Evaluation

Prevention is the optimal management strategy over the long-term when the probability of invasion is fairly certain. Most weed-free ecosystems are susceptible to invasion as a result of either direct or indirect human activity. Prevention is difficult to evaluate because the long-term maintenance of weed-free ecosystems requires a number of years to document. Prevention system efficacy over the short-term may be measured by evaluating system design. For instance, we can say a Weed prevention Area (WPA) is operating effectively when multiple proven strategies are being implemented. A prevention system may be operating ineffectively when critical strategies are missing. Prevention system efficacy may also be measured by documenting the number of participating landowners and the number of new invasions located with inventory efforts.

The cost of a prevention system can also be measured, and it may show how cost effective prevention is when compared to the resources needed to manage weeds. The small costs associated with prevention may yield ecological benefits that accrue indefinitely. Short-term estimates indicate the cost to protect weed-free rangelands from weed spread averages less than $0.10 per acre per year. This estimate is favorable when compared to the average $20 per acre per year to manage weeds after they become established. This mitigation cost is on-going and does not include costs associated with forage losses or reduced ecological value. The costs associated with prevention include educational brochures and signs, field tours, GPS equipment, all-terrain vehicles, seasonal weed scouts, and herbicides for small-scale eradication.

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Last Modified: 08/02/2007