Locusts are short-horned grasshoppers with the remarkable ability to transform from harmless individuals into destructive swarms. While typically solitary, specific environmental conditions can trigger a dramatic shift in their behavior and biology, leading to massive population explosions. This transformation has historically made them a notable threat to human societies, with records of plagues appearing in ancient texts and continuing to affect regions worldwide. The danger posed by locusts stems from their collective power when they form immense, highly mobile swarms.
The Power of the Swarm
Locusts undergo a unique biological and behavioral change known as “gregarization” or phase transformation. This shift from a solitary to a gregarious phase is primarily triggered by overcrowding and increased physical contact among individuals. Repeated tactile stimulation of their hind legs can increase serotonin levels in their brains, initiating a cascade of changes. This causes them to become more social, change color, and breed more abundantly.
Under favorable conditions, such as drought followed by rapid vegetation growth, locust populations can increase significantly, leading to higher densities. As these densities rise, the insects become attracted to each other, forming cohesive groups of wingless nymphs, known as bands, which later develop into swarms of winged adults. A large swarm can consist of billions of locusts, with densities reaching up to 80 million individuals per square kilometer. These swarms are highly mobile, capable of traveling vast distances, sometimes over 100-150 kilometers per day, aided by wind. Some historical swarms have even been reported to cross entire oceans.
Threat to Agriculture and Livelihoods
The immediate danger posed by locust swarms is their capacity for complete devastation of crops and vegetation. Locusts are voracious eaters, with an adult desert locust capable of consuming its own body weight, about two grams, in fresh food daily. A swarm covering just one square kilometer, containing 40 to 80 million locusts, can consume the same amount of food as 35,000 people.
This immense consumption leads to total crop failure, decimating agricultural fields and pastureland rapidly. Farmers and agricultural communities bear the brunt of this destruction, experiencing severe loss of income. The destruction of crops also directly threatens local food supplies, increasing food insecurity and potentially displacing farming populations.
Wider Societal and Economic Disruption
Beyond the immediate agricultural damage, widespread locust infestations trigger broader, long-term societal and economic disruptions. The destruction of crops can escalate into national food insecurity, increasing the risk of famine for millions of people in affected regions. For example, a severe outbreak has placed around 20 million people at acute food insecurity in East Africa. The World Bank estimates that without effective control, locust populations could grow exponentially, leading to damages and losses potentially amounting to billions of dollars.
These economic losses extend beyond lost crops, affecting national economies through decreased exports, increased food imports, and significant costs associated with relief efforts and pest control operations. The sustained impact on household incomes can perpetuate a cycle of poverty, particularly in regions where agriculture is a primary source of livelihood. Such widespread devastation can also contribute to social unrest and the displacement of populations as communities struggle to meet basic needs and resources become scarce. Controlling large-scale infestations presents a significant challenge due to the vast and often remote areas involved, political instability in some affected regions, and the need for continuous surveillance and response.