Ecosystem tipping points in the Laurentian Great Lakes
Abstract
The effects of human land use change are ubiquitous and pervasive. Anthropogenic changes to landscapes around the world have impacted terrestrial ecosystems in numerous ways. Because what human activities occur on the land often affects water, management of the use of the land becomes tantamount to preserving a precious natural resource, water. The overarching focus of this thesis is to examine how increased human land use affects the integrity of surrounding freshwater systems. The terrestrial and aquatic components characterizing these interactions are complex, adaptive, and dynamic, and as such, possess qualities of emergence and nonlinear behaviors, including characteristics of what some call 'tipping points'. Unfortunately the term 'tipping point', as used in the ecological literature, is poorly defined and is a topic of considerable debate. To address this concern, and clarify what is meant by the term 'tipping point', a conceptual framework for tipping points is presented in this thesis. In order to apply the theoretical framework of tipping points to real-world occurrences, data on stream-insect response to agricultural and urban land uses from the Great Lakes states of IL, WI, and MI are analyzed using the conceptual framework developed in Chapter 2. The application of tipping points in management is rather rare due to deficits in long-term monitoring capabilities, and reliable early warning signal measures or useful indicators. We are also unable to account for or predict emergent, unexpected properties, which may have large consequences on system dynamics and generate tipping points if they are of high magnitude. However, recognizing that the study of tipping points strictly related to the natural sciences is still in its infancy, there is currently ample opportunity for breakthrough developments in tipping point predictability, which in turn may yield valuable information about coupled natural human systems.
Degree
M.S.
Advisors
Pijanowski, Purdue University.
Subject Area
Forestry
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