SELECTION AND USE OF BIO-INDICATORS TO ASSESS THE POSSIBLE EFFECTS OFCLIMATE-CHANGE IN EUROPE

From paleoecological records it is well known that past climate change s have led to considerable changes in the species composition of ecosy stems and larger spatial units such as landscapes and even continents. The observed increase in average global temperature since the beginni ng of this century is strong compared to previous warming periods and, if the climate models are correct, future warming will be even strong er and faster. Especially in Western Europe, where the landscape has b een greatly fragmented by human activities, the ongoing and projected changes in climate will impose additional stress on the natural biodiv ersity which is already greatly reduced. In order to be able to detect responses of individual species to climate change, to assess 'critica l levels' and to develop anticipating measures, better information on climate sensitivity of species (and ecosystems) is essential. This pap er will discuss criteria and methods for the selection of bio-indicato rs for climate change. Examples of changes in distribution and phenolo gy of some western European species, which are possibly related to a c hanging climate, are given. The preliminary results of a pilot study o n the selection of indicator species for the Netherlands are presented and discussed. The paper concludes with a discussion on the need of, and possibilities for, more systematic long-term ecological research a nd monitoring of the effects of climate change on species and ecosyste ms in Europe.