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How to Fight Locusts Exactly? – Biodiversity Nepal
Biodiversity Nepal
For the Future Generation

How to Fight Locusts Exactly?

They're roving through croplands and flattening farms in a devastating salvo experts are calling an unprecedented threat to food security

A swarm of desert locusts flies above trees in a Kenyan village. Hundreds of millions of the insects have arrived in Kenya, where they're destroying farmland. BY Ben Curtis

Titanic swarms of desert locusts resembling dark storm clouds are descending ravenously on the Horn of Africa. They’re roving through croplands and flattening farms in a devastating salvo experts are calling an unprecedented threat to food security. On the ground, subsistence planters can do nothing but watch — staring up with horror and at their fields in dismay.

Locusts have been around since at least the time of the pharaohs of ancient Egypt, 3200 B.C., despoiling some of the world’s weakest regions, multiplying to billions and then vanishing, in irregular booms and busts.

If the 2020 version of these marauders stays steady on its warpath, the United Nations Food and Agriculture Organization says desert locusts can pose a threat to the livelihoods of 10% of the world’s population.

The peril may already be underway: Early June projections by the FAO are forecasting a second generation of spring-bred locusts in Eastern Africa, giving rise to new, powerful swarms of locust babies capable of wreaking havoc until mid-July or beyond.

Here are five things you need to know about locusts to understand the current crisis and why the tiny invaders are such a big deal.

A locust on a shea tree — a source of food and income for farmers. Photo by Sumy Sadumi

What is a locust?

There can be a lot of confusion about what exactly a locust is. To the average eye, it’s easy to mix up the critters with cicadas and crickets. The simple answer, though, explains Rick Overson of Arizona State University’s Global Locust Initiative, is that locusts are a very special kind of grasshopper.

As Overson explains, there are hundreds of species of grasshoppers, “but only a small handful of those are what we consider locusts.”

That raises a question: What makes a locust a locust? According to Overson, it comes down to a superpower possessed by locusts that enables them to go through a remarkable switch in development.

Most of the time, locusts exist in their “grasshopper phase” — they lead solitary lives, they’re green and pretty unremarkable.

“Nobody really notices them,” Overson says.

The timing of this varies, and the shifts are pretty irregular, but for years, locusts can live like this – alone, biding their time.

But when environmental conditions are right — usually when there’s a lot of rainfall and moisture — something dramatic happens: “They increase in numbers, and as they do so, they sense one another around them,” says Overson.

This is what biologists call the “gregarious phase” of the locust.

The creatures undergo a remarkable transformation. “They change their physiology. Their brain changes, their coloration changes, their body size changes,” Overson says. “Instead of repelling one another, they become attracted to one another — and if those conditions persist in the environment, they start to march together in coordinated formations across the landscape, which is what we’re seeing in eastern Africa.”

The ability to change dramatically like this in response to environmental conditions is called phenotypic plasticity. Many species, such as some types of coral, exhibit it. Though scientists can’t be certain why locusts developed the trait over time, many believe it’s because they typically live in temperamental and harsh environments.

“Locusts tend to live in areas where resources that they need are very unpredictable,” Overson explains. The Horn of Africa, for instance, is known for being arid, going for years without heavy rain until slammed suddenly by powerful downfalls. “The strongest hypothesis is that these crazy, unpredictable dynamics select evolutionarily for this ability to go through these dramatic changes, to respond when you can capitalize on a rare opportunity and also have the capacity to migrate.”

When locusts swarm like this, they ravage agriculture, devouring practically anything in sight.

Though they have teeth, locusts don’t bite humans. (Unless you, you know, jammed a finger into its mandible; it would maybe bite you then, Overson says.)

Where are the locusts swarming, and how big are the swarms?

Swarms are most intense in East African countries, including Kenya, Somalia and Ethiopia, but data from the FAO’s Desert Locust Watch documents steadily worsening infestations across Southwest Asia and the Middle East. Yemen, Saudi Arabia, Sudan, Uganda and Iran are among those afflicted.

Locusts swarm in a residential area of the Pakistani city of Quetta. The country is suffering its worst locust plague in 25 years. Photo by Banaras Khan

“In Kenya, it’s the worst outbreak they’ve had to face in the last 70 years,” says Keith Cressman, the U.N. Food and Agriculture Organization’s senior locust forecasting officer. “In India or Pakistan, it’s probably the worst they’ve had to face in the last quarter of a century.”

The swarms are gargantuan masses of tens of billions of flying bugs. They range anywhere from a square third of a mile to 100 square miles or more, with 40 million to 80 million locusts packed in half a square mile. They bulldoze pasturelands in dark clouds the size of football fields and small cities. In northern Kenya, Cressman says, one swarm was reported to be 25 miles long by 37 miles wide — it would blanket the city of Paris 24 times over.

