Huge swarms of locusts plaguing eastern Africa are the result of extreme weather events over the past two years.
Swarms of desert locusts (Schistocerca gregaria) are rampaging through several countries including Ethiopia, Somalia and Kenya. The locusts are devastating pastures and cropland, threatening the livelihoods of millions of people.
The Food and Agriculture Organization of the United Nations (FAO) said in a statement that the swarms are unprecedented: 鈥淓thiopia and Somalia have not seen desert locust swarms of this scale in 25 years, while Kenya has not faced a locust threat of this magnitude in 70 years.鈥�
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鈥淭here was one [swarm] in north-east Kenya that was 40 kilometres long and 60 kilometres wide,鈥� says Keith Cressman, the FAO鈥檚 senior locust forecasting officer in Rome, Italy.
Desert locusts are a kind of grasshopper. They are normally solitary, but if food is plentiful, they breed rapidly and gather into swarms that eat everything in their path.
The current swarms began when cyclones that formed in the Indian Ocean drenched the southern Arabian desert. In May 2018, Cyclone Mekunu hit the Arabian peninsula. Then in October that year, Cyclone Luban struck almost the same place.
The region is 鈥渉undreds and hundreds of towering sand dunes鈥�, says Cressman, and 鈥渢here were lakes forming between the sand dunes鈥�. The water brought vegetation, which allowed the desert locusts to feed and reproduce rapidly.
By early 2019, it was drying out and the locusts left. Some went north to Iran, which saw its first swarms in 50 years, while others moved south-west into Yemen. They might have been stopped there, but Yemen had no resources to tackle them because of its ongoing civil war, says Cyril Piou of the French Agricultural Research Centre for International Development in Montpellier.
From there they hit Ethiopia and Somalia in summer 2019. Both countries began spraying the swarms with pesticides. 鈥淚 was not overly concerned,鈥� says Cressman. Ethiopia鈥檚 weather turns cold and dry in winter, so he expected the locusts to be finished off by the end of 2019.
Then nature intervened. On 7 December 2019, Cyclone Pawan hit East Africa. 鈥淚t dumped enough rain for breeding conditions to continue to be favourable until about this June,鈥� says Cressman. 鈥淭hat was just perfect timing for the locusts.鈥�
It isn鈥檛 clear if climate change is responsible for the cyclones, and therefore the locust swarms. While there is evidence that cyclones in other ocean basins are being affected by climate change, records for the Indian Ocean are poor and studies are contradictory.
鈥淲hat we can say for certain is that, in the last 10 years, the frequency of cyclones in the Indian Ocean has increased, most notably in the last three years,鈥� says Cressman. The region typically gets one cyclone per year, but 2019 saw eight. It could be a fluke, but 鈥渋f that trend continues, for sure we鈥檙e going to be facing more desert locust outbreaks in the Horn of Africa like the one we have now鈥�, he says.
The immediate problem is controlling the locusts. Several African countries are likely to be invaded soon, including Uganda and South Sudan. 鈥淭his needs people and resources set in place quickly,鈥� says Piou. The FAO has for the region.
In the longer term, the locusts in Ethiopia will breed throughout the spring. By summer, the winds will change and carry them north-east towards India and Pakistan. 鈥淚ndia, for the first time in a long time, could have a substantial swarm invasion at the beginning of summer,鈥� says Cressman. 鈥淭hey鈥檙e doubling the number of control teams they had last summer.鈥�
