Swansea / Freiburg (dpa) - The climate balance of wildfires as in Siberia is apparently not as devastating as previously thought. More than ten percent of the carbon released from such fires, according to a study, does not escape into the atmosphere as CO2 but is bound in the long term as charcoal in the soil.

In the long term, this effect could sometimes even remove carbon dioxide from the atmosphere. Because over time, the growing vegetation through photosynthesis again take up as much carbon from the atmosphere as was previously bound in the form of plant matter. However, this is only the case when the entire vegetation has regrown, emphasize the researchers in the journal Nature Geoscience. In extreme cases, this could take centuries.

Recently, large forest fires have caused a sensation in, for example, Siberia and Alaska - also because of the resulting carbon dioxide (CO2), which promotes climate change. The researchers around Matthew Jones from Swansea University in Wales now calculated how much so-called fumed carbon remains after such fires on the ground. In the period from 1997 to 2016, 12 percent of the carbon released by the world's fires remained bound in charcoal. These carbon remain stored in soils or water sediments for hundreds to thousands of years, they stress.

During regrowth, the vegetation deprives the atmosphere of carbon again. However, depending on the landscape, regrowth varies in length, the researchers write: Grasslands, for example, take less than a year, some forests decades. In extreme cases, such as in tropical moorland or in the Arctic, a complete recovery may be expected only after centuries. "The restoration of plant life is important because carbon, which is not captured again, remains in the atmosphere and thus contributes to climate change," emphasize the authors.

Nevertheless, the pyrogenic carbon would thus be a significant, so far overlooked CO2 sink in the long term. Scientists call for this to be included in calculation models for fire emissions. First author Jones speaks of "good news", "although rising CO2 emissions from human activities such as deforestation and the burning down of some moorlands continue to seriously threaten the global climate."

In general, the CO2 emissions caused by wildfires are enormous: every year, an area the size of India burns in the world, write the researchers. These fires therefore emit more CO2 than car, rail, air and sea traffic together.

Johann Georg Goldammer, fire ecologist and director of the UN-coordinated Global Fire Monitoring Center in Freiburg, considers the researchers' calculations plausible. The big difference to the burning of fossil fuels by humans lies in the fact that the nature of the atmosphere withdraws the CO2 later.

In the Arctic and Siberia, large-scale fires had raged recently. Even though fires in the far north would occur again and again in the summer, the number is many times higher than in previous years, the EU-funded Copernicus Atmosphere Monitoring Service said. Among other things, the experts are responsible for climate change.

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