in our last article. However, this increase peaked in the late 1990s and has subsequently declined. The UK’s wintering waterbird populations can be impacted by several factors, which include breeding success or failure in the countries where they breed, the availability of suitable habitat in the UK, and changes in migratory patterns, “at least some of which are known to have been affected by climatic changes.” [13]

The RSPB report says that climate change is already having an impact on the abundance and distribution of the UK’s wintering waterbirds, with projections indicating that temperature and habitat changes could have a significant impact on numbers in the future. The report highlights two main reasons for the decline: firstly, reduced productivity in the breeding season may be limiting the numbers of some winter migrants; and secondly, milder winters on the continent mean that fewer birds need to migrate to the UK to avoid colder conditions. On the first, research on the future impact of climate change predicts that the breeding ranges of Arctic and sub-Arctic species that winter in the UK could be reduced by 50% by the end of the century, which may cause further declines due to reduced productivity.

Wintering Waterbirds: Changes in migratory patterns and distribution

However, the RSPB report says that in many cases the decline of the UK’s wintering waterbirds is explained by changes in distribution, linked to milder winters across the Continent, and particularly evident in the reduced use of sites along the UK’s east coast. The report cites research that has demonstrated a north-eastward shift in the range of some wintering waterbirds in north-west Europe, including the UK, associated with the trend for milder winters. For instance, a study of grey plovers and curlews wintering in north-west Europe has shown that their distribution had shifted nearly 120km to the north-east in the two decades between 1981 and 2000. On the other hand, the RSPB report says that in severe cold winters, such as the winter of 2010/11, the numbers of bar-tailed godwits visiting the UK were higher than in the mid-2000s, “probably because they were escaping cold conditions in north-west Europe.”

The importance of habitat for the UK’s resident and wintering waders

Wintering waterbirds receive a certain amount of protection across the UK through a wide range of sites that are designated as Special Protection Areas: “Special Protection Areas are strictly protected sites classified in accordance with Article 4 of the EC Birds Directive, which came into force in April 1979. They are classified for rare and vulnerable birds (as listed in Annex I of the Directive), and for regularly occurring migratory species.” [14] These protected areas span the length of the UK and include a wide range of locations frequented by wintering waterbirds, such as the Dee estuary, the Northumberland coast, the North Norfolk coast, the Humber estuary, the Mersey estuary, Portsmouth harbour, Morecambe Bay, a number of lochs in Scotland, and the Isles of Scilly. [15]

The RSPB report says it is likely that most of these areas will continue to support internationally important numbers of wintering waterbirds, despite changes in the distribution and abundance of populations due to climate change. It highlights the importance of these protected areas during particularly cold winters (such as the winters of 2009/10 and 2010/11), “when the trend for wintering further east was reversed, and numbers on UK sites were much higher.” The report also notes that many of the species that have recently colonised the UK, “or which appear to be on the verge of doing so,” are associated with wetlands, with most of these species first becoming established in these protected areas. The list of these colonists include night herons, cattle egrets, great white egrets, black-winged stilts, spoonbills and little bitterns, though the numbers of breeding pairs may be no more than a single figure. [16]

As well as wetlands, the RSPB report also highlights the importance of the non-estuarine coast for some species of waders wintering in the UK. For instance, the Northumberland coast is visited by purple sandpipers and turnstones who migrate from north-east Canada for the winter. The report says the majority of purple sandpipers, turnstones, ringed plovers and sanderlings present in midwinter are to be found on these non-estuarine coastal areas, and the species using these areas are “considered vulnerable to the impact of climate change and changes to invertebrate communities” (i.e. changes to the availability of food such as shellfish). For example, figures from the Breeding Bird Survey show a 23% decline in the resident oystercatcher population during the 1995 to 2015 period. Trends for wintering waterbirds produced by the British Trust for Ornithology also show declines in the oystercatcher population, both over a 25-year period (a 26% fall from 1989/90 to 2014/15) and over a 10-year period (a 15% fall from 2004/2005 to 2014/15). In terms of numbers, the oystercatcher is still second in the top ten of waterbird populations according to the Wetland Bird Survey, but internationally the oystercatcher is considered to be Near Threatened on the IUCN Global Red List. [17] The report says that “the sustainable management of shellfish fisheries and habitat protection is considered vital for the future conservation of this species.”

Trends for wintering waterbirds produced by the British Trust for Ornithology also show long-term and short-term declines in the numbers of ringed plover, turnstone, and purple sandpiper wintering in the UK. The RSPB report says that the possible explanations include shifts in distribution, as noted above, and declines in breeding productivity, both of which could be related to climate change. Local environmental factors, such as changing sewage treatment and disposal practices, may also play a role.

“Building ecological resistance”: Helping the UK’s breeding waders

To help species to be more resilient to the impact of climate change, both current and potential, the RSPB report advocates building ecological resistance. Building ecological resistance is one of the objectives in the UK Government’s National Adaptation Programme (see below) and encompasses various land management measures, such as the creation of new habitat and the restoration and sustainable management of existing habitat. The report says that land managers across the UK have been developing a range of such actions, “from coastal realignment to increasing micro-climate heterogeneity.” These schemes are aided by a growing body of research that has investigated various ways of helping species to cope with climate change. We have already seen how research has identified ways of helping golden plovers and other waders that breed in upland areas, including measures to offset the drying out of peatland areas that will help to increase the abundance of cranefly populations. The report also describes ways of helping lowland breeding waders during the breeding season:

“Lowland breeding waders such as lapwings, redshanks and black-tailed godwits require shallow pools and moist soil for foraging. Current measures to increase water availability in the face of lower rainfall and higher temperatures include storing water for the breeding season, and maintaining wet features by digging shallow channels. Conversely, for black-tailed godwits, existing breeding habitat in the UK is only found in wet meadows used for floodwater storage; in years with high levels of rain they have lower breeding success. To safeguard the population from increased flood risk, additional unflooded grassland is being created for those occasions when adjacent washlands are flooded.”

New wetlands for potential colonists and current species

Research on climate change adaptation has also investigated ways of helping the UK’s potential colonists. As mentioned above, many of the species that have colonised the UK in recent times are associated with wetlands. One study has said that many of these colonists require large areas of this type of habitat, and has suggested that large areas of new wetland will be required to encourage further colonisation. Coastal realignment schemes such as the Wallasea Island Wild Coast Project, described as “the largest coastal wetland to be constructed in the UK,” are cited as examples of what is required:

“The re-establishment of breeding by spoonbills, great white egrets and little bitterns in the UK has all occurred at large wetland expanses. However, there are very few large wetlands capable of supporting large breeding colonies of such waterbirds. Wetland habitat creation to benefit current species as well as potential colonists would therefore be best focused on providing a small number of very large wetland complexes in the vicinity of existing habitats.”

The RSPB report explains how a coastal realignment scheme can help our current species as well as potential colonists:

“Little terns and common terns nesting on low-lying coastal islands require sites to be raised using shingle as the sea level rises and sites become more vulnerable to storms. In managed realignment areas new nesting islands can be created. Island nesting sites are important because in many nesting areas, breeding success is reduced by high levels of disturbance and impacts of ground predators.”

Wallasea Island is situated in Essex, a few miles from Southend, and it is here in the south-east of England where most of the potential colonists from the Continent will first arrive, according to the research on climate change adaptation. However, the south-east of England is likely to experience “greater warming, more reduced rainfall, and the greatest level of human pressure.” Consequently, “future management of wetlands needs to take into account increased climate-related drying and increasing human demand for water in the region.” [18]

Heathland restoration

In addition to schemes that will help waterbirds, wetland birds and coastal species, residents and colonists alike, adaptation schemes have also been developed to help the UK’s heathland species, such as the Dartford warbler and the nightjar. The report says that these birds are characteristic species of lowland heathlands, and that “restoration and re-creation of these scarce and fragmented habitats to the north of the core area for these species will aid northward expansion.” Heathland restoration involves optimising the level of grazing, cutting and/or burning to maintain structure and condition, and managing fire risk, “which is projected to increase with warming temperatures and reduced rainfall.” The report also stresses the importance of protected areas for the Dartford warbler, which have been key to its expansion as 74% of the expanded population were located in protected areas.

A “National Adaptation Programme”

Protected areas have not only been key to the expansion of the Dartford warbler, but have also been important for the UK’s wintering waterbirds and recent colonists, as mentioned above. The RSPB report says that “protected areas are going to be a vital part of responding to climate change, enabling conservation management as a priority.” It also stresses the importance of wildlife corridors: “Connectivity between protected areas by increasing habitat availability in the wider countryside will also be an important factor in facilitating the movement of species under climate change.”

In July 2013, the UK Government published a National Adaptation Programme which set out “what government, businesses and society are doing to become more climate ready.” [19] With regard to action on the natural environment, the programme specifies four overarching objectives:

• “Building ecological resilience to the impacts of climate change: To build the resilience of wildlife, habitats and ecosystems (terrestrial, freshwater, marine and coastal) to climate change, to put our natural environment in the strongest possible position to meet the challenges and changes ahead.”
• “Preparing for and accommodating inevitable change: To take action to help wildlife, habitats and ecosystems accommodate and smoothly make the transition through inevitable change.”
• “Valuing the wider adaptation benefits the natural environment can deliver: To promote and gain widespread uptake in other sectors of adaptation measures that benefit, or do not adversely affect, the natural environment.”
• “Improving the evidence base: To improve the evidence base to enhance the knowledge and understanding of decision makers, land managers and others of the impacts of climate change on the natural environment and how best we can influence adaptation or accommodate change.”

The first two objectives stress the importance of protected areas and connectivity, while the fourth stresses the need for monitoring and research. On the third, the RSPB report cites the examples of coastal realignment and catchment management, both of which provide wider benefits:

“Climate change has impacts on people as well as wildlife and the way society adapts to the threats it faces may have positive or negative impacts for birds and other species. One of the clearest examples is where hard sea defences designed to reduce coastal flooding may prevent natural readjustment of the shoreline and lead to a loss of coastal habitats. By allowing natural processes to create new habitats through managed realignment, we can have more natural solutions to flooding which will have multiple benefits: reducing the risks of flooding to people, creating extensive wetlands, as well as carbon capture in the intertidal habitats created. Other examples include upland catchment management for wildlife and water, trees in shaded open spaces for people in urban environments, and re-naturalising river systems to reduce flow rates and retain flood waters.”

The National Adaptation Programme is due to be updated this year, and this week the UK Government will also be publishing its 25-year plan for the natural environment. The intention to produce such a plan was first announced in October 2015 when it responded to a set of recommendations from the Natural Capital Committee [20]. It will be interesting to see how the Government’s plan deals with the current and projected impact of climate change on the natural environment, and conservationists will be hoping that this long-anticipated document is worth the wait.


Photograph: Jubilee Marsh, near Southend, Essex: View east at low tide to Breach Two, the River Roach and Foulness, taken 8th October 2017 © Copyright John Myers and licensed for reuse under this Creative Commons Licence. Jubilee Marsh forms part of the Wallasea Island Wild Coast Project, which the RSPB says is a landmark conservation and engineering scheme and the largest of its type in Europe:

“The Wallasea Island Wild Coast Project is in the middle of transforming this island into a magical landscape of marshland, lagoons, ditches and sea. More than 3m tonnes of earth was brought by boat from the tunnels and shafts created by the Crossrail scheme in London. This allowed us to raise the land above sea level and place the soil in way that created a new 115ha intertidal area of saltmarsh, islands and mudflats (known as Jubilee Marsh).”

The saline lagoons are managed using sluices to control water levels with the aim of creating a variety of depths of water to suit different species. The RSPB says Jubilee Marsh needs minimal management “as the tide comes in and out bringing with it sediment, seeds and other bits of plants plus the invertebrates and fish which the birds then feed on.” Sea water entered the marsh for the first time in July 2015. See the RSPB website at: https://www.rspb.org.uk/reserves-and-events/reserves-a-z/wallasea-island-wild-coast-project.


[1] Hayhow DB, Ausden MA, Bradbury RB, Burnell D, Copeland AI, Crick HQP, Eaton MA, Frost T, Grice PV, Hall C, Harris SJ, Morecroft MD, Noble DG, Pearce-Higgins JW, Watts O, and Williams JM. The state of the UK’s birds 2017 (SUKB 2017). Published by the SUKB Partnership, Sandy, Bedfordshire. Retrieved as a PDF document from https://www.rspb.org.uk/globalassets/downloads/documents/conservation-science/sukb-2017—web-version.pdf. The SUKB Partnership consist of the Royal Society for the Protection of Birds (RSPB), the British Trust for Ornithology (BTO), the Wildfowl & Wetlands Trust (WWT), the Department of Agriculture, Environment and Rural Affairs (Northern Ireland) (DAERA), the Joint Nature Conservation Committee (JNCC), Natural England (NE), Natural Resources Wales (NRW), and Scottish Natural Heritage (SNH).

[2] For details of the studies cited in the report, see the references in [1].

[3] This is clearly an error as the figures for the treecreeper and the dunnock that are tabled in the RSPB report are exactly the same as those produced by Defra. In the case of the grey heron however, the RSPB report says that the data comes from the Heronies Census (1982 to 2015), and it is unclear what periods are covered in the long-term or the short-term. There is an overall agreement however that the grey heron population is in decline. It is important to note that there are several discrepancies between the figures produced by Defra and those reproduced in the RSPB report, most notably in the figures for seabirds (see Note 10 below). There are three explanations for why these figures should diverge, apart from the most obvious one of an error in the calculations or the transcription. Firstly, the periods covered in the calculations. Defra’s figures for the most part cover the periods from 1970 to 2015 (the long-term comparison) and from 2010 to 2015 (the short-term comparison). The figures produced in the RSPB report however cover a range of periods, including not only those used in the Defra report but also longer periods for some short-term calculations (1995 to 2015 for instance). As increases and decreases are calculated from a baseline, this means that whilst a species might show a long-term increase over the last 45 years, for instance, it might also show a long-term decline if calculated over the most recent 20-year period. Secondly, the surveys used for the calculations can also produce different results. Defra’s report combines a number of survey results to give a composite figure, whilst the RSPB report tends to use the most representative surveys for particular categories. Thirdly, the use of a “smoothed index” and an “unsmoothed index” in the calculations. The former is intended to compensate for peaks and troughs in seasonal variations, such as an extremely cold winter, whereas the latter can produce a slightly different result when these are not taken into account. For the most part however, the figures in the RSPB report and those presented in our analysis of Defra’s figures both use the smoothed index.

