Last update: 3/2/04

PIs: Marc Coram, Greg Dwyer, Cathy Pfister, J. Timothy Wootton, Mei Wang

Understanding human impacts on the environment ultimately requires an understanding of how those impacts will affect other living things. Such an understanding is most useful if it allows quantitative prediction. The goal of our work is therefore to create models that can predict how human activities will affect population growth and interactions among species other than humans. Although this task has a long history in ecology, most existing models are deterministic, and therefore are of limited usefulness in real-world applications. Our immediate goals are therefore to develop stochastic models of population growth and species interactions, and to develop methods for choosing among models. For concreteness, we focus on particular organisms, but the models that we are developing, and our methodology for choosing among models, are not specific to any particular organism or group of organisms. Our intent is that the models that we produce will become part of environmental protocols for assessing the impacts of pollutants on ecological processes, or for tracking changes in environmental indicators of ecosystem health. Our work falls into two sub-projects, a population growth project, and a species interaction project.

Population Growth

The population growth sub-project has been examining the impacts of individual variation on predicting population growth rates. Past ecological studies have used matrix algebra to predict population growth rates and population health. These studies divide populations into distinct age or size groups and, in their analysis of population health, generally assume that age-specific vital rates are sufficient to provide accurate predictions. Cathy Pfister’s past work, however, has shown that there are additional sources of variability that must be accounted for, notably growth autocorrelation, before such models will be useful for predicting population growth rates.

Species Interactions

Models that consider the growth of a single species can be useful for species that interact only weakly with other species, or for species whose interactions with other species are at equilibrium. Many organisms, however, do not match these assumptions, and so a second main area of our research is aimed at understanding interactions among different species, and how such interactions determine population growth rates. As with our work on population growth, our ultimate goal is to predict how anthropogenic change will affect species interactions, and so to predict the effects of human activities on ecosystems.