Interactions Among Human, Biological, and Physical Processes Within Large Lake Ecosystems

Booms in lake-based human activities have consistently followed increases in the quality of large lake ecosystem services, including abundant gamefish, clear water, and uncontaminated water for drinking and swimming. For example, substantial improvements in water quality and clarity in Lake Erie achieved in the 1970s and 1980s through the reduction in external phosphorus loadings from point sources have been followed by a period of lakeside recreational and residential development that extends to the present. More recently, increases in phosphorus concentrations and the frequency of harmful algal blooms in the lake have combined with other biophysical conditions to generate "surprise events," such as the, expansion of the summertime "Dead Zone" and adult gamefish kills. While linkages between the human and biophysical systems clearly are key factors producing these changes, their underlying structural dynamics and the extent to which the linkages have led to fundamental and perhaps irreversible changes in biological and human processes is unknown. This interdisciplinary research project will examine the coupled linkages between lake functioning and lake-related human activities and explore how these couplings generate nonlinear changes in ecological outcomes, such as water quality and fish stocks, and human behavior, including land use and lake-based recreational activities. Of particular interest are the conditions under which coupled linkages lead to bifurcations or other "surprise" outcomes that may not occur in their absence and the influence of fine-scale variations, time-delayed feedbacks, and stochastic processes that may be embedded in the couplings. The objectives of this research are (1) to construct a simple, coarse-scale model of a generic large lake ecosystem with coupled human-biophysical interactions that can be used to examine system dynamics and the role of human-biophysical couplings; (2) to develop a more detailed, fine-scale model by increasing the models spatial and temporal resolution and, parameterizing the model using Lake Erie data and use this model to test hypotheses regarding the impact of human activities on lake eutrophication and the impact of these ecological changes on land and economic development in the Lake Erie region; and (3) to use this set of models to study the impacts of historical policies and new management strategies of large lakes on both human and biophysical processes. A combination of analytical, statistical, and computer simulation methods, including agent-based modeling, will be used to build these models. Dynamical systems techniques, including numerical simulations and bifurcation analysis, will be used to analyze the models. Much of the historical data on lake dynamics, water quality, fish stocks, land use, and recreational activities are already available. Additional data will be generated using geographical information systems, remote sensing, and household surveys of residents and lake recreational users. The project will provide both scientific and societal benefits. By testing hypotheses regarding the coupled linkages between human and biophysical large lake processes and examining the way in which these interactions influence the self-organization and resiliency of biological and human systems, the project will make an original contribution to the scientific understanding of large lake biocomplexity. The research will make methodological contributions by advancing methods used to study the stability and multiscale properties of complex, coupled systems. By providing a better understanding of how feedbacks occur between lake functioning and human behavioral responses, the results will generate social benefits by providing information to policy makers who seek to protect lake resources while also providing high-quality amenities to people. The project will integrate biocomplexity research and education through the development of a new biocomplexity course; through training a new generation of interdisciplinary biocomplexity researchers; and through incorporation of research ideas and results into K-12 educational materials and programs aimed at policy makers and the broader public. This project is supported by an award resulting from the FY 2004 special competition in Biocomplexity in the Environment focusing on the Dynamics of Coupled Natural and Human Systems.