Africa Fights Locust Plagues

Brian Handwerk
National Geographic Channel
January 7, 2005
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.

"Part of our forecasting system is looking at satellite information on vegetation and identifying desert areas where locusts are likely to be found," Elliott said. "We provide information to countries, so that they can target their surveys to those areas. It doesn't always work, but it has proven useful."

Approximately 42,500 square miles (11 million hectares) of African land was sprayed last year with fixed-wing aircraft and helicopters.

While the process may control locusts, it also introduces large amounts of environmentally harmful pesticides. It's a problem the FAO says it is attempting to address.

"Most of the spraying has been done with conventional organophosphate pesticides," Elliott noted. "The FAO is trying to promote use of more environmentally friendly pesticides. But it's taking longer than we'd like to get it off of the ground."

One possible alternative control method uses a naturally occurring fungus, Metarhizium anisopliae, to create a bio-pesticide dubbed green muscle. The fungus is deadly to locusts and grasshoppers but has proven harmless to other insects, plants, and animals—including people.

"Conveyor Belts"

Elliott reports that, while the desert locust plague situation remains serious, hopes are high that heavy control operations in fall 2004 have made an impact.

"We don't know whether we could be into a plague by September of this year, or if by May the whole thing will have petered out," he said.

While controlling locust plagues is the FAO's first priority, understanding the ecological role of the massive outbreaks is also important. Thus far, the latter goal has proven somewhat elusive.

"We can think of locust swarms as giant conveyor belts of nutrients that move tons and tons of organic material from one place to another," Lockwood said. "Frankly we have a poor understanding of how this fits into nutrient cycling in Africa."

Although not fully understood, the massive outbreaks are generally believed to have an important ecological role.

"You could think of a locust outbreak as a sort of metabolic wildfire. We don't have the capability to do it, but … the thought of totally eliminating locust outbreaks would give most ecologists a shiver up their spine," he said. "We just don't know enough about the possible effects."

More on TV
For more on this subject, watch the National Geographic Explorer documentary The Perfect Swarm, airing Sunday, January 9, at 8 p.m. ET/PT on the National Geographic Channel.

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