[4] Defra’s statistics include figures for 130 species of common birds, defined as species with populations of at least 500 breeding pairs that are native to (and breed in) the UK. The species that have increased in the long term include the long-tailed tit, blue tit, coal tit, bearded tit, chaffinch, pied wagtail, stonechat, Dartford warbler, Cetti’s warbler, woodlark, siskin, great spotted woodpecker, green woodpecker, jay, sparrowhawk, raven, buzzard, red kite, peregrine falcon, carrion crow, hooded crow, magpie, jackdaw, wood pigeon, stock dove, collared dove, red grouse, goldfinch, cirl bunting, oystercatcher, mallard, coot, tufted duck, pochard, teal, goosander, red-breasted merganser, gadwall, greylag goose, mute swan, black-headed gull, great black-backed gull, razorbill and common guillemot, and some summer migrants including the blackcap, chiffchaff, redstart, lesser whtethroat, reed warbler, swallow, sand martin, Arctic tern, sandwich tern, and avocet. See last month’s article ‘Defra releases latest statistics on the UK’s wild bird populations’ for the details.

[5] For the details, see the ENA article above [4].

[6] See: ‘Lapwings hit new low; further declines in breeding waders revealed’, British Trust for Ornithology, July 2012. Retrieved from: https://www.bto.org/news-events/press-releases/lapwings-hit-new-low-further-declines-breeding-waders-revealed.

[7] Ibid: see [6].

[8] See ‘A chance for the new Environment Secretary, Michael Gove, to “listen and learn”‘, Martin Harper, RSPB, June 2017. Retrieved from: http://www.rspb.org.uk/community/ourwork/b/martinharper/archive/2017/06/14/a-chance-for-the-new-environment-secretary-michael-gove-to-listen-and-learn.aspx.
Martin Harper says that thirteen years ago the RSPB “made the case that Ofwat should change the rules that governed water company investment in catchments.” The partnership involved in the Sustainable Catchment Management Programme “developed a new approach to managing the land which complied with the Habitats Regulations, enhanced biodiversity and improved the quality of the water abstracted for drinking, as well as providing an enhanced source of income for tenant farmers. As the approach has broadened and been taken up by other water companies, we have seen huge benefits as restoration of habitat has led to increased species populations and improved water quality.”

[9] These figures are taken from Defra’s statistics. See last month’s article ‘Defra releases latest statistics on the UK’s wild bird populations’ for more details on the UK’s seabird populations.

[10] Sandeels are commercially fished by Denmark under the terms of the Common Fisheries Policy. Recent research led by the RSPB has shown a correlation between the breeding success of kittiwakes on the Yorkshire coast and the abundance of sandeels at Dogger Bank. See: ‘Protecting our Seabirds in Post-Brexit Waters’, Euan Dunn, RSPB, 14 June 2016. Retrieved from: http://www.rspb.org.uk/community/ourwork/b/martinharper/archive/2017/06/14/protecting-our-seabirds-in-post-brexit-waters.aspx. The research paper ‘Kittiwake breeding success in the southern North Sea correlates with prior sandeel fishing mortality’ was published in Aquatic Conservation: Marine and Freshwater Ecosystems in June 2017 and is available at http://onlinelibrary.wiley.com/doi/10.1002/aqc.2780/full.

[11] It is important to note that percentage increases are relative and say nothing about actual numbers. This means that if an increase is calculated from a low base, a high percentage rise does not necessarily equate to a large population. This is the case with the roseate tern. The RSPB says that the roseate tern is one of our rarest seabirds “whose severe, long-lasting and well documented decline make it a Red List species.” The current estimate of its UK population is 111 pairs, according to the RSPB website. The report says: “&hellip species which are exhibiting rapid population increases may be coming back from extremely low numbers. For example, roseate terns increased 229% between 2000 and 2015, but this was calculated from 56 apparently occupied nests in the last census (Seabird Monitoring Programme 2000) to 113 in 2015, and numbers are still well below the 950 pairs observed between 1969 and 1970.” Defra’s statistics, showing data for species with at least 500 breeding pairs, exclude figures for the roseate tern, gannet and great skua, whilst the figures reported by the RSPB exclude figures for the herring gull. It is also important to note that figures produced by the RSPB from the Seabird Monitoring Programme differ widely from those produced by Defra from the same source and virtually the same period – 1986 to 2014 (Defra) and 1986 to 2015 (RSPB). Consequently, the possible explanations for divergences do not seem to apply here (see Note 3). As an example, both sets of figures agree that the numbers of razorbill, guillemot, Arctic tern, and black-headed gull have all increased in the long term, but they disagree over the percentages. In contrast, Defra’s figures show a long-term increase of 7% for the great black-backed gull but the RSPB’s figures show a 1% decline; and Defra’s figures show a long-term decline of 7% for the cormorant but the RSPB figures show a 4% increase. Given that statistics are used as part of the evidence base for determining conservation priorities, it would be useful if not vitally important to see some consistency in these figures.

[12] On the divergence in statistics, see [11].

[13] Wild Bird Populations in the UK, 1970-2016, Biodiversity Statistics Team, Department for Environment, Food and Rural Affairs, 23/11/2017. Available as a PDF document from: https://www.gov.uk/government/statistics/wild-bird-populations-in-the-uk.

[14] The quote comes from the Joint Nature Conservation Committee (JNCC). See the JNCC website at: http://jncc.defra.gov.uk/page-162.

[15] A full list is available from the JNCC website: see [14].

[16] The report also says that, in recent years, “purple herons have bred in Kent, a pair of glossy ibises have built a nest in Lincolnshire, and male white-spotted bluethroats have held territory,” while other potential colonists, described as “great rarities in the UK”, include zitting cisticolas, short-toed eagles and short-toed treecreepers. Other rare visitors include the two pairs of bee-eaters which were spotted nesting alongside sand martins in a quarry in Cumbria in the summer of 2015. A similar number had also nested successfully in previous years in the Isle of Wight and in County Durham. See: ‘Rare bee-eater birds found nesting in Cumbrian quarry,’ BBC News, 31 July 2015. Retrieved from: http://www.bbc.co.uk/news/uk-england-cumbria-33732567.

[17] The IUCN (International Union for Conservation of Nature) uses a range of categories to assess the status of a species with regard to its population and the priorities for conservation. These are: 1. Extinct; 2. Extinct in the wild; 3. Critically Endangered; 4. Endangered; 5. Vulnerable; 6. Near Threatened; 7. Least Concern; 8. Data deficient; and 9. Not evaluated. Defra’s statistics show little change in the number of oystercatchers wintering in the UK, together with a long-term increase in the number of oystercatchers resident in the UK. However, this long-term increase covers a forty-year period from 1975 to 2015, whereas the RSPB figures cover shorter and more recent periods. (See Note 3 on explanations of divergences.)

[18] The Environment Agency produced a report in 2011 on future water availability (‘The case for change: Current and future water availability,’ Report: GEHO1111BVEP-E-E), while Defra produced a climate change risk assessment for the water sector in 2012. The RSPB report summarises the outcome of these assessments: “Overall reductions in water availability, particularly in the south-east, are expected to be exacerbated by increased demand for water for agriculture, industry and services.”

[19] See ‘The National Adaptation Programme: Making the country resilient to a changing climate’, UK Government policy paper, July 2013. Available as a PDF document from: https://www.gov.uk/government/publications/adapting-to-climate-change-national-adaptation-programme”.

[20] See the ENA UK article ‘Defra responds to recommendations of the Natural Capital Committee’. In fact, the plan is expected to be published tomorrow (11th January).


Recent Research – The impact of air pollution on human health

Evidence shows that traffic-related air pollution is a contributory factor to a wide range of diseases

But the most harmful pollutants are currently unregulated

September 22nd 2017

The last few years has seen an increasing amount of research into the impact of traffic-related air pollution on human health. Much of the research has focused on the harmful impact of nitrogen dioxide (NO2) and particulate matter (PM), tiny particles that are emitted by diesel vehicles and other sources. In the UK, nitrogen dioxide emissions have exceeded the legal limit as set by the EU for the last seven years and have been the subject of a long-running legal dispute – see last month’s article ‘Air Pollution in the UK – Seven years of illegal NO2 emissions’. Nitrogen dioxide emissions are known to cause breathing difficulties and have been linked to respiratory symptoms and illnesses such as asthma and bronchitis, while PM particles have been found in the bloodstream, the lungs, and more recently in the brain, with research suggesting links with cardiovascular disease and neurological disorders such as Alzheimer’s disease. [1] In this article, we look at a cross-section of the most significant findings, including research on the impact of air pollution on children, research on the possible links between air pollution and a number of illnesses (such as diabetes, cardiovascular disease, and neurological disorders), and the implications of this research for measures to tackle traffic-related air pollution.

The impact of air pollution on London’s schoolchildren

Two years ago, researchers based at King’s College and Queen Mary College, University of London, published the results of a research project that set out to investigate the effects of air pollution on schoolchildren living within London’s Low Emission Zone. The research was funded by the National Institute for Health Research, NHS health trusts and other bodies. The study focused on 8-9 year-old children from schools located at various distances from a number of air pollution hotspots in the east London boroughs of Hackney and Tower Hamlets. The Low Emission Zone, set up in 2008, was predicted to have a significant effect on PM10 and NO2 concentrations, and the researchers hypothesized that “reduced exposure to traffic emissions would result in a reduction in the prevalence of respiratory/allergic symptoms associated with traffic-related pollutants.” [2]

Data was collected over three consecutive winters, November to March, 2008 to 2011. Respiratory and allergic symptoms were assessed using parent-completed questionnaires. These were collected at each visit, when health assessments were also carried out to examine lung function and collect biological samples. Around 1,800 children at 23 schools were invited to take part in the study, with around a thousand (56%) deciding to participate. Computer modelling techniques were used to gather data on air pollution exposure for the duration of the study (including measurements of NO2 and PM10 levels). Statistical analysis of the data “confirmed the previous association between traffic-related air pollutant exposures and symptoms of current rhinitis,” and also identified a direct correlation between exposure to air pollution and a reduction in lung growth. Speaking to the Sunday Times, Ian Mudway, a respiratory toxicologist at King’s College London, said: “The data shows that traffic pollution stops children’s lungs growing properly. The evidence suggests that by 8-9 years of age, children from the most polluted areas have 5 to 10 per cent less lung capacity and they may never get that back.” [3]

“No evidence that Low Emission Zones can reduce pollution”

Additionally the researchers found that, in contrast to the predicted effect, the Low Emission Zone “did not reduce ambient air pollution levels, or affect the prevalence of respiratory/allergic symptoms over the period studied.” They conclude: “Importantly, the London Low Emission Zone has not significantly improved air quality within the city, or the respiratory health of the resident population in its first three years of operation. This highlights the need for more robust measures to reduce traffic emissions.” [4] Professor Chris Griffiths, who coordinated the research, is a GP and Professor of Primary Care at Queen Mary College, University of London, and the Co-Director of the Asthma UK Centre for Applied Research. He said it was very disappointing that the Low Emission Zone, “which was specifically designed as a major public health intervention, has so far brought about no change. This raises questions over the government’s current consultation on air quality, which is based around the idea of creating similar low emission zones in up to 30 other polluted urban areas. There appears to be no evidence that these low emission zones can reduce pollution or improve health.” [5] In fact, these plans were dropped in the Government’s latest plans to tackle air pollution, as we explained in last month’s article, in favour of the long-term ambition of ending the sale of all new diesel vehicles by 2040, whilst in the shorter-term local authorities will be expected to come up with air quality plans.

The social inequalities of air pollution

The impact of air pollution on London’s schoolchildren was also the subject of a report commissioned by the Greater London Authority which was completed in 2013. Last year, however, the Guardian revealed that Boris Johnson, during his period of office as London’s Mayor, had prevented the full report from being published. [6] Speaking to the Guardian, the report’s author Katie King said that the Greater London Authority had publicly disclosed the positive conclusions in the report – namely, that the number of people exposed to illegal NO2 emissions would fall by 2020 – but had held back the negative findings. “The crux of the report was about understanding the inequalities of air pollution,” she said, “so they chose not to make public the findings regarding inequality. The information that they did take from the report was the positive, that exposure was predicted to fall in the future.” The positive findings were highlighted by the Mayor in a progress report on his air quality strategy, delivered in July 2015. These were the predictions that the number of Londoners exposed to illegal NO2 emissions would drop from 1 million in 2015 to around 300,000 in 2020 as a result of the Mayor’s policies on Low Emission Zones. The Mayor’s progress report also noted that deprived communities were more likely to be exposed to poor air quality, but the Guardian says that “it failed to mention the unpublished report’s revelation that in 2010, 433 of the city’s 1,777 primary schools were in areas where pollution breached the EU limits for NO2. Of those, 83% were considered deprived schools, with more than 40% of pupils on free school meals. Of the remaining schools located in areas below the pollution limit, less than a fifth were in deprived areas.” In response, Boris Johnson denied that there had been any cover-up, saying he had highlighted the problem of primary schools and poor air quality in areas of deprivation. However, the Guardian reports that his office did not deny he had stopped the full report from being released. And given the results of the NHS-funded research, mentioned above, the predictions on the impact of London’s Low Emission Zone may turn out to be unduly optimistic as regards the effects on human health.

