Assessing the role of adaptation in evaluating vulnerability to climate change

Three types of adaptation can influence significantly a system's prospectiv e longevity in the face of climate change. The ability to cope with variati on in its current environment can help a system adapt to changes over the l onger term. The ability to take advantage of beneficial changes that might coincide with potentially harmful ones can play an even larger role; and fo cusing attention on maximizing a system's sustainable lifetime can highligh t the potential for extending that time horizon and increasing the likeliho od that an alternative structure might be created. A specific economic appr oach to adaptation demonstrates that research can serve two functions in th is regard. Research can play an important role in diminishing future harm s uggested by standard impact analyses by focusing attention on systems where adaptation can buy the most time. It can help societies learn how to becom e more robust under current conditions; and it can lead them to explore mec hanisms by which they can exploit potentially beneficial change. Research c an also play a critical role in assessing the need for mitigating long-term change by focusing attention on systems where potential adaptation in both the short and long runs is so limited that it is almost impossible to buy any time at all. In these areas, switching to an alternative system or inve sting in the protection of existing ones are the last lines of defense. Rea l "windows" of tolerable climate change can be defined only by working in a reas where these sorts of adaptive alternatives cannot be uncovered.