In African savanna wild herbivores are increasingly displaced by cattle and that is not without consequences. Where many cows graze, the soil becomes poorer because the cows do not sufficiently fertilise the soil where they graze. They mainly drop their dung at night when they are kept fenced-in to protect them from lions. This impoverishes the soil, which reduces the productivity and quality of the grass. However, when elephants are present, this soil depletion does not occur; the soil is even enriched. Elephants bring down trees in the savanna, which accelerates the return of nutrients to the soil. But more importantly, elephants compete with cattle for the same available food, which results in less grazing by cattle. This also means that cows export less dung away from the place where they graze, while dung deposition of wild herbivores is stimulated, which in turn feeds the soil. The combination of domestic cattle and elephants might therefore be a form of sustainable management for African savanna.
You can find the paper here, and read the news item by Mark E. Ritchie in Nature Sustainability and the highlight in Science.
Reference: Sitters, J., Kimuyu, D.M., Young, T.P., Claeys, P., Venterink, H.O.. (2020) Negative effects of cattle on soil carbon and nutrient pools reversed by megaherbivores. Nature Sustainability https://doi.org/10.1038/s41893-020-0490-0
Picture: Elephants and cattle have contrasting effects on soil fertility at Mpala Research Centre (Photo: Dino J. Martins)