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How to Stop a Plague of Locusts

Step one: pray.

Despite calling to mind biblical curses, locust plagues are actually a very modern problem. Right now, Argentina is preparing for the worst locust plague it's seen in 60 years, and there's evidence that warmer temperatures and more intense weather events influenced by climate change are causing locust plagues to shift globally. They're descending on new locations, and, in some cases, becoming more frequent and more severe. When you take a look at what a locust plague looks like, it's a pretty disturbing thought. So what are we doing to stop it?


For years, our main strategy has been to simply watch the weather.

"We know locust plagues are affected by weather patterns, so understanding those patterns has helped us better predict where plagues might occur," said Arianne Cease, a sustainability researcher at Arizona State University who investigates the spread—and mitigation—of locust plagues. "We're looking to find any outbreak pockets of locusts when they're young, before they start flying, and then targeting them with pesticides. That's where we're at right now, but we think that we can take a step back even before that."

That's what they're doing in Argentina: spraying pesticides in a frantic attempt to decrease the locust population before it matures into adults, grows wings, and becomes a cloud of destruction decimating the country's cotton and sunflower crops. The jury is still out on what led to the locust population surge there, but after a series of warm, wet winters, some officials are pointing to climate change as a contributing factor. Climate change has also contributed to more severe locust outbreaks in China, and the United Nations Food and Agricultural Organization recently warned that climate change could lead to more locust outbreaks in parts of Africa.

Because locusts are an important part of their ecosystems, scientists don't want to just wipe them out.

There are about 20 species of locusts in the world and each of them is impacted differently by the weather, said Cease. That means environmental factors are not one-size-fits-all, although it's clear changes in weather mean changes in locust populations. But generally speaking, hotter, longer summers hasten the locusts' development cycle, which can lead to more generations of locusts in a season, creating a high population density. Wetter, warmer winters can have a similar effect by promoting growth of grasslands where locusts like to hang out (heavy rains can also wipe them out early in their development cycle).


Locusts are solitary insects most of the time, but when the population density reaches a certain point, their instinct to travel together and form a swarm kicks in, Cease said. That means the only time to strike is to find locusts when they're young. But it gets more complicated: because locusts, in manageable populations, are an important part of their ecosystems, scientists like Cease don't want to just wipe them out. They're hunting for solutions to keep locusts at bay without eradicating them, which is a tricky balancing act.

To solve this problem, Cease thinks scientists need to go beyond just weather monitoring if we hope to prevent and mitigate widespread locust outbreaks. Her lab takes a multi-pronged approach to locust studies, which is precisely why I wanted to talk to her. Monitoring the weather and killing off dense populations of locusts works some of the time, but it's not a great solution. Cease's lab is one of the few that's trying to find other ways to fight back. Rather than looking at it as a purely ecological problem, Cease and her colleagues consider the economical and cultural influences at play, too.

Her work, and the work of others, has shown land use has as much of an impact on locust population numbers as climate and weather patterns, for example. Cutting down forests, which act as a barrier between locust populations, can increase population density. Overgrazing, too, creates a hotbed for locust growth. By understanding these influences, policies and strategies can be put in place that limit or prevent locust outbreaks altogether, Cease said.

There are political influences at play, too. In the past, civil conflicts have prevented effective locust management—like spray pesticides when the population grows too dense—in places like Mali and Niger, leading to outbreaks. There are a lot of factors at play, and Cease says the only way to predict and prevent plagues is to consider all of those influences.

The solutions are pretty dry on paper—ideas like creating incentive programs for farmers to help them make better crop choices and prevent the spread of locusts—but if it results in fewer terrifying swarms of giant, crop-dissolving grasshoppers, maybe some dry policy research is exactly what we need.