Africa’s forests are now emitting more CO2 than they absorb

African forests now emit more carbon dioxide than they absorb, a fundamental shift that will make it harder for the world to reduce its net emissions to zero.

The continent's forests and bushland were previously among the world's largest carbon sinks, accounting for 20 percent of all CO2 absorbed by plants. The lion's share of this comes from the Congo rainforest, the second largest in the world after the Amazon. Sometimes called the “lungs of Africa”, it absorbs about 600 million tons of CO2 per year. However, this number is declining as tropical forests are destroyed by logging and mining.

Now, researchers have found that after accumulating biomass from 2007 to 2010, African forests lost 106 million tons of biomass per year from 2011 to 2017. This is equivalent to approximately 200 million tons of CO2 emissions per year. The reason for this was the deforestation of the tropical forests of the Congo, says Heiko Balzter at the University of Leicester, UK.

“If we lose tropical forests as a means of mitigating climate change, then we will essentially have to reduce greenhouse gas emissions from burning fossil fuels even faster to achieve near-zero emissions,” he says.

Balzter and his colleagues estimated the amount of biomass using satellite measurements of the color and moisture of the forest canopy, as well as its height at certain points. They compared this with measurements taken on the ground, although there are few in Africa.

But Simon Lewis University College London says satellite data cannot identify the type of trees in a forest and is not reliable for estimating the carbon sequestered by intact, high-biomass forests or released by forests degraded by selective logging. Dense hardwood such as mahogany can contain more carbon than, for example, lightweight balsa wood of the same size.

“Deforestation in the Democratic Republic of Congo… is higher than in the 2000s. And we all know it,” he says. “But whether this will be enough to change the entire carbon budget of the entire continent is unknown.”

The study also did not include the wet peatlands found beneath much of Congo's rainforest, which absorb small amounts of CO2 each year and contain about 30 billion tons of ancient carbon.

The Amazon rainforest, which was also once a major carbon sink, emitted more CO2 than it absorbed in the last few years. But while deforestation in the Amazon has become the target of a government crackdown, it grows in Congo.

In the Democratic Republic of Congo, impoverished farmers often destroy rainforests for slash-and-burn agriculture. Companies, many of them foreign-owned, illegally harvest colorful hardwoods such as African teak and coral.

On COP30 Climate Summit in the Amazon this month, Brazil announced Object “Rainforests Forever”a fund that would pay its investment earnings to tropical countries at a rate of $4 per hectare of remaining forest. But countries have so far donated only $6.6 billion to the fund, falling short of the $25 billion goal.

Balzter says the mechanism could be more effective than carbon credits, which reward “avoided” emissions and have proven useless in many cases.

“It's really important to get this Rainforest Forever project working, and get it working fast enough to try to reverse this trend where the biomass of African trees is actually releasing carbon into the atmosphere,” he says.