Locust plagues may predate biblical times, but today scientists still struggle to fully understand and control the swarms that can bring famine to thousands.
In Guinea-Bissau, West Africa, desert locusts (Schistocerca gregaria) currently threaten to decimate the cashew crop on which nearly two-thirds of the nation's farmers depend.
The current outbreak comes on the heels of heavy locust damage in numerous West African countries this past summer and fall.
Food shortages loom in the hardest-hit areas. In Mauritania government officials estimate that one-third of the nation's 2.8 million inhabitants could go hungry next year. Others in the Sahel region, the semidesert southern fringe of the Sahara, will share the misery.
The recent plagues mark the worst locust upsurges in 15 years. "The last big infestation was between 1986-89," said Clive Elliott, a locust expert with the UN Food and Agriculture Organization (FAO) in Rome, Italy. "I've spoken to lots of people in the field this year who say that the size and density of the swarms they've seen [in western and northwestern Africa] is larger than in 1988."
If there is a pattern to the plagues, scientists have yet to find it. Twentieth-century plagues occurred in 1926-1934, 1940-1948, 1949-1963, 1967-1969, and 1986-1989. Plagues are spurred by recurrent rainfall during the insect's breeding season.
"We've looked for regularities, but locust population dynamics are so driven by the weather we don't find [predictable cycles]," said University of Wyoming entomologist and locust expert Jeff Lockwood, "We can forecast locust [plagues] about as well as we can forecast the weather."
During massive plagues, desert locusts can appear over a land area of nearly 12 million square miles (30 million square kilometers) in some 60 nations—comprising over 20 percent of Earth's land surface.
The insects inflict heavy crop damage that's devastating for subsistence farmers, many of whom must flee land that can no longer support their families.
The FAO's Desert Locust Information Service reports that during the biggest plagues, the insects may endanger the livelihood of one in every ten people on Earth.
Control Efforts
To control locust plagues, FAO coordinates international efforts and helps national authorities battle the ancient pests with modern technology that includes satellites, pesticides, and helicopters.
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