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Climate change may cause insects to gobble more crops, study finds

The future may bring plagues of locusts to devastate crops as global warming worsens, these experts say.
Image: FILE PHOTO: Arnaud Caron, a French farmer drives an old Mc Cormick F8-413 combine as he harvests his last field of wheat, in Vauvillers
Arnaud Caron, a French farmer drives an old Mc Cormick F8-413 combine as he harvests his last field of wheat, in Vauvillers, northern France on July 23, 2018. A new study predicts wheat crops, especially, will be hit by insects as global warming worsens.Pascal Rossignol / Reuters file

Insects are going to love it when the world turns hotter in the coming years. Not only will they spread more disease — they will eat more crops, researchers reported Thursday.

That’s because as temperatures rise, insects become more active and reproduce more, which makes them hungrier, the researchers reported in the journal Science.

These increasingly voracious insects will hit North America and Europe right in the breadbasket, the researchers predicted.

Wheat, corn and rice crops will all be damaged — to the tune of 10 percent to 25 percent for every 1 degree Celsius (1.8 degrees F) that average global temperatures rise, according to the report.

“Crop losses will be most acute in areas where warming increases both population growth and metabolic rates of insects,” they wrote. “These conditions are centered primarily in temperate regions, where most grain is produced.”

There is no doubt that the global climate is warming and no real debate about one big cause: human activity.

The effects are already being seen with heat waves, droughts, floods and stronger storms as ocean currents and atmospheric patterns are disrupted.

Global loss of crop production owing to the impact of climate warming on insect pests.
Global loss of crop production owing to the impact of climate warming on insect pests. Crop production losses for (A) wheat, (B) rice, and (C) maize are computed by multiplying the fractional change in population metabolism by the estimated current yield loss owing to insect pests, summed over worldwide crop locations.Science Magazine

Public health experts have noted an increase in insect-borne diseases, from Zika, West Nile and chikungunya viruses spread by mosquitoes, to a rise in infections such as Lyme disease, which is spread by ticks.

Now a team, including experts at the University of Washington, the University of Vermont, and the University of Colorado, has projected the effects that warmer temperatures will have on insect damage to major food crops.

"First, warmer temperatures increase insect metabolic rates exponentially,” said Curtis Deutsch, an oceanographer at the University of Washington who worked on the study.

“Second, with the exception of the tropics, warmer temperatures will increase the reproductive rates of insects. You have more insects, and they're eating more,” Deutsch said in a statement.

Farmers can deal with to some degree, the researchers said.

“Agricultural practices will shift as the climate warms. Changes in planting dates, cultivar use, and planting locations are already under way and will become more pronounced as the rate of climate warming increases,” they wrote.

They’ll also move to sometimes unpopular farming practices, said Rosamond Naylor, a professor in the Department of Earth System Science at Stanford University, who also worked on the study.

"Increased pesticide applications, the use of GMOs, and agronomic practices such as crop rotations will help control losses from insects,” Naylor said in a statement. “But it still appears that under virtually all climate change scenarios, pest populations will be the winners, particularly in highly productive temperate regions, causing real food prices to rise and food-insecure families to suffer."

Wheat, corn and rice account for 42 percent of calories eaten directly by humans globally, the researchers said.

Temperate regions hit hardest

Wheat crops will be hit the hardest. A 3.6 degree F rise in average temperature could cause a 46 percent increase in crop loss due to insect damage for wheat, the researchers projected.

Temperate regions will be more affected because insects start slowing down if it gets too hot, and tropical areas are already nearer to that limit.

Rice losses will taper off as the temperature rises above a certain point," said Scott Merrill, an ecologist at the University of Vermont.

"The overall picture is, if you're growing a lot of food in a temperate region, you're going to be hit hardest," Merrill said in a statement.

Things could get even worse than what’s predicted by the study, said Markus Riegler of the Hawkesbury Institute for the Environment at Western Sydney University in Australia.

“For example, many insect pests are vectors of plant pathogens that also cause crop losses,” Riegler, who was not part of the research team, wrote in a commentary.

“Predictions based on population growth and metabolic rates may thus underestimate crop damage due to insect vectors under global warming.”