GIS/EM4 - Predicting Animal Responses to Ecological Changes

Predicting Animal Responses to Ecological Changes:

a spatial model incorporating edge effects

GIS/EM4 No. 26

Thomas D. Sisk
Barry R. Noon
Haydee M. Hampton

Abstract

The detrimental effects of habitat fragmentation on animal populations are widely documented, however the development of practical tools to predict the effects of fragmentation and design appropriate mitigation efforts has progressed slowly. The Effective Area Model (EAM) is designed to provide a predictive tool to link field and remotely sensed data in a landscape model that permits comparison of the impacts of alternative land use strategies on animal populations.

Keywords

Ecological modeling, human-environment interactions, edge effects, animal abundance, animal density, spatial model, conservation biology.

The detrimental effects of habitat fragmentation on animal populations are widely documented and thoroughly appreciated in the management of sensitive, threatened, and endangered species (Whitcomb et al. 1981, Lynch and Whigham 1984, Wilcox and Murphy 1985, Robinson et al. 1995). In contrast, the development of practical tools to predict the effects of fragmentation and design appropriate mitigation efforts has progressed only slowly (Saunders et al 1991, Wiens 1995). The Effective Area Model (EAM) is a predictive tool for estimating the density and abundance of mobile animal species in heterogeneous landscapes (Sisk and Margules 1993, Sisk et al. 1997).

Habitat quality often has been inferred from patterns in animal abundance. The development of ecological theory underlying source:sink dynamics and metapopulations has demonstrated that simple assessments of abundance, and correlation of these patterns with habitat attributes, however detailed, does not adequately describe habitat quality. Survival and reproductive rates can be governed by landscape-scale factors, including edge and matrix effects, suggesting that habitat quality is as much a product of landscape- and regional-scale factors as it is proximate factors, within a given habitat patch. As terrestrial landscapes become increasingly fragmented by human activities, a predictive approach that accounts for broad-scale ecological factors is needed to guide habitat management and conservation.

We will present recent progress in the development of a modeling approach that is empirically based and designed to capture many of the influences of landscape composition and structure that have been ignored by most previous efforts. The EAM incorporates field data on animal responses to habitat edges and predicts abundances under various land management scenarios. For example, the model can be used to predict changes in the number of individuals of a certain bird species, in a specific study area, given alterations to landscape structure or vegetation characteristics.

The EAM uses two types of input data - the edge response of each species and a detailed landscape map identifying habitat patches and their location in the landscape mosaic - to generate predictions of the distributions of organisms, resources, or environmental conditions in heterogeneous landscapes. The edge response function quantifies the species-specific influence of habitat edges. It can be conceptualized as the population density (or other population or environmental variable of interest) at increasing distances from the habitat edge. Although we are designing the model for use primarily in predicting population variables, it can be used more generally to distribute the results of any function associated with linear features across the landscape. The model is being developed as an extension to ArcView GIS (ESRI, Redlands, California) using the Avenue scripting language.

References used

Lynch JF, Whigham DF. 1984. Effects of forest fragmentation on breeding bird communities in Maryland, USA. Biological Conservation 28:287-324.

Robinson SK, Thompson III FR, Donovan TM, Whitehead DR, Faaborg J. 1995. Regional forest fragmentation and the nesting success of migratory birds. Science 267:1987-90.

Saunders DA, Hobbs RJ, Margules CR. 1991. Biological consequences of ecosystem fragmentation: a review. Conserv Biol 5:18-32.

Sisk TD, Margules CR. 1993. Habitat edges and restoration: methods for quantifying edge effects and predicting the results of restoration efforts. In: Saunders DA, Hobbs RJ, Ehrlich PR, editors. Nature conservation 3: reconstruction of fragmented ecosystems. Sydney, Australia: Surrey Beatty & Sons. p 57-69.

Sisk TD, Haddad N, Ehrlich PR. 1997. Bird assemblages in patchy woodlands: modeling the effects of edge and matrix habitats. Ecol Appl 7 (4):1170-80.

Whitcomb RF, Robbins CS, Lynch JF, Whitcomb BL, Klimkiewicz MK, Bystrak D. 1981. Effects of forest fragmentation on avifauna of the eastern deciduous forest. In: Burgess RL, Sharpe BM, editors. Forest island dynamics in man-dominated landscapes. New York: Springer-Verlag. p 125-206.

Wiens JA. 1995. Habitat fragmentation: island v landscape perspective on bird conservation. Ibis 137:S97-S104.

Wilcox BA, Murphy DD. 1985. Conservation strategy: the effects of fragmentation on extinction. American Naturalist 125:879-887.

Authors

Thomas D. Sisk, Assistant Professor, Center for Enviromental Science and Education
Northern Arizona University, . NAU Box 5694, Flagstaff, Arizona, United States 86011-5694.
Email: thomas.sisk@nau.edu, Tel: +1-520-523-7183, Fax: +1-520-523-7423.

Barry R. Noon, Associate Professor, Department of Fisheries and Wildlife Biology Colorado State University, 240 J.V.K. Wagar, Fort Collins, CO 80523.
Email: brnoon@cnr.colostate.edu, Tel: +1-970-491-7905, Fax: +1-970-491-5091.

Haydee M. Hampton, Spatial Analyst, Center for Environmental Science and Education
Northern Arizona University, NAU Box 5694, Flagstaff, Arizona, United States 86011-5694.
Email: haydee.hampton@nau.edu, Tel: +1-520-523-0872, Fax: +1-520-523-7423.