Modelling the benefits of farmland restoration: methodology and application to butterfly movement

The overall quality of the landscape is important for conserving biodiversity. In a fragmented landscape, movement and dispersal capacity are important factors in determining which species are able to persist. To examine the role of landscape structure and pattern on movement, we developed a simple model to predict the “least-cost” pathway a species would take through an agricultural landscape matrix between habitat fragments by assigning friction values to different habitat types. Our model was validated by using empirical data on inter-patch movement for two butterfly species. As a measure of the ecological distance between habitat patches, the least-cost path model was a better predictor of butterfly movement than Euclidean distance. Ranking several hypothetical management scenarios, illustrated the potential of the model as a decision-support tool. Removal of all infrastructure from within arable fields would significantly reduce rates of inter-patch movement. However, if all boundaries between arable fields were restored to grassy banks this would significantly increase the connectivity between sub-populations. Planners widely recommend using corridors to connect fragments of remnant habitat despite relatively little empirical evidence to show that dispersal of individuals is enhanced by this practice. Our model showed that important aspects of species movement and, hence, survival can be expressed in models suitable for area planning and management.