Climate change and food production

2009-10-27

in Economics, Politics, Science, The environment

A recent report from the International Food Policy Research Institute highlighted the degree to which climate change threatens global agricultural output:

In parts of the developing world some crop yields in 2050 could be only half of their 2000 levels. Irrigation may not help: climate change will hit irrigated systems harder than rain-fed ones. And the hope that gainers from climate change will outweigh losers looks vain: the damage from higher temperatures and erratic rainfall will be too big.

Couple that with ever-increasing population, and you have a recipe for a lot of suffering and strife.

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{ 4 comments… read them below or add one }

. November 12, 2010 at 10:10 am

As it turns out, there is at least one other thing on which Mediterranean leaders concur, at least in theory: the need to protect their sea and its shore from the worst effects of a looming ecological threat that could make it much harder to produce all that healthy fruit, wine and oil. According to Dimitri Zenghelis, a co-author of the 2006 Stern report on climate change, the region can expect to see a drop in precipitation of 25-30% by the middle of the century, with wide variation either side of the mean. If rainfall on bits of the northern Mediterranean coast were to fall by, say, 50%, the landscape could become more like the southern shore—and the struggle to save bone-dry forests from fire might become nearly hopeless. With all that in mind, representatives of 17 Mediterranean countries—including Recep Tayyip Erdogan, prime minister of Turkey—joined Mr Papandreou in pledging to work for “low-carbon, resource-efficient and climate-resilient” economies.

. December 9, 2010 at 7:34 pm

The IPCC thus sees agriculture as being not too badly affected by 2°C of warming, as long as you stick to global averages. Above that (probably towards the end of the century) things look bad. Some think they look bad well before that. One worry is that a lot of harm may be done if temperatures breach certain thresholds even briefly. A fine-grained analysis of historical data from the United States by Wolfram Schlenker of Columbia University and Michael Roberts of North Carolina State University found such thresholds for maize (corn), soya and cotton, America’s largest crops by value. One extremely hot day, their model suggests, can cut annual productivity by 7%. Applying their findings to models of a world with unabated emissions, they found yield declines of 63-82% by the end of the century, with hefty drops even in the relatively clement first half.

. April 7, 2011 at 9:42 pm

Days above 30°C are particularly damaging. In otherwise normal conditions, every day the temperature is over this threshold diminishes yields by at least 1%. Moreover, days where the temperature exceeds 32°C do twice the harm of those at 31°C. And during a drought, things are worse still. Then, yields take a hit of 1.7% per day over 30°C.

This matters because increasing the average temperature only a bit can multiply the number of the hottest days a lot. The research predicts that a 1°C rise in average temperature will reduce yields across two-thirds of the maize-growing region of Africa, even in the absence of drought. Add drought and that effect spreads over the entire area.

. May 31, 2011 at 7:33 pm

Climate change and crops
Hindering harvests
Changes in the climate are already having an effect on crop yields—but not yet a very big one

May 5th 2011 | from the print edition

THE problems climate change looks likely to bring in the future may increasingly be visible in the records of the past. Not just in the far-off ages of surging sea levels following ice-age thaws, spikes in prehistoric temperatures correlated with natural releases of greenhouse gas and ancient civilisations brought low by drought, but in records from living memory—which are based on reliable measurements made at the time. Using such data researchers have now compiled an estimate of global changes in crop yields which can be put down to recent increases in temperature and decreases in rainfall (the world as a whole is getting wetter, but the rain has stayed away from some agricultural plains). The bad news is that they find that climate change has lowered the amount of maize (or corn, if you prefer) and wheat produced in a given area. The good news is that the effect is so far reasonably small.

David Lobell and Justin Costa-Roberts, of Stanford University, and Wolfram Schlenker, of Columbia University, first put together temperature and precipitation figures for the parts of the world where four staple crops—wheat, maize, rice and soya—are grown. Those four crops, between them, account for about 75% of the calories people end up eating, although a lot of the soya is fed to animals first.

It turns out that during the seasons in which crops grow, these arable areas had on average become significantly warmer in the 29 years after 1979. Some bits of Europe that grow wheat, for example, have heated up by a couple of degrees since 1980. The researchers then assembled models of how the yields changed from year to year, and against the longer trend, to find changes linked to temperature and rainfall that are independent of improvements through better farming. Finally they compared today’s yields with what their models say yields would have been with today’s farming but in the 1980’s climate.

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