Executive summary


Climate Change and Biodiversity Conservation



A main objective of the UN Framework Convention on Climate Change (UNFCCC) is to stabilize levels of greenhouse gases in the atmosphere within a time frame that ensures the rate of climate change is slow enough to allow ecosystems to adapt naturally.




Current levels of greenhouse gas emissions will cause climatic changes that many species and ecosystems will not be able to adapt to.




The observed warming trend over the last 100 years is probably due to the build­up of greenhouse gases in the atmosphere. Evidence of recent global warming comes from temperature records and analysis of tree growth rings. Worldwide, melting glaciers provide physical evidence of warming, as does the catastrophic drought in sub­Saharan Africa.




Ecological indicators of warming are being recorded from around the globe:



  • Yellowstone National Park, USA: increased risk of wildfires due to warming and drying trends

  • Caribbean and Pacific islands: warm water episodes cause coral reefs to die from "bleaching"

  • Barro Colorado Island, Panama: long­term drying trend leading to extinction of tropical forest species

  • Bermuda: die back of coastal mangrove forests as a result of sea­level rise.





Certain ecosystems can be identified as most vulnerable to climate change. These "front line" ecosystems include:



  • Temperate and boreal forests

  • Tropical montane cloud forests

  • Coastal mangrove forests

  • Coastal marshes

  • Coral reefs

  • Alpine/high montane systems

  • Arctic ecosystems.






Predicting climate change impacts on species and habitats is difficult because of the complexity of ecosystems. Each species will react differently, and many ecosystems will break up and disappear entirely. Ecosystems already under stress from human pressures such as pollution or development are likely to be the most sensitive. Uncertainty as to the degree of threats is not a reason for inaction, but rather an argument for greater precaution.




Despite surviving past climatic changes, for instance between ice ages, many species will be unable to adapt to a rate of warming which will be the fastest experienced in at least 10,000 years. For many tree species, such as Scots pine and Douglas fir, the speed of change will be more than 20 times the speed with which they can "migrate" to keep up with suitable climatic conditions.




There are clear limits of ecosystem tolerance to climatic change. A 1°C warming will have significant negative impacts on many ecosystems, and a rate of change of 0.01°C per decade is probably a threshold level for many species. This means an order of magnitude less than IPCC (Intergovernmental Panel on Climate Change) predictions of global warming. Sea­level rise of less than 1 cm per decade can harm many coastal habitats.




One response to expected climate change is to increase investment in conservation and protected area management. The more resilient ecosystems are to current environmental pressures, the better they will be able to cope with global warming. Larger protected areas, better managed buffer zones and corridor systems between reserves will help to soften the blow of climate impacts.




The best strategy to reduce climate impacts is to reduce greenhouse gas emissions down to levels which will ensure that climatic changes will remain within the boundaries of known ecological limits. A first step towards this objective would be to cut industrialized country greenhouse gas emissions to 20 per cent below 1990 levels by the year 2000.




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Copyright 1996, The World Wide Fund For Nature