Managing soil organic carbon in grazing lands in Africa

Abstract:

Grazing lands contain large amount of soil organic carbon (SOC) making them important to mitigate climate change, improve water infiltration and storage, improve nutrient cycling, increase land productivity and increase below and potentially above ground biodiversity, hence improving livelihoods. The key determinants of SOC sequestration potential in grazing lands in sub-Saharan Africa are climate (rainfall amount and regime) and soil type. In general, it can be said that (i) sustained grazing pressure in mesic environments is likely to lead to land degradation (and therefore may cause SOC to decrease) and (ii) in dry areas with high rainfall variability, land degradation from sustained grazing may not be as apparent because grazing effects are overridden by rainfall effects. We found no significant differences in SOC following two decades of annual prescribed burning in Burkina Faso and three decades of reducing livestock grazing pressure management in Ethiopia. There may be instances in which there are large social costs to SOC sequestration and by making sequestration the primary goal, a situation could arise where the social or economic burdens of the project could be greater than the climate change mitigation benefits. Therefore, we recommend that SOC sequestration for climate change mitigation should be treated as a co-benefit rather than the target of a project/ activity. Projects also need to prioritize to avoid grazing land degradation and SOC losses in dry grazing lands which have less carbon sequestration potentials. Gaps in our understanding of the determinants of SOC sequestration potential are further discussed and general recommendations for future projects and other activities addressing SOC sequestration in grazing lands highlighted.

Keywords: land degradation, drylands, climate change, mitigation, restoration