Global Warming Threatens World's Wheat Crop

New Study: Global Warming Threatens World's Wheat Crop

It could be much more difficult than we thought to feed everyone in a warmer world.

- Common Dreams staff

A study released Sunday afternoon finds that wheat crop yields could plunge due, in part, to climate change.
Extreme temperatures are already cutting wheat yields in India (Narinder Nanu/AFP) The study, published in Nature Climate Change, researchers warn that current projections underestimate the extent to which hotter weather in the future will accelerate this process. Extreme heat causes wheat crops to age faster and reduce yields, the Stanford University-led study shows, underscoring the challenge of feeding a rapidly growing population as the world continues to warm.

* * *

New Scientist magazine reported Sunday:

It could be much more difficult than we thought to feed everyone in a warmer world. Satellite images of northern India have revealed that extreme temperatures are cutting wheat yields. What's more, models used to predict the effects of global warming on food supply may have underestimated the problem by a third.

Two-thirds of wheat in poor countries, and 23 per cent in rich countries – nearly half the world's total crop – is at risk from warming.In India's breadbasket, the Ganges plain, winter wheat is planted in November and harvested as temperatures rise in spring. David Lobell of Stanford University in California used nine years of images from the MODIS Earth-observation satellite to track when wheat in this region turned from green to brown, a sign that the grain is no longer growing.

He found that the wheat turned brown earlier when average temperatures were higher, with spells over 34 ºC having a particularly strong effect. [...]

Lobell's work suggests losses could be sooner and greater. "This is an early indication that a situation that was already bad could be even worse," says Andy Challinor of the University of Leeds, UK.

Two-thirds of wheat in poor countries, and 23 per cent in rich countries – nearly half the world's total crop – is at risk from warming, says Hans-Joachim Braun of CIMMYT. Previous estimates suggested that by 2050, warming could cut wheat yields by 30 per cent in places like India – a figure that may now be optimistic. Yet global yields need to rise 50 per cent by then to feed the growing population.

* * *

Reuters reports:

Extreme heat can cause wheat crops to age faster and reduce yields, a U.S.-led study shows, underscoring the challenge of feeding a rapidly growing population as the world warms.

Scientists and farmers have long known that high heat can hurt some crops and the Stanford University-led study, released Sunday, revealed how the damage is done by tracking rates of wheat aging, or senescence.

Depending on the sowing date, the grain losses from rapid senescence could reach up to 20 percent, the scientists found in the study, published in the journal Nature Climate Change. [...]

Climate scientists say that episodes of extreme heat are becoming more frequent and more prevalent across the globe, presenting huge challenges for growing crops.

Wheat is the second most produced crop in the world after corn and the United Nation's Food and Agriculture Organization says global food production must increase by 70 percent by 2050 to feed a larger, more urban and affluent population.

Wheat is particularly sensitive to temperature and is typically sown in late autumn or early winter and harvested before the heat of summer.

* * *

In November, the UN's climate science panel concluded that man-made climate change has boosted the frequency or intensity of heat waves, and that such extreme weather events are virtually certain to increase in the future.Agence France-Presse adds:

Wheat also faces another possibly climate-related threat: aggressive new strains of wheat rust disease have decimated up to 40 percent of harvests in some regions of north Africa, the Middle East and Central Asia.

Wheat rust is a fungal disease that attacks the stems, grains and especially the leaves of grains including wheat, barley and rye.

Global warming and increased variability of rainfall have weakened the plants even as these emerging rust strains have adapted to extreme temperatures not seen before, scientists say.

In November, the UN's climate science panel concluded that man-made climate change has boosted the frequency or intensity of heat waves, and that such extreme weather events are virtually certain to increase in the future.

If greenhouse gas emissions continue unabated, one-in-20-year heat peaks would likely occur every five years by about 2050, and every year or two by the end of the century, the Intergovernmental Panel on Climate Change (IPCC) said in a 1,000-page report.