Sub-Sahara’s severe nature losses

Sub-Saharan Africa has already lost nearly a quarter of its biodiversity since pre-industrial times, according to a major new African-led study.

The research, published on Wednesday in Nature, found that on average, populations of plants and animals across the region have declined by 24%, with some species — especially large mammals — suffering far more severe losses.

Yet the analysis also delivers a crucial insight: more than 80% of the region’s remaining wild plants and animals persist outside formally protected areas, surviving instead in largely untransformed natural forests and rangelands, where people coexist with and depend on biodiversity. 

“Conserving and restoring biodiversity, while working towards just and sustainable development, requires a focus on these working lands that sustain more than 500 million people,” said the study, which represents the most comprehensive assessment to date of biodiversity intactness in sub-Saharan Africa.  

Its strength lies in an unprecedented collaborative approach: over five years, a team of 200 Africa-based experts – including researchers, field ecologists, rangers, tour guides and museum curators – pooled their ecological knowledge to build a continent-wide picture of biodiversity change.

“Many global biodiversity assessments do not represent African conditions well because they rely on sparse local measurements and draw insights from more data-rich regions of the world, where contexts are very different,” said the study’s lead author, Hayley Clements from Stellenbosch University’s Centre for Sustainability Transitions (CST). 

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

Filling a long-standing gap

The contributors independently estimated how human pressures – from croplands and livestock grazing to urbanisation – have affected species in different ecosystems, before refining these estimates through facilitated discussions. 

Their assessments underpin a new continent-wide Biodiversity Intactness Index (BII), which measures the percentage of original species abundances that remain compared with pre-industrial levels.

African countries often lack fine-scale biodiversity data for policy and planning, while global models frequently mischaracterise regional patterns. For the first time, governments and regional bodies have access to an indicator built on in-country ecological expertise.

The study shows striking variation across regions, ecosystems and species groups. Disturbance-tolerant plant species have declined by as little as 10% but large mammals — including elephants, lions and several antelope species — have lost more than 75% of their historical abundance. 

This is driven mainly by habitat loss to croplands, unsustainable harvesting and intensive grazing.

Central Africa retains some of the continent’s highest intactness levels thanks to the survival of humid forests. In contrast, West Africa shows some of the lowest, owing to widespread forest and savanna degradation linked to agricultural expansion and over-harvesting.

Rwanda and Nigeria have the lowest biodiversity intactness (<55%), while Namibia and Botswana rank highest (>85%). Losses are driven by cropland expansion in grasslands and fynbos, by non-agricultural degradation in forests, and by a combination of both in savannas.

Across the region, more than four-fifths of remaining wild species live in working landscapes that provide essential ecosystem services – clean water, pollination, grazing resources, wild foods, building materials and carbon storage – but are under increasing pressure.

This shifts where and how biodiversity conservation on the continent is approached. Despite being a major global conservation strategy, strictly protected areas sustain less than 10% of the remaining indigenous plants and animals of the region because of their limited extent.

“Protected areas are particularly important for large mammals, which are especially vulnerable to human impacts,” Clements said. “Megafauna have BII levels half those of other species groups and are largely absent outside protected areas.”

However, countries like Namibia and Botswana show that large-mammal conservation can be successfully integrated into broader land governance systems through models such as community conservancies and wildlife economies that empowering local people as the custodians of biodiversity, she said.

Alone, protected areas are insufficient, Clements pointed out. “Sustainable management of shared working landscapes is key to maintaining biodiversity and supporting livelihoods.”

Existing models – such as community-led wildlife conservancies, sustainable pastoralism and biodiversity-positive farming – already show how this balance can be achieved, she said.

Agriculture and the path forward

The analysis identified cropland expansion as the greatest threat to biodiversity across sub-Saharan Africa. 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.

Countries with the most cropland—Nigeria and Rwanda—also show the lowest biodiversity intactness. This contradicts global models that suggest these heavily farmed landscapes remain more than 90% intact, with “serious potential implications for national and regional policy”. 

“We found that biodiversity intactness of the high-yielding intensive croplands in this region—most of which lie in the grasslands—is notably less than its least-intensive, smallholder croplands that are more common in the savannas,” the study said.

These trends have stark implications given that cropland is projected to double and cereal demand to triple in sub-Saharan Africa by 2050, the authors said. 

They noted that this increase will likely entail significant changes to current agricultural practices in a region where 75% of the cropland comprises smallholder farming, which have some of the lowest crop yields in the world.

These findings underscore the need to limit the impacts of intensive commercial agriculture while strengthening biodiversity-friendly aspects of smallholder and agroecological farming systems promoted under global sustainability frameworks.

A new policy tool for African decision-makers

The assessment provides African governments with a long-needed evidence base for national biodiversity planning, land-use decisions and global reporting. Its expert-driven method could also be applied to other regions to capture local complexities that global assessments often miss, the authors said.

“This study showcases the depth of ecological expertise across Africa,” said Oonsie Biggs, the co-director of the CST and a co-author of the study. “By grounding biodiversity measurement in local expertise, we now have a more credible evidence base to support development strategies that sustain both nature and people.”

By combining local ecological knowledge with spatial data, the authors said their study provides a tool showing not only where biodiversity is at risk, but also where it is being sustained, offering practical guidance for policies that support both ecosystems and human well-being.