Responses of African savanna trees to large herbivore extinction and rewilding

Authors: COVERDALE, TYLER - University Of Notre Dame; SANKARAN, MAHESH - National Centre For Biological Sciences; DAVIES, ANDREW - Harvard University; RATNAM, JAYASHREE - National Centre For Biological Sciences; WIGLEY, BENJAMIN - Nelson Mandela University; Augustine, David

Submitted to: Ecology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2026
Publication Date: 3/12/2026
Citation: Coverdale, T., Sankaran, M., Davies, A., Ratnam, J., Wigley, B., Augustine, D.J. 2026. Responses of African savanna trees to large herbivore extinction and rewilding. Ecology Letters. 29(3). Article e70360. https://doi.org/10.1111/ele.70360.
DOI: https://doi.org/10.1111/ele.70360

Interpretive Summary: Rangeland vegetation can change dramatically in response to both the removal and addition of large herbivores. In the savannas of Africa, which are primarily managed for livestock production, it is important to understand how the removal and addition of native herbivores, such as elephants and antelope, affect the vegetation. We conducted a long-term study of how the density, size, and types of trees are affected by the removal and subsequent addition of elephants and antelope, which are browsers that mainly consume tree leaves and branches. We found that tree cover and density more than doubled in the first decade after large herbivore removal, and then stabilized at approximately 70% cover for the next 7 years. When large herbivores were reintroduced to the study plots in year 17 of the experiment, tree cover declined continuously over the next 8 years. Based on current rates of change, we project the vegetation will return to return to similar conditions as sites where herbivores were never removed by the 10th year after reintroduction. These findings show that elephants and antelope collectively maintain low density and cover of thorny trees and saplings, thereby increasing access for livestock to grasses in the understory.

Technical Abstract: The global decline of large mammals over the last 50,000 years has caused sweeping changes in the ecosystems they once inhabited. Trophic rewilding holds promise for restoring lost ecological function and returning ecosystems to more desirable states, but there remains considerable uncertainty surrounding the efficacy of rewilding. To address this uncertainty, we experimentally excluded a diverse, African savanna mammal community from replicated plots for eighteen years to simulate extinction. Herbivore exclusion caused a rapid increase in tree cover, which was underlain by shifts in community composition and increases in canopy area, growth rate, and density. We then removed the exclosure fences, simulating rewilding. Reintroducing herbivores rapidly reduced tree cover and largely reversed individual phenotypic shifts, but tree density remained elevated despite increased mortality rates after rewilding. Our results suggest that even short-term extinction can lead to complex shifts in vegetation communities, some of which may be resistant to rewilding.