Forecasts of butterfly future richness change in the southwest Mediterranean. The role of sampling effort and non-climatic variables

Abstract

We estimated the potential impact of Global Warming on the species richness of Iberian butterflies. First, we determined the grid size that maximized the balance between geographic resolution, area coverage and environmental representativeness. Contemporary richness was modelled in several alternative ways that differed in how sampling effort was controlled for, and in whether the non-climatic variables (physiography, lithology, position) were incorporated. The results were extrapolated to four WorldClim scenarios. Richness loss is to be expected for at least 70% of the area, with forecasts from the combined models being only slightly more optimistic than those from the purely climatic ones. Overall, the most intense losses are predicted for areas of highest contemporary species richness, while the potential slightly positive or nearly neutral changes would most often concentrate in cells of low to moderate present richness. The environmental determinants of richness might not be uniform across the geographical range of sampling effort, suggesting the need of additional data from the least intensively surveyed areas.Implications for insect conservationRe-assessing richness and its environmental determinants in the area proves necessary for more detailed forecasts of the climate-driven changes in butterfly species richness. The expected future conditions imply widespread losses of regional richness, even under the less severe scenarios. Since the negative impact of warming is expected to be extensive, long term conservation plans should concentrate in the present protected areas of highest richness as these are most likely to represent the last refuges for mountain species.