Experts say the upsurge is likely to be tied to extreme weather events: According to Cressman, powerful cyclones in 2018 dumped water in Oman, Yemen and the Horn of Africa. The wet conditions have persisted, creating ideal bug breeding conditions.

Once they enter the gregarious phase, a generation of locusts can multiply twentyfold every three months. So when they boom, they do so exponentially, and things quickly get out of hand.

How far can locusts travel?

Locusts are migratory, transboundary pests. They ride the winds, crisscrossing swaths of land until they find something they want to munch on. They especially love cereal grain crops, planted extensively across Africa.

“They are powerful, long-distance flyers, so they can easily go a hundred plus kilometers in a 24-hour period,” Overson notes. “They can easily move across countries in a matter of days, which is one of the other major challenges in coordinated efforts that are required between nations and institutions to manage them.”

In 1988, swarms originating in North Africa crossed the Atlantic Ocean and made it successfully to the Caribbean and South America. Even today, they routinely traverse the Red Sea — a distance of 186 miles. Projections show that current locust populations are poised to spread “all the way from eastern to western Africa by June or July,” Overson says. “There are major concerns there.”

How do locusts affect food security?

Locusts are ravenous eaters. An adult desert locust that weighs about 2 grams (a fraction of an ounce) can consume roughly its own weight daily. And they’re not picky at all. According to the FAO, a swarm of just 1 square kilometer — again, about a third of a square mile — can consume as much food as would be eaten by 35,000 people (or six elephants) in a single day.

“When they do descend, they can have almost total devastation,” Overson says. “They can cause 50 to 80% of crops to be destroyed, depending on the time [of year].”

The last large locust outbreak, which started in 2003 and lasted until 2005, resulted in an estimated $2.5 billion in crop damage. Studies found that the economic effect was largely felt by subsistence farmers. Children who grew up during the period were much less likely to go to school, and girls were disproportionately affected.

Making matters worse, many of the countries slammed with the worst infestations are already hobbling from protracted crises — recovering from recessions, fighting natural disasters, racked by conflict and now the coronavirus outbreak.

“We’re talking about a corner of Africa that’s really, really vulnerable,” Cressman says. “They’ve had successive years of drought, and then this year, they’ve had heavy rains and floods. So even without the locusts, they’re already in a precarious situation.”

Now, Cressman says the potential hunger threat is tremendous in a region where 42 million were already slated to face acute food insecurity.

“The locusts are in your field for a morning, and by midday, there’s hardly anything left in your field,” he says. “It’s just eaten.”

How are countries fighting locusts?

Ugandan soldiers spray trees in an effort to kill locusts. Photo by Sumy Sadurmi

There’s a slate of international institutions that coordinates locust management and response. The primary effort is conducted by the United Nations Food and Agriculture Organization, which runs the Desert Locust Watch to surveil and track locust migration patterns and oversee regional response efforts.

In individual nations, a lack of cash, competing priorities and domestic challenges make it hard to mount a long-range pest management strategy. Because locust numbers ebb and flow, Overson says it’s been difficult for countries — such as Kenya, which hasn’t seen an infestation in 70 years — to build up intermediate and long-term infrastructure to address outbreaks proactively. That’s why so many governments are now scrambling to come up with solutions.

“It’s hard to maintain funding and political will and knowledge and capacity building when you have these unpredictable boom and bust cycles that could play out over years or decades,” he says. “The drama and spectacle of the outbreak right now is important to cover, but the more nuanced narrative involves the slow, ratchet method of building infrastructure: If you wait until it’s reactive and forget about it until it happens again, we’re going to be in this situation forever.”

Right now, the most effective way to fight outbreaks involves mass aerial sprays of pesticides to kill locusts. Overson says that’s not ideal, given the adverse effect such chemicals have on biodiversity and human health.

But emerging technologies may hold promise for the future. For example, the National Oceanic and Atmospheric Administration recently partnered with the United Nations to repurpose technology used to track smoke plumes from fires to predict the migrations of locusts, the Scientific American reported. And in terms of locust extermination, Overson says biopesticides have untapped potential — although lots of research and development is still needed in the area.

Considering all of the other worldwide emergencies that have hit in 2020, aid resources are stretched thin. Pesticide deliveries have been delayed. But Cressman is hopeful that the needed funds will materialize. The FAO has already raised half of the $300 million it expects to need for this effort.

“The international community is very well committed and they’re very much on board — even though there’s a lot that’s being asked of them for many other things at the moment,” he says.

Written by Pranav Baskar published June 14, 2020 in

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