East Africa is in the midst of a crisis that sounds like something out of the Book of Exodus: A plague of locusts is spreading across the region, threatening the food supply of tens of millions. City-sized swarms of the dreaded pests are wreaking havoc as they descend on crops and pasturelands, devouring everything in a matter of hours. The scale of the locust outbreak, which now affects seven East African countries, is like nothing in recent memory.
The insects behind the mayhem are desert locusts, which, despite their name, thrive following periods of heavy rainfall that trigger blooms of vegetation across their normally arid habitats in Africa and the Middle East. Experts say a prolonged bout of exceptionally wet weather, including several rare cyclones that struck eastern Africa and the Arabian Peninsula over the last 18 months, are the primary culprit. The recent storminess, in turn, is related to the the Indian Ocean Dipole, an ocean temperature gradient that was recently extremely pronounced, something that’s also been linked to the devastating bushfires in eastern Australia.
Unfortunately, some experts say it may be a harbinger of things to come as rising sea surface temperatures supercharge storms and climate change tips the scales in favor of circulation patterns like the one that set the stage for this year’s trans-oceanic disasters.
“If we see this continued increase in the frequency of cyclones,” says Keith Cressman, senior locust forecasting officer with the Food and Agriculture Organization, “I think we can assume there will be more locust outbreaks and upsurges in the Horn of Africa.”
Tracking a plague
According to Cressman, the desert locust crisis traces back to May 2018, when Cyclone Mekunu passed over a vast, unpopulated desert on the southern Arabian Peninsula known as the Empty Quarter, filling the space between sand dunes with ephemeral lakes. Because desert locusts breed and reproduce freely in the area, this likely gave rise to the initial wave. Then, in October, Cyclone Luban spawned in the central Arabian Sea, marched westward, and rained out over the same region near the border of Yemen and Oman.
Desert locusts live for about three months. After a generation matures, the adults lay their eggs which, under the right conditions, can hatch to form a new generation up to 20 times larger than the previous one. In this way, desert locusts can increase their population size exponentially over successive generations, Cressman says. Ultimately, these two 2018 cyclones enabled three generations of wildly successful locust breeding in just nine months, increasing the number of insects buzzing over the Arabian desert roughly 8,000-fold.
Then the locusts started to migrate. By the summer of 2019, swarms were leapfrogging over the Red Sea and the Gulf of Aden into Ethiopia and Somalia, where they enjoyed another bout of successful breeding in subsequent months, Cressman says. This might have been as far as the locusts got were it not for the fact that last October, East Africa experienced unusually widespread and intense autumn rains, which were capped in December by a rare late season cyclone that made landfall in Somalia. These events triggered yet another reproductive spasm.
As the locusts continue to multiply, they’re invading new areas. By late December, the first swarms were starting to arrive in Kenya, moving quickly throughout the country’s northern and central areas; by January, the country was experiencing its worst infestation in 70 years. Djibouti and Eritrea also started developing locust infestations, and on February 9, swarms of the insects started arriving in northeast Uganda and northern…