Although fire is the least expensive method of treating mesquite, its role is as a maintenance treatment to prolong the life of more expensive brush control treatments. Previous research has concentrated on identifying herbicides that do not negatively impact the environment and determining the most cost effective means of applying these tested and approved herbicides. The research reported here measured the costs in lower production of NOT reducing mesquite brush and calculated the economic benefits to reducing brush with herbicides alone or herbicides with the low-cost treatment of fire to keep brush levels at sufficiently low levels that livestock profitability was not unduly reduced. We consider beginning to burn 10, 15 and 20 years after initial treatment with a root-killing herbicide that has a treatment life of approximately 20 years.
Economic returns over the 30 year time period being considered are all economically feasible since net present values are greater than zero. Even herbicide treatment alone without the back-up maintenance of fire is very rewarding economically compared to not treating the mesquite brush. The burn after 10 years treatment showed the highest economic value in spite of the burning costs involved. Although the 15-year follow-up burn treatment results in a slowly declining carrying capacity, the lower costs associated with fewer prescribed burns results in a higher net present value compared to the herbicide with-no-follow-up-burn treatment. Even if burning begins in year 20 after herbicide application, the associated economic value slightly exceeds that of the treatment with no-follow-up-burn because of the further rapid decline in the number of cattle that can be supported as a result of increasing mesquite brush when fire is not applied.
The numbers of acres needed to support a cow with herbicide treated compared to untreated mesquite and with different post-herbicide prescribed burn scenarios: (a) burning after 10 years, (b) burning after 15 years, and (c) burning after 20 years.
This analysis indicates that reducing mesquite brush is definitely desirable in economic terms as well as in terms of protecting our urban and rural water supply. The use of herbicide alone is economically feasible but fire is also an important management tool because using it in a maintenance role provides an economic advantage when the canopy cover of mesquite brush reaches 10-15% after the application of root-killing herbicide. Waiting beyond this point will result in increasingly prohibitive costs for restoring the productive capacity of rangelands.
Our study suggests that such a mesquite management strategy would be economically superior to using herbicide with no follow-up burn. In times of below average rainfall, burning can be very difficult or impossible to implement. At such times reducing stock numbers and burning only 10-12% of the grazing management unit each year would help considerably in ensuring regular burns.
Table 1. Net present value for treating mesquite with root-killing herbicides followed by prescribed fire at intervals of 10, 15 and 20 years after herbicide application compared to not treating mesquite brush.
|Herbicide Treatment Longevity||Scenario Description||Treatment Cost||NPV|
|No follow-up burn
Follow-up burns after 10 years (6yr cycle)
Follow-up burns after 15 years (6yr cycle)
Follow-up burns after 20 years (6yr cycle)
It is very important to keep mesquite brush levels at relatively low levels because as brush increases, ecological thresholds may be reached from which it may be impossible to regain a rangeland plant community that is suitable for livestock or wildlife and the ability of the landscape to provide urban areas with sufficient quality water may be permanently impaired.
Van Lieu, D., J. Richard Conner, Urs P. Kreuter and W. Richard Teague. 2009. An Economic Comparison of Prescribed Extreme Fire and Alternative Methods for Managing Invasive Brush Species in Texas: a Modeling Approach. The Open Agricultural Journal, (In press).
Teague, W. R., R.J. Ansley, U.P. Kreuter. 2003. Economics of fire as a follow-up to herbicide treatment of mesquite. Rangelands in the New Millennium. Proceedings of the 7th International Rangeland Congress, Durban, South Africa. 26 July-1 August, 2003.
Teague, W. R., R.J. Ansley, U.P. Kreuter, W.E. Pinchak and J.M. McGrann. 2001. Economics of managing mesquite in north Texas: a sensitivity analysis. Journal of Rangeland Management 54:553-560.