https://phys.org/news/2018-06-corroborates-role-wildlife-world.html

The new study in PNAS looked for patterns among 123 previous experiments comparing plant communities in areas with and without animals. These experiments were distributed across the globe and usually used fences to keep animals out of the experimental plots.

For most ecosystems, the scientists found that herbivores strongly reduced plant abundances, plant biomass (weight), plant survival, and the ability for plants to reproduce. This provides evidence that wildlife is important for regulating plant communities like forests and grasslands. It also means that ecosystems where animals have become rare, such as where there is hunting, may have distinct vegetation characteristics from more protected habitats.