What's behind the locust swarms damaging crops in Southern Africa?

In this article, originally published by theconversation.com, Prof Frances Duncan of the School of Animal, Plant and Environmental Sciences at the University of the Witwatersrand, whose research involves investigating the survival strategies of brown locusts, explains what is behind the migratory locust outbreak ravaging crops and pastures across Southern Africa.

Africa is currently experiencing two locust outbreaks, both due to unusual climatic conditions.

These two outbreaks are unrelated, but are the result of the unusually high rainfall and flooding in the areas where low densities of the locusts occur. The desert locust (Schistocerca gregaria) is producing a plague type outbreak in North and East Africa, which started in June 2019, and the threat is still there.

Then there are localised swarms of the African migratory locust (Locusta migratoria migratorioides) in Southern Africa. Two other locust species, the red locust (Nomadacris septemfasciata) and the brown locust (Locustana pardalina), are known to have swarmed and caused agricultural damage in Southern Africa, affecting seven million people in Botswana, Namibia, Zambia and Zimbabwe.

How swarms form

Locusts are grasshoppers that have the potential to form a swarm of thousands to hundreds of thousands of individuals. They undergo phase polymorphism, which means that they can change from a solitary form into a gregarious form, congregating in large numbers. These forms have different colours and different behaviours.