Africa now emits more carbon than it stores

As the population grows, more land is used for agriculture to produce food, and fossil fuel use increases, the trend will continue

Africa is no longer the carbon dioxide sink of the world and is now emitting as much of the chemical compound as it stores, according to a new study.

The research, led by the Future Ecosystems for Africa Programme at the University of the Witwatersrand (Wits University) found that from 2010 to 2019, the continent moved from being a net carbon sink to a net source. In other words Africa is releasing more carbon dioxide into the atmosphere than it absorbs.

Overall, it is estimated that Africa is a source of 4.5 petagrams — 4.5 billion tonnes — of carbon dioxide equivalents a year. This is a measure used to compare the emissions from various greenhouse gases based on their global warming potential.

The researchers in their paper, titled The African Regional Greenhouse Gases Budget (2010– 2019), pointed out that until now, the continent has been producing about 4% of the human-caused greenhouse gases that lead to climate change, and it has also been offering climate services to the world.

This is largely through the intact ecosystems in the tropics, which have been sequestering more greenhouse gases than were released through human-caused activities. Carbon sequestration is the process of capturing and storing atmospheric CO2.

And although Africa still serves this purpose, in the past decade the rate at which carbon dioxide is being released from the continent has increased.

“In terms of global numbers, this means Africa still hovers around 4% of fossil fuel emissions, but actually emits nearly 40% of the global emissions from land use, and is now contributing 3% to 5% of the growing amount of greenhouse gases in the atmosphere,” said Sally Archibald, principal investigator at the Future Ecosystems for Africa programme and a professor in the school of animal, plant and environmental sciences at Wits University.

Africa’s population sits at about 1.4billion people, but is set to exceed two billion by 2040 and the trend is likely to continue, noted Yolandi Ernst, a researcher at the Wits Global Change Institute and the study’s lead author.

“If we don’t change our ways, we are just going to release more and more carbon because the population is growing and climate change is exacerbating all the problems. We have increasing people, increasing food requirements and then you have climate change making all that worse,” Ernst said.

Key factors causing the rise of greenhouse gases on the continent include fossil fuel burning, methane emissions from livestock, soil carbon losses and nitrous oxide emissions as land is converted for agricultural use, according to the researchers.

“Anywhere where you lift up the soil — so when you plough your lands, even if it has had croplands and you plough it again — every time, you release the soil carbon. Basically whenever you disturb the soil, then you are going to take out the stored carbon,” said Ernst.

She added that nitrous oxide is one of the three major greenhouse gases (after carbon dioxide and methane) and the emissions were, for example, from fertilisers used for farming.

Although natural ecosystems continue to act as carbon sinks across the region and are taking up about 30% of what is being emitted to the atmosphere through human activities, Ernst said that greater swaths of land than ever before are being used for agriculture, and livestock numbers are increasing, with the “net result being that these changes in land use have affected Africa’s role in the global carbon cycle”.

To make their estimates, the authors followed the budget assessment protocol laid out by the Global Carbon Project’s Regional Carbon Cycle Assessment and Processes.

They took a comprehensive look at all major potential carbon sources, including human sources such as agriculture and fossil fuel emissions as well as natural sources such as termites and wildfires.

They also considered natural sinks — grasslands, savannas and forests — that still cover much of the continent.

“Our grasslands and savannas are really important to store carbon,” Ernst said. “I think afforestation plans — these huge tree-planting initiatives — have to be careful not to disturb the natural ecosystems because what we need to protect is the processes that make the system work.”

“If you just start randomly planting trees in a grassland, you are not necessarily going to get the benefit you would want. I’m not saying all of it is bad, but they have to think it through.”

The researchers noted that land use emissions are higher than fossil fuel emissions. But both are growing rapidly, they said.

Over the past year, the total emissions resulting from human activity, including trade, livestock and fuel burning, were estimated at 1.2 petagrams of carbon dioxide. Moderate climate conditions and high productivity of the tropical forests helped natural ecosystems to take up about 0.6 petagrams of carbon dioxide a year, leaving about 0.6 petagrams of CO2 as the net flux released into the atmosphere.

Their research on Africa’s carbon budget is key to identifying which aspects of the greenhouse gas cycle are most important to be managed in the quest to achieve net zero, and possibly restore the continent’s role as the world’s carbon sink.

According to Ernst, investing in carbon-neutral energy sources could reduce about 30% of Africa’s humancaused emissions, but novel ways to manage landscapes for livelihoods and carbon storage would be needed to slow the emissions from agriculture and land use.

“As demand for food production increases, we need a focus on climate-smart agricultural practices on the continent, as well as investments that address socio-economic challenges in nature-preserving ways across Africa,” Ernst said.

Protecting, managing and restoring the landscapes helping to take up the excess carbon dioxide is an important part of the solution, “but there are challenges with making carbon storage the main goal of conservation and it can conflict with biodiversity and water provision”, she said.

Ernst added that the Future Ecosystems for Africa Programme is working with scientists, policymakers and carbon projects across the continent.

“It’s a consortium with scientists, policymakers and land owners so we get the information from the people that live on the land and not just from a science point of view,” she explained.

Getting their input ensures that the programme is linked with the “right science”, Ernst added.

‘Afforestation plans – these huge treeplanting initiatives – have to be careful not to disturb the natural ecosystems’