The amount of carbon dioxide released from Australian soils may be lower than previously predicted, according to a study online in Nature Geoscience. Carbon dioxide emissions from soil are an order of magnitude greater than all human-made carbon dioxide emissions put together. As global warming continues, increasing temperatures look set to increase the decomposition of soil carbon, releasing more and more carbon dioxide and making matters worse.

Australian researchers have analysed soil samples stored in archives from hundreds of sites across Australia and according to their analyses, charcoal (or black carbon), which forms in wildfires, makes up a significant proportion of the total soil carbon. By including realistic stocks of charcoal in their climate prediction models, the amount of carbon dioxide predicted to be released from two Australian savannah regions under a 3ºC warming scenario was 18.3% and 24.4% lower than previously calculated.

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Dr Evelyn Krull leads the Aquatic Biogeochemistry and Ecology research group at CSIRO Land and Water. She is one of the study’s authors.

“Our research from a large dataset of Australian soils has shown that charcoal makes up a significant portion of the soil organic carbon pool. Charcoal is highly stable and resides in the soil over much longer (decades to centuries, up to millennia) time periods compared with other soil carbon fractions. Current climate models do not take into account the proportion as well as the variability of charcoal in soils globally. Thus, their calculated response of CO2 release from soils is likely to be an over-estimate as it does not incorporate the charcoal. pool. Our research in other parts of the world has shown that charcoal is ubiquitous in soils and it is critical to adequately account for this proportion so that models that include the carbon cycle climate feedback can achieve reliable results.”