Sub-Saharan Africa has lost nearly a quarter of its biodiversity

The study, published in Nature, provides the most comprehensive assessment of biodiversity intactness yet produced for sub-Saharan Africa. A unique feature of the project is that it brings together a wide range of ecological knowledge from 200 experts in Africa’s diverse plants and animals, including researchers, field ecologists, rangers, tour guides, and museum curators working in the region’s changing landscapes. This enormous undertaking took over five years to complete.

Bottom-up method

By working directly with the people who study and manage African ecosystems, the researchers were able to capture a much more realistic picture of where biodiversity is declining, where it is being sustained, and why.

“This assessment addresses a major gap for African countries, which often lack the biodiversity information needed to inform policy, reporting and land-use planning. We now have a more credible evidence base to support development strategies that sustain both nature and people,” says Prof Oonsie Biggs, researcher at the Centre and co-author on the study.

Large variations across ecosystems and countries

The result is a continent-wide map of the Biodiversity Intactness Index (BII), which measures the percentage of original abundances of all species that remain in an area relative to pre-industrial levels.

The study found large variations across ecosystems, countries and species groups. While plants that can withstand environmental disturbances have experienced declines as small as 10%, large mammals such as elephants, lions and some antelope species have lost more than 75% of their historical abundance. These declines are primarily due to habitat loss for croplands, and unsustainable levels of harvesting and livestock grazing.

Central African countries retain some of the highest levels of intactness due to the persistence of humid forests, while West Africa shows low intactness due to severe degradation of forests and savannas from overharvesting and agricultural expansion.

Protected areas are important but not enough

Crucially, over 80% of remaining wild populations of plants and animals occur in working lands – forest and rangelands where people coexist with nature. These landscapes support more than 500 million people and underpin crucial ecosystem services such as clean water, pollination, building materials, grazing resources, wild foods and carbon storage.

“This fundamentally shifts where and how we think about biodiversity conservation in Africa. Protected areas remain vital, especially for Africa’s large mammals, but alone they are insufficient to curb biodiversity loss. Sustainable management of shared working landscapes is key to maintaining biodiversity and supporting livelihoods,” says lead author Dr Hayley Clements, from the Centre for Sustainability Transitions at Stellenbosch University.

Agriculture and rangelands are key

The assessment found that cropland expansion is one of the greatest pressures on biodiversity, with the lowest intactness recorded in Nigeria and Rwanda, the two countries with the highest cropland coverage. Intensive, high-yield agriculture reduces habitat diversity and increases chemical inputs, with significant impacts on a wide range of species. In contrast, traditional smallholder systems tend to maintain more ecological complexity and support higher levels of biodiversity.

With cropland projected to double and cereal demand expected to triple by 2050, the authors argue that biodiversity-positive farming practices will be critical to reconciling food security and ecosystem health.

Rangelands – grassy systems where wildlife and livestock graze – are also key, both in harbouring biodiversity and driving losses when intensively managed. The study shows that lower-intensity pastoralism supports higher biodiversity than intensive livestock farming, although increasing restrictions on herd mobility are threatening this balance.