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IMPACTS OF MULTIPLE STRSSORS ON COMMON LOONS IN NEW HAMPSHIRE, USA: A DEMONSTRATION STUDY FOR STRESSOR EFFECTS ACROSS SPACE
Citation:
WALTERS, S., A. KUHN, J. S. GREAR, M. C. NICHOLSON, J. L. COPELAND, S. A. REGO, AND D. E. NACCI. IMPACTS OF MULTIPLE STRSSORS ON COMMON LOONS IN NEW HAMPSHIRE, USA: A DEMONSTRATION STUDY FOR STRESSOR EFFECTS ACROSS SPACE. Presented at US Chapter of the International Association for Landscape Ecology, San Diego, CA, March 28 - April 01, 2006.
Description:
Factors that significantly impact wildlife population dynamics, such as resource availability and exposure to stressors, frequently vary over space and thereby contribute to the heterogeneous spatial distributions of organisms. The spatial co-occurrence of organisms, environmental factors, and multiple stressors has important implications for ecological risk assessment and conservation management strategies. We are evaluating modeling tools for predicting population responses to multiple stressors in a spatially explicit framework. The goal of the present study is to illustrate how localized effects of spatially heterogeneous stressor distributions can impact the regional persistence or decline of wildlife populations. Using the modeling package RAMAS-GIS, we explored the impact of spatial dependence in organism and stressor distributions, using common loon (Gavia immer) populations in New Hampshire and exposure to chemical and land use stressors as a case study. Environmental data and lake-specific loon demographic information, population and habitat suitability models, and estimates of dispersal behavior were integrated in RAMAS to simulate localized population and regional metapopulation trends in NH under hypothetical unstressed conditions. These results were then compared with dynamics under simulated stressor-induced decreases in fecundity on source versus sink lakes. Decreases in fecundity on source lakes resulted in metapopulation occupancy rates and probabilities of persistence that were lower than those observed under unstressed conditions. However, comparable decreases in fecundity on sink lakes did not appreciably alter dynamics relative to those observed under unstressed conditions: only when accompanied by reductions in dispersal rates did impairment within sinks result in lower occupancy rates. The results illustrate the importance of accounting for spatial heterogeneity in population and stressor distributions, as well as understanding the degree to which dispersal connects localized populations, when assessing ecological risks from multiple interacting stressors. Further analyses will be used to explore and test effects of stressors of concern, such as lake acidification and increases in human development.