The BREATHE project: A study of air pollution and child development

Further evidence of the impact of traffic-related air pollution on child development has come from Spain, where a number of research institutions collaborated on a project called BREATHE (also known as ‘Brain Development and Air Pollution Ultra-fine Particles in Schoolchildren’), which was funded by the European Research Council. [7] The research was based in Barcelona and set out to evaluate the impact of air pollution exposure on cognitive development in primary schoolchildren. The researchers say that air pollution concentrations in Barcelona are among the highest in Europe, partly attributed to high traffic density with a large proportion of diesel-powered vehicles (around 50%), relatively low precipitation, high population density, and an urban landscape characterized by high-storey buildings and narrow streets, which reduces the dispersion of pollutants. Of the 416 schools in Barcelona, 40 schools were selected to obtain the greatest contrast in traffic-related air pollution levels, as measured by NO2 concentrations. Of the 40 schools, 39 accepted the invitation to participate and about 2,700 schoolchildren took part in the project. [8]

Air pollution increases the risk of developing myopia

Data gathered from the BREATHE project and published in April this year showed a link between exposure to traffic-related air pollution and myopia in schoolchildren aged 7 to 10 years of age, as measured by the use of spectacles. In their introduction to the study, the authors state:

“Exposure to traffic-related air pollution is associated with a wide range of adverse health outcomes, with the lungs being one of the most commonly affected organs, mainly because of their constant direct exposure to air pollutants. Similarly, the eyes are directly exposed to air pollution, making them a prime target organ for the adverse effects of such an exposure. In addition to the short-term effects of air pollution on the eye, such as irritation of the ocular surface and its accompanying symptoms and complaints, chronic exposure to air pollution has been associated with long-lasting ocular conditions such as dry eye disease and cataract. Although air pollution could induce myopia through systemic inflammation and oxidative stress, to date no studies have reported on the potential effect of air pollution on the development of myopia.” [9]

In this case, data was collected over a three-year period from 2012 to 2015. Air pollution was calculated by monitoring exposure to NO2 and black carbon particles at school, and by the predictive modelling of exposure to NO2 and PM particles (PM2.5) at home. As a result of their analysis, the researchers conclude that exposure to traffic-related air pollution increases the risk of developing myopia, as indicated by the number of children using spectacles.

Air pollution affects cognitive development

More results from the BREATHE project were published in March 2015. This investigation set out to assess whether exposure to traffic-related air pollution has an impact on children’s cognitive development. [10] As in the previous investigation, around 2,700 schoolchildren aged 7 to 10 years from 39 schools in Barcelona participated. The schools were located in both high and low polluted areas, as measured by traffic-related NO2 concentrations. The children were assessed using computerized tests every three months over four week-long visits in a 12-month period from January 2012 to March 2013. During each visit, air pollution was monitored for levels of NO2, elemental carbon and ultra-fine particles with a dimension of 10–700 nm (i.e. 10 to 700 nanometres), both outside and inside the classroom. Analysis showed that those schools that were closest to major roads had the highest concentrations of pollutants in their classrooms. The children’s cognitive development was assessed through their performance in the tests and an analysis of the long-term changes in working memory and attentiveness. Statistical analyses of the data indicated that children from highly polluted schools had a smaller increase in cognitive development over time compared to children from lowly polluted schools. Children with attention deficit / hyperactivity disorder were even more vulnerable to pollution levels. The researchers conclude: “Importantly, these findings do not prove that traffic-related air pollution causes impairment of cognitive development. Rather, they suggest that the developing brain may be vulnerable to traffic-related air pollution well into middle childhood, a conclusion that has implications for the design of air pollution regulations and for the location of new schools.”

Evidence of slower brain growth in schoolchildren

Further news of these findings was reported in Horizon: the EU Research and Innovation Magazine in July this year. [11] The report mentions some findings that were not reported in the 2015 publication. Anthony King reports the finding that even one high-pollution day before a test could effect a child’s performance. Additionally, he says that the researchers used magnetic resonance imaging (MRI) to examine 350 children, which showed that “high pollution was linked to slower growth in the front of the brain, in an area believed to be important in decision-making, social behaviour and complex thinking.” Professor Jordi Sunyer is a senior researcher at the Barcelona Institute for Global Health and a lead scientist on the BREATHE project. He says that the harmful effects detected in the research are due to ultra-fine PM particles, mainly emitted by diesel vehicles. Ultra-fine PM particles refers to particulate matter that has an aerodynamic diameter smaller than 0.1 micrometres (< 0.1µg/m3 or < 100 nm); these are far smaller than the fine PM particles (PM2.5) which have an aerodynamic diameter smaller than 2.5µg/m3. These ultra-fine particles are tiny particles of carbon that are breathed into the lungs, cross into the bloodstream and travel to the brain, he said: they "stimulate immune cells and produce an inflammatory effect at various levels of the brain." On the implications of the research for the building of new schools, he said: "If you move traffic 50 metres from a school, ultra-fine particle amounts drop by more than half. At 200 metres, you get 10 times less." As well as reducing the number of diesel vehicles in Europe, Professor Sunyer recommends that local authorities take short-term measures to alleviate the problem by creating barriers between air pollution and citizens, including natural barriers such as trees, hedges and 'green walls'.

Links with diabetes

Air pollution may also contribute to the development of diabetes, affecting children in particular. Research published by the American Diabetes Association in 2016 suggests a link between long-term exposure to air pollution (PM10 and NO2) and insulin resistance in the general population, “mainly attributable to pre-diabetic individuals” (i.e. individuals whose blood sugar is abnormally high, a condition that increases the risk of contracting diabetes and cardiovascular disease). [12] The American Diabetes Association has also published evidence which suggests that exposure to elevated concentrations of NO2 and PM2.5 may contribute to the development of type 2 diabetes “through direct effects on insulin sensitivity and β-cell function”. This latter research, published in January this year, studied children aged 8 to 15 years who were classed as overweight or obese and were followed over a three-year period. [13]

Effects on the unborn child?

Research has also investigated the effects of air pollution exposure on children at the foetal stage. A longitudinal study was published two years ago by the American Medical Association in its journal JAMA Psychiatry. [14] The participants included a sample of 40 urban youth who were followed up prospectively from the foetal stage up to the ages of 7 to 9 years. The research in this case focused on the effect of polycyclic aromatic hydrocarbons, described as ubiquitous and toxic environmental pollutants. The researchers detected a “close-response relationship” between exposure to these pollutants and reductions in the white matter of the brain in later childhood. These reductions “were confined almost exclusively to the left hemisphere of the brain and involved almost its entire surface.” The reduced white matter in the left hemisphere was closely associated with a slower speed in processing information during intelligence tests and more severe behavioural problems, including symptoms of attention deficit / hyperactivity disorder. The authors of the study also suggest that postnatal exposure contributes to additional disturbances in the development of white matter in later childhood, a finding that shares similarities with the slower brain growth detected in the BREATHE project, as mentioned above.

Links with cardiovascular disease, strokes and heart failure

There is a growing body of research that has demonstrated a link between particulate air pollution and the development of cardiovascular disease, such as furring of the arteries. [15] For those people already suffering from heart disease, air pollution can worsen their condition. A study published in the British Medical Journal shows that short-term exposure to air pollution increases the risk of a stroke, with a risk of hospitalisation or death from heart failure in the following week, [16] while a study published in the American Heart Association journal Circulation shows that short-term exposure to high levels of air pollution can trigger a heart attack (“myocardial infarction”). [17] The British Heart Foundation (BHF) says air pollution “is a particular problem for the 570,000 people in the UK living with heart failure.” [18] At the British Heart Foundation’s Centre for Cardiovascular Science based at the University of Edinburgh, a team of researchers have analysed data from twelve countries covering more than four million people living with heart failure “and found they had an increased risk of hospitalisation and death where pollution levels were high.” Lead researcher Professor David Newby said: “People with heart failure are a vulnerable group and, when the air quality falls, more of them are admitted to hospital.”

Research at the BHF Centre for Cardiovascular Science

Recent research at the Centre for Cardiovascular Science has been particularly concerned about “nanosized particulate matter in air pollution, such as that derived from vehicle exhaust.” [19] This nanosized particulate matter refers to the ultra-fine particles of air pollution that were featured in the research findings described above. The teams working at the Centre for Cardiovascular Science have published research demonstrating “that acute exposure to diesel exhaust causes vascular dysfunction, thrombosis, and myocardial ischaemia in healthy individuals and in patients with coronary heart disease” (‘myocardial ischaemia’ is a blockage or a hardening of the coronary arteries, resulting in a reduction of the blood flow to the heart muscle). [20] However, while research has demonstrated the links between exposure to particulate air pollution and the development of numerous vascular ailments, the mechanisms through which inhalation could trigger acute cardiovascular events, such as strokes and heart attacks, are only beginning to be understood, and there is a major area of uncertainty surrounding the question of how precisely inhaled particles influence the progression of systemic cardiovascular disease, particularly whether inhaled particles are transported from the lungs, enter the bloodstream and make a direct contribution to cardiovascular disorders.

This was the question that researchers set out to answer in a study that was published by the American Chemical Society in April this year and was carried out by scientists from the UK and the Netherlands. The scientists were based at the BHF Centre for Cardiovascular Science, the Medical Research Council Centre for Inflammation Research (also based at the University of Edinburgh), the University of Edinburgh School of Chemistry, the National Institute for Public Health and the Environment (Netherlands), and Utrecht University and VU University (both in the Netherlands). This particular research was motivated by the growth in engineered nanomaterials and concerns over the potential for human exposure. In their introduction, the scientists say that engineered nanoparticles have “potential similarities to environmental nanoparticles that are associated with significant cardiorespiratory morbidity and mortality.” These environmental nanoparticles are the ultra-fine particles whose dimension is far smaller than the so-called fine particles (PM2.5), as mentioned above. Consequently, the research has implications for our understanding of how precisely air pollution may contribute to the development and progression of cardiovascular disease.

The fate of ultra-fine particles

To find an answer to this question, the researchers recruited 14 volunteers who were exposed to biologically inert, and hence harmless, gold nanoparticles of varying sizes. The volunteers were all male, non-smokers, and aged 18 to 35. Prior to exposure, none of the volunteers had gold detectable in the bloodstream, but gold was detectable in the bloodstream as early as 15mins after exposure in some subjects and was present in the majority at 24 hours. Further research was carried out using 12 volunteers who were suffering from a “cerebrovascular accident,” the medical term for a stroke, and were waiting to undergo surgery. As a result of this research, the scientists were able to conclude that inhaled nanoparticles are transported from the lung into the bloodstream, “where they accumulate at sites of vascular inflammation” (‘vascular inflammation’ is a condition characterised by the build-up of a fatty plaque on the walls of the arteries). The smaller particles were more likely to accumulate, indicating that the ultra-fine particles of air pollution, such as the tiny carbon particles emitted by diesel vehicles, are the most harmful to human health.

News of these findings was reported in the New Scientist in April this year by Michael Le Page, who says that the gold nanoparticles could still be found in blood and urine samples three months after inhalation. [21] Mark Miller, who led the research at the Centre, says that the team was “really surprised that levels were so high three months afterwards.” He described the health implications of the research as follows. When nanoparticles get into the body, he said, they accumulate in the fatty plaques that can grow inside arteries, causing heart attacks and strokes, and the reactive compounds found in air pollution could have all sorts of harmful effects, from impairing the contraction of blood vessels to promoting clotting. The New Scientist also quotes a statement from Frank Kelly, Professor of Environmental Health at King’s College London, who said the study goes a long way towards explaining how air pollution causes vascular injury and disease. “If these findings with gold particles reflect the movement of exhaust-generated carbon particles, then the increased production of very small particles by modern engines is a cause for further concern,” he said.

“Efforts to regulate air pollution are focusing on the wrong particles”

The research also has significant implications for the monitoring of air pollution. The technological devices that are widely used to measure air pollution at the roadside are able to measure the total mass of PM particles in a cubic metre of air, but they are unable to measure the number of such particles. And legal limits for PM emissions, as set by the EU, are based on these measures of total mass. However, thousands of ultra-fine particles can weigh much less in total than a small number of larger-sized particles, and it is the ultra-fine particles that are the most dangerous. This has led Professor David Newby to comment that current efforts to regulate air pollution are focusing on the wrong particles. “We are potentially looking in the wrong place,” he said. And Mark Miller says: “Ideally, we would measure numbers, but the technology is not there.” [22] A further problem is that, while EU legislation sets limits for particulate matter smaller than 2.5µg/m3 (PM2.5), there is no separate regulation for these far smaller ultra-fine particles.

Professor Newby also thinks that the number of ultra-fine particles has risen in the past decade over Europe as a result of diesel emissions, which means that the risk to human health has increased. This is in contrast to those who claim that air pollution has improved over the last few decades because the mass of PM2.5 particles has fallen in most of Europe, as measured by the widely used technology. According to a recent EU assessment of its Ambient Air Quality Directive, PM2.5 levels exceeded the legal limit in just six member states in 2014: the Czech Republic, Poland, Bulgaria, France, Hungary and Italy. [23] And, although the UK has broken the legal limit for NO2 emissions over the last seven years, the EU assessment records that in 2013 the UK was within the legal limit for both PM10 and PM2.5 particles. The EU legal limits that are intended to regulate air pollution mean therefore that the UK Government is under less pressure to tackle the problem of ultra-fine particles. [24]

Legal limits are not safety limits

There is also a further problem here in the disparity between the EU’s definition of legal limits and what the World Health Organization (WHO) regards as safety limits. The WHO guideline values for particulate matter are 20μg/m3 for PM10 and 10μg/m3 for PM2.5, whereas the EU legal limits are 40μg/m3 for PM10 and 25μg/m3 for PM2.5, taken as the average over a twelve-month period. In short, the WHO sets higher standards for safety limits. The WHO published a database in May last year of air pollution statistics from urban areas across the globe. These figures show that the UK breached what the WHO describes as safety limits for PM10 and PM2.5 particles in towns and cities across the UK. Safety limits for PM10 were breached in ten towns and cities. These were: London, Glasgow, Leeds, Nottingham, Southampton, Oxford, Scunthorpe, Port Talbot, Eastbourne, and Stanford-Le-Hope in Essex. Safety limits for PM2.5 were breached in 39 towns and cities. These include the ten already mentioned and Middlesbrough, Carlisle, York, Hull, Manchester, Liverpool, Stoke-on-Trent, Birmingham, Bristol, Newport, Cardiff, Swansea, Plymouth, Portsmouth, Brighton, Southend, and Norwich. If we add to this the problem of measuring and regulating the currently unregulated ultra-fine particles, which scientists now regard as the most harmful to human health, it becomes obvious that current regulatory mechanisms are inadequate to tackle the problem of air pollution. [25]

Pathways to the brain

Returning to recent research, we mentioned above that scientists working on the BREATHE project have said that ultra-fine particles are breathed into the lungs, cross into the bloodstream and travel to the brain, with an MRI scan showing an association between a high level of air pollution and a slower development of a child’s brain. [26] However, other researchers have found that airborne pollutants can enter the brain through an alternative pathway: namely, directly through the nose and the olfactory nerve. Further, the finding that PM particles can enter the brain has led some to suggest there may be a link between air pollution and neurological diseases such as Alzheimer’s disease and Parkinson’s disease.

