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Department of Agricultural, Environmental, and Development Economics


New Research from Professor Irwin Offers Analysis of the Interaction between Humans and Ecosystem Thresholds

Jan. 28, 2013

In the November 2012 Journal of Environmental Economics and Management, AEDE’s Professor Elena Irwin, former AEDE doctoral student Yong Chen, now a faculty member at Oregon State University, and Ciriyam Jayaprakash from the Department of Physics at Ohio State offer new analysis on the dynamic interaction between humans and ecological systems in the article “Threshold management in a coupled economic-ecological system”.

The study investigates threshold management in a hypothetical scenario that demonstrates an ecosystem’s response to the cumulative impacts of individuals due to amenity-led migration and, in return, the response of the individuals to subsequent changes in the ecosystem.  While the model is conceptual, it captures the basic features of thresholds that are common in many ecosystems. For example, algae blooms and dead zones, a condition of reduced dissolved oxygen in water that can lead to fish kills, are common in Lake Erie in the summer months. They are the result of a gradual build-up of phosphorous in the water that causes cascading effects and leads to these tipping points.

In the paper, the researchers aim to offer policymakers new information on how policies can respond to the dynamic interaction of humans and the environment and plan for better legislation for more sustainable ecosystems. As the researchers note in the study, in many cases human activities are a major determinant of ecological thresholds and thus policies that improve ecosystem services without addressing potential behavioral feedbacks are likely to be inefficient and may unintentionally degrade ecosystem services and reduce ecosystem resilience. The research is important for understanding the way humans and ecosystems interact and to understand these dynamics to better formulate policies that protect a region’s environment.

Additionally, the research offers new information to the field as though previous economic models of optimal ecosystem management have long accounted for the direct effects of pollution policies on improvements to ecosystem services, relatively little research to-date has accounted for the indirect effects of these policies that arise if individuals respond to these ecological improvements, which Irwin, Chen and Jayaprakash’s study takes into account.  As the researchers note, the optimal management of such a system rests on the consideration of both these direct and indirect effects.

To conduct their research, the researchers developed a model of a regional economy with a lake ecosystem and considered the role of a specific behavioral feedback: amenity-led growth that responds to changes in water quality. The lake ecosystem in the study was subject to threshold dynamics in which nutrient loadings generated by human activities, including increased land use, caused a shift from an oligotrophic to eutrophic lake state, which drastically reduced water quality. These dynamics are a common characteristic of large lakes.

Through their analysis the researchers were able to show that policies that ignore the relationship between the impacts of land use and the human migration response to changes in ecosystem services result in pushing the lake ecosystem closer to such thresholds than is optimal. In contrast, the optimal policy, which accounts for both ecological impacts and the human migration response, permits ecological degradation but avoids overdevelopment that pushes the system across the threshold.

The study was supported through funding from the National Science Foundation (DEB Grant 0410336) and the Ohio Sea Grant program. Irwin, fellow AEDE faculty Professor Brian Roe and several AEDE graduate students are now involved in a follow-up study that is examining the effect of policies on agricultural land management practices and Lake Erie water quality changes.  Click here for more information on this project.

To see the full study from Irwin, Chen and Jayaprakash see the Journal of Environmental Economics and Management.