Locusts are a collection of certain species of short-horned grasshoppers in the family Acrididae that have a swarming phase. These insects are usually solitary, but under certain circumstances they become more abundant and change their behaviour and habits, becoming gregarious. These grasshoppers are normally innocuous, their numbers are low, and they do not pose a major economic threat to agriculture. However, under suitable conditions of drought followed by rapid vegetation growth, serotonin in their brains triggers a dramatic set of changes: they start to breed abundantly, becoming gregarious and nomadic (loosely described as migratory) when their populations become dense enough. They form bands of wingless nymphs which later become swarms of winged adults. Both the bands and the swarms move around and rapidly strip fields and cause damage to crops. The adults are powerful fliers; they can travel great distances, consuming most of the green vegetation wherever the swarm settles. A typical swarm can be made up of 150 million locusts per square kilometre and is carried on the wind, up to 150 km in one day. Even a very small, one-square-kilometer locust swarm can eat the same amount of food in one day as about 35 000 people.
In India, groups of swarms which attacked Gujrat have continued to move east and to the central States of Madhya Pradesh and Maharashtra, these movements were associated with the strong westerly winds of Cyclone Amphan.
Impact Of Climate: The desert locust (Schistocerca gregaria) is probably the best known species owing to its wide distribution (North Africa, Middle East, and Indian subcontinent) and its ability to migrate over long distances. During quiet periods—known as recessions—desert locusts are usually restricted to the semi-arid and arid deserts of Africa, the Near East and South-West Asia that receive less than 200 mm of rain annually. In normal conditions, locust numbers decrease either by natural mortality or through migration. Hotter climate and Wet weather favours multiplication of locusts. The worst outbreak of locust swarms seen in decades in East African Region and, Oman and Yemen and current outbreak of locust swarms in India is linked to the climate change. Widespread, above average rain that pounded the Horn of Africa from October to December 2019 were up to 400 per cent above normal rainfall amount and extended rainfall in west Asia ,oman and yemen cause the sand became heavily moisture laden, facilitating the formation of several locust Chans. These abnormal rains were caused by the Indian Ocean dipole, a phenomenon accentuated by climate change. The changing pattern of winds, warming of India Ocean and Frequent cyclones are linked to locust swarms. A pattern of warming in the Indian Ocean triggers a phenomenon called the Indian Ocean Dipole. The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperature between two areas (or poles, hence a dipole) – a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia. The IOD tend to have an outsized impact in bringing excessive rains to India and West Asia. A ‘positive’ dipole is when the western part is hotter by a degree or more than the eastern. This dipole had brought torrential rainfall — the most India has seen in decades. The frequent cyclones in Indian Ocean bring torrential rainfall in coastal areas of Gujrat, Pakistan, Arabian peninsula and north-Eastern Africa .This creates the good breeding grounds for locusts. The favourable winds, helps swarm to fly and breed in traditional grounds in Iran, Afghanistan, Pakistan and India. This is clear from the fact that In India, groups of swarms which attacked Gujrat have continued to move east and to the central States of Madhya Pradesh and Maharashtra, these movements were associated with the strong westerly winds of Cyclone Amphan.
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