Tropical rainforests store enormous amounts of carbon, the protection of which represents a vital component of efforts to mitigate global climate change. Currently, tropical forest conservation, science, policies, and climate mitigation actions focus predominantly on reducing carbon emissions from deforestation. This study shows that selective logging, forest fires and other factors lead to carbon loss equivalent to as much as 40% of that from deforestation in the Amazon.

Every year vast areas of the humid tropics are disturbed by selective logging, understorey fires, and habitat fragmentation. There is an urgent need to understand the effect of such disturbances on carbon stocks, and how stocks in disturbed forests compare to those found in undisturbed primary forests and regenerating secondary forests.

This article presents the findings of the largest field study to date on the impacts of human disturbances on carbon stocks above and below ground in tropical forests. The researchers find that live vegetation, the largest carbon pool, is extremely sensitive to disturbance: studied forest areas that experienced both selective logging and understorey fires stored, on average, 40% less above-ground carbon than undisturbed forests and were structurally similar to secondary forests. Edge effects also played an important role in explaining variability in above-ground carbon stocks in disturbed forests.

By comparing their findings with Brazilian government assessments of the total forest area annually disturbed in the Amazon, the researchers estimate that emissions from the loss of carbon due to forest degradation could represent up to 40% of the carbon loss from deforestation in the region.

The study helps to fill a gap in knowledge about the combined effects of multiple forms of disturbance on different carbon pools, and thus to identify management priorities for avoiding further losses and restoring already degraded forests. It concludes that conservation programmes aiming to ensure the long-term permanence of forest carbon stocks, such as REDD+, will remain limited in their success unless they effectively address degradation as well as deforestation.

Read the article (external link to journal)