BOULDER, COLORADO, U.S. – With warmer climates expected, the increase of insect populations is projected to decrease grain yields in regions with warm weather.
A study, published in the journal Science, models increase in insect populations and their metabolic rates in a warmer world. It projects a 50% to 100% increase in pest-induced crop losses in European wheat and 30% to 40% increases in North American maize even if countries meet their existing commitments to reduce greenhouse gas emissions.
"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," said Joshua Tewksbury, co-lead author of the research, a research professor at University of Colorado, Boulder, and a director of Future Earth, an international research network for global sustainability.
The study noted insect pestilence already reduces net yields of wheat, maize and rice. Combined, these grains provide 42% of total calorie consumption worldwide. However, models assessing the agricultural effects of climate change rarely consider losses due to insects.
“Future bugs, however, in a warmer climate are expected to be even hungrier and more numerous,” the study said. “Warmer temperatures have been shown to accelerate an individual insect's metabolic rate, leading it to consume more food during its lifespan. And while pest populations may decline in some hotter tropical areas, they are expected to increase elsewhere as temperatures rise and additional ecosystems become favorable to the insects.”
The researchers calculated the potential for crop damage through 2050 by combining robust climate projection data, crop yield statistics, insect metabolic rates and other demographic information.
The study finds that Europe's bread basket could be among the hardest hit. Currently the most productive wheat producing region in the world, pest impacts on European wheat could create total annual pest-induced yield losses that could top 16 million tons. Eleven European countries are predicted to see 75% or higher increases in insect-induced wheat losses, including the U.K., Denmark, Sweden and Ireland.
Insects could also create major impacts on maize and rice yields in North America and Asia, respectively. The U.S., the world's largest maize producer, could see an almost 40% increase in insect-induced maize losses under current climate warming trajectories, a reduction of over 20 million tons annually. Meanwhile, one-third of the world's rice production comes from China, where future insect-induced losses could top 27 million tons annually.
"On average, the impacts from insects add up to about a 2.5% reduction in crop yield for every degree Celsius increase in temperature," said Tewksbury. "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."
The study recommends changes to global agricultural practices, including increased selection for heat- and pest-resistant crops and new crop rotation patterns to reduce vulnerability to insects. In some extreme cases, greater pesticide use may become necessary to secure regional food supplies, even at the cost of possible associated health and environmental damage.