A sobering presentation by Marshall Burke of Stanford on future agriculture. He and colleagues looked at historical climate and yield data for various crops in various parts of the world and projected the relationship they found into various future climates as found in the IPCC. As the IPCC itself reported, much of the tropics did badly in this analysis, and the worst performer was maize in southern Africa which was down in yield by about 30% by 2030.
More granular data run out to 2050 showed similar or worse trends, and the rest of Africa did pretty badly too. So did other crops in the same countries, such as millet and sorghum, though as Andy Jarvis of Biodiversity International pointed out from the floor, this may be somewhat worst case. You don’t just go on growing the same thing as the situation gets worse and worse. As climates change so will the crops farmers grow, which should help a bit.
While the IPCC has already predicted that tropical agriculture will have its productivity hit by any climate change, it said it expected that in temperate zones modest warming might help productivity. In at least one case Burke went into — maize in the US — there are studies suggesting things start going wrong much sooner than that, with yield losses of 30% or so by 2030. Modest rises have been seen: sharp downturns are to come. Burke says that an economic model fed with these and other gloomier-than-common yield assumptions suggests that prices are set to rise more steeply than the IPCC has foreseen: a 1ºC rise in temperature looks like a 25% increase in prices, hurting some poor farmers and a lot of poor consumers.
As Burke pointed out, we care about these food security issues because we care about people. A World Bank study suggests that the food crisis of 2007-2008 pushed 100m people into poverty. Reduced yields are normally bad for poor farmers, for whom consequent price increases rarely make up for lost production. They are also bad for the urban poor, who just see the price increases. That 25% increase in prices will some poor farmers and a lot of poor consumers. And on current trends that’s just the beginning.