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The Effect of Climate Change on Birds by David Leech   2. Global climate change   Evidence for global climate change, especially warming, as a result of man's activities is accumulating. Mean global temperatures are currently 0.4-0.8°C higher than they were in the late 1800s (Houghton et al., 2001) and are expected to continue to rise during this century as the atmospheric concentration of carbon dioxide continues to increase. The Special Report on Emissions Scenarios (SRES) (Nakicenovic and Swart, 2001) published by the Intergovernmental Panel for Climate Change (IPCC) predicted an increase in mean global temperatures of 0.6-2.4°C between 2000 and 2050, and an increase of 1.2-5.6°C by 2100 (summarised in McCarthy et al., 2001).   Increases in mean temperature are likely to have direct consequences for the ecology of both plant and animal populations. These temperature increases may not be equivalent in all regions. The UKCIP98 scenarios, which predict potential changes in the British climate over the next 100 years, suggest that, whilst temperatures will increase across the whole of Britain and Ireland, increases in the south of Britain will exceed those in the north of the country. Changes in the relative temperatures of different regions may lead to shifts in patterns of atmospheric and oceanic circulation, which in turn may influence precipitation levels and the direction and strength of prevailing winds. Heavy precipitation events in the UK, for example, are predicted to increase in winter, whilst decreasing in summer, and weather conditions in the north of the country are expected to become progressively wetter.   Responses of plant communities to increasing atmospheric temperatures have been widely studied (Walther et al.,2002). Higher temperatures have resulted in increased photosynthetic activity and extended the length of the growing season in many regions. The timing of reproductive activity has also shifted, with spring events such as leaf emergence advancing by an average of 6 days in Europe between 1959 and 1993. Similarly, advances in emergence and spawning dates have been observed for Lepidoptera and amphibians respectively. Several studies have also presented evidence for expansion and contraction of lepidopteran ranges in response to climatic variation.   A growing body of evidence suggests that the direct and indirect effects of global climate change may also influence the size, distribution and phenology of bird populations.   Back to ECC Contents

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