Tropical forests gradually store less carbon


Published on 5 March 2020

View of the Ivindo National Park (Gabon)
View of the Ivindo National Park (Gabon)
(© Kath Jefferey)

Tropical forests are gradually losing their capacity to store carbon. If no timely action is taken, they could even start emitting carbon by 2035. This is demonstrated by a large-scale study in which the AfricaMuseum played a leading role.

Tropical forests are a powerful weapon against climate disruption. They form a gigantic reservoir of 250 billion tons of carbon in the trees alone. Because of their growth, they continue to store more and more carbon.

But this capacity to store carbon seems to be coming to an end sooner than expected. This is shown by a study of 565 undisturbed tropical forests in the Congo and Amazon basin over 30 years by more than 100 academic institutions, including the AfricaMuseum.

In the 1990s, undisturbed tropical forests still stored 17% of the CO2 emitted by man. In the 2000s this was still 9%, in the 2010s 6%.

In the 1990s, undisturbed tropical forests removed approximately 46 billion tons of CO2 from the atmosphere, compared to an estimated 25 billion tons in the 2010s. The difference - 21 billion tons - corresponds to a decade of fossil fuel emissions from the United Kingdom, Germany, France and Canada combined.

The main cause of carbon loss lies in dying trees, scientists believe. ‘Normally CO2 stimulates the growth of trees, but because of the climate disruption - higher temperatures, drought,... - growth slows down and some trees may even die’, Wannes Hubau explains, affiliated with the AfricaMuseum and lead author of the publication in the prominent journal Nature that presents the research.

If no urgent action is taken against the climate disruption, the decline will continue until tropical forests will emit net carbon from 2035 onwards.

These insights are extremely important for policymakers. They mean that the calculations for carbon sequestration in forests need to be revised and the emission targets adjusted. After all, the current targets assume that tropical forests can serve as a "carbon sink" for decades to come.

‘This study provides the first large-scale evidence that carbon sequestration by the world's tropical forests is already showing an alarming downward trend today’, Hubau says. ‘This is decades earlier than even the most pessimistic climate models predict. So there is no time to lose in tackling climate change.’

The researchers also point out that it is crucial that the tropical forests continue to be closely monitored. This requires not only funding for new studies, but also support for local scientists, who live closer to the forests and are thus able to monitor developments more easily.

To determine how much carbon a tree absorbs, its diameter and height are measured regularly
To determine how much carbon a tree absorbs, its diameter and height are measured regularly (Salongo National Park, DR Congo) (@ Simon Lewis - University of Leeds)

Laboratory in Yangambi

A good example of such a forest research center is located in the Yangambi biosphere reserve in the DR Congo. A wood biology laboratory was established there by the AfricaMuseum, with the support of the European Union. The laboratory now has the necessary equipment to study wood anatomy and wood rings ("dendrochronology"). This makes it possible to better understand how forests contribute to slowing down and adapting to climate disruption.

‘In the past, Congolese scientists had to come to Europe to analyze wood samples, which was very cumbersome. Now they can do it on the spot, right next to the forest', Hans Beeckman says, wood biologist at the AfricaMuseum. ‘A laboratory in the middle of the Congo basin will make studies cheaper, easier and more inclusive.’

The AfricaMuseum also measures carbon uptake in the forests of Yangambi and the nearby Yoko forest reserve. There will even be a research tower that will reach above the canopy. The tower will continuously measure the exchange of greenhouse gases between the atmosphere and the forest.

Chris Simoens

The AfricaMuseum is an important partner of the Belgian Development Cooperation.