Wild fires turn millions of hectares of vegetation into charcoal each year. An international team of researchers has now shown that this charcoal does not remain in the soil, as previously thought. Instead, it is transported to the sea by rivers and thus enters the carbon cycle. The researchers analyzed water samples from all over the world. They demonstrated that soluble charcoal accounts for ten percent of the total amount of dissolved organic carbon.

Earlier it was thought charcoal was resistant. They thought, once it is incorporated into the soils, it would stay there. But if that were the case, the soils would be black. Most of the charcoal in nature is from wild fires and combustion of biomass in general. When charcoal forms, it is typically deposited in the soil. From a chemical perspective, no one really thought it dissolves, but it does. It doesn't accumulate like we had for a long time believed. Rather, it is transported into wetlands and rivers, eventually making its way to the oceans.

The international team, which also included researchers from Skidaway Institute of Oceanography in Georgia, Woods Hole Research Center in Massachusetts, the USDA Forest Service, and the University of Helsinki in Finland, had taken 174 water samples from all over the world, including rivers like the Amazon, the Congo, the Yangtze as well as Arctic sites.

Surprisingly, in any river across the world about ten percent of organic carbon that is dissolved in the water came from charcoal. According to these estimates, about 25 million tons of dissolved charcoal is transported from land to the sea each year.