The total area burned by wildfires globally and the associated carbon dioxide emissions have decreased since the 1930s as population density and cropland area have increased, according to a study in Nature Communications this week. The study suggests that the reduction in fire emissions associated with population density increase has resulted in an increased uptake of carbon by land.
Vivek Arora and Joe Melton quantify the effects of increasing cropland area and population density on wildfires between 1850 and 2014, and the associated impact on carbon uptake by land. Using model simulations, which they compare to sediment charcoal records and satellite observations between 1997 and 2014, they find that reduced wildfire carbon dioxide emissions from expanding cropland areas do not enhance land carbon uptake. However, those that result from fire suppression and landscape fragmentation, associated with increasing population density, have enhanced uptake by 130 million tonnes of carbon per year between 1960 and 2009. This is equivalent to approximately 19% of the global land carbon uptake for that period.
The authors suggest that a global reduction in carbon dioxide emissions from wildfires is one of a number of mechanisms currently contributing to the uptake of carbon on land.