̽��ֱ�� of Cambridge - Renata Retkute

Early warning tool will help control huge locust swarms

jg533 — Thu, 19 Dec 2024 19:00:34 +0000

Desert locusts typically lead solitary lives until something - like intense rainfall - triggers them to swarm in vast numbers, often with devastating consequences.

This migratory pest can reach plague proportions, and a swarm covering one square kilometre can consume enough food in one day to feed 35,000 people. Such extensive crop destruction pushes up local food prices and can lead to riots and mass starvation.

Now a team led by the ̽��ֱ�� of Cambridge has developed a way to predict when and where desert locusts will swarm, so they can be dealt with before the problem gets out of hand.

It uses weather forecast data from the UK Met Office, and state-of the-art computational models of the insects’ movements in the air, to predict where swarms will go as they search for new feeding and breeding grounds. ̽��ֱ��areas likely to be affected can then be sprayed with pesticides.

Until now, predicting and controlling locust swarms has been ‘hit and miss’, according to the researchers. Their new model, published today in the journal PLOS Computational Biology, will enable national agencies to respond quickly to a developing locust threat.

Desert locust control is a top priority for food security: it is the biggest migratory pest for smallholder farmers in many regions of Africa and Asia, and capable of long-distance travel across national boundaries.

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

“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 Dr Renata Retkute, a researcher in the ̽��ֱ�� of Cambridge’s Department of Plant Sciences and first author of the paper.

“ ̽��ֱ��important thing is to respond quickly if there’s likely to be a big locust upsurge, before it causes a major crop loss. Huge swarms can lead to really desperate situations where people could starve,” said Professor Chris Gilligan in the ̽��ֱ�� of Cambridge’s Department of Plant Sciences, senior author of the paper.

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

̽��ֱ��team noticed the need for a comprehensive model of desert locust behaviour during the response to a massive upsurge over 2019-2021, which extended from Kenya to India and put huge strain on wheat production in these regions. ̽��ֱ��infestations destroyed sugarcane, sorghum, maize and root crops. ̽��ֱ��researchers say the scientific response was hampered by the need to gather and integrate information from a range of disparate sources.

“ ̽��ֱ��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 Retkute.

Although models like this have been attempted before, this is the first that can rapidly and reliably predict swarm behaviour. It takes into account the insects’ lifecycle and their selection of breeding sites, and can forecast locust swarm movements both short and long-term.

̽��ֱ��new model has been rigorously tested using real surveillance and weather data from the last major locust upsurge. It 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).

̽��ֱ��researchers say countries that haven’t experienced a locust upsurge in many years are often ill-prepared to respond, lacking the necessary surveillance teams, aircraft and pesticides. As climate change alters the movement and spread of major swarms, better planning is needed - making the new model a timely development.

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

Reference: Retkute, R, et al: ‘A framework for modelling desert locust population dynamics and large-scale dispersal.’ PLOS Computational Biology, December 2024. DOI: 10.1371/journal.pcbi.1012562

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

̽��ֱ��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.

Renata Retkute

Keith Cressman, FAO

Locust swarm fills the skies in Ethiopia

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Widespread facemask use could shrink the ‘R’ number and prevent a second COVID-19 wave – study

fpjl2 — Wed, 10 Jun 2020 07:22:07 +0000

Population-wide use of facemasks keeps the coronavirus ‘reproduction number’ under 1.0, and prevents further waves of the virus when combined with lockdowns, a modelling study led by the ̽��ֱ�� of Cambridge suggests.

̽��ֱ��research suggests that lockdowns alone will not stop the resurgence of SARS-CoV-2, and that even homemade masks with limited effectiveness can dramatically reduce transmission rates if worn by enough people, regardless of whether they show symptoms.

̽��ֱ��researchers call for information campaigns across wealthy and developing nations alike that appeal to our altruistic side: 'my facemask protects you, your facemask protects me'. ̽��ֱ��findings are published in the Proceedings of the Royal Society A.

