Climate change threatens future crop yields in southern Africa

                                                                                                                  R.Thompson

I have come across a lot of studies dedicated to understanding how climate change can affect crops and food security. What has always caught my eye is the varied results that come from these studies. The suggested impacts vary significantly from one region, country, district and community to the other in such a way that it is difficult to say for sure what the impacts would be. How much are crop yields going to be affected? Where is the highest impacts going to be? what crops are most at risk etc. These are questions that these different studies couldn't satisfy me on. Yet, these studies remain the most solid and authoritative works on climate change, agriculture and food security and therefore the go-to for policy makers, development agencies and governments etc for insight into possible avenues for action to adapt to climate change. What appeared to be a lack of coherence and consistence in these different studies would surely discourage action, i thought. If one study said maize yields would decline significantly yet another says maize yields could increase, that to me simply screamed "We aren't sure what we are talking about, so maybe you [farmer, policy guy, development agency etc.] should just wait and see." These end users of scientific research would be forgiven for thinking "These guys [scientists] need to make up their minds" and sitting on their hands.

Uncertainty about how the impacts of climate change on agriculture and food security will unfold is daily bread for scientists. They spend entire careers advancing our understanding of what we dont know about these impacts as a way of being more sure about what we know. However, this may not be of interest to end users who may simply view this as a sign that the science is not yet solid enough to encourage action. This as i found out in a recent study is not the case. There is a strong enough message coming from climate change impact studies on crop production to warrant action. 

I carried out a review study with collegues Olivier Crespo and Sepo Hachigonta which was published in the Global and Planetary Change Journal and summarised in a policy brief. The study focused on southern Africa, my home region. Multiple reports have alluded to the fact that this is one of the most vulnerable agricultural regions regions in the world owing to low adaptation capacity, low incomes, high dependence on natural resources and climate dependent agriculture. We sought to investigate this assertion by reviewing multiple studies carried out over the region and drawing an overall picture of what the studies said about the impacts of climate change on crop production in the region.

Map of southern Africa

The message was quite clear. Climate change threatens crop yields in the region. Most important food crops in the region where studied including maize, sorghum, groundnuts, millet, beans and wheat. The most studies crop being maize, the staple crop of the region. The study clearly showed that maize yields would likely decline by up to 18 % by the end of the 21st century. Given the importance of maize in southern Africa, this suggests that food security in the region is under threat from climate change and therefore action towards adaptation is warranted. This is especially so for smallholder farmers that are the most vulnerable to climate induced crop failures. The study also showed that the severity of climate change impacts on crop yields are likely to increase as we move further into the 21st century. climate change impact on crop yields for the early 21st century (up to 2039) was uncertain, on average showing no change in crop yields. Further into the mid century (2050s), crop yields were projected to decline by up to 18 % and even further decline by up to 30 % towards the end of the 21st century. 

While uncertainty remains and is clearly highlighted in the study, a consistent message was obtained when studies were viewed as a whole, which suggests crop yields in the region will likely suffer from a changing climate and therefore there is need for adaptive action in southern Africa, especially for vulnerable farming groups like rain dependent smallholder farmers. What remains unclear however is the impact of climate change on crops at the at the local level. The region is too big to make generalisation and therefore further research for particular locations and crops is necessary especially if we are to target smallholder farmers for adaptation. Given this backdrop, a wait and see attitude is not defensible.