A new modeling study published today warns that the dry-season irrigated rice in West Africa’s Sahel region has reached the critical threshold of 37 degrees Celcius – the tipping point. Further temperature rise could devastate rice yields in this region due to decreasing photosynthesis at high temperatures.
This is an ominous sign as yield reductions will directly translate into severe food shortages in a highly vulnerable region. Rice has fast become the preferred food of the Sahelian countries – critical for food security and political stability of the region. Rice consumption has been increasing dramatically, mainly because of changes in eating habits and rapid population growth.
According to the Intergovernmental Panel on Climate Change (IPCC), the Sahel will experience increasingly higher average temperatures as well as changes in rainfall patterns over the course of the 21st century. These changes threaten food security and the livelihoods of the region’s predominantly rural population.
“Our model shows that without adaptation, irrigated rice yields in West Africa’s Sahel region in the dry season would decrease by about 45%, but with adaptation, they would decrease significantly less – by about 15%,” explained the lead author Dr Pepijn van Oort, Crop Modeler at Africa Rice Center (AfricaRice).
Dr van Oort clarified that it is important to keep in mind that this is a West Africa average, and that there are big differences within West Africa. “Things are better in the cooler coastal regions and a lot worse in the hotter inland sites,” he added.
“Also, more investigation is needed to understand clearly photosynthesis processes at extreme temperatures, as there has been almost no research conducted on rice at such high temperatures,” Dr van Oort cautioned. “In addition, we need to explore further adaptation options, such as shifting sowing dates more into the cold dry season.”
Although rice thrives well in hot and warm climates, high temperatures of more than 35 degrees Celcius can damage plant processes and lead to lower yields. Rice is also vulnerable to cold temperatures, which can slow growth.
The modeling study forecasts that in East Africa, rising temperatures will create new opportunities for rice. In East Africa rice is grown mostly in the highlands, which are now often too cold for the crop, and this will improve with higher temperatures. Also, rice could benefit from increased CO2. However, improved water and nutrient management will be needed to have the maximum benefit.
The study analyzed rice yield changes for four Representative Concentration Pathways (RCP) climate change scenarios comparing the 2000s with the 2070s and identified causes of yield declines.
It revealed that overall yield decline is found in all scenarios if farmers continue using the current rice varieties. But the trend becomes positive, if farmers adopt varieties that can tolerate increased temperatures.
The findings were revealed in the article by Pepijn van Oort and Sander Zwart, entitled “Impacts of climate change on rice production in Africa and causes of simulated yield changes,” published in the top journal Global Change Biology. The paper appears online on 12 December 2017 at http://dx.doi.org/10.1111/gcb.13967
According to Dr van Oort, this is the first comprehensive study that addresses the impact of climate change on rice productivity across Africa. Projections of the likely impacts of climate change on rice yields were evaluated using the ORYZA2000 crop growth simulation model.
“This is an important milestone, because climate change effects on rice in Africa are still poorly understood and rice in Africa has until now received limited attention from the crop modeling community,” said Dr van Oort.
The research work was supported with funding from the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS); the CGIAR Research Program on Rice Agri-food Systems (RICE); the Federal Ministry for Economic Cooperation and Development (Germany); and Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ).