Environmental Policy

Grassland Ecosystems and the Spread of Invasive Species

Cattle grazing a barren western landscape

The spread of alien invasive species such as cheatgrass is a serious environmental problem in the Intermountain West. Environmental Policy reseacher Aaron Strong is working to identify the factors that exacerbate the threat to native sagebrush grassland. Strong and ecologist Timothy Seastedt (University of Colorado) first constructed a bio-economic model of cattle stocking that, unlike previous studies, included different scenarios for how cattle graze.

This allowed them to identify four main factors behind the increase OR decrease of invasions: (1) external causes such as global warming (2) poor land management (3) cattle grazing makes the grassland less productive, and (4) cattle actually act as a biocontrol to prevent or mitigate the invasion.

They tested these factors using satellite imagery for Boulder County, CO, over 10 years, dividing the plains according to public or private ownership. Results of this phase of the study found no difference in the productivity of the land owned publicly or privately, suggesting that poor land management is not a significant cause of cheatgrass invasion.

Professor Strong will be presenting the results of this study on Monday, November 5, at the Wisconsin Institute of Discovery, University of Wisconsin – Madison. His talk is titled, General Equilibrium Ecosystem Modeling with Alternative Preference Specifications.