Crop losses to insects will accelerate as the globe warms: study

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  • Insects already eat between 5 and 20 percent of the most important grain crops produced around the world — and new research finds that they could be responsible for even more crop damage in the near future as global temperatures continue to rise.
  • Insect-driven losses of wheat, rice, and maize — the three major grain crops, which together provide more than 40 percent of calories consumed by humans worldwide — will increase 10 to 25 percent for every degree Celsius the average surface temperature of planet Earth rises, according to a study published in Science late last month.
  • While bug populations may actually decline in some tropical areas, major grain-producing regions in northern climates are projected to be among the hardest-hit.

Insects already eat between 5 and 20 percent of the most important grain crops produced around the world — and new research finds that they could be responsible for even more crop damage in the near future as global temperatures continue to rise.

Insect-driven losses of maize, rice, and wheat — the three major grain crops, which together provide more than 40 percent of calories consumed by humans worldwide — will increase 10 to 25 percent for every degree Celsius the average surface temperature of planet Earth rises, according to a study published in Science late last month.

A team of researchers led by scientists at the University of Washington and the University of Colorado Boulder (CU Boulder), both in the United States, used projected rises in global temperatures, crop yield statistics, and data on 38 insect species’ population growth and metabolic rates to predict the impacts climate change will have on losses of the three grain crops. While bug populations may actually decline in some tropical areas, major grain-producing regions in northern climates are projected to be among the hardest-hit.

“Crop losses will be most acute in areas where warming increases both population growth and metabolic rates of insects,” the authors write in the study. In other words, hotter temperatures will lead to bigger populations of pests and each of those insects will require more energy, driving them to eat more. “These conditions are centered primarily in temperate regions, where most grain is produced.”

Even in a scenario where countries meet their existing commitments to reduce their greenhouse gas emissions, the researchers found, Europe, the most productive wheat-growing region in the world, stands to lose 16 million tons of wheat every year, possibly more. Eleven European countries, including Denmark, Ireland, Sweden, and the U.K., could see increases in insect-induced wheat losses of 75 percent or higher, the study projects.

Global maize and rice output could be curtailed, as well, as hungrier and more numerous insects impact major producers in North America and Asia. In the U.S., the largest maize producer in the world, more than 20 million tons of the crop could be lost to insects every year if the current trajectory of global warming holds, a 40 percent increase. Meanwhile, more than 27 million tons of rice could be lost annually in China, which is responsible for one-third of the world’s rice production.

“In some temperate countries, insect pest damage to crops is projected to rise sharply as temperatures continue to climb, putting serious pressure on grain producers,” Joshua Tewksbury, a research professor at CU Boulder and co-lead author of the study, said in a statement.

“On average, the impacts from insects add up to about a 2.5 percent reduction in crop yield for every degree Celsius increase in temperature. For context, this is about half the estimated direct impact of temperature change on crop yields, but in north temperate areas, the impact of increases insect damage will likely be greater than the direct impact of climate on crop yields.”

Insect pests like the Southwest Corn Borer, seen here in its larval stage, could become more numerous and even hungrier as the globe continues to warm, leading to a 40 percent increase in maize losses to insects in the U.S. Photo via Wikimedia Commons, licensed under CC BY 3.0 US.

CITATION

• Deutsch, C. A., Tewksbury, J. J., Tigchelaar, M., Battisti, D. S., Merrill, S. C., Huey, R. B., & Naylor, R. L. (2018). Increase in crop losses to insect pests in a warming climate. Science, 361(6405), 916-919. doi:10.1126/science.aat3466

This story first appeared on Mongabay

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