BIODIVERSITY Climate change and the ecologist
Wilfried Thuiller
The evidence for rapid climate change now seems overwhelming. Global temperatures are predicted to rise by up to 4 °C by 2100, with associated alterations in precipitation patterns. Assessing the consequences for biodiversity, and how they might be mitigated, is a Grand Challenge in ecology.
How serious is climate change compared with other factors affecting biodiversity?
Very — but it tends to act over a longer time scale. The ecological disruption wrought by climate change is generally slower than
that caused by other factors. Such factors include habitat destruction through changes in land use; pollution, for example by nitrogen deposition; the invasion of ecosystems by non-native plant and animal species (biotic exchange); and the biological consequences of increased levels of carbon dioxide in the atmosphere (Fig. 1, overleaf). In the shortto- medium term, human-induced fragmentation of natural habitat and invasive species are particular threats to biodiversity. But looking 50 years into the future and beyond, the effects of climate are likely to become increasingly prominent relative to the other factors.
What are the effects of climate change?
Most immediately, the effects are shifts in species’ geographical range, prompted by shifts in the normal patterns of temperatures
and humidity that generally delimit species boundaries. Each 1 °C of temperature change moves ecological zones on Earth by about
160 km — so, for example, if the climate warms by 4 °C over the next century, species in the Northern Hemisphere may have to move northward by some 500 km (or 500 m higher in altitude) to find a suitable climatic regime. Higher temperatures are likely to be accompanied by more humid, wetter conditions, but the geographical and seasonal distribution of precipitation will change. Summer soil moisture will be reduced in many regions such as the Mediterranean basin, thus increasing drought stress. Overall, the ability of species to respond to climate change will largely depend on their ability to ‘track’ shifting climate through colonizing new territory, or to modify their physiology and seasonal behaviour (such as period of flowering or mating) to adapt to the changed conditions where they are.
NATURE|Vol 448|2 August 2007
