The study published by Scientific Reports last month (14 November) shows that approaches such as the addition of manure, mulching, conservation tillage, soil fertility management, agroforestry and rotational grazing are good in assisting soils to absorb carbon from the atmosphere, a process called carbon sequestration.
Rolf Sommer, a co-author of the study, says that their aim was to quantify the carbon sequestration potential of global cropland soils.
“This could catalyse investments in soil protection and rehabilitation.”
Rolf Sommer, International Center for Tropical Agriculture
Sommer, from International Center for Tropical Agriculture in Nairobi, Kenya, notes that the global distribution of soil carbon is strongly influenced by temperature and precipitation. Soil carbon is generally lower in the tropics although the tropics also offer large opportunities for increasing carbon in soils.
“Africa, taken altogether with over 2.6 million kilometre squared of cropland, shows a large potential for soil carbon storage, ranging from 0.15 to 0.31 petagrams of carbon per year,” he tells SciDev.Net.
The study identified North America as the region with the highest potential for total carbon storage, with carbon storage potential of 0.17 and 0.35 petagrams of carbon a year. The corresponding figure for South Asia and Europe was 0.11–0.23 petagrams of carbon a year.
According to Sommer, the study involved use of available maps on the distribution of cropland and soils and reasonable assumption about soil carbon sequestration rates.
The uniqueness is that such global estimate has never been done in a spatially explicit manner, he adds.
“The study will increase awareness of policymakers at national and regional scale in terms of soil carbon sequestration potentials,” he explains. “This could catalyse investments in soil protection and rehabilitation, which is of fundamental importance to sustain the resource basis for current and future food production.”
Sommer recommends incentivising farmers to manage soils through access to seeds of green manure cover crops or access to affordable credit and insurance schemes, adding that doing so could stimulate sustainable intensification of production systems that increase the productivity and climate change mitigation of smallholder farmers.
Leigh Ann Winowiecki, a soils scientist at Kenya-headquartered World Agroforestry Centre (ICRAF), agrees with the findings of the study, adding that soil organic carbon (SOC) is significant in climate change mitigation and overall land and agricultural productivity.
“For instance, severe land degradation is leading to out-migration in farming communities in the Ethiopian highlands, and restoration efforts can create new livelihood opportunities,” Winowiecki says. She explains that because of the complex SOC dynamics, efforts to assess carbon sequestration need to also consider processes of land degradation and management.
Winowiecki recommends incorporating local knowledge in interventions aimed at scaling-up innovations for helping smallholders conserve soil carbon to boost productivity.
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.