Large herbivores prevent harmful liana infestation in an African savanna

What is it about?

African savannas are among the last ecosystems to support near-historic densities and diversities of large mammalian herbivores. With these species in decline, there is uncertainty about how their loss will affect broader savanna ecosystems. We show that the loss of wild megaherbivores (e.g., elephants, giraffes, impala) cause a rapid increase in the dominance of climbing woody vines (lianas), which smother trees. Lianas reduce tree growth and reproductive output, with potentially long-term consequences for savanna plant communities.

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Photo by howling red on Unsplash

Photo by howling red on Unsplash

Why is it important?

The balance between trees and grasses is a primary focus of savanna ecology research. Comparatively little is known about the role of other plant growth forms in savannas, however, including lianas. Significant changes in the composition and density of large mammalian herbivore communities can have cascading effects on ecosystems, yet the exact nature of these changes is often unanticipated. We show that lianas can come to dominate savanna plant communities, and that the relative scarcity of this growth form in savannas currently is likely a reflection of the strong top-down pressure exerted by large herbivores. Importantly, however, the dominant liana at our study site is toxic to domesticated livestock, so the replacement of wildlife with livestock is unlikely to mitigate liana encroachment.

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