A significant discovery which made national news was published in September last year in the journal PNAS: Proceedings of the National Academy of Sciences of the USA. [27] The research was carried out by scientists from the UK, Mexico, and the USA, and led by Professor Barbara Maher at the University of Lancaster. The scientists analysed samples of brain tissue from 37 people. Some of the samples came from 29 people who had lived and died in Mexico City and whose ages ranged from 3 to 85. The rest of the samples came from 8 people from Manchester whose ages ranged from 62 to 92 and included some who had suffered from severe to moderate forms of Alzheimer’s disease. The scientists found tiny particles of iron oxide, also known as magnetite, in all of the 37 samples. Small quantities of magnetite can occur naturally in the brain, and in the PNAS paper the authors point out that “biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over twenty years ago.” However, in their research the scientists “used magnetic analyses and electron microscopy to identify the abundant presence in the human brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source.” Further, these magnetite nanoparticles matched precisely “the high-temperature magnetite nanospheres, formed by combustion and/or friction-derived heating, which are prolific in urban, airborne particulate matter.”

The authors say that, because many of the airborne magnetite pollution particles are so small, they can enter the brain directly through the olfactory nerves (i.e. the cranial nerves supplying the smell receptors to the nose) and by crossing the damaged olfactory unit. The importance of this discovery is that nano-scale magnetite can respond to external magnetic fields and is toxic to the brain. Nano-scale magnetite is implicated in oxidative cell damage which has a causal link to neurodegenerative illnesses such as Alzheimer’s disease; hence, the authors argue, “exposure to such airborne PM-derived magnetite nanoparticles might need to be examined as a possible hazard to human health.”

Millions of nanoparticles in a single gram of brain tissue

Speaking to BBC News, lead researcher Professor Barbara Maher said she had previously identified magnetite particles in air samples gathered next to a busy road in Lancaster and outside a power station, and she suspected that similar particles might be found in the brain samples. [28] Her suspicions were confirmed by the results which she described as shocking, as a magnetic extraction showed there were a million of these particles in a single gram of brain tissue. It was the shape of the nanoparticles detected in the microscopy that gave a clue as to their origins. Naturally occurring particles of magnetite have a jagged shape, but the majority of the millions of particles found in the tissue samples were smooth and rounded, and displayed features that Professor Maher said could only be created in the high temperatures of a vehicle engine or braking system. “They are spherical shapes and they have little crystallites around their surfaces, and they occur with other metals like platinum which comes from catalytic converters,” she said. These particles were 100 times more numerous than the naturally occurring particles. Professor Maher said it was the first time such particles had been found in the human brain and the discovery opened up a new area of investigation: namely, the question of whether “these magnetite particles are causing or accelerating neurodegenerative disease.”

Links with neurodegenerative disease?

David Allsop is a Professor of Neuroscience at Lancaster University who specialises in neurological diseases and is a co-author of the PNAS paper. Speaking to BBC News, he said that pollution particles could be an important risk factor for conditions such as Alzheimer’s and Parkinson’s disease. “There is no absolutely proven link at the moment but there are lots of suggestive observations,” he said. “Other people have found these pollution particles in the middle of the plaques that accumulate in the brain in Alzheimer’s disease so they could well be a contributor to plaque formation. These particles are made out of iron and iron is very reactive so it’s almost certainly going to do some damage to the brain. It’s involved in producing very reactive molecules called reaction oxygen species which produce oxidative damage and that’s very well defined. We already know oxidative damage contributes to brain damage in Alzheimer’s patients so if you’ve got iron in the brain it’s very likely to do some damage. It can’t be benign.” [29]

However, Dr Clare Walton, Research Communications Manager at the Alzheimer’s Society, said there was no strong evidence that magnetite causes Alzheimer’s disease or makes it worse. “This study offers convincing evidence that magnetite from air pollution can get into the brain,” she said, “but it doesn’t tell us what effect this has on brain health or conditions such as Alzheimer’s disease. The causes of dementia are complex and so far there hasn’t been enough research to say whether living in cities and polluted areas raises the risk of dementia. Further work in this area is important, but until we have more information people should not be unduly worried.” [30]

The search for evidence

In the last twelve months there have been a number of studies that have investigated possible links between air pollution and neurodegenerative illnesses such as Alzheimer’s and Parkinson’s disease . A recent study was published in the journal Environmental Health Perspectives last month. [31] The aim of the research was to examine whether exposure to PM air pollution is related to the risk of contracting Parkinson’s disease. In their introduction, the authors state: “Toxins in air pollution have been shown to promote inflammation and oxidative stress, both of which are thought to contribute to Parkinson’s disease.” The researchers, based at a number of institutions in the USA, followed over 50,000 men in the Health Professionals Follow-up Study, a large cohort of men in the USA which included 550 cases of Parkinson’s disease. They estimated the cumulative average exposure to various sizes of PM up to two years before the onset of Parkinson’s by linking each participant’s place of residence throughout the study with location-specific PM models. Statistical analysis of the results did not show any significant associations between PM exposure and the risk of contracting the disease. They conclude: “In this study we found no evidence that exposure to air pollution is a risk factor for Parkinson’s disease in men.”

Other researchers however have found associations between air pollution exposure and the development of Parkinson’s disease. A review of the available literature on the subject was published in the journal Reviews on Environmental Health in July this year. [32] The review focused on a broad range of studies that investigated possible links between a number of pollutants (including PM particles of various sizes, NO2, and airborne metals) and the development of Parkinson’s disease. The author states: “Air pollution exposure is linked to numerous adverse effects on human health, including brain inflammation and oxidative stress, processes that are believed to contribute to the development and progression of Parkinson’s Disease.” The review produced mixed results: some showed a strong association; some showed a moderate association, and some showed none at all. The author found that the studies that looked at air pollution exposure over a longer time span were more likely to find a positive association. The types of pollutants that were investigated in the studies include PM particles (PM2.5 and PM10), traffic-related NO2 emissions, airborne metals, and second-hand smoking.

The problem of size

In the main, research on the impact of air pollution on human health has tended to focus on the impact of NO2 and PM pollution and, because existing data is more readily available, and because new data can be gathered more easily, on PM2.5 and PM10 particles in particular. There has been far less research on the impact of the smaller ultra-fine particles that have featured in the BREATHE project and the PNAS paper. A nanometre is one billionth of a metre, and the nanoparticles (or ‘nanospheres’) in the PNAS study are less than 200 nanometres in diameter. Writing for BBC News, David Shukman draws a comparison with a human hair, which is at least 50,000 nanometres thick. As the size of the particles decreases, the number of pathways increases, together with the potential to do harm. “While large particles of pollution such as soot can be trapped inside the nose,” he says, “smaller types can enter the lungs and even smaller ones can cross into the bloodstream. But nanoscale particles of magnetite are believed to be small enough to pass from the nose into the olfactory bulb and then via the nervous system into the frontal cortex of the brain.” [33] Airborne particles of a smaller size, such as the ultra-fine particles of carbon emitted by diesel vehicles, would find it just as easy to follow this pathway to the brain. In the search for links between air pollution and neurodegenerative disease, it may be the case therefore, as Professor David Newby suggested above, that researchers have been focusing on the wrong particles.

PM particles classified as carcinogenic by the World Health Organization

The Department for the Environment, Food and Rural Affairs (Defra) says: “Generally, if you are young and in a good state of health, moderate air pollution levels are unlikely to have any serious short-term effects.” However, it continues, elevated levels or long-term exposure to air pollution can affect the respiratory system and “can also lead to more serious conditions such as heart disease and cancer.” [34] The link with cancer was given an authoritative status in October 2013 when the International Agency for Research on Cancer (IARC), an agency of the World Health Organization, issued a press release in which it announced that it had classified outdoor air pollution as carcinogenic to humans (Group 1). [35] This followed a press release issued in June 2012, in which IARC declared diesel engine exhaust to be carcinogenic to humans (Group 1), “based on sufficient evidence that exposure is associated with an increased risk for lung cancer.” [36] The press release on outdoor air pollution, issued in 2013, said:

“After thoroughly reviewing the latest available scientific literature, the world’s leading experts convened by the IARC Monographs Programme concluded that there is sufficient evidence that exposure to outdoor air pollution causes lung cancer (Group 1). They also noted a positive association with an increased risk of bladder cancer. Particulate matter, a major component of outdoor air pollution, was evaluated separately and was also classified as carcinogenic to humans (Group 1). The IARC evaluation showed an increasing risk of lung cancer with increasing levels of exposure to particulate matter and air pollution. Although the composition of air pollution and levels of exposure can vary dramatically between locations, the conclusions of the Working Group apply to all regions of the world.” [37]

What do we know?

The World Health Organization estimated in 2014 that, globally, around 7m premature deaths a year can be attributed to air pollution, while an assessment published in the journal Nature in September 2015 estimates that air pollution contributes to more than 3m premature deaths a year worldwide, “predominantly in Asia.” [38] As regards the UK, a report published in 2016 by the Royal College of Physicians says that each year in the UK, “around 40,000 deaths are attributable to exposure to outdoor air pollution.” [39] And as regards specific outcomes, the World Health Organization has said that evidence published in 2013 “strengthened the causal link between fine particles (PM2.5) and cardiovascular and respiratory ill health. It also showed that long-term exposure to PM2.5 can trigger a range of problems, such as atherosclerosis, adverse birth outcomes and childhood respiratory diseases, and suggested possible links with neurological development, cognitive function and diabetes.” [40]

However, evidence of an association between two phenomena does not mean that one is a cause of the other. Research has shown that traffic-related air pollution can trigger asthma attacks in those suffering from severe forms of asthma, but there is no definitive proof that air pollution is one of the causes of asthma. In the case of diabetes, there is evidence that air pollution increases the risk of contracting the disease in certain individuals, but again there is no scientific evidence of causation. In the case of cardiovascular problems and heart disease, research has shown that air pollution can trigger a stroke and is a significant contributory factor in the development of heart disease, with a growing body of evidence that acute exposure to diesel exhaust does indeed cause a number of cardiovascular problems (see the research at the BHF Centre for Cardiovascular Science, above). But in the case of dementia and other neurological illnesses, the evidence for an association with air pollution is contradictory. What we do know however is that PM particles of different sizes can enter the lungs, the bloodstream and the brain, and have a significant impact on young adults; we don’t know whether this increases the risk of contracting a neurodegenerative disease in later life. The links with respiratory illnesses, lung cancer and cardiovascular disease are more certain. And research has shown that air pollution has a significant impact on children, with consequences for their mental capacity, their physical and cognitive development, and their physical health.

The Call for Action

Four years ago, following the announcement that IARC had classified outdoor air pollution and PM particles as carcinogenic to humans, the World Health Organization said the evidence “reveals the urgent need to take action at the local, regional and global levels to reduce the health threat posed by outdoor air pollution.” [41] It repeated an earlier call to all countries “to develop policies and implement measures to improve air quality to meet WHO guidelines” and “to implement the European Union (EU) legislation on air quality in full, with stricter values for air pollution limits.” The UK Government’s response, as discussed in last month’s article, has been inadequate to say the least, and its actions have been motivated less by the need to take urgent action to reduce a health threat and more by economic concerns, in particular by the need to avoid fines from the EU. Whilst the UK Government’s actions have been ineffective, the World Health Organization said in 2016 that there were signs of hope. The good news was that “awareness is rising and more cities are monitoring their air quality,” according to the WHO’s Director of Public Health, Dr Maria Neira. [42] The research discussed in this article suggests that more needs to be done as regard monitoring, particularly with the methods and the technology used to measure ultra-fine particles, now viewed as the most dangerous for human health. More investment in the research and technology in this area would obviously help. That, together with rectifying the lack of regulation in this area, and resolving the disparity between EU legal limits and WHO safety limits, might create some extra signs of hope.


Photograph: London Borough of Camden Air Monitoring Station © Copyright Mike Quinn and licensed for reuse under this Creative Commons Licence.


