Last updated June 21, 2018 at 1:37 pm
Modelling forecasts increased volatility and simultaneous failures in harvests.
Global warming is likely to result in multiple and simultaneous poor maize harvests across the globe, leading to price hikes and food shortages, new modelling shows.
A study led by Michelle Tigchelaar of the University of Washington in the US confirms earlier research that predicted the maize harvest would decrease as the climate continues to heat up, but also finds an increasing degree of volatility in year-on-year forecasts, meaning that poor yields in different regions are likely to overlap, putting pressure on global supply.
Maize is the most widely grown crop in the world, for both human and stock consumption. The United Nations Food and Agriculture Organisation (FAO) forecasts 2018 production to be 1046 million tonnes – down on 2017 because of a big shift in China away from the crop.
China, however, grows primarily for domestic use and is a negligible exporter. Much of the international trade in the grain – some 87 per cent – is grown by four countries: the US, Brazil, Argentina and the Ukraine.
According to modelling by Tigchelaar’s team, under current prevailing climate measurements the chance of a 10 per cent decline in crop yield occurring in more than one of those countries in any given year is virtually zero.
However, under a projected two-degree Celsius warming, the risk of simultaneous shortages increases to 7 per cent. If greenhouse gas mitigation policies fail and the climate warms by four degrees by the end of the century, the risk skyrockets to 86 per cent.
Extreme heat the problem
“When people think about climate change and food, they often initially think about drought,” Tigchelaar said.
“But it’s really extreme heat that’s very detrimental for crops. Part of that is because plants grown at a higher temperature demand more water, but it’s also that extreme heat itself negatively affects crucial stages in plant development, starting with the flowering stage and ending with the grain-filling stage.”
The researchers say their predictions may be conservative. Their modelling assumes that changes to rainfall patterns induced by warming will not be greater than existing seasonal variations, and that temperature swings will not increase in intensity.
The paper published in the journal Proceedings of the National Academy of Sciences.