The areas of sub-Saharan Africa where the cultivation of key crops - including maize, banana and beans - will probably become unviable due to climate change are mapped in a paper published online this week in Nature Climate Change. The modelling study suggests that fundamental changes to agriculture within this century may be necessary to maintain food security in a changing climate.

Julian Ramirez-Villegas and colleagues investigate the timing and geographical pattern of climate driven changes in the viability of nine key crops that together account for half of total agricultural production in the region. They find that some form of transformational change - such as farmers switching to different crop types or moving out of agriculture - may be required this century for all major crops, but that, for most, this need for transformation is limited to small pockets of their currently suitable area (about 15%). However, the required transformation is much more widespread for maize and banana (about 30% of currently suitable area) and greatest for beans (about 60% of currently suitable area).

The authors suggest three phases of adaptation will be needed to enable farmers to make the required transformational changes: first, an incremental phase focused on improvements to crops and management; second, a preparatory phase that establishes policies and enablers of change; and finally, a phase in which farmers actually substitute crops, explore alternative livelihoods, or relocate.

In an accompanying News & Views article, William Travis writes: “The results are both encouraging and concerning. Some crops are geographically robust, shifting little over this century, so that they are able to maintain their role in regional food production even on a markedly warming planet. Others are squeezed from much of their current territory, signalling the need for proactive adaption planning to avoid serious production losses.”