Thousands of years of livestock dung have stimulated fertile and ecologically diverse wildlife hotspots in Africa, according to a study published in the journal Nature, suggesting that manure-driven soil enrichment has a long-term impact on the landscape.
Many iconic wild African landscapes have been moulded by the exploits of prehistoric herders, according to lead author Fiona Marshall, anthropologist at Washington University, US.
“The longevity of these nutrient hotspots demonstrates the surprising long-term legacy of ancient herders whose cattle, goats and sheep helped enrich and diversify the vast savannah landscapes of Africa over three millennia,” Marshall says.
With satellite imaging and detailed soil analysis of five Neolithic sites in southern Kenya, the researchers shed light on how fertile oval-shaped hotspots evolved in grasslands that were naturally low in nutrients.
Nomadic herders, who migrated south from the Sahara 2000 to 5000 years ago, sought green pastures for their livestock to graze and herded their cattle into oval-shaped corrals at night for their protection. The animals’ dung piled up and created the fertile soil, which in turn attracted a diversity of wildlife – and still does.
Wild herbivores including gazelle, wildebeest, zebra and warthogs forage in the hotspots, stimulating plant regrowth and nutrient turnover. Soil life thrives as the nutrients support worms, dung beetles and other insects. In turn, these provide sustenance for birds, geckos, reptiles and elephants.
Previous research has suggested that fire, termite mounds and volcanic sediments contribute to the richness of savannah soils. But this study confirms that livestock dung has played a pivotal role.
The ancient pastoral settlements had significantly higher levels of phosphorous, magnesium, calcium, nitrogen, carbon and phosphate than surrounding grasslands, arising directly from the dung and indirectly from the carcasses of grazing animals.
“Ecologists have shown that when present-day herders are mobile and live at relatively low densities, they have few long-term negative impacts on the environment and some significant positive ones,” Marshall says.
“Our findings provide a new perspective on how human herding activities have influenced, and sometimes enriched, the ecology of African grasslands.”
Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.
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