Desert Locust Plague 2020: A Threat to Food Security

Countries across East Africa have been hit with the worst locust plague the region has seen in decades, creating concerns for the food and job security of millions. Now, as the biblical-sized swarms ravage crops and pastureland, scientists and forecasters are racing against the clock to understand and combat these pests. Read on to find out how people are being affected by the outbreak, why locust swarms form and how experts are working to prevent this from happening in the future.

As the novel coronavirus swept across the globe, another crippling epidemic was making its way through East Africa. A plague of migratory locusts – the worst the region has witnessed in decades – has been tearing through vast swathes of crop and pastureland, from the Horn of Africa to the deserts of Kenya. So far this year, infestations have been recorded in dozens of countries, including Ethiopia, Somalia, Kenya, Eritrea, Uganda, India, Pakistan, Iran, Yemen, Oman and Saudi Arabia, with East African regions being hit the worst.¹ In Ethiopia and Somalia, plagues of this scale have not been seen in 25 years, while in Kenya, not in over 70.² 

Introducing: The Desert Locust

The perpetrator behind this destruction is none other than the desert locust (Schistocerca gregaria), a species of short-horned grasshopper which inhabits arid grasslands and desert regions from West Africa to India. What gives the desert locust species (along with a handful of other grasshopper species) their ’locust’ nickname is a unique behavioural trait: out of some 12,000+ grasshopper species, only a dozen can form swarms under the right conditions. In other words –  the only difference between a desert locust and its fonder-known relative, the grasshopper, is how they behave.³

Discover how polycultures can help keep pests in check

How Much Damage Can A Desert Locust Swarm Cause?

Desert locusts have won the title for the world’s most dangerous migratory pest – and for good reason. It’s been estimated that swarms of migratory locusts can cover some 20% of Earth’s land surface and affect the livelihood of 1 in 10 people on the planet.⁴ Each desert locust swarm can contain billions of individuals, spanning hundreds of kilometres (in fact, a recent swarm recorded in Kenya contained approximately 20 billion locusts and measured 2,400 sq km, roughly the size of Luxembourg).⁵

Like an unrelenting army, these voracious eaters migrate from one area of vegetation to the next, stripping every last piece of plant life in their path. While tropical crops are safe from the pest since it only thrives in dry regions, other major cash and food crops – like cashew nuts, vegetables, maize, cotton and wheat are at risk.⁶ 

During this insatiable quest for food, locusts cover distances of up to 200 km a day and eat their weight in food along the way.⁷ At just the size of a paperclip, this might not sound like a great deal. But on mass, the potential for destruction is immense: to paint a picture, a relatively modest swarm of 40 million individuals eats the same amount of food in a single day as 35,000 people.⁸ If left unmanaged for even a week, a swarm this size will have eaten enough calories to feed a quarter of a million people.

Food Sources for People & Livestock At Risk

With figures like this, it’s easy to see why mounting desert locust populations pose a very serious threat to agricultural production, food security and rural livelihoods. In regions hit by the outbreak, vast areas of crop and pastureland have been severely damaged, with over 190,000 hectares (and counting) of Kenyan cropland destroyed.⁹ Disrupting food production at this scale has severe consequences, exacerbating the vulnerability of many communities in affected regions suffering from acute food shortage. Across Kenya, Ethiopia and Somalia, 11.9 million people are already considered ‘food insecure’, with many regions experiencing ‘stressed’ or ‘crisis’ levels of food insecurity.¹⁰

What's more, locusts don’t just reduce human food sources, but livestock food sources as well – as desert locust swarms obliterate rangeland, rural pastoralists feel the brunt, as cattle are left with nowhere to graze.¹¹

Destabilising Economies 

Aside from leaving many vulnerable to hunger, locust swarms have the potential to destabilise national economies – especially in East Africa, where agriculture makes up the region’s mainstay. In Kenya, for example, up to 75% of the population earns their wage through agricultural work, which generates a third of the country’s GDP. Similarly, in Ethiopia, agriculture makes up 75% of the nation’s workforce, comprising nearly half of its GDP and 80% of its exports.^12,13 

Is It Possible To Control This Plague? 

With so much at stake, controlling migratory and desert locust plagues before they cause more damage is vital – but this is no easy feat – made exponentially harder when swarms get to this size, breadth and distribution. Spraying pesticides on infested cropland remains the most effective and widespread treatment method, but this comes with considerable drawbacks. First, treating hordes of locusts over vast areas of cropland is expensive and doesn’t guarantee protection. As Keith Cressman, senior locust forecasting officer with the Food and Agriculture Organization (FAO) explains:

“The last major outbreak in Northwest Africa between 2003-2005 required 25 million litres of pesticides to bring under control and cost over $600 million. Despite these efforts, the region still lost a further $2.5 billion in crop damage and in some countries, 90% of household heads went into debt”.

Tracking and spraying highly migratory locust plagues also requires huge amounts of resources – and, given several countries affected, including Kenya and Uganda, have not witnessed a swarm of this magnitude in decades, many are without the equipment, pesticides or manpower necessary to effectively halt invasions.⁹ 

Aside from the economic and resource aspect, there is also an environmental impact to consider. The FAO, along with others, have urged the importance of minimising pesticide use wherever possible, given extensive spraying may lead to adverse effects on human health and the environment.¹⁴ 

But Why Do Locusts Swarm?

