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Swarms of locusts devastate vegetation in eastern Africa

Locust swarm (photo: Niv Singer)Locust swarm (photo: Niv Singer)Billions of desert locusts are swarming across Kenya, Somalia and Ethiopia in East Africa. They have reached Tanzania and Uganda, and are approaching South Sudan. Some of the swarms are huge: one in northeastern Kenya measured 60 kilometres long by 40 kilometres wide (37 by 25 miles). They can be dense enough to block out the sun. Desert locusts eat all the vegetation, including crops, they come across, each insect consuming an amount equal to its own body weight each day. A square kilometre (an area the size of almost 250 football pitches) of swarming insects can include 40 to 80 million locusts capable of eating as much food as 35,000 people. There have been seven major desert locust plagues since the 1900s, the last of which was in 2003–05. The current swarms are the worst to hit Ethiopia and Somalia in 25 years, and Kenya in 70 years.

Locust swarm, Isiolo county, Kenya, Feb 2020Video credit: Kulayo Happi Kulayo

Spraying locusts in Tanzania (ChriKo)Spraying locusts in Tanzania (ChriKo)


In addition to destroying crops in a region where tens of millions of people face food shortages due to long droughts, swarms of locusts also eat the vegetation that cattle graze on in just a few hours. There are already concerns for South Sudan, where many people face hunger as the country emerges from a long civil war. 

To kill the insects, pesticides can be sprayed from planes but there are more of them than the authorities can handle. Many of the locusts are breeding in the Puntland region of Somalia where al-Shabab, the Islamist terrorist group, is in control, making it impossible to carry out aerial spraying.


The swarms are reaching such an unusual size now because of heavy rains on the deserts of Oman following a cyclone in December 2019, creating perfect breeding conditions. In the past 10 years, the frequency of cyclones in the Indian Ocean has greatly increased—a likely consequence of climate change

Desert locusts breeding (C. Kooyman)Desert locusts breeding (C. Kooyman)The next rainy season in eastern Africa starts 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, the locusts lay egg pods of about 80 eggs that usually hatch within two weeks. Each pod produces about 16 to 20 adult locusts, which mature in two to four months and start the cycle again. By the time the dry season arrives in June, the current population of desert locusts could multiply by up to 500 times. 


Adult desert locust in flightAdult desert locust in flight

Desert locusts

Desert locusts are short-horned grasshoppers. They live in dry grasslands and semi-deserts of Africa and Asia. They grow to about 7 centimetres (2.75 inches) long—about the length of a finger—and have strong back legs for jumping. Their drab colours help them to blend in with the dry grass and other desert plants. 

Hoppers (young, flightless locusts)Hoppers (young, flightless locusts)When it rains in the grasslands and plants start to grow, the locusts reproduce rapidly to take advantage of the new source of food. New young locusts born after the rains, small wingless versions of the adults called hoppers, are brightly coloured. The hoppers roam along the ground, eating the new young shoots. They band together in groups hundreds of thousands strong. 

Locust moultingLocust moulting
The hoppers shed their skins (moult) every so often so that they can grow. After moulting about five times, they develop wings and become adults. They have shorter bodies and they change colour, first to brownish-red, then to yellow. Once adults, if weather conditions are suitable and the supply of food plentiful, the locusts swarm in their millions—or even billions. This swarming behaviour is triggered when the adults produce a hormone, called a pheromone. This acts as a kind of chemical signal, causing them all to be attracted to one another: they become "gregarious".

Locust swarm, Madagascar (Iwoelbern)Locust swarm, Madagascar (Iwoelbern)Adult locusts can eat their own weight in food every day. When swarms of hundreds of millions of them descend on an area, they will strip it completely bare of all vegetation in a matter of minutes. No predator can stop them—there are simply too many of them. The locusts are strong flyers, capable of travelling 100 kilometres (60 miles) per day—faster when wind-assisted—so migrating swarms can do immense damage across a wide area in just a few weeks.


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