University of Cambridge tool will help predict locust swarms that devastate crops in Africa and Asia

A tool that predicts the behaviour of desert locust populations has been developed to help national agencies manage huge swarms before they devastate food crops in Africa and Asia.

While desert locusts typically lead solitary lives, some conditions - like intense rainfall - trigger them to swarm in vast numbers, which can have devastating consequences.

A swarm covering one square kilometre can consume enough food in one day to feed 35,000 people - destruction that can push up local food prices and lead to riots and mass starvation.

A team led by the University of Cambridge has developed a way to predict when and where desert locusts will swarm, using weather forecast data from the UK Met Office and computational models of the insects’ movements in the air to predict where swarms will go as they seek feeding and breeding grounds.

It means the areas likely to be affected could be sprayed with pesticides.

Climate change is expected to lead to more frequent desert locust swarms by causing trigger events like cyclones and intense rainfall. These bring moisture to desert regions, which allows plants to thrive and provides food for locusts that triggers their breeding.

The model is published in the journal PLOS Computational Biology.

“During a desert locust outbreak we can now predict where swarms will go several days in advance, so we can control them at particular sites. And if they’re not controlled at those sites, we can predict where they’ll go next so preparations can be made there,” said first author Dr Renata Retkute, a researcher in the Department of Plant Sciences.

“The important thing is to respond quickly if there’s likely to be a big locust upsurge, before it causes a major crop loss,” said senior author Prof Chris Gilligan, from the same department.

“Huge swarms can lead to really desperate situations where people could starve.

“Our model will allow us to hit the ground running in future, rather than starting from scratch as has historically been the case.”

Desert locusts are the biggest migratory pest for smallholder farmers in many regions of Africa and Asia and are capable of long-distance travel across national boundaries.

There was a massive upsurge between 2019 and 2021, which extended from Kenya to India and put huge strain on wheat production.

The infestations destroyed sugarcane, sorghum, maize and root crops.

“The response to the last locust upsurge was very ad-hoc, and less efficient than it could have been. We’ve created a comprehensive model that can be used next time to control this devastating pest,” said Dr Retkute.

Until now, predicting locust behaviour has been hit and miss, failing to predict swarm behaviour rapidly or reliably.

The new model takes into account the insects’ lifecycle and their selection of breeding sites, and can forecast locust swarm movements both short and long-term. It has been tested using real surveillance and weather data from the last major locust upsurge and will inform surveillance, early warning and management of desert locust swarms by national governments and international organisations like the Food and Agriculture Organisation of the United Nations (FAO).

Countries that have not experienced a locust upsurge for years are often poorly prepared when it does happen, lacking the surveillance teams, aircraft and pesticides to respond.

With climate change altering the movement of swarms, better planning is key.

The project involved collaborators at the FAO and the UK Met Office and was funded by the UK Foreign, Commonwealth and Development Office and the Bill and Melinda Gates Foundation.