[1] The UK Government’s Department for the Environment, Food and Rural Affairs says nitrogen dioxide (NO2) irritates the airways of the lungs, increasing the symptoms of those suffering from lung diseases, while fine particles (PM) can be carried deep into the lungs where they can cause inflammation and a worsening of heart and lung diseases. “People with lung or heart conditions may be more susceptible to the effects of air pollution,” it says. See ‘Effects of air pollution’ at https://uk-air.defra.gov.uk/air-pollution/effects. As well as causing breathing difficulties, high levels of NO2 can trigger asthma attacks for those who suffer from a severe form of the condition. See the Asthma UK website at https://www.asthma.org.uk/advice/triggers/pollution/.
[2] Wood, H., et al. (2015) Effects of Air Pollution and the Introduction of the London Low Emission Zone on the Prevalence of Respiratory and Allergic Symptoms in Schoolchildren in East London: A Sequential Cross-Sectional Study. PLoS ONE 10(8): e0109121. https://doi.org/10.1371/journal.pone.0109121. Retrieved from: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0109121.
[3] Quoted by Laura Donnelly in ‘Air pollution stunting children’s lungs, study finds’, The Telegraph, 25/10/2015. Retrieved from: http://www.telegraph.co.uk/journalists/laura-donnelly/11953613/Air-pollution-stunting-childrens-lungs-study-finds.html.
[4] Ibid: see [2].
[5] Ibid: see [3].
[6] Adam Vaughan and Esther Addley, ‘Boris Johnson “held back” negative findings of air pollution report’, The Guardian, 17/05/2016. Retrieved from: https://www.theguardian.com/environment/2016/may/17/boris-johnson-held-back-negative-findings-of-air-pollution-report. The report’s author Katie King is Director of the environmental consultancy Aether, based in Oxford.
[7] See the BREATHE Project website at http://www.creal.cat/projectebreathe/.
[8] Dadvand, P., et al. (2017) Traffic-related air pollution and spectacles use in schoolchildren. PLoS ONE 12(4): e0167046. https://doi.org/10.1371 /journal.pone.0167046. Retrieved from: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0167046.
[9] Ibid: see [8].
[10] Sunyer, J., et al. (2015) Association between Traffic-Related Air Pollution in Schools and Cognitive Development in Primary School Children: A Prospective Cohort Study. PLoS Med 12(3): e1001792. https://doi.org/10.1371/journal.pmed.1001792. Retrieved from: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001792.
[11] Anthony King, ‘Traffic pollution prevents children’s brains from reaching their full potential’, Horizon, 17/07/2017. Retrieved from: https://phys.org/news/2017-07-traffic-pollution-children-brains-full.html.
[12] Wolf, K., et al. (2016) Association Between Long-Term Exposure to Air Pollution and Biomarkers Related to Insulin Resistance, Subclinical Inflammation and Adipokines. Diabetes, 65(8): db151567. https://doi.org/10.2337/db15-1567. Retrieved from: http://diabetes.diabetesjournals.org/content/early/2016/08/16/db15-1567.
[13] Alderete, T., et al. (2017). Longitudinal Associations Between Ambient Air Pollution with Insulin Sensitivity, β-Cell Function, and Adiposity in Los Angeles Latino Children. Diabetes, 66(1): db161416. https://doi.org/10.2337/db16-1416. Retrieved from: http://diabetes.diabetesjournals.org/content/early/2017/01/27/db16-1416.long.
[14] Peterson, B., et al. (2015). Effects of Prenatal Exposure to Air Pollutants (Polycyclic Aromatic Hydrocarbons) on the Development of Brain White Matter, Cognition, and Behavior in Later Childhood. JAMA Psychiatry, 72(6), 531−540. https://doi.org/10.1001/jamapsychiatry.2015.57. Retrieved from: https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2205842.
[15] Brook, R., et al. (2010). Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association. Circulation, 121, 2331−2378. https://doi.org/10.1161/CIR.0b013e3181dbece1. Retrieved from: http://circ.ahajournals.org/content/121/21/2331.
[16] Shah, A., et al. (2015). Short term exposure to air pollution and stroke: systematic review and metaanalysis. British Medical Journal, 350: h1295. Retrieved from: http://www.bmj.com/content/350/bmj.h1295.
[17] Peters, A., et al. (2001). Increased particulate air pollution and the triggering of myocardial infarction. Circulation, 103, 2810−2815. https://doi.org/10.1161/01.CIR.103.23.2810. Retrieved from: http://circ.ahajournals.org/content/103/23/2810.
[18] ‘Research that shows how air pollution can affect our hearts’, British Heart Foundation. Retrieved from the BHF website at:
[19] Miller, M. et al. (2017). Inhaled Nanoparticles Accumulate at Sites of Vascular Disease. ACS Nano, 11(5), 4542–4552. https://doi.org/10.1021/acsnano.6b08551. Retrieved from: http://pubs.acs.org/doi/abs/10.1021/acsnano.6b08551.
[20] Ibid: see [19]. The relevant research was published in the European Heart Journal and Circulation as follows:
(a) Lucking, A., et al. (2008). Diesel exhaust inhalation increases thrombus formation in man. European Heart Journal, 29, 3043−3051.
(b) Mills, N., et al. (2005). Diesel exhaust inhalation causes vascular dysfunction and impaired endogenous fibrinolysis. Circulation, 112, 3930−3936.
[21] Michael Le Page, ‘Pollution nanoparticles may enter your blood and cause disease’, New Scientist, 26/04/2017. Retrieved from: https://www.newscientist.com/article/2128923-pollution-nanoparticles-may-enter-your-blood-and-cause-disease/.
[22] Ibid: see [21].
[23] Implementation of the Air Quality Directive. A study for the European Parliament’s Committee on Environment, Public Health and Food Safety. Nagl, C., Schneider, J., and Thielen, P. April 2016. Retrieved from: http://www.europarl.europa.eu/RegData/etudes/STUD/2016/578986/IPOL_STU(2016)578986_EN.pdf.
[24] In stark contrast to the EU’s assessment, the authors of the study on London’s Low Emission Zone, published in 2015, state: “Levels of traffic-related air pollution in London are among the worst in Europe, with European Union (EU) limit values for particulate matter with an aerodynamic diameter of < 10μm (PM10) and nitrogen dioxide (NO2) regularly exceeded in many areas of the city" (ibid: see [2]). The Environmental Research Group at King's College London provides real-time data on London's air pollution levels via the London Air Quality Network. The network consist of a number of monitoring stations spanning London and the South-East, funded by local authorities and other bodies, and complemented by modelling techniques that can 'fill in the gaps' to provide the missing data between the stations. For further info, see http://www.londonair.org.uk/LondonAir/General/about.aspx.
[25] The World Health Organization database, including notes on measurements and safety limits, is available as a spreadsheet from the WHO website at: http://www.who.int/phe/health_topics/outdoorair/databases/cities/en/. The full list of the 39 towns and cities in breach of the WHO’s safety limits for PM2.5 in 2016 is: Armagh, Belfast, Londonderry, Prestonpans, Middlesbrough, Carlisle, York, Hull, Manchester, Salford, Warrington, Wigan, Liverpool, Birkenhead, Stoke-on-Trent, Birmingham, Leamington Spa, Bristol, Chepstow, Newport, Cardiff, Swansea, Plymouth, Saltash, Portsmouth, Brighton, Southend, Thurrock, and Norwich. For a summary of the WHO’s findings and reactions to the figures, see: Ian Johnston, ‘Air pollution in UK “wreaking havoc on human health,” WHO warns’, The Independent, 12/05/2016. Retrieved from: http://www.independent.co.uk/environment/dozens-of-british-cities-are-breaching-air-pollution-limits-in-public-health-crisis-a7025401.html. The WHO database was updated in April 2017, with more towns and cities added to the list. For the EU legal limits, see: ‘Air Quality Standards’, European Commission, last updated 22/09/2017. Accessed from: http://ec.europa.eu/environment/air/quality/standards.htm.
[26] Ibid; see [11].
[27] Maher, B., et al. (2016). Magnetite pollution nanoparticles in the human brain. PNAS: Proceedings of the National Academy of Sciences of the USA, 113(39), 10797−10801, 27/09/2016. https://doi.org/10.1073/pnas.1605941113. Retrieved from: http://www.pnas.org/content/113/39/10797.
[28] David Shukman, ‘Pollution particles “get into brain”‘, BBC News, 05/09/2016. Retrieved from: http://www.bbc.co.uk/news/science-environment-37276219.
[29] Ibid: see [28].
[30] Ibid: see [28].
[31] Palacios, N., et al. (2017). Air Pollution and Risk of Parkinson’s Disease in a Large Prospective Study of Men. Environmental Health Perspectives, 125(8): 087011, 18/08/2017. https://doi.org/10.1289/EHP259. Retrieved from: https://ehp.niehs.nih.gov/ehp259/.
[32] Palacios, N. (2017). Air pollution and Parkinson’s disease – evidence and future directions. Reviews on Environmental Health, 21/07/2017. https://doi.org/10.1515/reveh-2017-0009. Retrieved from: https://www.degruyter.com/view/j/reveh.ahead-of-print/reveh-2017-0009/reveh-2017-0009.xml.
[33] Ibid: see [28]. In June this year, the journal Current Environmental Health Reports published a review of the literature on the ways in which air pollutants can find a pathway to the brain. The authors state: “Accumulating research indicates that ambient outdoor air pollution impacts the brain and may affect neurodegenerative diseases, yet the potential underlying mechanisms are poorly understood.” They conclude that, to exert effects on the central nervous system, “multiple direct and indirect pathways in response to air pollution exposure likely interact in concert.” See: Jayaraj, R., et al. (2017). Outdoor Ambient Air Pollution and Neurodegenerative Diseases: the Neuroinflammation Hypothesis, Current Environmental Health Reports, 4(2), 166−179. https://doi.org/10.1007/s40572-017-0142-3. Retrieved from: https://link.springer.com/article/10.1007%2Fs40572-017-0142-3.
[34] Ibid: see [1].
[35] ‘Outdoor air pollution a leading environmental cause of cancer deaths’, IARC Press Release No. 221, 17/10/2013. Retrieved from: http://www.iarc.fr/en/media-centre/iarcnews/pdf/pr221_E.pdf. IARC categories (1, 2a, 2b and 3) are based on an evaluation of the evidence, Group 1 indicating “there is sufficient evidence of carcinogenicity in humans”.
[36]’DIESEL ENGINE EXHAUST CARCINOGENIC’, IARC Press Release No. 213, 12/06/2012. Retrieved from: http://www.iarc.fr/en/media-centre/pr/2012/pdfs/pr213_E.pdf.
[37] Ibid: see [35].
[38] Lelieveld, J., et al. (2015). The contribution of outdoor air pollution sources to premature mortality on a global scale. Nature, 525, 367−371. https://doi.org/10.1038/nature15371. Retrieved from: https://www.nature.com/nature/journal/v525/n7569/full/nature15371.html. For the World Health Organization estimate, see: ‘7 million premature deaths annually linked to air pollution’, WHO News Release, 25/03/2014. Retrieved from: http://www.who.int/mediacentre/news/releases/2014/air-pollution/en/.
[39] Every breath we take: the lifelong impact of air pollution, Royal College of Physicians, February 2016. Available as a PDF from: https://www.rcplondon.ac.uk/projects/outputs/every-breath-we-take-lifelong-impact-air-pollution.
[40] ‘Outdoor air pollution a leading environmental cause of cancer deaths’, World Health Organization News, 17/10/2013. Retrieved from: http://www.euro.who.int/en/health-topics/environment-and-health/air-quality/news/news/2013/10/outdoor-air-pollution-a-leading-environmental-cause-of-cancer-deaths.
[41] Ibid: see [40].
[42] Quoted by Ian Johnston in ‘Air pollution in UK “wreaking havoc on human health,” WHO warns’, The Independent, 12/05/2016. Retrieved from: http://www.independent.co.uk/environment/dozens-of-british-cities-are-breaching-air-pollution-limits-in-public-health-crisis-a7025401.html.

New research will investigate the impact of climate change on the UK’s woodlands

How will increased levels of CO2 affect forest ecosystems?

Birmingham Institute of Forest Research launches carbon enrichment facility to find out

April 19th 2017

Scientists at Birmingham University’s Institute of Forest Research are carrying out a ground-breaking research project that will investigate the impact of climate change on our woodlands. The project will help us to understand how our forests and woodlands will respond to future increases in atmospheric carbon dioxide, including the effects on tree growth and their resilience to agricultural pests and diseases.

The Birmingham Institute of Forest Research (BIFoR) was established some years ago thanks to a £15m. donation from a former professor, and the Institute is supported by the Forestry Commission, Natural England, the Woodland Trust, and a number of other organisations. [1] The project is being carried out in woodlands in Staffordshire and involves “treating 30-metre plots of semi-natural oak woodland to the concentrations of carbon dioxide expected to prevail in 2050. Autonomous sensors and instrumented trees will allow scientists to take measurements continuously and remotely, over timescales ranging from seconds to decades, and to follow the carbon as it is taken up by the plants and moved through the woodland ecosystem.” [2]

The Free-Air Carbon Dioxide Enrichment Facility (FACE)

The apparatus for the field experiment is called a Free-Air Carbon Dioxide Enrichment (FACE) facility and the experiment, the first of its kind in Europe, is one of four similar research projects in other countries with different climates. [3] When combined, BIFoR says this will form the largest machine ever built to study how landscapes will respond to our changing climate. Planning permission for constructing the facility was awarded by Staffordshire County Council in December 2014. Work has been progressing since late spring 2015 on protecting the ecology of the woodland, building the apparatus, and spending a year taking vital baseline measurements before subjecting three of six plots in the woodland to elevated levels of CO2, which started a couple of weeks ago.

BIFoR says that the basic element of the FACE facility is a cylindrical ring structure, supporting pipes that deliver CO2 in such a way that the woodland inside the ring is immersed in elevated CO2 while the rest of the woodland remains largely unaffected. Winds disperse the CO2 continuously so it must be replenished using substantial gas-handling facilities; otherwise, the CO2 would be vented directly to the atmosphere. Six completely open cylindrical rings, 30m wide and as high as the tree canopy, are served by these gas-handling facilities, which store 100 tonnes of liquid CO2 and vaporise and deliver up to 15 tonnes of CO2 per day to 3 of the 6 rings via 25m masts. [4]

“Big Science”

The scientists say that a FACE experiment requires bespoke control engineering which responds rapidly to changes in wind speed and direction “so that CO2 is introduced into the ring always on the upwind side and in just sufficient quantity to maintain the target concentration. A successful experiment will expect to provide CO2 within 10% of the target concentration at least 98% of the time when operating for the entire duration of the CO2 application. In order to detect a signal, and to eliminate effects of the FACE installation itself, control rings must be built in which ambient air is used instead of CO2-enriched air.”

BIFoR describes forest FACE experiments as “big science” and liken the BIFoR programme to a terrestrial ecology version of a space programme, large physics experiments, or advanced manufacturing centres in terms of the requirements for sustained and stringent quality assurance and quality control: “Only in this way, can we ‘follow the carbon’ to establish the true contribution of mature forests to the removal of CO2 from the air.”

