Locust Plagues: A Global Agricultural Threat
Overview
Locust plagues are a recurring environmental and agricultural phenomenon characterized by the sudden, massive swarming of locusts, a type of short-horned grasshopper. While solitary locusts are relatively harmless, under specific ecological conditions, they undergo a behavioral and physiological transformation known as gregarization, forming dense swarms that can travel great distances and consume enormous amounts of crops and vegetation.
Causes of Locust Plagues
Several factors contribute to the formation of locust plagues:
Climate Conditions: Prolonged periods of rainfall in arid or semi-arid regions can trigger rapid vegetation growth, providing abundant food for locusts and encouraging breeding.
Environmental Changes: Human activity, such as deforestation and overgrazing, can create ideal breeding grounds.
Locust Life Cycle: Under crowded conditions, locusts shift from a solitary to a gregarious phase, becoming more mobile, social, and voracious.
Behavior and Impact
Swarming: Locust swarms can contain billions of insects, covering hundreds of square kilometers. They can travel up to 150 kilometers in a single day, guided by wind currents.
Crop Destruction: Locusts consume almost all green vegetation in their path. A single swarm can destroy enough food to feed thousands of people. Major crops affected include cereals, vegetables, and fruit trees.
Economic and Social Effects: The destruction of crops leads to severe food shortages, increased prices, and economic instability. Locust plagues disproportionately affect rural communities that rely on subsistence farming.
Historical Significance
Locust plagues have been documented for millennia, with references in biblical texts, Chinese chronicles, and ancient Egyptian records. Modern outbreaks continue to occur in regions such as the Horn of Africa, the Middle East, and South Asia. Notable plagues in recent decades include the 2003–2005 outbreak in West Africa and the 2020–2021 East Africa outbreak, which affected millions of people.
Management and Control
Effective management of locust plagues involves a combination of early warning systems and direct interventions:
Monitoring: Satellite imagery and ground surveys help detect early signs of locust breeding.
Chemical Control: Insecticides are commonly used to reduce swarm sizes, though they pose environmental and health risks.
Biological Control: Natural predators and biopesticides can help reduce locust populations sustainably.
International Cooperation: Locust plagues often cross national borders, making regional coordination essential for effective control.
Conclusion
Locust plagues remain one of the most destructive natural threats to global agriculture. Climate variability, population growth, and land-use changes are likely to influence the frequency and severity of future outbreaks. Early detection, coordinated intervention, and sustainable agricultural practices are critical to mitigating the impact of these devastating swarms.
Swarm of desert locusts at sunset, Morocco (U.S. Forest Service)
Desert locusts consuming small melon (Alan Schroder).
Desert locust swarm in Eritrea (Allan Showler).
Desert locusts consuming small melon (Alan Schroder).
Swarm near Satrokala, Madagascar during a 2014 outbreak
The Economist Panos
What locust swarms do to vegetation
Ravenous consumption: A swarm as small as 1 km² can hold up to 80 million locusts and eat as much food in one day as ~35,000 people. Locusts also consume their own weight daily and can fly up to ~150 km/day, stripping crops and pasture along the way. (FAOHome)
Rapid population explosions: Under favorable conditions, numbers can increase 20× every ~3 months, 400× in 6 months, and 8,000× in 9 months, driving explosive outbreaks. (FAOHome)
Documented crop/pasture damage: During the 2019–2021 upsurge, Ethiopia alone recorded about 200,000 hectares damaged. Region-wide, FAO-coordinated control operations reported hectares treated in the millions and losses averted of ~4.5 million tonnes of cereal valued around US$1.85 billion (2020–2021). (Nature, FAOHome)
Human impacts
Food insecurity (millions at risk): In early 2020–2021 assessments, 25.3 million people in six East African countries were already facing high acute food insecurity (IPC Phase 3+) in locust-affected areas, with many more in “Stress” (IPC Phase 2) and vulnerable to shocks. Other contemporaneous estimates placed 20–33 million people at risk if swarms were not contained. (IP Location Info, Axios)
Macro-/household losses: The World Bank estimated potential damages and losses up to US$8.5 billion in 2020 for East Africa and Yemen without effective control—reflecting destroyed crops, lost livestock forage, and broader livelihood shocks. (World Bank)
Impacts on children & human capital: Evidence from past and recent plagues links locust shocks to reduced school enrollment and child stunting in affected areas, as households reallocate scarce resources to basic survival. (World Bank, World Bank)
Costs and scale of response
Historical benchmark (West Africa 2003–2005): Ending that plague required ~US$400–450 million and still resulted in about US$2.5 billion in crop damage; ~12.9 million ha were sprayed with >13 million liters of pesticides. (World Bank, World Bank)
2019–2021 upsurge (Greater Horn of Africa & Yemen): FAO-led operations reported ~4.5 million tonnes of cereal losses averted (worth ~US$1.85 billion) thanks to large-scale surveillance and control, including aerial/ground treatments across multiple countries. (FAOHome)
Environmental and health considerations
Heavy insecticide use: In East Africa 2018–2020, about 1.6 million hectares were treated, often with broad-spectrum organophosphates/pyrethroids (e.g., chlorpyrifos, malathion, fenitrothion). Studies and field reports note non-target mortality (e.g., honeybees and birds) and risk concerns where pastoralism and beekeeping are common. (Nature)
Trade-offs: Chemical control can be lifesaving for crops and livelihoods during upsurges, but it raises biodiversity and exposure risks; FAO and partners increasingly promote early warning + targeted spraying + biopesticides to reduce collateral harm. (FAOHome)
Why outbreaks are getting harder to manage
Climate signals: Strong Indian Ocean Dipole events and unusual cyclones/rainfall preceded the 2019–2021 upsurge, creating ideal breeding conditions. With warming seas and more extreme weather, future outbreaks are likely to intensify without improved regional prevention. (World Bank)
Key numbers at a glance
1 km² swarm = up to 80M locusts ⇒ food of ~35,000 people/day; can travel ~150 km/day. (FAOHome)
Ethiopia damage (2020): ~200,000 ha. (Nature)
Food insecurity (East Africa, 2020–2021): ≥25.3M (IPC 3+ in affected countries); risk up to 33M if uncontrolled. (IP Location Info, Axios)
Losses averted (2020–2021 response): ~4.5 Mt cereal, ~US$1.85 B. (FAOHome)
Historic West Africa plague (2003–2005): US$400–450 M to end; ~US$2.5 B crop damage; ~12.9M ha sprayed, >13M L pesticides. (World Bank, World Bank)