The spatial extent of contaminants and the landscape scale: an analysis of the wildlife, conservation biology, and population modeling literature.

Many contaminant releases to the terrestrial environment are of small areal extent. Thus, rather than evaluating the ecological impact on species in the immediate vicinity of the release, it may be more ecologically meaningful to determine if population impacts occur at the landscape level. In order to do this, the cumulative impact of all releases in the landscape under consideration must be evaluated. If the release sites are viewed as localized areas that are no longer available for use by ecological receptors (i.e., no longer part of the habitat), this can be thought of as a form of habitat fragmentation. Habitat fragmentation is typically viewed as the loss of large areas of habitat within a landscape, leaving small isolated patches of intact habitat within a hostile matrix. Small-scale contaminant releases, on the other hand, result in small uninhabitable areas within a primarily intact habitat. With this consideration in mind, we analyzed the wildlife and conservation biology literature to determine if information on habitat size requirements such as home-range or critical patch size could inform us about the potential for impact at the landscape level from release sites based on the size of the release alone. We determined that evaluating the impact of release size had to be conducted within a contextual basis (considering the existing state of the landscape). Therefore, we also reviewed the population modeling literature to determine if models could be developed to further evaluate the impact of the spatial extent of chemical releases on the landscape. We identified individual-based models linked to geographic information systems to have the greatest potential in investigating the role of release size with respect to population impacts at the landscape level.