Climate change will force farmers to reshuffle what is grown where
For a look behind the scenes of our data journalism, sign up to Off the Charts, our weekly subscriber-only newsletter. Agricultural yields have been rising for decades, defying predictions that the worlds population would outgrow its food supply. Such gains stem largely from scientific advances in areas like fertilisers and genetics. This pace of discovery could slow down. Even so, farmers could still increase yields by changing a lower-tech part of their job: picking what to plant where. A surprisingly large share of farmland is used for crops that do not maximise nutritional or economic value. One study in Nature Geoscience showed that by changing what is planted on existing fields, output could rise enough to feed 825m more people, while reducing water use by 10%. And global warming is likely to make the current distribution of crops even less efficient: a paper in Nature Food found that climate change could cut maize yields by 6-24% by the late 21st century. Today, crop-site mismatches tend to be most extreme in poor countries. Of the 12 crops analysed in a recent study in the Proceedings of the Royal Society, those most often planted in unsuitable locations were cassava, rice, sorghum and potatoes. The first three are favourites of smallholder and subsistence farmers. Because such producers need to feed their families every year, they often prioritise resistance to poor weather over maximising yield. There is no practical way to get millions of small farmers to switch their crops. But global warming could force even agribusiness firms, which do much of the farming in richer countries, to change what they plant. Maize, Americas biggest crop, is sensitive to heat, and may need genetic modification to remain viable even under moderate warming scenarios. Soyabeans, grown on nearly half of Brazils farmland, are also expected to suffer. And coffee struggles with extreme temperatures, which climate change will make more common. In contrast, breadfruit, which can live for months without rain, should do well at low latitudes. But bumper breadfruit harvests will do little for caffeine-starved office workers. Warming will also generate opportunities. Parts of Russia, Canada, China and the north-western United States should become prime areas for wheat, which resists heat and drought better than maize doesthough chopping down forests in these regions would accelerate climate change. A few hotter, poorer areas could benefit too: increased rainfall might improve rice production in India and west Africa. Although such forecasts reflect the best estimates of how climate change will affect individual crops in specific regions, they are highly uncertain. Rather than preparing for a single scenario, the best defence is for farmers to learn about a wide variety of crops. The only guarantee is that global warming will transform agriculture in ways that cannot be fully foreseen. For more coverage of climate change, sign up for the Climate Issue, our fortnightly subscriber-only newsletter, or visit our climate-change hub. Chart sources: Climate analogues suggest limited potential for intensification of production on current croplands under climate change, by T.A.M. Pugh et al., Nature Communications, 2016; The Economist