4. Ecological limits to climate change


Climate Change and Biodiversity Conservation



Climate change will add to the stresses causing environmental degradation, but the actual impacts of this additional stress factor are hard to predict. It is therefore necessary to try and make some generalizations about the potential ecological limits to climate change in order to set emissions reductions targets under the UNFCCC. Ecological limits can be set using a combination of both scientific data and subjective policy criteria. Within the context of the convention, the policy criteria of most relevance to individual Parties will vary from country to country. Whichever methodologies or forms of ecological risk assessment techniques are used in this process, political and value judgements will still need to be made.


There have been very few attempts to suggest critical levels of climate change for ecosystems. This is partly due to the inappropriateness of using global averages for ecosystem vulnerability analysis. For example, while the Intergovernmental Panel on Climate Change (IPCC) predictions of global sea­level rise are 4 cm per decade over the next century, actual relative sea­level rise for any particular coastal site is determined by a combination of local sea­level rise, land subsidence, and sediment accretion rates, and is further influenced by human coastal management and transient events such as storms. Actual, relative sea­level rise rates for 18 sites on the east coast of the USA have been estimated to range from 0.9 mm per year to 13.0 mm per year.




It makes sense to predict and analyse climate change impacts at local and regional levels



The question of whether biomes or ecosystems are threatened by climate change also needs to be looked at in the context of spatial scale. The coral reef biome may not be in great danger from climate change on a global scale (it may even expand into new areas), but at a local level numerous individual reefs or reef species may be threatened with extinction, with serious consequences for the local fishing communities which depend on coral reefs for their livelihood. Sensitivity of individual reefs is increased by multiple and varying types of anthropogenic stresses.


Scientifically supportable assessments require a regionally based approach if they are to be of use to policy­makers. Whilst biodiversity conservation is a global goal, and its achievement is to the benefit of humankind, its practice is generally focused on national and site­specific actions. It makes sense, therefore, to try to identify critical climate change criteria and potential indicator systems and species for different regions. In the Netherlands, for instance, it has been suggested that changes in distribution of climate­sensitive species such as the long­eared owl, swallowtail butterfly, or prickly lettuce will make good indicators. In addition to monitoring of biological indicators, the predictive capacity of regional climate changes will need to be radically improved in order to quantify threats to biodiversity and conservation at a local scale.




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Copyright 1996, The World Wide Fund For Nature