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Updated Feb 12, 2020

Locusts swarming their way across East Africa, numbering in the hundreds of billions, pose a catastrophic threat to millions of people. 

The swarms originated on the southern Arabian peninsula in Oman, then spread to Iran and Yemen before crossing into East Africa. Two of the worst-affected countries are Ethiopia, which is now experiencing the worst swarms it’s seen in twenty-five years, and Kenya, which hasn’t seen swarms this destructive and large–some are the size of major cities–in seventy years. These particular swarms’ magnitude is caused by a combination of biological and natural factors creating a perfect cocktail for rapid locust growth and destructive capability.

Locusts are a particular variant of grasshoppers known for their gregariousness, a biological term referring to the phenomenon in which they physically alter their bodies as they group up into swarms. It’s an adaptation due to their hostile environment. When food supplies grow short, especially in desert regions, they form into swarms to migrate in search of new nourishment. A locust can travel about ninety miles (one hundred forty-four kilometers) in a single day, consuming its body weight daily as it does so. In one day, a locust swarm can consume as much food as thirty-five thousand people.

Their gregariousness transforms them into meatier insects, with larger legs and a striking black-and-yellow coloration that indicates to potential predators that they are toxic. To maintain their new size, they focus on consuming excessive amounts of carbohydrates. Grains, rich in carbohydrates, become their meal of choice, which poses a threat to food security, as grains are also a staple of most human diets.

Water is another factor that has affected the destructiveness of these swarms of locusts. Rain is crucial for vegetation to flourish, especially in a desert environment, and desert locusts need to lay their eggs–as many as one thousand per square meter–in moist soil to keep them hydrated. Heavy rains in 2018 and the two cyclones that followed flooded the southern Arabian peninsula with enough water to allow vegetation to grow for six months, which was enough food for two generations of locusts to grow and spread. Due to the exponential nature of locust breeding, each generation sees a twenty-fold increase in its population, meaning two generations resulted in a four-hundred-fold population explosion.

Finally, the remote position of where this recent spate of locusts first matured, in a completely underdeveloped region of Oman, made it more difficult for their populations to be controlled via pesticide management, as early detection and action are crucial. When they crossed into Yemen they were also left untouched, as the ongoing war made it impossible for pesticide-spraying squads to perform their work, and then heavy rains hit that country, too, resulting in more generations of locusts. The swarms then moved north towards Iran and hopped the Red Sea to land in Somalia, resulting in the East African tragedy that is still unfolding.

 

https://www.wired.com/story/the-terrifying-science-behind-the-locust-plagues-of-africa/

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