Warmer soils can’t store as much carbon

All eyes are on soil carbon at the moment, and its potential to store some of the atmosphere’s carbon dioxide through agricultural management. But experts have cautioned that climate change will affect soil carbon storage capacity – with changing rainfall patterns and other effects interfering with soils.

Now, research by UK and Swedish scientists has confirmed that globally, the heating earth itself will cause soils to release carbon dioxide.

The researchers analysed data from 9,300 soil samples around the world, finding that increasing temperatures cause soil carbon storage potential to “decrease strongly”. Their analysis is published in Nature Communications.

“Because there is more carbon stored in soils than there is in the atmosphere and all the trees on the planet combined, releasing even a small percentage could have a significant impact on our climate,” says co-author Professor Iain Hartley, a researcher from the college of life and environmental sciences at the University of Exeter, UK.

The researchers used soil samples from the World Soil Information database, examining the top 50 centimetres of soil.

They found that soil storage capacity decreased by 25% for every 10°C of warming.

“Even bleak forecasts do not anticipate this level of warming, but we used this scale to give us confidence that the effects we observed were caused by temperature rather than other variables,” says Hartley.

They also found that the amount of carbon that could be released varied depending on soil type. Clay-rich, or fine textured soils, could keep three times more carbon than coarse-textured soils.

“Our analysis identified the carbon stores in coarse-textured soils at high-latitudes (far from the equator) as likely to be the most vulnerable to climate change,” says Hartley.

“Such stores, therefore, may require particular attention given the high rates of warming taking place in cooler regions.

“In contrast, we found carbon stores in fine-textured soils in tropical areas to be less vulnerable to climate warming.”

The researchers hope to use these results to further refine modelling and projections on greenhouse gas emissions.

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