Optimal rangeland stocking rates: Biological and economic modeling aspects of livestock grazing in the semi-arid American Southwest

The impetus behind this research on livestock grazing in the American Southwest is the proposition that left to their own means, livestock grazing enterprises will tend to overgraze, and hence, degrade the range resource on both public and private lands. Overgrazing of the range has frequently been attributed to the profit motive of the ranch operator. In order to test the validity of this proposition, as well as to promote optimal use of the range resource, the stocking rate and forage biomass dynamics of a profit maximizing stocker cattle operation in south central New Mexico are explored.; The stocker operation is modeled such that empirically established cattle and range relationships are fully integrated into the economic framework of the profit maximizing production firm. A theoretical optimal stocking rate model that combines the profit maximizing production function of the livestock grazing enterprise with the forage dynamics of the semi-arid western range is derived and solved in terms of stocking rate and forage stock time paths for the year. Numerical solutions of the model explore the effects of changes in climatic, biological, and economic parameters on the optimal paths. The sensitivity of stocking rate and forage stock to the parameter values of precipitation, initial forage stock levels, beef prices, ranching costs, and discount rates are tested. The optimal stocking rate paths as predicted by the theoretical model are then compared to recommended stocking rates and stocking strategies for the area.; The results of the numerical solutions of the livestock grazing model predict higher returns to a flexible stocking rate strategy in periods of high or low annual precipitation. However, the stocking rates generated by the optimal flexible stocking rate strategy are often indicative of overstocking for the area, and suggest that a ranching concern with a goal of short term profit maximization has an incentive to overgraze the range in some situations. The adoption of the flexible stocking rate model by ranching operations in south central New Mexico offers the possibility of increased returns in high and low precipitation years, but increased exposure to risk and above average losses in highly variable precipitation years.