Effects of cattle grazing on North American arid ecosystems: A quantitative review

A quantitative review was conducted of the effects of cattle grazing in ari d systems on 16 response variables ranging from soil bulk density to total vegetative cover to rodent species diversity. Various studies from North Am erican arid environments that used similar measures for assessing grazing e ffects on the same response variables were used for the review; each study was assigned to serve as a single data point in paired comparisons of graze d versus ungrazed sites. All analyses tested the 1-tailed null hypothesis t hat grazing has no effect on the measured variable. Eleven of 16 analyses ( 69%) revealed significant detrimental effects of cattle grazing, suggesting that cattle can have a negative impact on North American xeric ecosystems. Soil-related variables were most negatively impacted by grazing (3 of 4 ca tegories tested were significantly impacted), followed by litter cover and biomass (2 of 2 categories tested), and rodent diversity and richness (2 of 2 categories tested). Vegetative variables showed more variability in term s of quantifiable grazing effects, with 4 of 8 categories testing significa ntly. Overall, these findings could shed light on which suites of variables may be effectively used by land managers to measure ecosystem integrity an d rangeland health in grazed systems.