Until now, research assumed that the vast forest area of the Congo Basin, like other tropical forests, releases large amounts of nitrous oxide and binds methane. Researchers have now shown that it behaves differently: methane is released, while nitrous oxide emissions are smaller than thought.

Other tropical forests are known to be a major source of nitrous oxide and a sink for methane. But because comparable data are lacking for the Congo, the study of how these greenhouse gases behave there has so far been limited to modelling . The data used for the models comes from the Amazon, Indonesia and the tropical part of Australia; thus scientists assumed until today that the Congo Basin behaved similarly to these other tropical forests.

Now, an international research team led by ETH Professor Johan Six has partly filled this blank spot. In an elaborate and difficult measurement campaign lasting several years, the scientists determined how much methane and nitrous oxide the tropical forest of the Congo Basin absorbs or releases. Their study — one of the first available on the subject for that part of the world — has just been published in the journal Nature Communications.

Between 2016 and 2020, the researchers measured gas fluxes at multiple sites in three different forest types in the Congo Basin. The forest types studied include montane forest, lowland tropical forest and periodically flooded swamp forest.

Divergent gas fluxes

This shows for the first time that the gas fluxes of the tropical forests of the Congo Basin differ from those of other tropical regions of the world. For example, nitrous oxide emissions from the forest are comparatively low. «This was unexpected,» says Matti Barthel, a research associate with Six and the study’s lead author. «Our measurements from both the first short measurement campaigns and subsequent long-term studies didn’t confirm the model assumptions,» he says.

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Materials provided by ETH Zurich. Original written by Peter Ruegg. Note: Content may be edited for style and length.