Africa's ecosystems now run on less than two-thirds of their historical energy, with the decline of elephants, lions, and rhinos reshaping landscapes and livelihoods
Africa’s ecosystems are running on less than two-thirds of the natural energy they once had – a dramatic decline that threatens the vitality of the continent’s landscapes and the livelihoods they sustain.
This is according to the findings of a new study, led by Oxford University, which links changes in biodiversity directly to the functioning and stability of Earth’s life-support systems.
The research, published in Nature on Wednesday, draws on the Biodiversity Intactness Index for Africa, developed by Hayley Clements, a senior researcher at the Centre for Sustainability Transitions at Stellenbosch University and co-author on the paper.
She convened 200 African biodiversity experts to estimate ecological change across the continent, creating the foundation for the study’s analysis. By mapping how energy flows through African wildlife food webs, the analysis found that total ecological energy has fallen by more than one-third since precolonial times.
These steep losses are largely because of the decline of large-bodied species such as elephants, rhinos and lions – animals that once shaped and sustained entire ecosystems.
The most important and alarming result is the collapse of ecosystem functions performed by Africa’s megafauna, said Ty Loft, the study’s lead author and a researcher at Oxford’s Environmental Change Institute, in a statement.
“Large wild animals are ecological engineers,” he said. “Their roles can’t simply be replaced by smaller species or livestock. The loss of these giants has the potential to transform Africa’s ecosystems and landscapes.”
Using an “ecosystem energetics” approach, the team quantified how energy moves through food webs, from sunlight captured by plants to the animals that consume them.
Drawing on data from more than 3 000 bird and mammal species across 317 000 African landscapes, they combined six major ecological datasets, including the newly-built Biodiversity Intactness Index for Africa.
This energy-based lens provides a vivid picture of not just how much biodiversity has been lost, but how those losses affect the very functioning of nature. While large mammals have suffered the greatest declines, smaller animals such as rodents and songbirds now dominate Africa’s remaining energy flow.
Africa’s ecosystems, the researchers report, are increasingly powered by these smaller species. Small birds and mammals – those weighing under 3kg – now account for nearly 80% of all the energy consumed in African ecosystems, up from about 70% in the past. In contrast, the share of energy consumed by large animals heavier than 65kg has dropped from 16% to just 7%.
Even though small creatures make up far less of total biomass, they use disproportionately more energy: rodents historically made up 17% of biomass but consumed 31% of energy, and today account for 24% of biomass and 36% of energy use. Passerine birds — small perching birds such as songbirds — continue to use about 8% of energy despite representing only 2% of biomass.
This shift means smaller animals now play a growing role in controlling how nutrients, water and materials move through ecosystems. Yet they cannot replace the unique functions once performed by large animals, such as spreading seeds over long distances or reshaping vegetation through their feeding and movement.
Historically, elephants were by far the biggest drivers of ecological energy in Africa. They once made up about 16% of total bird and mammal biomass and 10% of total energy flow — more than any other species.
Their feeding, movement and dung dispersal helped shape entire landscapes and even influenced how much carbon ecosystems could store. Today, elephants remain vital but much diminished.
The analysis found that underground-dwelling rodents, particularly mole rats, may consume an unexpectedly large share of ecosystem energy due to their abundance and high food intake relative to their size. However, their true impact on soil and vegetation remains poorly understood and is a “ripe subject” for further research.
Energy flow is the “shimmering web” that holds together an ecosystem, said Yadvinder Malhi, co-author of the study, who is also from Oxford’s Environmental Change Institute.
“By mapping how this web weakens or strengthens as animals decline or recover, we can see how life itself is reorganising across the continent. This approach turns the concept of biodiversity loss into something physically meaningful.”
Across Africa, ambitious restoration programmes are already underway to bring wildlife back and repair degraded landscapes.
Yet until now, ecologists have struggled to predict how shifts in animal communities — such as the replacement of elephants and buffalo by smaller antelope in Mozambique’s Gorongosa National Park — affect ecosystem processes, such as vegetation growth and water cycling.
“Restoration isn’t just about bringing animals back, it’s about bringing back what they do,” Loft added.
“An energetics approach gives practitioners a way to measure that and to prioritise the functions that make ecosystems resilient.”
The authors highlight the next steps for research: expanding these energy-based assessments to the global level, incorporating domesticated and invertebrate species and linking animal energy data with vegetation models to understand how ecosystems respond to change.
Clements noted that it’s not all doom and gloom, because beyond diagnosing decline, the study offers a way forward. “Our approach can help governments, conservationists and companies meet the growing demand for metrics that track not only species numbers but also ecosystem functionality – a true measure of recovery.”
The study is timely because it comes as world leaders prepare for the COP30 climate summit in Brazil next month, where climate and nature will be in focus, she said.
“Our novel ecosystem energetics approach could help refine global biodiversity targets by linking biodiversity losses or gains more clearly to the functioning and stability of the planetary system on which humanity depends.”
The loss of animal energy flow is not just an ecological story, “it’s a Planet Earth story,” Malhi noted.
“It connects the fate of individual species to the functioning and stability of the biosphere itself.”