Species richness changes lag behind climate change

Abstract

Species-energy theory indicates that recent climate warming should have driven increases in species richness in cool and species-poor parts of the Northern Hemisphere. We confirm that the average species richness of British butterflies has increased since 1970-82, but much more slowly than predicted from changes of climate: on average, only one-third of the predicted increase has taken place. The resultant species assemblages are increasingly dominated by generalist species that were able to respond quickly. The time lag is confirmed by the successful introduction of many species to climatically suitable areas beyond their ranges. Our results imply that it may be decades or centuries before the species richness and composition of biological communities adjusts to the current climate.

Figure 1

Geographical patterns in Britain at 20×20 km grid resolution of butterfly species richness: (a) observed species richness in 1970–82, (b) observed species richness in 1995–99, (c) predicted species richness in 1970–82 and (d) predicted species richness in 1995–99 (pale grey: less than or equal to 15 species; dark grey: 15–25 species; black: more than 25 species). Predictions are based on mean predictions using 1970–82 GLM models. In all maps, white represents squares excluded from analyses due to sampling effort (see §2).