Using least-cost models to plan and evaluate measures reducing habitat fragmentation by roads.
Adriaensen, Frank*,1, Matthysen, Erik1, 1 University of Antwerp, Antwerp, Belgium
ABSTRACT- 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 have used least-cost modelling (available as a toolbox in GIS-systems) to calculate effective distance, a measure for distance modified with the cost to move between habitat patches based on detailed geographical information on the landscape as well as behavioural aspects of the organisms studied. We will discuss the modelling technique as well as some results of the application of the method to a small-scaled agricultural system subject to different scenarios (e.g. tree lines along road sides) and to the construction of a wildlife bridge across a highway. Least-cost modelling is not a tool to measure effectiveness of mitigating measures. The key role for least-cost models is in the planning phase, in modelling the potential effects of measures given that these measures will function as predicted. There are some very important aspects on restoring connectivity that may be modelled using least-cost models. - Different locations for mitigating measures can be evaluated for their effect on a local as well as on a larger scale, taking into account other corridors and barriers even if they are located at some distance . - Different locations can be evaluated on their accessibility from source populations of the target species. - Especially in complex landscapes the evaluation of different scenarios may become a very complex problem. Least-cost models are able to generate more integrated landscape-wide 'pictures'. The model is shown to be a flexible tool in scenario building and evaluation in wild life protection projects and applied land/infrastructure management projects. (Adriaensen, F. et al. 2003. The application of 'least-cost' modelling as a functional landscape model. Landscape and Urban Planning 996, 1-15).
Key words: least-cost, modelling, landscpae connectivity
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