Creating both effective and sustainable measures to protect ourselves from incoming plagues hinges on our understanding of why locusts swarm in the first place. Desert locusts start life as reclusive, ground-dwelling ‘hoppers’ which pose no immediate threat to crops or food security. Actively avoiding the company of other desert locusts, these hoppers live in arid landscapes with little rainfall. However, if conditions are just right, something extraordinary happens – the hoppers go through a profound, Jekyll-and-Hyde-esque transformation: they develop an entirely new set of behaviours and morph into their ‘gregarious’ phase.¹⁵ In this phase, desert locusts seek each other out and start to collectivise. At the same time, their bodies change to equip them for migration; their muscles develop, their wings grow, and their colour changes from a dull green to a vibrant yellow. When this phase kicks in, desert locusts become a force to be reckoned with, eating and breeding at dramatically fast rates – able to increase their population 20-fold in just three months.³

What Weather Conditions Trigger Locusts to Swarm?

So, what makes desert locusts go from harmless critters to merciless eating machines? The rain. When rain finally falls on the desert terrains locusts call home, the landscape becomes alive with transient vegetation. Solitary locusts flock to these new pastures, eat their fill and rapidly reproduce. However, as drought prevails and food levels start to decrease, groups of locusts are herded into dwindling pockets of vegetation, forcing these usually solitary insects into closer proximity. It is this initial crowding that sets everything into motion: when the hoppers brush up against one another, it activates a chemical release in their nervous system, which triggers their metamorphosis and prompts swarm behaviour ¹⁶  

Between 2018 and 2019, the Arabian Peninsula and Horn of Africa were hit by abnormally wet weather, including several rare cyclones which together created perfect conditions for a locust plague to develop: where heavy rains fell across these usually dry regions, vegetation soon shot up, providing abundant feeding and breeding grounds (desert locusts prefer to lay their eggs in wet soil as this prevents them from overheating). Spurred on by these prolonged and successive rains, the locusts multiplied to roughly 8,000 fold in under a year.¹⁷

Is Climate Change To Blame?

Several media reports have questioned whether climate change could be responsible for the cyclones that caused the outbreak. How? Well, the unseasonably wet weather that led to swarms developing is connected to a wider climate system called the Indian Ocean Dipole (IOD), an ocean circulation pattern that typically affects weather from East Africa and the Arab Peninsula to Indonesia, Papua New Guinea and Australia. As ocean temperatures rise and fall across the Indian Ocean, the dipole fluctuates between ‘positive, negative and neutral’ states. When in a ‘negative’ state, warm waters are channelled from the Horn of Africa towards Australia, leading to increased convection and rainfall over the continent. When in a ‘positive’ state, this pattern runs in reverse: so in autumn 2018, when the dipole shifted into a pronounced ‘positive’ state, warm waters (and rains) became redirected over towards East Africa, creating the unexpected cyclones which stoked the outbreak.¹⁸ 

As ocean temperatures continue to rise due to global warming, there has been an incline of positive IOD states, with increased cyclone activity as a result.¹⁹ A study published this year revealed that positive IOD phases have continued to rise over the 20th century and could become more common in a warming world.²⁰ Another study even stated that if the planet were to warm by a further 1.5 degrees, positive IOD phases could double, creating even more cyclones.²¹

More Locust Outbreaks in a Warming World? 

But does this mean locust outbreaks will become more frequent in the future? Possibly. However, at this stage, it’s too early to tell if climate change will directly lead to more outbreaks. 

“What we can say with certainty, is that conditions favourable for outbreaks will become more common”,

explains Philipp Lehmann, a researcher of insects and the environment at Stockholm University.

Preventing Desert Locust Plagues

While it's currently unclear whether we can expect more migratory locust plagues in a warming world, it's an alarming possibility – one we need to be prepared for. Preventing swarms from forming, rather than treating them when they arrive, remains the best way to protect farmers, save money, reduce food insecurity and minimise our environmental impact. 

Many experts would agree the most effective way to prevent plagues from developing is to track and monitor locust populations consistently: the more we know about where desert locusts are concentrating, as well as where they might be breeding, the sooner we can carry out preventative efforts to control small populations before they have a chance to inflict serious damage. 

Tracking Locusts on the Ground

For the last four decades, the Desert Locust Watch – FAO’s international centre for global desert locust surveillance and management – has been helping affected countries combat infestations. In line with this, the FAO has developed eLocust3, a GPS reporting device for field teams and farmers to send instant alerts on the presence and location of locusts, as well as their stage of development. These alerts are sent via satellite to national locust centres and the Desert Locust Watch, based in Rome. Using this data, experts can pinpoint the location of locusts in real-time, mobilise control efforts and provide early warnings to countries soon to be affected.²² 

Predicting Locusts From Outer Space 

Satellites also monitor swarms and migrations, but not by tracking the locusts themselves. Instead, satellites can steer forecasters to environmental changes that could create future feeding and breeding grounds.²³ For example, satellites can provide data on which areas have recently received rainfall and where new vegetation might be growing.

"Monitoring these factors is crucial because it shows you where vegetation might arise and therefore where locusts might be breeding” 

Cyril Piou, an expert in locust population dynamics and scientist working as part of the acridology team at CIRAD, explains. 

What’s more, certain satellites can even indicate soil moisture – pointing experts to where desert locusts may have laid eggs.²⁴ Once informed predictions have been made using this data, field teams carry out targeted missions to these areas and if infestations are found, early control operations are launched to stop swarms in their tracks. 

While the current outbreak may sound more akin to the Book of Exodus, today's swarms offer as important of a message now as they did then – a reminder of the intricate balance between our climate and the living beings within it. If we can leverage our technologies to stay attuned to Earth’s environmental cues, we can stay one step ahead of the pest and prevent the damage that once brought civilisations to their knees.