Elephants Reverse the Depletion by Cattle of Soil Carbon and Nutrient Pools

Elephants and cattle in Africa. (photo Dino Martins)
Elephants and cattle in Africa. (photo Dino Martins)

Conserving wildlife with livestock in Africa

Truman Young, UC Davis.
Truman Young, Department of Plant Sciences, UC Davis.

Truman Young, professor in the Department of Plant Sciences, UC Davis, is a co-author of the new article, “Negative effects of cattle on soil carbon and nutrient pools reversed by megaherbivores,” in the journal Nature Sustainability. Authors are Judith Sitters, Duncan M. Kimuyu, Truman P. Young, Philippe Claeys, and Harry Olde Venterink.

“This is one of several papers from our experiment which show that megaherbivores (elephants, mainly) mitigate the negative effects of cattle on a tropical savanna rangeland,” said Young. “One pathway is that cattle actually feed less on pasture that they share with elephants, likely because elephants remove (eat) the most desirable forage plants, leaving the cattle to spend more time searching for these key plants, and less time actually feeding.”

Young is co-PI and project director of the Kenya Long-term Exclosure Experiment (KLEE), the most productive field experiment ever carried out in the continent of Africa, and the site of this research. Article co-author Duncan Kimuyu, along with Wilfred Odadi, and former UC Davis graduate students Kari Veblen and Corinna Riginos, are also co-PIs of KLEE.

Article Abstract

Wild herbivore populations are declining in many African savannas, which is related to replacement by livestock (mainly cattle) and the loss of megaherbivores. Although some livestock management practices may be compatible with the conservation of native savanna biodiversity, the sustainability of these integrated wild herbivore/livestock management practices is unknown. For instance, how will these herbivore mixes influence key processes for the long-term functioning of savanna ecosystems, such as soil carbon, nitrogen and phosphorus pools and cycling? The Kenya Long-term Exclosure Experiment studies the ecosystem consequences of manipulating the presence and absence of wild herbivores and cattle at moderate densities in a ‘black cotton’ savanna. Here we show that after 20 years, cattle presence decreased total soil carbon and nitrogen pools, while the presence of megaherbivores (mainly elephants) increased these pools and even reversed the negative effects of cattle. Our results suggest that a mix of cattle at moderate densities and wild herbivores can be sustainable, provided that the assemblage of wild herbivores includes the largest species.

Read the full article here.

Sustainability in savannas

In the News & Views section of Nature Sustainability, Professor Mark Ritchie of the Department of Biology at Syracuse University, in his “Supersizing sustainability in savannas” article, reviews the Sitters et al. article, noting:

Increasing pressure for communities to conserve wildlife in mixtures with livestock faces scepticism about whether such management is sustainable. The study by Sitters et al. shows that wildlife–livestock coexistence may be sustainable, but only if megaherbivores are included.

Following a review and analysis of the article, Ritchie closes with:

While the path to successfully mixing humans, livestock and wildlife is still unclear, this study shows the importance of including the full complement of large animal species in the plan. …(S)tudies such as that of Sitters et al. advance the knowledge base for finding future working solutions to conserving the iconic herds of Africa.

Read the full review here.

(Article by Ann Filmer, Communications, Department of Plant Sciences, UC Davis. March 24, 2020.)