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NGSS: Core Idea: LS2.C

CCSS: Reading Informational Text: 2

TEKS: 6.2E, 6.12D, 7.13A, 8.11B, B.12E, E.4D

Locust Invasion!

Billions of flying bugs have swarmed parts of Africa and Asia, destroying any crops in their path. Can they be stopped?

AS YOU READ, THINK ABOUT how the rapid growth of an organism’s population can affect an ecosystem.

In 2018, a population of winged insects called desert locusts suddenly exploded in an isolated region of the vast Arabian Desert in western Asia. Storms had soaked the normally dry area with rain, causing plants to grow. With plentiful food available, the locusts began to breed. It was a disaster in the making for the people living in the region.

Monstrous swarms of locusts can contain billions of the insects and stretch over hundreds of miles. When these huge groups take flight, they sweep across an area and devour any vegetation in sight. A relatively small swarm of 40 million desert locusts can eat the same amount of food in a day that 35,000 people consume. These ravenous insects can destroy a whole season’s crop in a single morning—spelling serious trouble for farmers.

In 2018, a population of flying insects called desert locusts suddenly exploded. The bugs were living in part of the vast Arabian Desert in western Asia. Heavy rains had soaked the normally dry area. That caused plants to grow. With plenty of food to eat, the locusts began to breed. It was a disaster in the making for the region’s people.

Giant swarms of locusts can contain billions of insects. The swarms can stretch over hundreds of miles. When these huge groups take flight, they eat any plants in their path. A relatively small swarm might contain 40 million locusts. They can eat the same amount of food in a day as 35,000 people. These hungry bugs can destroy a whole season’s crop in one morning. That spells big trouble for farmers.

ISAK AMIN/ARETE/FAO SOMALIA

CREEPY CRAWLY: Locusts can grow up to four inches long and normally live for three to five months.

Keith Cressman is a locust forecasting expert at the United Nations’ Food and Agriculture Organization, based in Rome, Italy. He had been monitoring the unusual rain in the Arabian Desert and had a hunch a massive locust invasion was on the horizon. “We started to see waves and waves of locust swarms fly out of that remote area into the neighboring countries of Yemen and Saudi Arabia,” says Cressman. “That’s when I knew something really bad had happened.”

Throughout 2019 and 2020, swarms erupted from the Arabian Desert and descended upon the Middle East, spreading southwest into Africa and as far east as India and Pakistan (see Spreading Swarms). Back-to-back seasons of heavy rain have fueled these continuous swarms, leading to the largest locust invasion in decades. If the swarms continue, they stand to threaten the food supply of millions of people and the livelihoods of 10 percent of the world’s population.

Keith Cressman is a locust forecasting expert. He works at the United Nations Food and Agriculture Organization, based in Rome, Italy. He had been monitoring the unusual rain in the Arabian Desert. And he had a hunch a big locust invasion was coming. “We started to see waves and waves of locust swarms fly out of that remote area into the neighboring countries of Yemen and Saudi Arabia,” says Cressman. “That’s when I knew something really bad had happened.”

Throughout 2019 and 2020, swarms erupted from the Arabian Desert. They descended on the Middle East, spreading southwest into Africa. They went as far east as India and Pakistan (see Spreading Swarms). Back-to-back seasons of heavy rain have kept these swarms going nonstop. They’ve led to the largest locust invasion in decades. If the swarms continue, they could threaten the food supply of millions of people. And they could affect the income of 10 percent of the world’s people.

INSECT TRANSFORMATION

Locust swarms don’t happen often. In fact, they occur only when the insects undergo a remarkable transformation. In small numbers, locusts are harmless, says Hojun Song, an entomologist, or insect scientist, at Texas A&M University. The bugs don’t move around much and mostly avoid one another. Scientists call this the locusts’ solitary phase (see Locust Life Cycle).

But when locust populations start to grow in response to changing conditions in their environment, like they did in the Arabian Desert in 2018, the insects go through a dramatic change. Their colors shift from dark green to bright yellow and black. The insects also group together and become more active. When a locust transforms, “It’s like the Hulk,” says Song. The insects enter a gregarious, or social, phase. They form swarms with a single purpose: finding food.

Locust swarms don’t happen often. They occur only when the insects go through a big change. In small numbers, locusts are harmless, says Hojun Song. He’s an entomologist, or insect scientist, at Texas A&M University. The bugs don’t move around much. They mostly avoid one another. Scientists call this the locusts’ solitary phase (see Locust Life Cycle).

When changes in the environment cause locust populations to grow, the insects change. Their colors shift from dark green to bright yellow and black. The bugs also group together. And they become more active. When a locust transforms, “It’s like the Hulk,” says Song. Scientists call this the gregarious, or social, phase. Locusts form swarms with one goal: finding food. That’s what happened in the Arabian Desert in 2018.

For thousands of years, no one realized that green solitary locusts and yellow gregarious locusts were the same species. A Russian scientist named Boris Uvarov made the discovery in 1920, when he raised locusts in two different environments: alone or crowded in cages. When by themselves, the locusts stayed calm and docile. But when packed together, they switched to their destructive black-and-yellow form.

This ability to transform is an adaptation that helps locusts survive in a harsh desert environment where food is often scarce. Grouping into a fast-moving and determined swarm gives them a better chance of locating something to eat. This adaptation is good for the insects but bad for people.

