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CLIMATE CHANGE | Insect activities due to global warming cause more crop losses: study

WASHINGTON — American researchers found that climate change was expected to accelerate rates of crop loss due to growth of insect pests.

The study published in the journal Science described how insect pests that attack three staple crops, rice, corn and wheat, would respond under a variety of climate scenarios.

They found that rising global temperature would lead to an increase in crop losses from insects, especially in temperate regions and that losses are projected to rise by 10 to 25 percent per degree of warming.

A two-degree rise in global average temperature will result in total crop losses of approximately 213 million tons for the three grains, according to the study.

Specifically, the median losses in yield would be 31 percent for corn, 19 percent for rice and 46 percent for wheat. Under those conditions, total annual crop losses would reach 62, 92 and 59 million tons, respectively.

“When the temperature increases, the insects’ metabolism increases so they have to eat more,” said Scott Merrill from the University of Vermont, a co-author of the study.

The losses will come from an increase in insect metabolism, and from faster insect population growth rates, according to Merrill.

Also, insects have an optimal temperature where their population grows best. If the temperature is too cold or too hot, the population will grow more slowly. That is why the losses will be greatest in temperate regions, but less severe in the tropics.

According to the study, wheat, which is typically grown in cool climates, will suffer the most, as increased temperatures will lead to greater insect metabolism, as well as increased pest populations and survival rates over the winter.

Corn, which is grown in some areas where insect population rates will increase and others where they will decline, will face a more uneven future.

In rice, which is mostly grown in warm tropical environments, crop losses will actually stabilize if average temperatures rise above 3 degree Celsius, as insect population growth drops, counteracting the effect of increased metabolism in the pests.

That means that the most substantial yield declines will happen in some of the world’s most productive agricultural regions, said Merrill.

“I hope our results demonstrate the importance of collecting more data on how pests will impact crop losses in a warming world,” said Curtis Deutsch of the University of Washington, who co-led the study with Joshua Tewksbury, director of Future Earth at the University of Colorado, Boulder.

France, China and the United States, which produce most of the world’s maize, are among the countries that are expected to experience the largest increases in crop losses from insect pests.

Also, France and China, as major producers of wheat and rice, respectively, are also expected to face large increases in losses of those grains as well.

Reduced yields in these three staple crops account for 42 percent of direct calories consumed by humans worldwide.

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