The experiment will continue to 2026 at least, and the scientists will be measuring a number of aspects over the next decade, including tree growth and interactions with surrounding ecosystems such as leaf litter, soil and insects. BIFoR’s Director, Professor of Atmospheric Science Rob MacKenzie, said the findings will provide evidence on which to base strategies for the protection of iconic landscape features, such as oak woodlands, into the future.

“The entire experiment depends on changing the woodland as little as possible”

There have been a number of experiments across the globe using FACE facilities, including a project in Australia called AGFACE (the Australian Grains Free Air CO2 Enrichment facility), which “enables the exposure of field-grown crops to elevated CO2 levels under dry-land field conditions.” [5] However, BIFoR chose the woodland at Mill Haft because similar experiments in woodlands have only been carried out on young trees in plantations, whereas Mill Haft Wood is an unmanaged woodland of mature trees. In a paper delivered to the 2016 General Assembly of the European Geosciences Union, the scientists describe the woodland as a “mature oak and hazel coppice-with-standards woodland,” with the oaks estimated to be 150 years old. [6] Reporting on this month’s launch of the experiment, the BBC’s environment correspondent Roger Harrabin says the woodland is part of the former hunting ground of the Earl of Lichfield: “It covers 25 hectares and is thought to have been under continuous tree cover for more than than 300 years.” [7]

In the planning and design stage of the experiment, a major challenge for the scientists was how to build the facility without damaging the delicate natural ecosystem as “the entire experiment depends on changing the woodland as little as possible.” No concrete foundations were used and major elements of the infrastructure were put in place by helicopter. The scientists “nestled all of the experimental equipment into the woodland by hand” while the ancillary buildings were designed to blend in with the woodland. The lighting is low-level and non-intrusive to minimise interference with wildlife and to ensure that the facility sits unobtrusively in its location. The whole site is surrounded by a 3m fence.

On the amount of CO2 that will be used in the course of the experiment, BIFoR says: “Our monthly usage is equivalent to one return transatlantic flight so, although not carbon neutral, our experiment is not as profligate as it sounds and is of course directed at understanding the implications of climate change on our fragile ecosystem.”

Looking after our forests: The need for research

Trees soak up carbon dioxide in the atmosphere via the process known as photosynthesis, releasing oxygen and storing carbon. As humans need oxygen, our relationship with trees is a mutually beneficial one in which trees are fed by CO2 which would otherwise remain in the atmosphere and contribute to global warming, while we are fed by the oxygen. However, estimates of how much of the carbon produced by burning fossil fuels is currently stored by trees varies from 25% to 60%. [8]

As CO2 acts as a plant fertiliser, scientists believe that trees will be able to absorb more CO2 as levels increase, storing carbon in their trunks, roots and organic matter in the soil. On the other hand, however, they also believe that the ability to absorb increased levels of CO2 will be mitigated over time by factors such as rising temperatures, a lack of water and a lack of nutrients, which will counterbalance the fertilizing effect. The question is, how long will trees continue to absorb CO2 as levels increase before these mitigating effects come into play? How will our woodlands respond to future increases in atmospheric CO2, and what will the impact be on tree growth and a plant’s resilience to pests and diseases? [9]

Those are the questions that BIFoR’s research is aiming to answer. Talking to BBC News, BIFoR’s Director Rob MacKenzie said: “The impact of changing CO2 should show up in the leaf chemistry of exposed trees within days, and in the soil within weeks. Within three years stem growth, canopy structure, and a host of other structural forest elements should be different in the patches exposed to elevated CO2. Continuing out to 2026, the ‘push’ provided by the elevated CO2 will pass through all the checks and balances of a mature forest ecosystem, allowing, as each year passes, increasingly better estimates to be made of the extent and capacity of the land carbon sink in 2050 and beyond.” The experiment may also reveal other intriguing effects, he said. For instance, trees in a mature forest, in which the intake and the release of CO2 are in balance, might adapt to high CO2 levels by reducing their pores, which in turn would make them more tolerant to drought.

In the UK, our woodlands face a whole raft of problems specific to the region, such as inadequacies in forestry management and a variety of tree diseases, all of which provide further reasons why this research is vital, as BIFoR explains: [10]

“Forests are critical components of global carbon, nutrient and water cycles, influencing the thermal balance of the planet directly and indirectly, and are home to more than half of all known species. As human populations have expanded, increasing pressures have been placed on forests, with the 20th century witnessing the steepest rise in rates of deforestation. The UK has the lowest woodland cover of any large European country, and what remains is under serious threat from climate change and imported tree diseases such as ash dieback, responsible for the loss of 60-90% of ash trees in Denmark and now identified at 600 sites in the UK. Our forest industries struggle to compete effectively with imports, which now constitute 70-80% of our timber use, and our level of skills in forest management is on the decline just when a leap to sustainable stewardship of our landscape is urgently required. FACE experiments study to what extent these environmental benefits will persist into the future.”


[1] In an article for BBC News, Roger Harrabin said the experimental site in Staffordshire has been funded by a Birmingham alumnus and philanthropist, Professor Joe Bradwell, who made money selling diagnostic medical kits developed at the university, mainly in the USA. BIFoR’s Director Rob Mackenzie said Professor Bradwell calculated that to offset his carbon footprint he needed to plant 300,000 trees, and the research project was part of his commitment. See “Sci-fi forest tracks carbon impact,” BBC News, April 3rd 2017, at http://www.bbc.co.uk/news/science-environment-39472425.

[2] “Unique forest experiment given the green light,” Birmingham University news, 18th December 2014, at http://www.birmingham.ac.uk/news/latest/2014/12/Unique-forest-experiment-given-the-green-light.aspx.

[3] One such research project is focused on an old-growth forest in the Amazon basin near Manaus, Brazil. See “Amazon FACE” at https://amazonface.org/about/.

[4] “The Birmingham Institute of Forest Research (BIFoR),” Birmingham University website at http://www.birmingham.ac.uk/university/building/bifor.aspx and “The BIFoR Vision,” Birmingham University website at http://www.birmingham.ac.uk/research/activity/bifor/about/bifor-vision.aspx#visionimpact.

[5] “AGFACE (Australian Grains Free Air CO2 Enrichment),” Primary Industries Climate Challenges Centre. The researchers say: “To successfully adapt crop production practices and agro-ecosystem management in the face of increasing CO2, plant production must be studied in a range of environments under field conditions… The FACE (Free Air CO2 Enrichment) technique is used internationally at more than 30 sites, investigating a multitude of ecosystems including cropping systems, pastures, and forests.” See http://www.piccc.org.au/research/project/252.

[6] The abstract is available as a PDF from the Copernicus website at http://meetingorganizer.copernicus.org/EGU2016/EGU2016-4919.pdf.

[7] See [1].

[8] “Forests and Climate Change,” Food and Agriculture Organization (FAO) of the United Nations, at http://www.fao.org/docrep/005/ac836e/AC836E03.htm. The FAO says: “The increase of CO2 in the atmosphere has a ‘fertilizing effect’ on photosynthesis and thus plant growth. There are varying estimates of this effect: + 33%, + 25%, and + 60% for trees, and + 14% for pastures and crops.” The figures are taken from Climate Change 2001 – IPCC Third Assessment, published by the IPCC (Intergovernmental Panel on Climate Change).

[9] See our article “Conifers and Climate Change” for news of research on the impact of climate change on conifers. Two research projects have produced results that appear to be contradictory.

[10] “About BIFoR,” Birmingham University website at http://www.birmingham.ac.uk/research/activity/bifor/about/index.aspx.


Photograph: The view towards Mill Haft Wood from the tunnel underneath the Shropshire Union Canal, near Norbury Junction, Staffordshire © Copyright Roger Kidd and licensed for reuse under this Creative Commons Licence. The caption to the photograph says the mile-long embankment supporting the Shropshire Union Canal here was the cause of years of delay to its final opening in 1835: “its height here is about 14m and the distance through the tunnel is about 60m.” Scientists from the Birmingham Institute of Forest Research have created a “living laboratory” at Mill Haft Wood to investigate the impact of increased levels of CO2 on our woodlands.

The State of Nature 2016 – New report examines the causes of wildlife decline in the UK

“The UK is among the most nature-depleted countries in the world,” says the report

56% of the species assessed have declined since 1970, whilst 15% are threatened with extinction

September 21st 2016

A partnership of 53 wildlife organisations published a report last week which gathers together data and expertise from a number of bodies to present “the clearest picture to date” of the status of the UK’s native species. The report, titled The State of Nature 2016, analyses a total of 7,964 species and reveals that 56% of the species assessed have declined since 1970, while 15% (1,199 species) are either extinct or are threatened with extinction in the UK, using internationally recognised Red List assessment criteria.

The partnership covers England, Wales, Scotland, Northern Ireland, the Isle of Man, Jersey and Guernsey and the 53 partners include the RSPB, the Wildfowl & Wetlands Trust, the British Trust for Ornithology, the National Trust, the Woodland Trust, the World Wildlife Fund, the Botanical Society of Britain and Ireland, the Centre for Ecology & Hydrology, the Chartered Institute of Ecology and Environmental Management, Friends of the Earth, and a number of rivers trusts and wildlife trusts as well as several specialist organisations concerned with bats, butterflies, bees, dragonflies, bugs, mammals, badgers, fungi, lichen, plants, amphibians, reptiles, frogs, sharks, whales, dolphins, freshwater habitats and marine ecosystems.

The report builds on a previous State of Nature report published in 2013 which analysed data for the period 2002–2013. The new report includes data for more species and takes a longer view by assessing the period from 1970 to 2013. One of the aims of the report is to examine the causes of wildlife decline and to use the diagnosis to highlight the need for conservation projects across the UK, UK Overseas Territories and Crown Dependencies. A further aim is to demonstrate through the use of case studies how targeted conservation is helping to tackle wildlife decline with projects that have benefited species and habitats. The report’s authors hope that success stories such as these will inspire individuals, organisations and governments to work together to reverse the decline and “bring nature back from the brink.”

“The drivers of change”

On the causes of wildlife decline, the report’s authors reviewed evidence concerning the long-term population trends of 400 terrestrial and freshwater species in the UK, sampled from a variety of taxonomic groups, the three main groups being insects, vascular plants and vertebrates. The authors were then able to quantify the impact, both positive and negative, of a broad range of drivers, spanning the period 1970–2012. Their findings were similar across the three main taxonomic groups included in the study.

They found that the largest driver of change by far is the intensification of agriculture, which has had an overwhelmingly negative impact on wildlife. Farming has changed dramatically over the forty-year period under review, the report says, “with new technologies boosting yields often at the expense of nature.” The transformation of agricultural land through intensive management has seen an abandonment of mixed farming systems; the intensification of grazing regimes; the increased use of pesticides and fertilisers; the loss of marginal habitats, such as ponds, hedgerows and small woodland; and a switch from spring to autumn sowing, reducing food and habitat for many species. According to the report, however, this last practice has also had a positive impact, leading to “the increased winter survival of some species that eat autumn-sown crops” (though milder winters are also a factor here).

The second biggest driver is climate change, but the impact here has been both positive and negative. For instance, more species from southerly climes have extended their range into the UK than those species from northerly climes that have been lost. In addition, milder winters have increased the survival rate of some species. However, the negative factors here include the loss of coastal habitat due to sea level rise; the adverse effect on marine ecosystems due to increases in sea temperatures; and the disruption to a species’ feeding and breeding habits due to changes in seasonal weather patterns, such as winter storms and wetter springs. The authors also warn that “novel interactions between species caused by changes to their distributions are likely to affect them in unpredictable ways.”

There are four drivers of change that have also had a negative impact on wildlife though to a lesser extent. These are, firstly, hydrological change. This is another land management issue, involving the drainage of wetlands, upland bogs, fens and lowland wet grasslands, and also a sustainability issue, involving the over-abstraction of water. Secondly, urbanisation, involving the loss of green space, including parks, allotments and gardens; the loss of wildlife-rich brownfield sites; and the loss of habitats, such as lowland heathland, to development. Thirdly, a decline in woodland management: the cessation of traditional management practices, such as coppicing, says the report, has led to the loss of varied-age structure and open habitats within woodland. And fourthly, a decline in managing other habitats, such as heathland and grassland: the abandonment of traditional management, including grazing, burning and cutting, is crucial for their maintenance, the report states.

A fifth driver of change is forestry, which has had both a negative and a positive impact on wildlife, and again is an issue of land management. An overall increase in the area of forestry plantations, whilst this has increased the habitat for species using coniferous plantations and woodland edges, has also reduced the habitat that plantations replace, particularly lowland heaths and upland habitats.

So what does the report say about positive drivers? The report summarises its analysis by saying, in general, the way habitats are managed has had a greater impact on wildlife than changes in the total amount of habitat. Whilst changes in habitat management have been substantial, changes to the areas occupied by different habitats during the forty-year period have been relatively small, compared to the extent of habitat loss in the past. It is therefore unsurprising that land management features in the positive drivers of change. According to the report, habitat creation and the low-intensity management of agricultural land have had the most beneficial impact on wildlife. Habitat creation, in particular, is classed as a positive driver with no negative impact, and the report cites the examples of the creation of new wetlands, either through conservation work or as a by-product of mineral extraction (see below), and the planting of new broadleaved and mixed woodland.

The low-intensity management of agricultural land involves the introduction of wildlife-friendly farming through programmes such as the Countryside Stewardship scheme. However, this is balanced by the negative consequence of reduced grazing, leading to the loss of some habitats. Increased management of other habitats through conservation management, often by reinstating traditional methods, also has a positive impact, but again is balanced by the negative impact of increased grazing pressure.

The report examines the causes of wildlife decline in more detail by focusing on specific habitats, with sections that deal with farmland; lowland semi-natural grassland and heathland; upland; woodland; coastal habitats; freshwater and wetland habitats; the urban environment, and the marine environment. There are also four separate reports that focus on England, Wales, Scotland and Northern Ireland, whilst a supplement to the main report includes a set of tables with statistical breakdowns for habitats, regions, and taxonomic groups. Taking the UK as a whole, the steepest rate of wildlife decline is found in grassland and heathland (a 60% fall), whilst the marine environment shows the smallest at 38%. Comparing regions of the UK, England fares the worst by far, with a 61% decline in vascular plants, a 62% decline in the butterfly population, and a 49% fall in the bird population.

