Predicting the distribution of ground beetle species (Coleoptera, Carabidae) in Britain using land cover variables.

Predictions of plant and animal species distributions are important for conservation and for the assessment of large-scale ecosystem change. Land cover data are becoming more widely available for use in land management and conservation. We use a logistic regression modelling approach to investigate the utility of these data for modelling. The relationship between the distribution of 137 British ground beetles species and land cover was investigated using data from 1,687 10 km national grid squares. Land cover data were simplified using ordination and the axes used as predictors in logistic regression with presence absence data for individual beetle species as response variables. Significant regression models were generated for all species with first and second axis scores. The amounts of variation explained by models were generally low, but predictions derived from models generally matched the known distributions of the species in Britain. Species with coastal preferences were poorly modelled and predicted to occur throughout lowland Britain whilst a number of species occurring in southern Britain were predicted to occur into Scotland. A validation exercise comparing model predictions with new data from a survey of 59 10 km(2) produced mixed results with the distribution of grassland species being better predicted than riverine species. Jack-knifing was used to assess the robustness of models for four species which differed in their apparent responses to the land cover variables. Methods for improving the predictive power of these models and their potential for use in assessing the impact of global climate change are discussed.

Comparative losses of British butterflies, birds, and plants and the global extinction crisis.

There is growing concern about increased population, regional, and global extinctions of species. A key question is whether extinction rates for one group of organisms are representative of other taxa. We present a comparison at the national scale of population and regional extinctions of birds, butterflies, and vascular plants from Britain in recent decades. Butterflies experienced the greatest net losses, disappearing on average from 13% of their previously occupied 10-kilometer squares. If insects elsewhere in the world are similarly sensitive, the known global extinction rates of vertebrate and plant species have an unrecorded parallel among the invertebrates, strengthening the hypothesis that the natural world is experiencing the sixth major extinction event in its history.

Responses of butterflies to twentieth century climate warming: implications for future ranges.

We analyse distribution records for 51 British butterfly species to investigate altitudinal and latitudinal responses to twentieth century climate warming. Species with northern and/or montane distributions have disappeared from low elevation sites and colonized sites at higher elevations during the twentieth century, consistent with a climate explanation. We found no evidence for a systematic shift northwards across all species, even though 11 out of 46 southerly distributed species have expanded in the northern part of their distributions. For a subset of 35 species, we model the role of climate in limiting current European distributions and predict potential future distributions for the period 2070-2099. Most northerly distributed species will have little opportunity to expand northwards and will disappear from areas in the south, resulting in reduced range sizes. Southerly distributed species will have the potential to shift northwards, resulting in similar or increased range sizes. However, 30 out of 35 study species have failed to track recent climate changes because of lack of suitable habitat, so we revised our estimates accordingly for these species and predicted 65% and 24% declines in range sizes for northern and southern species, respectively. These revised estimates are likely to be more realistic predictions of future butterfly range sizes.

Rapid responses of British butterflies to opposing forces of climate and habitat change.

Habitat degradation and climate change are thought to be altering the distributions and abundances of animals and plants throughout the world, but their combined impacts have not been assessed for any species assemblage. Here we evaluated changes in the distribution sizes and abundances of 46 species of butterflies that approach their northern climatic range margins in Britain-where changes in climate and habitat are opposing forces. These insects might be expected to have responded positively to climate warming over the past 30 years, yet three-quarters of them declined: negative responses to habitat loss have outweighed positive responses to climate warming. Half of the species that were mobile and habitat generalists increased their distribution sites over this period (consistent with a climate explanation), whereas the other generalists and 89% of the habitat specialists declined in distribution size (consistent with habitat limitation). Changes in population abundances closely matched changes in distributions. The dual forces of habitat modification and climate change are likely to cause specialists to decline, leaving biological communities with reduced numbers of species and dominated by mobile and widespread habitat generalists.