If people continue using and changing the land over the next century in the same way they currently do, soils will have limited potential to counter the effect of climate change and will become a net source of atmospheric carbon dioxide, experts have warned.

Experts have forecast that a quarter of the carbon found in soil in France could be lost to the atmosphere during the next 100 years. This could lead to soil becoming a net source of carbon dioxide to the atmosphere. At present soil is considered to absorb carbon dioxide and this partially counters the impact of man-made climate change.

The pace and nature of predicted changes in climate over the next century will make the soil less able to store carbon, while business-as-usual land use change has limited capacity to counteract this trend, according to experts from the University of Exeter, INRA and CERFACS in France and University of Leuven in Belgium, who worked together to look into this scenario.

If, as predicted, soils lose a significant amount of their carbon this will endanger their ability to produce food and store water and this could lead to increased soil erosion and flood damage.

Plans for an EU-wide Soils Directive that would have introduced measures to protect soils, such as already exists for other non-renewable resources, were scrapped by the European Commission in 2014, having been stalled at the draft stage for several years by a blocking minority of national governments, including the UK’s. In June this year, the UK government’s Environmental Audit Committee released its own report on soil health, which warned that the only protections for UK agricultural soils are currently linked to EU cross-compliance conditions on farm subsidies, but that these rules are too weak and too loosely enforced to prove effective. Furthermore, their sole focus is on preventing further damage to soil, not encouraging restoration and improvement, which is desperately needed if the government hopes to meet its targets of managing UK soils sustainable by 2030.

In the cross-Channel research looking at French soils, researchers made predictions for the 21st century by combining models of soil carbon and land use change with climate change predictions. They used France as a case study. The study shows 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.

Lead author Dr Jeroen Meersmans, from the University of Exeter, said, "A reduction in anthropogenic CO2 levels is crucial to prevent further loss of carbon from our soils. 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."

Co-author Dr Dominique Arrouays of the French National Institute for Agricultural Research (INRA) added, "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."