The Graph-based multi-attribute decision making: impact of road fencing on ecological network

Conservation and transport decision makers must deal with many competing criteria in order to find the optimal connectivity of habitat patches in order to maximize organisms' ability to traverse the landscape successfully. Thus, there is an increasing interest in prioritization of habitat patches by their contribution to overall landscape connectivity. Many different indices can be used to quantify structural and functional landscape connectivity. However, landscape connectivity indices alone do not clearly define conservation priorities for habitat patches. In this study priority values for each available habitat patch were calculated using multiple criteria spatial decision support techniques. As criteria for prioritization, spatial graph-based element properties (habitat patch size, number of corridors connected to a habitat patch, etc.) were characterized for each habitat patch. Graph-based connectivity rules for each habitat patch within a landscape (in conjunction with largest patch size, maximum number of corridors with a minimum length connected to a habitat patch, etc.) were defined and applied. Each criterion's importance was assessed. Criteria-based ranking of habitat patches within a graph better indicated exact critical habitat patches than connectivity index alone, especially when changes in network occur. Simulations in the case study of Lithuania showed that barriers (road fences to keep animals off the road) without prompt establishment of animal crossings may realign complexes of an ecological networks by reducing the importance of adjacent and increasing the importance of more distant patches. Such distant patches may become essential, and can sometimes be the only elements preserving the realigned ecological network.