“Our analyses support the immediate and universal adoption of facemasks by the public,” said lead author Dr Richard Stutt, part of a team that usually models the spread of crop diseases at Cambridge’s Department of Plant Sciences.

“If widespread facemask use by the public is combined with physical distancing and some lockdown, it may offer an acceptable way of managing the pandemic and reopening economic activity long before there is a working vaccine.”

Dr Renata Retkute, coauthor and Cambridge team member, said: “ ̽��ֱ��UK government can help by issuing clear instructions on how to make and safely use homemade masks.”

“We have little to lose from the widespread adoption of facemasks, but the gains could be significant.”

̽��ֱ��new coronavirus is transmitted through airborne droplets loaded with SARS-CoV-2 particles that get exhaled by infectious people, particularly when talking, coughing or sneezing.

For the latest study, Cambridge researchers worked to link the dynamics of spread between individuals with population-level models, assessing varying degrees of facemask adoption combined with periods of lockdown.

̽��ֱ��modelling included the different stages of infection, and transmission via surfaces as well as air. Researchers also considered negative aspects of mask use, such as increased face touching.

̽��ֱ��reproduction or ‘R’ number – the number of people an infected individual passes the virus onto – needs to stay below 1.0 for the pandemic to slow.

̽��ֱ��study found that if people wear masks whenever they are in public it is twice as effective at reducing ‘R’ than if masks are only worn after symptoms appear.

In all modelling scenarios, routine facemask use by 50% or more of the population reduced COVID-19 spread to an R less than 1.0, flattening future disease waves and allowing less-stringent lockdowns.

Viral spread reduced further as more people adopted masks when in public. 100% mask adoption combined with on/off lockdowns prevented any further disease resurgence for the 18 months required for a possible vaccine.

̽��ֱ��models suggest that – while the sooner the better – a policy of total facemask adoption can still prevent a second wave even if it isn’t instigated until 120 days after an epidemic begins (defined as the first 100 cases).

̽��ֱ��team investigated the varying effectiveness of facemasks. Previous research shows that even homemade masks made from cotton t-shirts or dishcloths can prove 90% effective at preventing transmission.

̽��ֱ��study suggests that an entire population wearing masks of just 75% effectiveness can bring a very high ‘R’ number of 4.0 (the UK was close to this before lockdown) all the way down to under 1.0, even without aid of lockdowns.

In fact, masks that only capture a mere 50% of exhaled droplets would still provide a 'population-level benefit', even if they quadrupled the wearer’s own contamination risk through frequent face touching and mask adjustment – a highly unlikely scenario.

̽��ֱ��researchers point out that crude homemade masks primarily reduce disease spread by catching the wearer’s own virus particles, breathed directly into fabric, whereas inhaled air is often sucked in around the exposed sides of the mask.

“There is a common perception that wearing a facemask means you consider others a danger,” said Professor John Colvin, coauthor from the ̽��ֱ�� of Greenwich. “In fact, by wearing a mask you are primarily protecting others from yourself.”

“Cultural and even political issues may stop people wearing facemasks, so the message needs to be clear: my mask protects you, your mask protects me.”

“In the UK, the approach to facemasks should go further than just public transport. ̽��ֱ��most effective way to restart daily life is to encourage everyone to wear some kind of mask whenever they are in public,” Colvin said.

Professor Chris Gilligan, coauthor from Cambridge’s Epidemiology and Modelling Group in the Department of Plant Sciences, added: “These messages will be vital if the disease takes hold in the developing world, where large numbers of people are resource poor, but homemade masks are a cheap and effective technology.”

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Even basic homemade masks can significantly reduce transmission if enough people wear them when in public, according to latest modelling. Researchers call for information campaigns that encourage the making and wearing of facemasks.

We have little to lose from the widespread adoption of facemasks, but the gains could be significant

Renata Retkute

Mike Licht

Wear a mask

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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