Rangelands across the western United States provide considerable benefits. However, with nitrogen deposition, climate change and invasive species, the composition of these grassland ecosystems have experienced changes in the flow of services that they provide and, in turn, in the value of the natural capital that characterized the ecosystem. Expanding on the methods developed in Fenichel and Abbott (2014) in conjunction with a General Equilibrium Ecosystem Model (GEEM), we illustrate how the value of these grassland ecosystems may change as invasive species alter the landscape. In particular, by modeling three grass species as opposed to a single grass stock, we are able to identify two major sources of value to the system. First, grasses that provide nutritional value to cattle stocked on the rangeland provide a final ecosystem service value. Second, different populations of grass species competing for energy against other species can both provide both positive and negative values from these indirect, supporting ecosystem services. Our results show that even with positive nutrition values, competition effects can render the total marginal value of some grasses negative depending on the state of the ecosystem. Finally, we provide a validation check to the method by noting that the value of the land estimated by the extension of the Fenichel and Abbott method for a relatively intact native grass ecosystem corresponds almost exactly to land prices observed for agricultural rangeland in Wyoming.
Table of Contents
Rangeland Ecosystem Model
Numerical Approximation of the Value Function
Choice of Nodes and Evaluation of Ecosystem Model
Discussion and Conclusion