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A new modelling study published today warns that the dry-season irrigated rice in West Africa’s Sahel region has reached the critical threshold of 37 degrees Celsius – the tipping point. Further temperature rise could devastate rice yields in this region due to decreasing photosynthesis at high temperatures

straw 230112 640The study shows that rice yields in West Africa’s Sahel region in the dry season would decrease by about 45 per cent. (Image source: 12019/Pixabay)

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 per cent, but with adaptation, they would decrease significantly less – by about 15 per cent,” explained the lead author Dr Pepijn van Oort, Crop Modeler at Africa Rice Centre (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 Celsius can damage plant processes and lead to lower yields. Rice is also vulnerable to cold temperatures, which can slow growth.

The modelling 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, available online.