Cost-effective species conservation in exurban communities: A spatial analysis

Exurban areas have increasingly become zones of conflict as conservation and development compete for the same finite land resources. Conversion of natural areas to land dominated by human use results in loss, degradation, and fragmentation of wildlife habitat which often lead to species endangerment or even extinction. Recently, reserve site selection models have begun to integrate spatial attributes in order to design more compact and connected reserve networks that are thought to improve long-term species persistence. While these models are a good step forward to designing conservation reserve networks, they might not be adequate for use in exurban areas that consist of heterogeneous mosaics of land uses where habitat fragmentation already exists and not all parcels are available for preservation. This paper presents a species conservation framework that expands upon traditional reserve site selection models in three ways. First, because of the focus on exurban areas, the framework used here allows for land conversion within core habitat patches. Second, the framework provides a more robust assessment of connectivity among patches by accounting for land-use heterogeneity in the dispersal matrix. And third, the framework explicitly incorporates species population dynamics. We apply our conservation framework to the case of pond-breeding salamanders in an exurban community in Rhode Island, USA. Comparisons are made between the outcomes for uniform conservation policies and more flexible policies that accommodate ecological and economic heterogeneity. As expected, policies that offer more flexibility in the decision-making process are less costly in terms of foregone development. Conservation planners should consider core habitat patches, dispersal matrix, and spatial scale in their decision making. By not assessing the potential impact of dispersal barriers, reserve site selection models will result in conservation plans that may not protect species over the long term, particularly for species residing in highly fragmented landscapes such as those found in many exurban communities.