Helping to halt the decline

The report describes a number of ways to protect the natural environment and of helping wildlife to thrive, including: protecting specific sites via national and international legislation; improving habitats; creating new wildlife sites; creating wildlife corridors between sites; taking action on behalf of particular species; and tackling pressures such as climate change.

However, the drivers of change are not the only source of pressure facing the natural environment. There is also the pressure of funding for conservation projects. The report states that government spending on biodiversity has fallen by 32% in the last eight years as a percentage of GDP. Many environmental charities would struggle to exist without funding from alternative sources, such as donations from the general public, whilst many conservation projects are heavily reliant on volunteers, whose help has been indispensable for their completion. In this context, it is fortunate that companies working in the mineral extraction and aggregate industries have demonstrated a strong commitment to playing a significant role in nature conservation, both financially and physically through specific restoration projects, a fact that is acknowledged in the report.

For instance, the Peak District National Park has formed a partnership with Tarmac which will see the company donate £20,000 a year for the next five years to help the National Park employ a new member of staff. The new member of staff will play a lead role in supporting the Park’s programme of conservation volunteering. Tarmac, which owns a quarry near Buxton, has set a target of delivering 50,000 volunteer hours a year by 2020 and, as part of the partnership with the National Park, its employees will help with projects across the Peak District for one day a month for the duration of the partnership. [1]

As another example, earlier this year the company Banks Mining established a £93,000 endowment fund to support the management of Pegswood Country Park in Northumberland, having completed the second phase of a programme of restoration and landscaping work at the 36.5 hectare site. The park includes the site of a former opencast mine which Banks operated between 1997 and 2005, and the first phase of the work, on land to the east of the former mine, was delivered in 2003 while the surface mine was still operational. The ongoing management of the park has now been handed over to the environmental charity Groundwork, and the landscaping work has included the planting of 575 bushes and trees along the side of a lake, the sowing of nectar-rich grasses, and 1.4km of new public footpaths. [2]

Back to nature: Creating new habitats

The RSPB is also involved in a number of partnerships with mineral extraction and aggregate companies, not only working with them on specific projects but also at a national level. The RSPB leads a nationwide minerals restoration programme in partnership with the Mineral Products Association, the British Aggregates Association, and Natural England. The partnership, called Nature after Minerals, recently launched a new website which provides advice on a range of land management issues, including priority habitat creation; species protection; and strategic minerals planning. The resource enables practitioners to share best practice and showcases case studies that illustrate how restoration projects have benefited biodiversity and have engaged the local community.

Moving on to specific projects, the RSPB recently announced a collaboration with Brett Aggregates and Boskalis, a dredging contractor, which will involve transporting clay, chalk and other construction spoil from tunnelling and building projects to a Brett Aggregates site at Cliffe in Kent, close to the Thames estuary, where it will be used to fill two lakes. Shallows and islands will then be created in the larger of the two lakes, providing an enhanced habitat for wading birds and other wildlife, and complementing the neighbouring 236-hectare RSPB Cliffe Pools nature reserve. A report by Agg-Net says that the Brette Aggregates site at Cliffe is ideally located “as materials from large projects such as the Thames Tideway Tunnel scheme and other commercial developments can be delivered by boat or barge to the wharf-side operation.” Julian Nash from the RSPB said this type of site is rare in the UK and is significant for both the internationally important wetland birds of the south Thames estuary and marshes, and as a nationally important saline habitat. In winter, Cliffe Pools can attract up to 7,000 dunlins, 2,000 lapwings and 3,000 ducks including teal, wigeon, shoveler, mallard, gadwall and pintail, as well as other species including redshank and grey plover plus birds of prey in the scrub and grassland areas, including marsh harriers.

Meanwhile, in Cambridgeshire, the RSPB is at the halfway stage in a 30-year partnership project with Hanson UK which will see the creation of the UK’s largest reed bed from a working sand and gravel quarry. In May, Hanson handed over a further 96 hectares of restored land at its Needingworth Quarry which will double the size of the RSPB Ouse Fen reserve. A report by Agg-Net says the handover will make the reserve bigger than 200 football pitches: “The Hanson-RSPB wetland project at Needingworth is the biggest planned nature conservation restoration scheme in Europe. It began in 2001 and is primarily being created for bitterns, a species that until recently was very rare in Britain. The reserve is also home to other scarce species such as marsh harriers, bearded tits, otters and water voles. Hanson will continue to hand over parcels of land as sand and gravel extraction is completed, eventually forming a 700-hectare reserve and recreating some of the lost wetland habitat that once dominated the Fenland landscape but was lost due to drainage and land-use changes. The reed bed will cover around 1.5 square miles, almost doubling the natural wetland habitat.”

The State of Nature report says that habitat creation is one of the most significant drivers of positive change for the UK’s wildlife and points out that much of this habitat creation has taken place at post-extraction mineral sites, “where old quarries are converted to new wetlands, including reed beds, marshes and open water.” Whilst this is an obvious benefit to wetland species, what about grassland and heathland, the habitat that shows the steepest rate of species decline across the UK?

Some wetland projects do incorporate grassland into the landscaping where this is feasible and desirable, but for a project that deals specifically with grassland we turn to another RSPB partnership, this one with CEMEX. As we reported in a previous news item, the RSPB is working with CEMEX to provide habitats for the twite in Derbyshire and for the turtle dove in Warwickshire. The company is managing hay meadows and creating conditions that will allow plant species more usually associated with arable land to flourish and to provide seeds for the birds to feed on at critical times of the year.

The plight of the turtle dove was highlighted last year when the IUCN added the turtle dove to its Red List list of bird species threatened with extinction. [3] Turtle doves are migratory birds that spend less than half a year in the UK but come here to breed, primarily in the east and south-east of England. Operation Turtle Dove reports that their numbers have fallen by 97% since the 1970s, the main reason being changes in arable farming practice which has had an impact on their habitat and food supply. Farmers and landowners in the east of England have subsequently taken up their cause via the Countryside Stewardship scheme, creating feeding habitat for the birds and allowing their food plants to return to the arable landscape.

Threatened with extinction

The turtle dove was not the only bird to be added to the IUCN Red List of bird species in the UK; the puffin, the Slavonian grebe, and the pochard were also added to the list. The causes of the puffin’s decline are thought to be their vulnerability to pollution and also a decline in their food supply, which has reduced the survival rate of young birds. The decline in Slavonian grebes in the UK is thought to be due to a reduction in successful breeding pairs, whilst the decline in the pochard population is thought to be due to hunting and the destruction of habitat. These additions mean that the Red List of bird species in the UK has doubled from four to eight. [4]

Reacting to the news last October, Martin Harper, the RSPB’s Director of Conservation, said: “Today’s announcement means that the global wave of extinction is now lapping at our shores… The erosion of the UK’s wildlife is staggering and this is reinforced when you talk about puffin and turtle dove now facing the same level of extinction threat as African elephant and lion, and being more endangered than the humpback whale.”

The RSPB said that several themes emerge from an examination of the changes to the UK’s birds in the IUCN Red List, including “a deterioration in the fortunes of some sea birds, such as puffin and razorbill; an ongoing and increasingly intense threat to wading birds, such as godwits, curlew, oyster catcher, knot and lapwing; and an increasing deterioration in the status of marine ducks, such as common eider, which joins the velvet scoter and long-tailed duck as species of concern.”

Returning to the State of Nature report, whilst there are a number of success stories with regard to targeted species, the overall picture remains one of general decline. The song thrush population has halved in the UK since 1970, whilst the hedgehog population has declined by a third in the last twenty years. An index of species status, based on abundance and occupancy data for 2,501 terrestrial and freshwater species in the UK, has fallen by 16% since 1970. In addition, using data for 213 priority species, an index describing the population trends of species of special conservation concern in the UK has fallen by 67% since 1970. The report also cites a new measure that assesses the health of a country’s biodiversity, and this suggests that the UK has lost significantly more nature over the long term than the global average. “The index suggests that we are among the most nature-depleted countries in the world,” says the report.

The report summarises the overall picture thus: “The loss of nature in the UK continues. Although many short-term trends suggest improvement, there was no statistical difference between our long and short-term measures of species’ change, and no change in the proportion of species threatened with extinction.”

The State of Nature 2016 was launched by David Attenborough at the Royal Society in London on September 14th and is available as a PDF download from the RSPB website.


[1] See the article ‘Tarmac backing conservation in Peak District,’ as reported by Agg-Net.

[2] See the article ‘Banks Mining complete Pegswood restoration,’ as reported by Agg-Net.

[3] The IUCN (International Union for Conservation of Nature) use a range of categories to assess the status of a species with regard to its population and the priorities for conservation. These are: 1. Extinct; 2. Extinct in the wild; 3. Critically Endangered; 4. Endangered; 5. Vulnerable; 6. Near Threatened; 7. Least Concern; 8. Data deficient; and 9. Not evaluated. The turtle dove is listed as ‘critically endangered’ in the UK and ‘vulnerable’ globally.

[4] See BBC News for a summary, but note that ‘critically endangered’ in the UK does not necessarily reflect the global status of a species, as in the case of the turtle dove above.


Photograph: Ouse Fen, Phase Seven © Copyright Hugh Venables and licensed for reuse under this Creative Commons Licence. The photograph was taken in 2012 and the caption says that sand and gravel extraction by Hanson has finished in this area, “which will now be re-profiled and covered in a peaty topsoil in preparation for the conversion to a reed bed as part of the RSPB Ouse Fen reserve.” The reed bed will eventually cover around 1.5 square miles, making it the largest reed bed in the UK. For more information, see RSPB Ouse Fen.

Scientists warn of widespread pollution from historic landfills

4,000 old landfill sites are at risk of flooding, some containing hazardous waste

March 9th 2016
Scientists at the British Geological Survey and Queen Mary College, University of London, are warning that the UK faces the risk of pollutants leaking out from the large number of historic landfill sites that pre-date EU waste regulations introduced in the 1990s. It is estimated that there are 21,027 historic landfills in the UK, with 1,264 sites situated in estuaries and coastal areas at risk of erosion, and a further 2,946 sites located on floodplains. Current regulations require landfills to be sealed with a protective lining, thereby insulating the waste from the surrounding land and watercourses. However, older landfill sites, some of which date from the late nineteenth century, are unlikely to have such protection, leaving them at risk of flooding from coastal erosion or severe weather such as heavy rain and storm surges.

A report produced by CIRIA in 2012 [1] says that the number of historic landfills is likely to be an under-estimate owing to a large number of unrecorded illegal sites. In addition, as the 21,000 historic landfills were developed when there were no legal requirements for their management or monitoring, records of the waste that was deposited in them can be incomplete or non-existent. Speaking to The Independent, Dr Daren Gooddy, an environmental chemist at the British Geological Survey, said he was particularly concerned about those historic landfills that are located in areas with a high flood risk and that contain dangerous substances such as hazardous chemicals and asbestos. He calculated that there are 1,655 such sites. “While it’s hard to say for sure, I would suggest that many of these legacy sites are vulnerable to flooding,” he said. “Even when flooding does not occur these sites leach out contaminated waste, which generally gets transported towards the nearest river.”

Dr Kate Spencer, environmental chemist at Queen Mary College, University of London, has been carrying out research to assess the potential impact of flooding and coastal erosion on historic landfill sites on low-lying coastal areas. Her research team is working with the Environment Agency to create a vulnerability ranking which will help to identify those sites that present the greatest danger, based on the risk of flooding and the contents of the landfill. “The work we’ve done in the South-East suggests that there has already been widespread pollution from historic landfills,” she said. “At one site we actually found a blue poison bottle from a pharmacist that had a skull and crossbones on it, with a stopper and liquid inside.”

In a blog post for Friends of the Earth, Guy Shrubsole reports on a visit in 2015 to a leaking landfill at Tilbury on the Thames estuary. Walking along the coast, he discovered that a two kilometre stretch of the Thames foreshore was filled with waste. “But this wasn’t just rubbish deposited by the waters of the Thames as it sweeps through London,” he says. “It was clearly eroding out of the sandy banks next to the shoreline, lapped by high tides. The remains of a former sea wall, derelict and ineffective, could still be seen below the high-water mark. It was providing no defence at all to the hungry estuary, which had chewed away at the land to reveal layers and layers of landfilled refuse.”

Guy Shrubsole says that maps produced by the Environment Agency show there are several historic landfills in the Tilbury area, but tidal defences at such sites are not maintained, leaving them with no protection from tidal surges and rising sea levels. “No one is taking any responsibility for the huge amounts of waste that is now very clearly leaking out of the old Tilbury landfills,” he says. “And this is just one example. If, as the research suggests, there are thousands of old landfills at risk of leaking their wastes into watercourses and the sea across the UK, then this is a massive, ticking time bomb.”

Dr Kate Spencer said that historic landfill sites “date back to a time when there were no protective linings, no regulation about what went in and little in the way of records about the contents. Many are on coastlines highly vulnerable to coastal erosion, storm surges and flooding and the big concern is that they will become even more vulnerable as climate change makes storms more frequent and intense.”

As we reported in a previous news item, scientists from the British Geological Survey have carried out research into river pollution from historic landfill sites. The focus of their investigation was Port Meadow which lies on the banks of the River Thames, north-west of Oxford, where 11 such sites are located. Their research, based on ammonium sampling, concluded that there are potentially thousands of historic landfill sites that are currently leaching large amounts of nitrogen into major rivers, which can damage water quality and trigger nutrient pollution. As climate change makes flooding more likely, leakages from landfills located on floodplains are also likely to increase.

[1] Cooper, N., Bower, G,. Tyson, R., Flikweert, J., Rayner, S., Hallas, A.: Guidance on the Management of Landfill Sites and Land Contamination on Eroding or Low-Lying Coastlines (C718). CIRIA, 2012.

