Climate Change Begins to Cut Into Crop Yields

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The hidden story of 2011 has been the record-breaking rise in global food prices. Global corn prices doubled between April 2010 and April 2011, while wheat prices are up some 60 to 80%. Exactly why food has gotten so expensive in recent months is the subject of an ongoing debate—biofuel policy, inflation, oil prices, natural disasters and growing consumption in the developing world all play a role. One area that’s been especially unclear is the responsibility, if any, of climate change. Scientists believe that warmer temperatures will ultimately have a negative impact on crop yields, perhaps a devastating one, though it’s difficult to be sure exactly how big that impact will be or when farmers will really begin to feel it. The general assumption, though, is that it would still take years before climate change before we could detect a clean, measurable effect on farming. In other words, we had time to prepare.

Turns out that might not be the case, however. A new study published in Science today by researchers at Stanford University, Columbia University and the National Bureau of Economic Research has found that the warming of the planet over the last few decades have already led to a measurable reduction in crop yields for major staple grains. Although better farming practices and research have still helped push yields up in recent years, climate change has reduced some of that growth—especially for countries like Mexico and Russia. Over all, climate change has reduced the yield of corn by 3.8% and wheat by 5.5% since 1980, compared to how yields might have fared in the absence of warming. (The production of rice and soybean—the two other main staple crops—haven’t shown much impact yet.) That adds about 6% to the cost of wheat and corn, and with temperatures expected to continue warming, the effect will only grow. As David Lobell of Stanford, one of the three authors of the paper, told Science magazine:

It’s a frustration having to always answer questions about the future and having everyone think of climate change as something in the future. It’s not something we have to anticipate. It’s something we have to learn from and deal with right now.

It’s important to realize, as the Economist points out, that crop yields have continued to rise globally over the past three decades—climate change has simply taken away some of that growth. The study also may downplay the ability of farmers to adapt to the long-term changes of global warming, as Ken Cassman, an agronomist at the University of Nebraska, told the Washington Post:

It’s not clear how well these analyses are capturing how well farmers can respond, and have been responding, to changing temperatures.

And there are ways to keep improving yields even if temperatures continue to rise, simply by improving infrastructure—that can help reduce the farming yield gap, the difference between maximum agricultural yields in rich nations, and the performance of poorer farmers who lack those advantages. Again from the Economist:

Then there is a point made by Richard Tol of VU University Amsterdam: farm yields show the worst of the situation. Easily achievable improvements in roads, markets and other things can increase the availability of food a lot even if farm yields stop rising. And people can adapt, at least to lowish levels of change; indeed the study provides evidence to help them do so as it shows which crops in a given country are the most affected by global warming. So Malthus looks beatable even when he sits astride the apocalyptic horse of climate change.

Moreover, there is a simple way more or less to abolish the effect of climate change on yield to date. According to William Cline of the Peterson Institute for International Economics in Washington, DC, at least 4% of the world’s grain is used to make ethanol for fuel. Most of this is doing little good for the environment, and stopping subsidies for such fuels would boost the supply of grain for feeding people on a scale similar to the hit that the past three decades of warming have provided.

No kidding. The Science study—like the new Arctic assessment that came out earlier this week—should serve as a reminder that for all the mindless political debate over climate change, warming is real, it’s happening and its impact is already being felt. Exactly how we’ll deal with warming in the future is still up for debate—any response on farming should include adaptation and simple aid, in addition to long-term efforts to reduce carbon emissions. The adaptation versus mitigation strategy is already irrelevant—as the Science study shows, we’re already doing both. But we’ll need to do them better if we want to ensure our global food system is capable of meeting the needs of billions more in the future.

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