Wildfires continue to emit carbon dioxide long after they have burned out

A recent study found that forests destroyed by wildfires continue to emit carbon dioxide (CO₂) for years after the flames are extinguished. The boreal forest, a major CO₂ sink that stretches across the Earth’s northern latitudes, plays a crucial role in removing carbon from the atmosphere. However, when these forests burn, they release large amounts of CO₂, exacerbating climate change.

Impact of forest fires on boreal forests

The researchconducted in central Sweden after the extreme wildfires of 2018, revealed that burned areas continue to emit CO₂ long after the fires have been extinguished. This continued emission is significant, as it doubles the amount of CO₂ released during the fire itself. Scientists measured the CO₂ exchange between the land and the atmosphere over four years, comparing burned and unburned areas, as well as areas subjected to different post-fire management strategies.

Emissions and post-fire recovery

In the study, areas where trees were killed by fire or removed through salvage logging released an average of 650 grams of carbon per square meter in the first four years. By comparison, an unburned forest of similar size would typically remove 1,200 grams of carbon from the atmosphere over the same period. The findings suggest that it could take more than 40 years for the burned forest to reabsorb the CO₂ lost in the fire.

Role of post-fire management

The study also highlighted the importance of post-fire management in forest recovery. Practices such as salvage logging and ground ploughing, which are common in Sweden, were found to slow down vegetation regrowth. This slowing down hinders the forest’s ability to become a carbon sink again. Conversely, if you leave surviving trees standing, they can continue to sequester carbon, albeit at a slower rate.

Implications for climate modelling

This study highlights the need to reconsider forest management practices as forest fires become more frequent due to climate change. It also calls for climate modelers to include long-term CO₂ emissions from burned forests when assessing the environmental impact of forest fires.