STATE OF THE WORLD ’ S BIRDS
Pressure : why birds are declining
The threats to birds are many and varied , but invariably of humanity ’ s making . Agricultural expansion , logging , overexploitation , urbanisation , pollution , disturbance and the effects of invasive alien species are all driving bird declines and diminishing the natural world . In the long term , humaninduced climate change may prove to be the most serious threat of all . Most species are impacted by multiple threats and many threats are interrelated . For example , land clearance for agriculture is often preceded by deforestation or wetland drainage . Similarly , climate change is extending the area of suitable habitat for Avian Malaria-transmitting mosquitoes .
Agriculture is the biggest threat to globally threatened birds
The expansion of agriculture , and the resultant habitat destruction , is one of the greatest threats to the world ’ s biodiversity . The area of Earth ’ s land surface given over to agriculture has increased more than six-fold over the past 300 years , from less than 6 % in 1700 to more than 38 % today . The conversion of natural habitats to farmland is now occurring most rapidly in tropical regions – driven by global demand for commodities such as coffee , cocoa , sugar , palm oil and soya . For globally threatened birds , agricultural expansion and intensification is the most pervasive menace , impacting 1,091 species ( 74 %). Logging affects 734 species ( 50 %); invasive alien species threaten 578 ( 39 %) species and hunting and trapping puts 578 ( 35 %) species at risk .
There is mounting evidence that neurotoxic insecticides known as neonicotinoids are having a detrimental impact on farmland birds . Neonicotinoids are widely used across North America , Europe and elsewhere to pre-treat crops , where they can collect in high concentrations in surface water and on the surface of seeds . A recent study from the USA found that migrating White-crowned Sparrows Zonotrichia leucophrys exposed to concentrations of neonicotinoids lost a quarter of their body mass and fat stores . The neurotoxin also impaired their migratory orientation .
Climate change is a growing concern
Climate change represents an emerging and increasingly serious threat – currently affecting 33 % of globally threatened species – and one that often exacerbates existing threats . A recent review of the scientific literature shows that nearly one quarter of bird species so far studied have been negatively affected by climate change . Given that scientific research has been largely limited to Europe and North America , this figure is certainly an underestimation , and indicates that even the relatively modest temperature increase experienced to date has
White-crowned Sparrow Zonotrichia leucophrys Photo Tim Lenz
had a considerable impact . Recent bird population trends in Europe and North America show a strong and consistent signal of climate change . Warm-adapted species have increased in abundance over recent decades , while cool-adapted species have decreased in numbers .
human overconsumption lies behind the biodiversity crisis
Behind all threats to birds are bigger-picture issues relating to a rise in population and individual consumption . These are worsened by imbalances in power and wealth , an outdated economic system and inefficient resource use . Addressing these underlying causes is challenging , and requires radical changes to the way we run our global economies and live our individual lives , yet it is essential if the impending biodiversity crisis is to be averted . Earth ’ s natural capital must now sustain 7.6 billion people , including a rapidly expanding global middle class that enjoys an unprecedented level of individual material consumption .
Humanity is now living beyond the biological capacity of the planet : demand for resources is now equivalent to more than 1.7 Earths . The natural systems that underpin all life are beginning to buckle . The race is on to develop sustainable methods of living before our vital ecological systems and cycles are irreversibly compromised .
16 birdlife • jul-sep 2018