The effectiveness of using targeted grazing for vegetation management: a meta-analysis

The use of targeted grazing to control undesired plants as a component of ecological restoration is gaining in popularity, but there is considerable uncertainty among land managers about the effectiveness of this approach. We synthesized existing literature on the use of livestock (ruminants, swine, and equids) to control undesired plants using a meta-analysis to address questions about the effectiveness of the approach. Seventy studies matched our inclusion criteria; these comprised 86% peer-reviewed journal articles and 14% gray literature. Studies were conducted in 17 countries but highly concentrated in the United States and Europe. Cattle, goats, horses, and sheep were used for vegetation management in the studies. Most target plant species were nonnative perennial forbs. Median study duration was 3 years, with a maximum of 10 years. We found that, overall, the use of targeted grazing significantly reduced undesired plants and significantly increased plant species richness. However, several important questions remain. In particular, further research is needed to differentiate temporary defoliation from actual plant mortality, to separate the contributions of native versus nonnative species to gains in plant species richness, and to address longer term outcomes following grazing cessation.