The response to global warming of plants restricted to north-western Britain

Abstract

If projected changes in climate occur during the next century, plant species which at present are growing at their southernmost limit in northwest Britain, are in danger of local extinction. To Investigate this possibility, forty-one plant species were selected which are at risk. Their European distribution was established from published maps and captured on computer using a 50 km grid; the same grid was used to record European bioclimate data for three variables. Using this information, Response Surfaces have been derived; these model the relationship between species distribution and present climate. The results show that distribution of all the species is determined by macroclimate and illustrate how climate has constraints upon each species. Simulated future distributions have been obtained using 2 x CO(_2) climatic scenarios derived from two alternative GCM's. These distributions show all of the species are likely to experience major changes in their "potential" range if climate changes occur. Many species would suffer substantial reductions in their numbers and range, and are threatened with extinction from the British Isles. Few plants, if any, will be able to maintain their range in equilibrium with the changing climate. To monitor what happens, five species were selected and sites for each identified in northwest England at which growth habits etc. were recorded. These sites can be revisited in future to assess the effects of "global warming". It is expected that the impact of changes in climate will vary depending upon the species and its habitat. The simulations of present and potential ranges take no account of other factors such as edaphic controls, photoperiodism, or the direct affect of CO(_2), all of which will determine future distributions of the species studied.