Targeted Grazing Impacts on Invasive and Native Plant Abundance Change with Grazing Duration and Stocking Density

Abstract

The science underpinning targeted grazing has been advancing for decades, supporting a major paradigm shift concerning the role of grazing in addressing critical natural resource management challenges across the globe. A next step for expanding adoption is to understand how conservation benefits derived from this practice may change depending on how the components of a targeted grazing strategy change. Using two studies on California annual rangeland, one with heifers and one with ewes, we evaluated how two stocking attributes that underpin a targeted grazing plan, animal density and grazing duration, influence the ability of livestock to reduce the abundance of the invasive annual grass medusahead (Taeniatherum caput-medusae [L.] Nevski) and increase the abundance of native plants. Across studies, conservation benefits tended to be higher (lower invasive plant abundance and greater native plant abundance) under higher stocking density and shorter stocking duration, but we also found evidence that stocking density could be relaxed in some situations, allowing some conservation benefits to be achieved by grazing fewer animals over a longer duration. For California annual rangelands where most vegetation growth occurs over a period of a few short weeks, the potential to achieve similar conservation benefits by extending grazing duration and using fewer animals represents a major opportunity to apply targeted grazing over larger areas in one season with a set number of grazing animals. These initial findings provide justification for more extensive research in how changes in targeted grazing strategies may alter conservation benefits from grazing. Such insight is essential for understanding the range of cost-benefit trade-offs that may occur with this practice.