Effects of livestock grazing on biodiversity: A meta-analysis on three trophic levels

Livestock impact is one of the main causes of habitat loss globally. However, the effects of livestock on flora and fauna diversity have been contradictory, observing cases with positive, neutral, and negative effects. We performed a meta-analysis of the scientific information published in the last 15 years, using Google Scholar and WoS for the search. The inclusion criteria were if the studies presented a) changes in abundance, richness, biomass, plant cover, and consumers; b) included replicas; c) the size of the sample; d) study on domestic cattle, and e) reported the mean and standard deviation of effects of each treatment. We found 2450 scientific publications of which we selected 67 publications that reported the effects a) of grazing on the richness, abundance, cover, and biomass of plants (producers), and b) on richness and abundance of primary and secondary consumers, comparing grazed and non-grazed (or weakly grazed) environments. Grazing did not significantly affect the abundance of the plants or animals studied, regardless of whether they were primary or secondary consumers. The magnitude and direction of the observed effects on plants and consumers could be influenced by livestock type, the natural environments evaluated (forests, grasslands, or scrublands), the spatial and temporal scales involved, and the plant species origin (i.e., native versus non-native). The significant effect of livestock on plants and consumers, also can be differentiated in the characteristics of the species (e.g., life-history traits, etc.) that go beyond their position in the food chains. Evaluating the livestock grazing effect in more than one trophic level helps understand how grazing affects the species according to their way of life, in contrast to evaluations of a single trophic level.