Princeton University-led researchers working in Kenya found that when herbivores — particularly large animals such as giraffes and elephants — are no longer present in African savanna ecosystems, dense fast-growing vines known as lianas rapidly take over plant communities. The findings demonstrate how human-driven declines in animal populations could disrupt the balance of both plant and animal species in this iconic ecosystem. (Photo by Morgan Kelly, High Meadows Environmental Institute)
What happens when large herbivores – such as giraffes and elephants – are no longer present in African savanna ecosystems?
According to a new study recently published in the Proceedings of the National Academy of Sciences, the consequence is a dramatic increase in dense, fast-growing vines known as lianas. This results in a disruption in the balance of both plant and animal species in this iconic ecosystem.
The researchers constructed a series of long-term “exclosure” experiments that prohibited herbivores of various sizes, from elephants down to the Chihuahua-sized antelopes known as dik-diks, from accessing enclosed landscapes. They found that the severity of liana infestation in these enclosures was greatest when large herbivores were excluded.
These findings coincide with the acceleration of human-mediated changes in the distribution of species, said Tyler Coverdale, a postdoctoral fellow at Harvard University and co-first author of the study.
“We conclude that savannas may be more vulnerable to harmful liana infestation than previously thought, particularly if the extinction of large wild herbivores continues to accelerate,” Coverdale said. “I think this is ultimately a story about how human impacts can cause ecosystems to change in unexpected ways, and how we need to do better to understand and predict those changes so we can mitigate them.”
