The benefits of carbon sequestration in soil

An international team of soil experts says carbon sequestration in soil has the potential to enhance food security and mitigate climate change.

In the article ‘Aligning agriculture and climate policy’, published in the journal Nature Climate Change, the experts provide a road map, implications and expected benefits to be gained if carbon can be sequestered by 4%₀ (four parts per 1000) year on year, which if accomplished would greatly reduce global temperature increases. The 4%₀ initiative is part of the Lima Paris Action Agenda and supported by the Food and Agriculture Organization of the United Nations, and connects to the UN’s sustainable development goals.

“It’s a big ask,” said study co-author Professor Louis Schipper, from the University of Waikato, “but I think people are awakening to the idea that carbon in soil is good for soil health and the atmosphere, and if we’re to capture CO₂ from the atmosphere then, like a healthy bank account, we’ve got to have more carbon going into the soil than coming out.

“Because soil is such an important reservoir of carbon, relatively small changes in the amount of carbon stored in soils could have significant effects on net greenhouse gas emissions. The challenge is implementing a program like this worldwide with varying climates and land uses.”

Carbon makes up about 50% of soil organic matter, and scientists need to know how much carbon each soil type contains, how much land is covered in each soil type and how the amount of soil carbon changes over time. In New Zealand, scientists use soil sampling and micrometeorological techniques to determine changes in carbon stocks.

New Zealand soils have relatively high carbon stocks, so maintaining or slightly increasing carbon sequestration from such a high base is a focus of Professor Schipper’s research. He and his colleagues have been researching grazed pastures, including the role of alternative pasture swards and pasture renewal as ways to increase carbon in the soil or avoid losses.

The focus for developing countries, meanwhile, is to introduce soil management systems that won’t threaten growers’ food security, particularly as land in these countries can be overused for growing food, feeding livestock, biofuels, home heating and cooking.

“They’re not going to leave the non-edible residues on the land if it can be used for fuel or animal feed, for example,” Professor Schipper said. “But what we’re proposing for developing countries is feasible when other social and economic constraints are considered because it doesn’t require large technological breakthroughs and it doesn’t stop agricultural or horticultural production.”

Image caption: Professor Louis Schipper.