Desert locust

The desert locust (Schistocerca gregaria) is a species of locust in the grasshopper family, Acrididae. A periodically swarming, short-horned bird grasshopper, it is found primarily in the deserts and dry areas of northern and eastern Africa, Arabia, and southwest Asia. During population surge years, its range may extend north into parts of Southern Europe, Eastern Africa, and Northern India. The desert locust shows periodic changes in its body form and can change in response to environmental conditions over several generations. It begins life as a solitary, shorter-winged, highly fecund (producing enormous amounts of offspring), non-migratory form, to a gregarious, long-winged, and migratory phase in which it may travel long distances into new areas. Due to this traveling, it may join groups, thus, forming locust plagues. This involves invading new areas where it may consume all vegetation including valuable crops. Although at other times, it may live unnoticed in small numbers in various areas.

During plague years, when the desert locust does group with others, it can cause widespread damage to crops as it is highly mobile and feeds on large quantities of any kind of green vegetation. A typical swarm can be made up of 150 million locusts per square kilometre (390,000,000 per square mile) and fly in the direction of the prevailing wind, up to 150 km (93 mi) in one day. Even a very small, 1-square-kilometre (0.39 sq mi) locust swarm can eat the same amount of food in a day as about 35,000 people.

As an international transboundary pest that threatens agricultural production and livelihoods in many countries in Africa, the Near East, and southwest Asia, its population has been routinely monitored through a collaborative effort between countries and the United Nations Food and Agriculture Organization (FAO) Desert Locust Information Service (DLIS), which provides global and national assessments, forecasts, and early warning to affected countries and the international community. The desert locust's migratory nature and capacity for rapid population growth present major challenges for control, particularly in remote semiarid areas, which characterize much of its range.

Locusts differ from other grasshoppers in their ability to change from a solitary living form into gregarious, highly mobile, adult swarms and hopper bands, as their numbers and densities increase. They exist in different states known as recessions (with low and intermediate numbers), rising to local outbreaks and regional upsurges with increasingly high densities, to plagues consisting of numerous swarms. They have two to five generations per year. The desert locust risk increases with a one-to-two-year continuum of favourable weather (greater frequency of rains) and habitats that support population increases leading to upsurges and plagues.

The desert locust is potentially the most dangerous of the locust pests because of the ability of swarms to fly rapidly across great distances. The major desert locust upsurge in 2004–05 caused significant crop losses in West Africa and diminished food security in the region. The 2019–2021 upsurge caused similar losses in northeast Africa, the Near East, and southwest Asia.

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