The potential of grain legumes for sustainable food production in sub-Saharan Africa under a changing climate

Integrating grain legumes into cropping systems may enhance sustainable intensification of agriculture in sub-Saharan Africa (SSA), which is getting increasingly urgent due to rising food demand as a result of population growth coupled with climate change challenges. Benefits of grain legumes can be twofold, i.e., enhanced protein production and contributing biologically fixed nitrogen to cropping systems. This study analysed how improved grain legume production via narrowing yield gaps, i.e., the difference between water-limited potential yield (Yw) and farmers' actual yield (Ya), can contribute to more sustainable food production today and in future with climate change across entire SSA. Sustainable intensification may increase digestible protein production by 51% and 141% when farmers’ yields are increased to 50% and 80% of Yw, respectively. Current relative yields (i.e., [Ya/Yw]*100%) are, on average, only 33% and, respectively, 23%, 27%, 40% and 40% for cowpea, common bean, groundnut and soybean. By 2050, despite considerable uncertainty in climate change projections and impacts, we estimated a higher Yw on average (+11%), though there was wide variation across regions (−32% to +65%). In order to fulfil future increased demand for digestible protein from the four grain legumes, a yield increase to 62% of Yw is required. Intensifying legume production was estimated to have a modest impact on the nitrogen supply to the cropping systems through return of grain legume residues.