Clouds of locusts are swarming through East Africa in historic numbers, forming a potentially catastrophic plague unlike anything some areas have seen in generations. The insatiable insects, which seem to be capitalizing on a mix of environmental conditions favored by climate change, pose a fast-growing threat to farmers and food availability across the region.

"The current desert locust situation remains extremely alarming and represents an unprecedented threat to food security and livelihoods in the Horn of Africa," the U.N.'s Food and Agriculture Organization (FAO) said in a Jan. 28 update. "This will be further exacerbated by new breeding that has commenced, which will cause more locust infestations."

desert locusts in Kenya, January 2020
'Ravenous swarms' of desert locusts, already unprecedented in size and destructive potential, threaten the entire East Africa subregion, the U.N. warned Jan. 20. (Photo: Tony Karumba/AFP/Getty Images)

The locusts have devoured hundreds of square kilometers of vegetation in Ethiopia since November, according to Oxfam, and are now erupting through Kenya and Somalia. Kenya has not experienced a locust outbreak like this in 70 years, an FAO official tells the Associated Press, while it's the worst Ethiopia or Somalia has seen in a quarter century.

These countries now have larger populations and already face other threats to food security, including both droughts and flooding. That has left them more vulnerable to a locust plague of this scale, along with nearby countries like Uganda and South Sudan.

"Uganda has not had to deal with a locust infestation since the '60s, so there is concern about the ability for experts on the ground to be able to deal with it without external support," the FAO's Rosanne Marchesich tells the AP. "And in a country like South Sudan, already 47% of the population is food insecure."

desert locusts in Kenya, January 2020
During plagues, desert locusts have the potential to damage the livelihood of a tenth of the world's population, according to the FAO. (Photo: Tony Karumba/AFP/Getty Images)

These are desert locusts, which are not only the most destructive kind of locust, but also "the most dangerous of all migratory pest species in the world," as one U.N. expert describes them.

They're normally solitary insects, but in certain environmental conditions, they undergo an incredible transformation, changing their appearance, physiology and behavior as they shift from solitary to "gregarious" mode. That means brighter coloring — like pink or yellow instead of brown — as well as broader shoulders, longer wings, higher metabolic rates and a more "restless and irritable" temperament. The two phases are so different that, until 1921, scientists thought they were separate species.

Most importantly, gregarious-phase locusts are compelled to swarm, mate and eat as long as they can find enough food to sustain them. Populations can explode in the right conditions, prompting them to ride high-level winds in search of food, sometimes covering 130 km (80 miles) or more in a day. They regularly cross the Red Sea, a distance of 300 km (186 miles), and have been known to travel even farther. Desert locusts flew from West Africa to the British Isles in 1869 and 1954, for example, and from West Africa to the Caribbean in 1988, a trip of 5,000 km (3,100 miles) they completed in about 10 days, according to the FAO.

desert locusts in Kenya, January 2020
Children swing sticks at locusts as they run through a swarm in Kenya's Larisoro village on Jan. 21. (Photo: Tony Karumba/AFP/Getty Images)

Locusts have plagued humanity for millennia, yet we still struggle to control them. People have tried a variety of tactics, including flamethrowers and explosives, but the swarms often grow too large and resilient too quickly. Our best bet seems to be catching them early or predicting their irregular surges, both of which have also proven difficult. Large amounts of insecticide can help, although that raises new issues for human and ecological health, and may be inadequate anyway once a swarm is big enough.

desert locusts in Kenya, January 2020
When solitary desert locusts transform into their 'gregarious' phase, they grow larger and change colors, from brown to pink (immature) and yellow (mature). (Photo: Tony Karumba/AFP/Getty Images)

There is no evidence to suggest desert locusts swarm after a specific number of years, according to the FAO. Their plagues seem to hinge more on circumstance than any kind of cycle.

Desert locusts need good places to lay eggs — with bare ground and moist, sandy soil 10 to 15 cm (4 to 5 inches) deep — plus lots of greenery for their young to eat. Ideal conditions often exist without sparking a plague, though, and predicting the rise and spread of locust swarms remains a challenge, despite long-running efforts of scientists at the FAO and elsewhere.

And while the threat of locusts is nothing new, it is becoming more dangerous. That's partly because of growing human populations, since food supplies are already thin in many places, and partly because of human-induced climate change, which promotes many of the conditions that favor locust plagues like the one now sweeping through East Africa.

desert locusts in Kenya, January 2020
A yellow shroud of desert locusts removes foliage from a shrub in Kenya's Samburu County. (Photo: Tony Karumba/AFP/Getty Images)

Desert locusts often thrive in warm, wet weather, which provides deeper moisture for their eggs and more vegetation to feed their offspring. East Africa had one of its rainiest years on record in 2019, as Nairobi-based climate scientist Abubakr Salih Babiker recently told the AP, and some parts of the region are still receiving heavy rains.

Babiker traces all that rainfall back to rapidly warming waters in the Indian Ocean, which helped create a barrage of storms off the eastern coast of Africa, including a high number of strong tropical cyclones.

Along with hot weather on the ground, this led to "exceptional" conditions for desert locusts to swarm. "Countries are trying to prepare," Babiker says, "but this took them by surprise."

desert locusts in Kenya, January 2020
Locusts swarm above a highway in Samburu County on Jan. 22. (Photo: Tony Karumba/AFP/Getty Images)

Even a small swarm of desert locusts can eat enough food for 35,000 people in a single day, according to the FAO, and plagues can become economically devastating. An outbreak from 2003 to 2005 covered 20 countries and cost more than $500 million to contain, along with more than $2.5 billion in crop losses.

Locusts have already covered 70,000 hectares (173,000 acres) in Kenya alone, according to PBS Newshour, including one swarm measuring about 60 kilometers long by 40 kilometers wide (37 by 25 miles). And as big as this plague already is, it could grow another 500 times larger by June, according to the FAO. Local authorities are scrambling to contain it before that happens, and the U.N. this week allocated $10 million to help with that effort, mainly via pesticides.

desert locusts in Kenya, January 2020
Locust swarms can cover hundreds of square kilometers, with as many as 80 million individual locusts per square kilometer. (Photo: Tony Karumba/AFP/Getty Images)

As with almost any pest, the need to control locusts probably shouldn't grow into a desire to eradicate them completely. They are wild animals performing a natural phenomenon, as Mashable points out, and simply wiping them out could have countless unintended consequences across many ecosystems.

"It's one of the wonders of the natural world," Iain Couzin, who studies locust swarms at the Max Planck Institute of Animal Behavior, tells Mashable. "We don't want to stop them. We just want to manage them."

That's easier said than done, of course. Researchers continue to work on better tactics, from safer pesticides to more accurate ways of forecasting locust swarms, not to mention ongoing efforts to curb the greenhouse gas emissions behind climate change.

And while it may have little effect on its own, there is also another ancient technique for taking a bite out of locust swarms. Locusts are rich in protein and easy to collect during a swarm, and since they eat our food, there is some justice in eating them instead. "Locusts are usually stir-fried, roasted or boiled and eaten immediately, or dried and eaten later," according to the FAO, which includes a list of recipes.

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.