Incorporating risk into the feasibility assessment of alternative brush management strategies for the Welder Wildlife Refuge

Abstract

Integrated brush management systems (IBMS) are designed and implemented for the purposes of woody plant management, herbaceous plant quality improvements, and maintenance of rangelands in South Texas. Encroachment of woody plant species has turned many of the primitive South Texas grasslands into brushlands. Sources of increased brush cover are varied, but the impacts are a reduction in domestic animal grazing capacity, alteration of wildlife habitat, and change in the ecological framework. Methods are available to manage and hinder brush plant invasion, but economic returns from their implementation are often uncertain. For this reason, a significant portion of range managers do not utilize brush management, and those who do use brush management systems are not always certain if they are getting adequate returns on their implementation costs. Investment analysis techniques are available to inventory and project net benefits, but these techniques typically exclude factors of uncertainty faced by range managers. The purpose of this study was to utilize available decision support procedures and developmental risk analysis techniques to analyze the cost-effectiveness of long-term brush management systems for the Welder Wildlife Refuge, a cattle and wildlife ranch in South Texas. This was accomplished by developing technically and economically feasible brush management alternatives for selected areas on the ranch. The implementation of these alternatives over a planning horizon was then assessed using a deterministic decision support system and a stochastic expected payoff simulation model. The simulation model was developed from range production data generated by PHYGROW, a hydrologic based range plant growth simulation model. Investment analyses were progressively conducted using solely deterministic parameters, stochastic production, and finally stochastic production and prices. The deterministic simulation was most comparable to the decision support system results. The stochastic production and price simulation was most representative of what a range manager might expect over a planning horizon. The analyses produced generally favorable net values for brush management systems. The deterministic techniques overestimated the net benefits associated with these systems. The stochastic techniques utilizing risk factors produced probabilistic outcomes that represent a range of outcomes that might be expected from the implementation of brush management systems.