Climate change might lead to bigger populations of hungrier insects. This could have serious consequences for grain-growing regions in the Northwest and across the world.
"And, of course, the impacts from these insects will come on top of whatever effect climate change is already having," says Curtis Deutsch, an earth scientist at the University of Washington. The paper, which Deutsch wrote with an interdisciplinary team of scientists, was published Thursday in the journal Science.
The researchers looked at the world’s three top grains: wheat, corn and rice. Based on their model, for each 2 degrees Celsius the temperature rose, the amount of crops consumed by bugs would increase significantly: by 19 percent for rice, 31 percent for corn and by 46 percent for wheat.
A burn scar near Moro, Oregon, from the Substation Fire.
Ericka Cruz Guevarra / OPB
So if the Earth warms by 4 degrees Celsius — which, scientists say, it is on track to do by the end of the century — wheat losses from insects would double.
To make that number easier to understand, Deutsch says it’s helpful to think of wheat losses due to insects in terms of bread. Right now, for example, insects consume an amount of grain equal to about one out of 12 loaves of bread, globally. If climate change continues unabated, they could be consuming two out of every 12 loaves.
There are two major factors driving this change.
Insects burn more calories the warmer it is. That means they eat more, says Deutsch. “That’s a very simple and well-known effect that’s gonna be true basically for any crop and any insect that eats it.”
But that’s not all: as the temperature rises, warmer air also means more bugs, up to a point. Really warm areas like the tropics might see insects decline. But in the cooler, temperate regions where grains are grown, populations could increase dramatically.
The researchers looked at 38 well-studied insects across the globe. By estimating how much more the insects in certain regions would eat, and combining those estimates with their predicted population changes, they were able to calculate how much grain could be lost.
For each degree the earth warms, insects could consume 25% more wheat than they already do. By the end of the century, losses due to insects could double. The red areas of the map show where wheat losses due to insects are projected to increase.
"Increase in crop losses to insect pests in a warming climate," Deutsch et al 2018, Science, doi:10.1126/science.aau0839
Wheat is a major product in Oregon and the Pacific Northwest, and Oregon and Washington were both among the top 10 wheat producing states in 2017. Per the Port of Portland, wheat is Oregon's top export by weight.
Deutsch says that according to their models, the Northwest has the right conditions to see a large increase in insect-related loss.
“Our calculations would suggest that even with a few degrees of warming, the amount that the insects can consume could easily double,” Deutsch says, though he notes their model becomes less accurate the smaller the area you look at.
Farmers might be able to combat the hungry bugs by rotating crops, introducing biological controls (like even hungrier predator bugs), or increasing their use of pesticides.
Sanford Eigenbrode, an entomologist at the University of Idaho, says the study is one of the most robust and comprehensive on climate change and insect-related crop loss he’s seen, though real life plant-crop interactions are more complex than any model could be.
And changes in temperature and carbon dioxide (CO2) emissions could also harm or help wheat, depending on the situation. Earlier this year, fires that were likely intensified by climate change destroyed a large portion of Oregon's wheat crop. A few studies have shown that the excess CO2, which plants use for photosynthesis, could initially boost the types of wheat grown in the Northwest. But many others have found that climate change will lead to a global decrease in wheat, corn and rice yields – even before insects are taken into account.
The picture isn't all bad. Heat waves in Montana lead scientists to test new, drought-resistant strains of wheat, though it remains to be seen if they'll be successful. Additionally, these models assume that carbon emission rates will continue at their current speed. "It will only warm as much as we let it," notes Deustch.