Study shows how soils could become source of CO2

A classic "Vierkant" farmhouse in the Mühlviertel.
When do agricultural lands become net sources of carbon, rather than carbon sinks? @bberwyn photo.

More conversion to forests and grasslands needed …

Staff Report

Aggressive land disturbance could turn Earth’s soils into sources of CO2 by the end of the century, researchers warned in a new study combining models of soil carbon and land use change with climate change predictions, using France as a case study.

Currently, soil is considered to be a net carbon sink, partially counteracting the impacts of CO2 emissions from fossil fuel combustion, but study projects that up to 25 percent of the carbon in found in soil in France could be lost to the atmosphere during the next 100 years.

Business-as-usual land use change has limited capacity to counteract this trend, experts from the University of Exeter, INRA and CERFACS in France and University of Leuven in Belgium say in the journal Scientific Reports. If soils lose a significant amount of carbon it will endanger their ability to produce food and store water, potentially leading to increased soil erosion and flood damage.

The study showed that land under almost all uses will be subject to dramatic losses of soil carbon by 2100. Only conversions of land into grass or forest result in limited additional storage of carbon in soils. Unfortunately these land changes are not likely to happen on a large scale because of the pressures on land resources imposed by urban expansion and food production.

“A reduction in anthropogenic CO2 levels is crucial to prevent further loss of carbon from our soils,” said lead author Dr Jeroen Meersmans, from the University of Exeter. “However, promotion of land use changes and management that contribute to soil carbon sequestration remains essential in an integrated strategy to protect soil functions and mitigate climate change.”

“Purposive, targeted land use and agricultural practice changes would be needed if climate change mitigation is to be maximized. Therefore, the efforts to enhance carbon sequestration in soils, as proposed by France during the COP21, should be promoted immediately,” said co-author Dr Dominique Arrouays of the French National Institute for Agricultural Research said.

The research collaboration involved academics from the Geography Department at the College of Life and Environmental Sciences at the University of Exeter (UK), the InfoSol Unit at INRA in Orleans (France), CECI, CERFACS – CNRS in Toulouse (France), the Geography and Tourism Research Group at the Department of Earth and Environmental Sciences at the University of Leuven (Belgium).

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