For thousands of years, no one realized that green locusts and yellow locusts were the same species. A Russian scientist named Boris Uvarov made the discovery in 1920. He raised locusts in two different environments. Some lived alone. Others were crowded in cages. When they were by themselves, the locusts stayed calm and green. But when packed together, they switched to their destructive black-and-yellow form.

This ability to transform is an adaptation. It helps locusts survive in a harsh desert environment where food is scarce. Grouping into a fast-moving swarm gives them a better chance of finding something to eat. This adaptation is good for the insects. But it’s bad for people.

VISHAL BHATNAGAR/NURPHOTO VIA GETTY IMAGES

INSECT INVASION: Swarms of locusts descend on the city of Jaipur, in India.

TAKING ACTION

The best way to stop swarms is to detect locust-breeding hot spots early. Then measures can be taken to reduce the number of insects before their population grows out of control. That’s why locust forecasters like Cressman work to predict where outbreaks will occur. He gathers information about Earth’s surface using satellite images—a technique called remote sensing. In particular, he looks at images taken with cameras that detect green wavelengths of light. These colors indicate the presence of plants. Patches of green in the desert, for example, are warning signs of impending locust booms.

That’s what Cressman saw in the Arabian Desert in 2018. But because the region was so hard to reach, it was difficult for locust survey teams to respond quickly. When a team arrived to assess the situation almost nine months later, it was too late—the swarms were already on the move. Now, says Cressman, the goal is to minimize the destruction caused by the locusts until drier weather returns. Then the insect numbers will die down naturally.

The best way to stop swarms is to find places where the locust population is growing. Then people can try to reduce the bugs’ numbers before they grow out of control. That’s why locust forecasters like Cressman work to predict where outbreaks will happen. He gathers information about Earth’s surface using satellite images. It’s a method called remote sensing. He looks at images taken with cameras that detect green light. These colors show where plants are growing. Patches of green in the desert are warning signs of locust booms coming soon.

That’s what Cressman saw in the Arabian Desert in 2018. But the region is hard to reach. So it was difficult for survey teams to respond quickly. When people arrived to check on the situation almost nine months later, it was too late. The swarms were already on the move. Now, says Cressman, the goal is to minimize the destruction the locusts can cause. When the weather gets drier, the insect numbers will drop again.

To try to hold back the swarms, affected countries send teams into the countryside to search for locusts. Once the bugs are spotted, a plane blankets the area with pesticides. Some nations, like India, are also using small flying robots called drones for both locust surveillance and spraying. But not all regions have the resources to mount an effective response to the swarms. Many of the hardest-hit countries are also dealing with other crises, from political unrest to the coronavirus pandemic. As a result, locusts have continued to multiply and spread.

To try to hold back the swarms, affected countries send people out to search for locusts. Once the bugs are spotted, a plane sprays pesticides. Some nations, like India, use small flying robots called drones. These help with keeping an eye on the bugs and with spraying. But some places don’t have the tools they need to fight the swarms. Many countries are also dealing with other crises. Those include political troubles and the coronavirus pandemic. So locusts have continued to multiply and spread.

END IN SIGHT?

It’s becoming increasingly clear that no country can succeed in battling the locust infestation on its own, says Cressman. Instead, he says, it will take a global effort. In May 2020, the U.S. National Oceanic and Atmospheric Administration joined in the fight by repurposing technology originally designed to track smoke from wildfires to track locusts instead. The technology works by forecasting wind patterns, which can help predict where swarms will travel next.

It seems that no country can win the battle against locusts on its own, says Cressman. Instead, he says, it will take a global effort. In May 2020, the U.S. National Oceanic and Atmospheric Administration joined the fight. It’s using technology that was built to track smoke from wildfires. Now these tools track locusts instead. The process relies on predicting wind patterns. That can help show where swarms will go next.

TONY KARUMBA/AFP VIA GETTY IMAGES

PEST CONTROL: A community volunteer in eastern Kenya sprays pesticide at a potential locust hot spot.

Scientists are developing biopesticides to make fighting locusts safer as well. These natural substances, which include certain fungi, kill locusts. But unlike toxic pesticides, they’re harmless to people and most other creatures. “Biopesticides are exciting tools because there is much less environmental damage,” says Rick Overson, a biologist at Arizona State University who studies ways to sustainably manage locusts.

Overson hopes these and other scientific discoveries will better equip people to combat locusts going forward. Some countries hadn’t experienced an outbreak of this size for 70 years and were left scrambling to find ways to beat back the bugs. The best method to prevent a similar disaster in the future, Overson says, is to be prepared. When it comes to a locust outbreak, “You need to catch it early. It’s very hard to control once it gets out of hand.”

Scientists are making biopesticides to fight locusts safely. These are natural substances that kill the bugs. Some are fungi. Unlike toxic pesticides, these substances are harmless to people and most other creatures. “Biopesticides are exciting tools because there is much less environmental damage,” says Rick Overson. He’s a biologist at Arizona State University who studies ways to manage locusts.

Overson hopes these and other scientific discoveries will help people fight locusts in the future. Some countries hadn’t had an outbreak this big for 70 years. They were scrambling to find ways to beat back the bugs. It’s important for countries to be prepared, Overson says. When a locust outbreak happens, “You need to catch it early. It’s very hard to control once it gets out of hand.”

VISHAL BHATNAGAR/NURPHOTO VIA GETTY IMAGES

ROTTING REMAINS: Dead locusts pile up at a farm in Somalia after pesticide spraying.

CONSTRUCTING EXPLANATIONS: Consider the conditions that spawned the locust outbreak. How might increased storms and rain, brought about by climate change, affect future swarms?

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