Shepherds in the African Savannah have been herding their flocks in the same places for more than 3,000 years, contributing to the enrichment of the land and the creation of green and rich surfaces in high nutrient grass, according to a new study published in the prestigious journal NATURE by an international team, including Prof. Ruth Shahak-Gross of the Department of Marine Civilizations at the University of Haifa (Ancient herders enriched and restructured African grasslands).
“This is a dramatic paradigm shift,” said Prof. Shahak-Gross. “To date, the perception has been that shepherds’ activities in the Savannah have been negative and damaging to the ecosystem, and here we find that it is precisely this human activity, which has been going on for thousands of years, that contributed to creating ‘green islands’ that enrich and diversify the ecosystem.”
Grasslands are one of the world’s most extensive terrestrial biomes and are central to the survival of herders, their livestock and diverse communities of large wild mammals. In Africa, tropical soils are predominantly nutrient-limited, but productive grassy patches in wooded grassland Savannah ecosystems grow on fertile soils created by geologic and edaphic (soil induced) factors, megafauna, fire and termites.
The biome concept organizes large-scale ecological variation. Terrestrial biomes are distinguished primarily by their predominant vegetation, and are mainly determined by temperature and rainfall.
Mobile pastoralists (Pastoralism is the branch of agriculture concerned with the raising of livestock) also create soil-fertility hotspots by penning their herds at night, which concentrates excrement—and thus nutrients—from grazing of the surrounding Savannah.
Historical anthropogenic hotspots produce high-quality forage, attract wildlife and increase spatial heterogeneity in the African Savannah. Archaeological research suggests this effect extends back at least 1,000 years—possibly as long as 3,000—but little is known about nutrient persistence at millennial scales.
The researchers used chemical, isotopic and sedimentary analyses to show high nutrient and 15N enrichment in on-site degraded dung deposits relative to off-site soils at five Pastoral Neolithic sites (radiocarbon dated to between 3,700 and 1,550 calibrated years before present (cal. bp)).
The study demonstrates the longevity of nutrient hotspots and the long-term legacy of ancient herders, whose settlements enriched and diversified African Savannah landscapes over three millennia.