Billions of desert locusts are swarming across eastern Africa—mainly affecting Kenya, Somalia, and Ethiopia but likely to spread further.

The swarms are massive; one of the largest in Kenya is about 37 miles long and 25 miles wide. For reference, that could cover more than half of Long Island. The swarms, which are dense enough at times to block out the sun, are the worst to hit Ethiopia and Somalia in 25 years, and the worst in Kenya in 70 years.

“This is an unprecedented situation that we are facing,” Dominique Burgeon, an emergency services director at the United Nations Food and Agriculture Organization, tells Nathanial Gronewold of Energy & Environment News.

Desert locusts eat all the vegetation they encounter, and the finger-length insects consume an amount equal to their body weight each day. Each square kilometer of swarm can include 40 to 80 million locusts and eat as much food as 35,000 people, according to the United Nations’ Food and Agriculture Organization (FAO).

“Even cows are wondering what is happening,” Ndunda Makanga, whose farm has been hit by the swarms, tells reporters for the Associated Press. “Corn, sorghum, cowpeas, they have eaten everything.”

In addition to destroying crops in a region where nearly 20 million people face food insecurity, swarms also consume the vegetation on cattle grazing land in a matter of hours. To manage the insects, Kenya and Ethiopia are spraying pesticides from airplanes. The countries have about five planes each, but as the locusts spread, there are more of them than the local systems can handle.

“So far we have decimated around five swarms in Samburu and Isiolo [counties in Kenya] but we keep on receiving more swarms every week, and that is a lot in terms of the ecosystem,” Isiolo’s chief agriculture officer Salat Tutana tells Time magazine. “They are trying to mate and reproduce, so we need more help and because we are racing against time.”

Aerial pesticide spraying is the only effective way to combat desert locust swarms, according to the FAO, which is seeking $70 million in aid to support additional efforts to contain the pests. But Somalia, which has declared the swarms an emergency, can’t deploy pesticide-spraying planes because of security concerns in the country, where some areas are controlled by the al-Qaida-linked al-Shabab extremist group, per the AP.

The swarms are reaching such an unusual size now because of cyclones that rained on the deserts of Oman last year, the FAO’s senior locust forecasting officer Keith Cressman tells Reuters’ Nita Bhalla.

“We know that cyclones are the originators of swarms - and in the past 10 years, there’s been an increase in the frequency of cyclones in the Indian Ocean,” Cressman tells Reuters. Eight cyclones occurred in 2019.

“Normally there’s none, or maybe one. So this is very unusual," Cressman says. "It’s difficult to attribute to climate change directly, but if this trend of increased frequency of cyclones in Indian Ocean continues, then certainly that’s going to translate to an increase in locust swarms in the Horn of Africa.”

The next rainy season in eastern Africa will begin in March, which will bring a new wave of vegetation growth and locust breeding. Female locusts only lay their eggs when the ground is damp. While swarming, which is also called their “gregarious” phase, the locusts lay egg pods of about 80 eggs that usually hatch within two weeks. Factoring in hatching and survival rates, each pod leads to about 16 to 20 adult locusts, which mature in two to four months and start the cycle again.

By the time the weather dries up again in June, the FAO estimates that the current population of desert locusts could multiply by a factor of 500. The swarms have already entered Ethiopia’s Rift Valley, according to the FAO’s most recent report, and they are approaching Uganda and South Sudan.

E&E News reports that FAO Director-General Qu Dongyu was assured by the United States secretary of agriculture that they would receive support from the department, and the U.S. Agency for International Development tells E&E News that it pledged $800,000 to the efforts.

“It’s a very critical time,” Qu tells E&E News. “The international community should act as quickly as possible.”