Prescription Grazing for Rangeland Weed Management A new look at an old tool.

Abstract

Invasion by exotic species is one of the most significant ecological threats of our modern era, rivaling even highly touted and researched concerns such as ozone depletion, global warming, and loss of biodiversity. An invasive plant on rangelands is defined as a plant spreading naturally (without direct humnan assistance) to significantly alter composition, sltructure or ecosystem processes. Weed invasion into rangeland communities often results in reduced biodiversity, increased soil erosion, degradation of wildlife habitat, and reduced carrying capacity for livestock. There are many challenges when controlling invasive plants on rangelands, including vast roadless areas that limit access for weed control and lands of low economic value that make chemical and mechanical control impractical. These challenges favor biological control methods. Insects and microbes for biocontrol can be quite effective but are difficult, expensive, and time consuming to develop. However, there is a readily available and under-exploited tool that is fast proving very effective for weed control livestock grazing. Along with fire, grazing of domestic livestock may be the earliest vegetation management tool employed by humans. We suggest that the challenges of rangeland weed management may be addressed with the careful sharpening of this old tool. Past success with sheep and goats to control several rangeland weeds, such as leafy spurge, has fueled interest in grazing for weed control (1, 2). Prescription grazing is the application of livestock grazing at a specified season, duration and intensity to accomplish specific vegetation management goals. Controlled grazing of this type is being employed tlhroughout North America on public and private land and is proving to be a promising tool in the battle against weeds. Furthermore, livestock grazing has one distinct advantage over other control methods; in the process of controlling an undesirable plant, grazing animals convert it into a saleable product.