Study: Forests degraded by humans, emitting CO2, not acting as carbon sink anymore

Tropical forests are so badly degraded they have become a source rather than a sink of carbon emissions, according to a new study that highlights the urgent need to protect and restore the Amazon and similar regions.

Researchers found that forest areas in South America, Africa and Asia – which have until recently played a key role in absorbing greenhouse gases – are now releasing 425 teragrams of carbon annually, which is more than the emissions from all the vehicular traffic in the United States.

The study went further than any of its predecessors in measuring the impact of disturbance and degradation, the thinning of tree density and the culling of biodiversity below an apparently protected canopy – usually as a result of selective logging, fire and drought.

This can reduce biomass by up to 75%. But it is more difficult for satellites to monitor than deforestation (the total clearance of foliage) because, when viewed from above, the canopy appears undisturbed despite the depletion underneath.