The application of `least-cost' modelling as a functional landscape model

The growing awareness of the adverse effects of habitat fragmentation on natural systems has resulted in a rapidly increasing number of actions to reduce current fragmentation of natural systems as well as a growing demand for tools to predict and evaluate the effect of changes in the landscape on connectivity in the natural world. Recent studies used `least-cost' modelling (available as a toolbox in GIS systems) to calculate `effective distance', a measure for distance modified with the cost to movebetween habitat patches based on detailed geographical information on the landscape as well as behavioural aspects of the organisms studied. We applied the method to a virtual landscape and a small-scaled agricultural system subject to different scenarios in a land re-allotment project. We discuss the importance of technical aspects and ecological assumption underlying this modelling method. The model is shown to be a flexible tool for modelling functional connectivity in the study of the relation between landscape and mobility of organisms as well as in scenario building and evaluation in wildlife protection projects and applied land management projects. Since `effective distance' has the same units as Euclidean distance (m), this effective distance may be a straightforward way to include landscape and behavioural aspects in other models which include distance as a measure for isolation. We show the importance of the `ecological' quality of the input maps and the choice of relevant landscape featuresand resistance values