Since the dawn of agriculture, humans have been unwillingly nourishing insects by growing plants that they then devour. Their mandibles consume somewhere between 10 and 20 percent of crops produced around the world. And these losses are likely to grow as the world slowly warms.
By looking at how insects will respond to rising temperatures, a team of researchers led by Curtis Deutsch and Joshua Tewksbury have calculated how rice, maize, and wheat—which provide 42 percent of humanity’s calories—will fare as the globe heats up. The results aren’t pretty.
They estimate that the portion of these grains that’s lost to insects will increase by 10 to 25 percent for every extra degree Celsius of warming.Some predictions say that we can almost certainly expect 2 degrees of warming by the end of the century. If that happens, and the team’s calculations are accurate, then every year, the burgeoning legions of insects will deprive the world of a further 19 million metric tons of wheat, 14 million metric tons of rice, and 14 million metric tons of maize. “We’re not talking about the collapse of agriculture, but we’re talking about significant losses,” says Deutsch, who works at the University of Washington.
Even if insects do nothing, warming temperatures are already likely to affect plants directly and reduce crop yields by around five percentage points per degree of warming, according to Deutsch. The losses triggered by insects will likely add on top of those, reducing yields by another two to four percentage points. Put it this way: If a farmer is currently growing 100 tons of grain per hectare, she’d likely get just 84 tons in a world that’s 2 degrees warmer.
If anything, May Berenbaum, an entomologist at the University of Illinois at Urbana-Champaign, thinks that those figures are probably underestimates. “Three decades of studies have shown that elevated carbon dioxide and temperatures can lower the nutritional quality of certain plants, and decrease the ability of plants to produce toxins to protect themselves,” she says. Both factors might drive insects to devour crops even more readily than they otherwise would…
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