Species presence in fragmented landscapes: modelling of species requirements at the national level

The fragmentation of ancient woodland has been identified as a cause of decline in biodiversity in the UK. Current policy advocates the targeting of resources to mitigate its effects. In this study a number of patch and landscape scale measures of ancient woodland distribution were derived from national data sets. These measures were translated into independent variables representing patterns of woodland cover using principal component analysis (PCA). Key species were selected according to differing sensitivities to fragmentation of ancient woodland. Logistic regression models of species distributions were constructed. A range of bird and mammal distributions were found to be correlated to landscape scale measures of fragment distribution, in contrast to butterfly and plant species, which exhibited a stronger correlation to patch-scale measures. The national distribution of a range of woodland species is predicted. New information is presented on the landscape requirements of woodland species, particularly those that enable them to persist in fragmented woodland landscapes. The different scales at which species show a sensitivity to fragment distribution are discussed. The results confirm the association between species and different aspects of the structure of the wooded landscape, and provide information of value in targeting national conservation expenditure in England. (C) 2002 Elsevier Science Ltd. All rights reserved.