🌍 Small disturbances in tropical forests weigh heavily on the climate

A study published in Nature reveals that small areas of deforestation, often less than 5 acres (about 2 hectares), in humid tropical forests are responsible for more than half of carbon losses over the past 30 years.

Africa and Southeast Asia are particularly vulnerable. Conducted by an international team led by the Climate and Environmental Sciences Laboratory (CEA/CNRS/UVSQ), this research highlights the disproportionate impact of small-scale human activities on forest carbon loss, underscoring the need for protection and anti-deforestation policies at all levels to safeguard these vital ecosystems.


Tropical forests have very high carbon stocks in their biomass and play an essential role in combating climate change. They store nearly half of the Earth's forest carbon but are severely threatened by human activities.

A recent study by an international team of researchers, incorporating high-resolution satellite data, shows that small disturbances (less than 5 acres, about 2 hectares, the equivalent of 2 soccer fields) represent only 5% of deforested areas but are responsible for 56% of net carbon losses. These losses are mainly due to the persistent conversion of forests to cropland, pasture, roads, or urban areas.

"Our study reveals that small forest disturbances, and not only the large deforestations or fires typically seen in the Amazon, are the source of the majority of tropical carbon losses. Protecting young regenerating forests is as essential as preventing deforestation," explains Yidi Xu, postdoctoral researcher at LSCE and lead author of the study.

The results highlight three priorities for climate protection:
- Reduce agricultural expansion and forest degradation, particularly in Africa and Southeast Asia, where these disturbances account for more than 97% of net carbon losses.
- Protect young regenerating forests, which play a key role in absorbing CO₂ and mitigating climate change.
- Strengthen surveillance of the most vulnerable forest areas, where carbon-rich forests are increasingly exposed.

"Our method can help countries better track their emissions and strengthen conservation programs. By identifying where carbon is lost and where forests are regrowing, we provide a powerful tool to protect one of the planet's main climate regulators," explains Philippe Ciais, research director at CEA and co-author of the study.

The study uses a spatially explicit biomass carbon accounting method with a 100-foot (30-meter) resolution, combining satellite data and biomass recovery curves. Unlike previous models that relied on simplified assumptions or continental averages, this approach, thanks to new high-resolution biomass maps provided by the European Space Agency, allows for a better understanding of the magnitude of different types of disturbances (fires, degradation, regeneration) on the carbon balance of tropical forests.

Some key figures:
- 15.6 ± 3.7 billion metric tons of carbon lost in humid tropical forests since 1990, while dry tropical forests have remained globally carbon neutral.
- Small clearings (less than 5 acres/about 2 hectares) represent only 5% of the disturbed forest area but are responsible for 56% of net carbon losses.
- Carbon losses due to fires in many dry tropical forest regions are partially offset by long-term regeneration after fires, unlike the persistent effects of small-scale deforestation and non-fire-related degradation.

This work was conducted as part of the One Forest Vision scientific initiative funded by the French Ministry of Higher Education and Research and the Ministry for Europe and Foreign Affairs.