Countries in North Africa and the Middle East have been treating thousands of hectares of cropland with insecticides and biological controls to prevent damage from an infestation of locusts currently besetting the region. Such precautionary measures over the next three months will be critical to ensuring that locusts don’t accumulate at summer breeding sites, which may allow them to spread further into western Africa, the UN’s Food and Agriculture Organization warns.
Some 85,000 hectares of cropland have so far been treated in Egypt, Eritrea, Saudi Arabia, and Sudan since December. People in the region rely heavily on locally grown rice, corn, wheat, sorghum, millet, and barley. Roughly half the region’s food supply must be imported during normal years.
Over the past few weeks, rapidly developing swarms of locusts have moved north along the Red Sea’s western border. A first generation of locusts was identified in December in breeding grounds along the coasts of Sudan and Eritrea, but now a second generation is spreading to Egypt, across the Red Sea to Saudi Arabia, and even farther north toward Iran. The FAO has declared the issue a threat to food security in Sudan, Eritrea, and Saudi Arabia.
Locust outbreaks arise when excessive rainfall occurs after periods of drought and stimulates vegetation growth. Above-average rainfall and a pair of cyclones that hit the Arabian Peninsula in late 2018 spurred plant growth along the Red Sea coast in early 2019, providing ideal locust breeding conditions. Locusts are typically solitary insects. But when population densities reach a certain threshold, locusts become gregarious, which encourages the formation of swarms. This change in behavior results from increased production of the neurotransmitter serotonin in the insects’ brain, research has shown.
The largest locust swarms can contain over a billion locusts and cover hundreds of square miles. At this size, swarms can consume nearly 100,000 tonnes of food and travel up to 150 kilometers a day. The last severe locust outbreak in the region occurred in Western Africa between 2003 and 2005, an event that cost about $750 million in crop treatments and food aid.
The satellite-derived maps below show NDVI anomalies in countries affected by the locust outbreak. (Greener areas indicate greater vegetative health relative to the mean for the same area over the period from 2001 to 2010.) The map on the left shows the status of plant health at the start of January, when the locust outbreak was detected in Eritrea. Heavy autumn rains contributed to greater than average plant growth around the Eritrean coast, which sustained the growing locust population. The map on the right shows plant-health status in mid-February. Orange shading indicates poor vegetative health around the Eritrean coast and in Saudi Arabia, where locust swarms have caused defoliation during their migrations. Green areas on the coast of Iran indicate a possible new destination for the locust swarms if they aren’t contained. There are also worries locusts could head west into the Nile Valley.