Document: THO-3-65-36

Assessing the impacts of landscape change on mobile animals.

SISK, T.D.* ¹, B.R.NOON ² and H.M.HAMPTON ¹

Northern Arizona University, Flagstaff, AZ 86011 USA ¹
Colorado State University, Fort Collins, CO 80523 USA ²

Abstract:
Terrestrial landscapes are being converted to novel states at increasing rates, due to accelerating human land use and its impacts. Remaining natural habitats are more fragmented and are often embedded in anthropogenic habitat types. Given this degree of dynamism, an approach for estimating changes in population density and viability that explicitly accounts for changes in the spatial patterning of habitats in the landscapes is essential. In addition to simple abundance responses, estimates should account for time lags and unexpected transient dynamics that accompany landscape change. We discuss a spatial modeling approach that incorporates empirical data on animal edge responses and predicts changes in animal abundance and distribution under various land management scenarios. In addition to typical patch size, shape, and distribution metrics, this model explicitly incorporates information on patch context. Inputs to the model include habitat maps and animal density response functions. Each response function describes animal density in terms of a probability distribution along a habitat gradient stretching between the interiors of adjacent habitat types. Preliminary model results show marked differences from the predictions of a null model that does not incorporate edge and matrix effects. Predictions of bird densities in a heterogeneous desert riparian ecosystem differ by factors of 0.6-2.7, and differences between predictions of the effective area model and null model tend to increase with increasing landscape heterogeneity.

Keywords: landscape ecology, effective area model, edge effects

This abstract is being presented at: 4:30 PM in session:
Oral Session #14: Disturbance Effects on Bird Populations.