Photograph: Cottenham Landfill, near Chittering, Cambridgeshire © Copyright Hugh Venables and licensed for reuse under this Creative Commons Licence.

Conifers and Climate Change

Europe’s conifers have been warming the planet, say scientists – But other scientists predict a widespread loss of conifers due to climate change

Feb 24th 2016

Two research projects into conifer trees and their relationship to climate change have produced two apparently contradictory results. One research project looked at forest management in Europe since 1750 and concluded that new conifer plantations have created a 0.1°C rise in temperature across the region; in other words, these conifers were contributing to climate change. However, a second research project has predicted a widespread loss of conifer woodlands in South-West USA and in the Northern Hemisphere precisely as a result of climate change.

Research into Europe’s Forests and the Impact of Afforestation

This research was carried out by scientists at the Laboratory of Climate Science and Environment in Gif-sur-Yvette, France, and received coverage on BBC News earlier this month (6th February). The research project set out to investigate the last 250 years of forestry in Europe, looking at historical data, forest management practice, and its potential impact on the climate through the use of computer models and simulations.

Historical data shows that the area covered by Europe’s forests decreased by about 190,000 square kilometres between 1750 and 1850, when woodlands were commonly used to supply fuel and for industrial use such as ship building. [1] The Industrial Revolution saw coal replace wood as the major fuel, and from 1850 to the present day the area covered by Europe’s forests has grown by around 386,000 square kilometres, roughly 10% more land than before 1850. The increase is largely due to afforestation programmes, and an estimated 85% of Europe’s woodlands is now managed by humans. [2]

Trees absorb carbon dioxide from the atmosphere naturally through the process of photosynthesis, and the commonly-held view is that planting more trees will generally mitigate the impact of climate change. However, the common forestry practice, driven by economics, is to plant fast growing, needle-leaved evergreens such as pine and spruce, thought to be more commercially valuable than the slower growing broadleaved trees such as oak. Lead researcher Dr Kim Naudts said this replacement of broadleaved trees with conifers has not had the positive impact one might expect, but rather was making a small contribution to climate change.

She explained: “By changing the forest, we also make changes to the amount of radiation, water, and energy that the forest releases.” Compared to broadleaved trees, conifers are darker and absorb more light, reflecting less solar radiation back into space. They also release less water into the atmosphere through evaporation, and consequently have a lesser cooling effect on the atmosphere. In addition, the management practice of fast growth and fast removal tends to release carbon that would otherwise be stored in forest debris, dead wood and soil. The researchers say this practice means far less carbon is being stored than would have been the case if nature was left to its own devices. Dr Kim Naudts said: “Even well managed forests today store less carbon than their natural counterparts in 1750.” [3]

To measure the impact on climate change, the researchers built computer models that incorporated 250 years of forestry data, including the distribution of tree species and the methods used to harvest wood. Whereas previous models have focused on changes in land types and their impact (such as farmland, forests, heath, and so forth), the model created by Dr Kim Naudts and her team examines how the forests were actually used. A three-dimensional representation of the forest canopy, and its changes in the last 250 years, allows the researchers to see differences in how various tree species interact with the atmosphere. The model also includes the removal of trees for wood products or fuel, and looks at how forestry practice, such as thinning the forest but not removing it entirely, might affect the climate.

The result of these simulations has led the researchers to conclude that the changes in Europe’s forests have created a 0.1°C rise in temperature in the region, with 0.08°C being attributed to the twin factors of solar radiation and evaporation, as explained above, and 0.02°C being attributed to the practice of removing trees for commercial use. The researchers calculate that this rise in temperature equates to 6% of the global warming attributed to the burning of fossil fuels. They say 6% is a significant amount and believe that similar impacts are likely in regions where the same type of afforestation has taken place.

“We shouldn’t put our hopes on forests to mitigate what is an emission problem,” Dr Naudts told BBC News. “Our results indicate that in large parts of Europe, a tree planting programme would offset the emissions but it would not cool the planet, especially not if the afforestation is done with conifers.” The researchers argue that a programme of replacement should be considered. This would mean replacing the conifers as they are harvested with broadleaved species.

The research was published in the journal Science, Vol. 351, Issue 6273, pp. 597-600. DOI: 10.1126/science.aad7270.

News of the research was reported by Patrick Monahan in a Science news release on 5th February. DOI: 10.1126/science.aaf4019.

Research into the Risk of Tree Mortality as a Result of Climate Change

The second research project was carried out by an international team of scientists led by forest ecologist Nate McDowell at the Los Alamos National Laboratory in New Mexico. The scientists set out to investigate the risk of tree mortality as a result of climate change, looking in particular at the impact of drought and rising temperatures on conifers in the pine and juniper woodlands of the South-West USA. In a five-year study, the research team developed and evaluated computational models and simulations which were validated by field experiments, the aim of which was to understand tree mortality at three levels: at the individual plant level; at a regional level; and at a global level.

A news release from the Laboratory explains the impact of drought on a needle-leaf tree as follows: During a prolonged drought, it says, “the very mechanism that a tree uses to preserve its water stores can be its undoing. The tree closes the stomata on its needles to prevent water loss, but this prevents the tree’s food source, CO2, from entering, halting photosynthesis. As the air becomes hotter and drier, subsequent pressure change pulls more water from the roots than can be supplied and the water tension in the plant’s vascular system (xylem) can become so great that the straw-like columns no longer support water flow. The hydraulic system can collapse or the tree undergoes the starvation process, and it subsequently becomes defenceless against bark beetles and disease since it can no longer secrete the thick resin that protects it. As the tree decays after death, the carbon stored in its tissues is released into the atmosphere as carbon dioxide.”

The researchers found that a key predictive element of a tree’s mortality is its ‘pre-dawn water potential.’ A plant’s pre-dawn water potential is a measure of water stress and indicates its water status, resulting in part from soil water availability and atmospheric water demands on the plant’s water use. Experimentally, the team found that dominant evergreens in the South-West died when the tree’s pre-dawn water potential fell to levels that impaired the transport and storage of water and carbon.

The news release explains that the team generated predictions using multiple process-based and empirical models which included data from two of the world’s largest drought studies, both based in New Mexico and developed by Los Alamos National Laboratory. These models were backed up and validated using observations and field experiments. In the field experiments, a large drought plot was installed at one site which manipulates precipitation to test the impacts of drought, and the researchers then monitored a tree’s reaction to these changes. Their field experiments restricted precipitation by 50% to mimic drought conditions, and this resulted in an 80% mortality rate in the mature pines.

The news release continues: “In parallel, the scientists developed cutting edge representations of tree mortality within their models and subsequently evaluated them against the drought-manipulation results as well as against an independent set of data from another site in Los Alamos where pre-dawn water potential was monitored monthly for more than two decades. This resulted in the generation, and subsequent confidence in, state-of-the-art models of forest stress and mortality during drought.” The news release says that the regional models “accurately predicted the pre-dawn water potential of evergreens and 91% of the predictions exceeded mortality thresholds this century due to rising temperatures.”

Moving on from a regional understanding, the scientists compared their regional models with results from global vegetation models to examine independent simulations. They discovered that the global models simulated mortality throughout the Northern Hemisphere that was of similar magnitude, but on a much broader spatial scale, as the evaluated ecosystem models predicted for the South-West USA. The press release says that the conclusion of widespread conifer loss in the Northern Hemisphere is consistent with widespread observations of accelerating forest mortality in North America. Lead researcher Nate McDowell said: “We have been uncertain about how big the risk of tree mortality was, but our ensemble of analyses – including experimental results, mechanistic regional models and more general global models – all show alarming rates of forest loss in coming decades.”

In their conclusion, the authors of the research state that the atmospheric demand for water (known as the vapour pressure deficit) is potentially the largest climate threat to survival because increasing temperatures are driving a chronic increase in evaporative demand despite increases in humidity. The press release says: “In other words, according to Nate McDowell, trees may suffer in many places around the world, even in humid climates, due to global warming.”

The research was published in the journal Nature Climate Change on December 21st 2015. DOI: 10.1038/nclimate2873.

Contradictory Results?

Comparing the conclusions of these two research projects, one might well be baffled by what appear to be contradictory findings: on the one hand, conifers are contributing to climate change; on the other hand, conifers will be wiped out by climate change. The comparison suggests that conifers are pursuing a course of self-destruction, and the driver of the course is the plant’s very structure, together with the biochemical processes that, in other species, ensure a plant’s survival.

However, there are a number of differences in the scope of the research projects, and in their conclusions. The most obvious is that the first project is concerned with the past whilst the second is concerned with the future. The first project looks at the historical record and the impact that forestry practice might have had on the climate. The second project makes use of figures that are predicted for rising temperatures over the next century to make predictions about tree mortality. Given that the impact of climate change (in terms of rising temperature) has been more dramatic in recent decades, what has happened over the last 250 years is not a reliable guide to what may happen in the next 250. In addition, conditions vary from one country to another, and even within smaller regions: in the UK in recent times, for instance, whilst parts of the country were suffering from continued rainfall and flooding, other parts were suffering from drought.

On the research into Europe’s forests, Patrick Monahan highlights the temptation to extend the results to other regions. Writing in Science Magazine, he says: “But Europe’s temperature increase was in large part due to the continent’s specific history of forestry, its location, and the kind of tree species that are present there. The tropics, especially, play by different rules – there, slowing deforestation is almost certain to contribute to cooling, because trees in the tropics release comparatively more water into the atmosphere, seeding clouds that reflect light.” He also quotes a scientist who wasn’t engaged on the Europe forestry project, who points out that their model is only one of many possible models: “If a different model were to use the same parameters, it might find different results.”

On the second project, the authors of the research note that there are uncertainties and assumptions that could make their models underestimate or overestimate potential tree mortality. The predictions are concerned with temperature rise and the impact of drought, but exclude other factors such as wildfire and ‘islands of survival.’ Nate McDowell says: “Resolving these uncertainties is a critical next step for the international community because we need forests now more than ever to absorb carbon dioxide, even as that carbon dioxide and associated warming is threatening their survival. Based on the outcomes of the recent climate talks in Paris, we need to protect our forest to reduce the warming, but we simultaneously need to know how the warming can take out forests.”

If we assume that the management of Europe’s forests does not change, and its conifer plantations add their contribution to a global rise in temperature, then we have the scenario whereby Europe’s conifers could be aiding the demise of their distant relations in South-West USA. Which leads us to conclude with that question on predictability framed by Edward Lorenz in 1979 in an address to the American Association for the Advancement of Science (AAAS): “Does the flap of a butterfly’s wings in Brazil set off a tornado in Texas?” [4]


[1] A typical ship built in the 1700s incorporated the wood of 3,000 large oak trees, according to figures in Forests and sea power: The timber problem of the Royal Navy, 1652-1862, Robert G Albion, 1926. Cited in Trade and Dominion, J H Parry, 1971.

[2] “Overall, human activity has removed roughly half of the world’s natural forests, with the greatest losses in densely populated countries. With the exception of Russia, less than 1% of Europe’s ‘old-growth’ forests remain, while some 95% of the continental United States’ forests have been logged since European settlement began.” AAAS Atlas of population & environment, University of California Press, 2000.

[3] Figures from the Carbon Dioxide Information Analysis Center at the Oak Ridge National Laboratory, USA, estimate that a conifer ecosystem complex stores 13 kilos of carbon per square metre, whereas a mid-latitude temperate broad-leaved forest complex stores 9 kilos of carbon per square metre. Cited in AAAS Atlas of population & environment, University of California Press, 2000.

[4] Cited in ‘The Butterfly Effect’, in Chaos – Making a New Science, James Gleick, 1979.


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Forestry Commission site, Mid Wales © Copyright Anthony Bloor and licensed for reuse under a Creative Commons Attribution-ShareAlike 4.0 International License.

New research shows cosmetic products contain large quantities of micro-plastics

“Up to 80 tonnes of micro-plastics could be entering watercourses in the UK every year,” say researchers

Oct 1st 2015

Researchers at Plymouth University have been analysing the quantities of small plastic particles contained in everyday cosmetic and cleaning products such as facial scrubs. The particles – known as micro-beads or micro-plastics – are tiny, measuring a fraction of a millimetre in diameter. Their research has shown that around 100,000 of these micro-plastics could be released into the environment with every application of these types of product.

A press release on the research says that the particles are incorporated as bulking agents and abrasives, and because of their small size it is expected many will not be intercepted by conventional sewage treatment. The researchers estimate this could result in up to 80 tonnes of unnecessary micro-plastic waste entering watercourses every year from the use of these cosmetics in the UK alone, eventually ending up in the oceans and with the potential to cause harm to marine life.

Micro-plastics have been used to replace natural exfoliating materials in cosmetics and have been reported in a variety of products such as hand cleansers, soaps, toothpaste, shaving foam, bubble bath, sunscreen and shampoo. Scientists point to growing evidence that the amount of plastics in marine waters is increasing, with around 700 species of marine organism being reported to encounter marine debris in the natural environment, with plastic debris accounting for over 90% of these encounters.

For the Plymouth University study, the researchers selected brands of facial scrubs which listed plastics among their ingredients, and these were subjected to vacuum filtration to obtain the plastic particles. Subsequent analysis using electron microscopy showed that a 150ml amount of the products could contain between 137,000 and 2.8 million micro-particles.

Lead researcher Imogen Napper said she was shocked to see the quantity of micro-plastics apparent in these everyday cosmetics. “Currently, there are reported to be 80 facial scrubs in the UK market which contain plastic material,” she said. “However, some companies have indicated they will voluntarily phase them out from their products.”

Richard Thompson, Professor of Marine Biology at Plymouth University, said: “Using these products leads to unnecessary contamination of the oceans with millions of micro-plastic particles. There is considerable concern about the accumulation of micro-plastics in the environment. Our previous work has shown micro-plastics can be ingested by fish and shellfish and there is evidence from laboratory studies of adverse effects on marine organisms.”

The research – titled “Characterisation, quantity and sorptive properties of microplastics extracted from cosmetics” – has been published in the Marine Pollution Bulletin.