Between June 2019 and February 2022, a major outbreak of desert locusts began developing, threatening food supplies in East Africa, the Arabian Peninsula and the Indian subcontinent. The outbreak was the worst to hit Kenya in 70 years, and the worst in 25 years for Ethiopia, Somalia, and India.
The locust infestations began when Cyclone Mekunu in 2018 produced heavy rains in the Rub' al Khali of the Arabian Peninsula; in spring 2019, swarms spread from these areas, and by June 2019, the locusts spread north to Iran, Pakistan, and India and south to East Africa, particularly the Horn of Africa. By the end of 2019, there were swarms in Ethiopia, Eritrea, Somalia, Kenya, Saudi Arabia, Yemen, Egypt, Oman, Iran, India, and Pakistan. By June 2020, a separate swarm appeared in South America, affecting Paraguay and Argentina.
In April 2020, travel and shipping restrictions precipitated by the spread of COVID-19 began to hamper efforts to control the locusts, preventing the transport of pesticides, equipment, and personnel, and contributing to the global incidence of COVID-19 related food insecurity.
Locust swarms worldwide faced a steady decline in size from May to October 2020, as countries and intergovernmental organisations instituted extensive aerial and ground pest control efforts, aided by low quantities of rainfall in several affected regions, as well as the absence of storm activity in the Indian Ocean. By October 2020, Ethiopia, Eritrea, Somalia and Yemen continued to harbour significant swarms of locusts, with the remainder situated in isolated pockets of Kenya, Sudan and Saudi Arabia. Locust swarms continued to threaten countries around the southern Red Sea and Gulf of Aden, as well as their immediate neighbours, until February 2022 when the surge was officially declared to be over.
Causes
When periods of heavy rainfall follow periods of relative drought, solitary desert locusts emerge to feed on new-growth foliage and lay eggs in the newly moist soil, which prevents them from drying out. The sight and smell of other locusts, as well as sensory stimulation from contact between locusts' hind legs, precipitates changes in the locusts' behaviour and morphology; the previously green, nocturnal and solitary creatures become larger, develop black-and-yellow colouring, and begin to seek out other locusts, a process known as gregarization. These changes result in the formation of large locust swarms that gregarize nearby locusts and breed profusely, allowing them to undergo rapid, exponential growth. The swarms proceed to feed on the newly abundant vegetation, making use of improved swarm coordination, the result of larger brain sizes, as well as increased range, the result of increased metabolic activity, larger muscles, and longer wings, to travel up to 130 km a day in search of new vegetation and moist weather, often propelling themselves by the wind.This particular desert locust plague traces back to May 2018, when Cyclone Mekunu passed over a vast, unpopulated desert on the southern Arabian Peninsula known as the Rub' al Khali, filling the space between sand dunes with ephemeral lakes, which allowed locusts to breed undetected. This was exacerbated in October 2018 by Cyclone Luban, which spawned in the central Arabian Sea, moved westward, and rained out over the same region near the border of Yemen and Oman. The Indian Ocean Dipole, an irregular oscillation in sea surface temperatures between the western and eastern parts of the Indian Ocean, has increased in magnitude due to the effects of climate change. This shift has resulted in increased cyclone activity over the last decade in the Persian Gulf, previously home to very few cyclones, and is associated with flooding in countries along the western Indian Ocean, dry weather in the east, and bushfires in Australia.
The two cyclones created conditions conducive to mass locust reproduction, enabling three generations of locusts to breed over a nine-month period, which increased their number in the Arabian Desert roughly 8,000-fold.
Affected countries
Locust swarms had infested 23 countries by April 2020. East Africa was the epicenter of the locust crisis—with Ethiopia, Kenya, Somalia, and Uganda among the affected countries. However, the locusts had traveled far, wiping out crops in Pakistan and damaging farms in Yemen, a fragile country already hit hard by years of conflict.
Africa By the summer of 2019, swarms had reached over the Red Sea and the Gulf of Aden into Ethiopia and Somalia, where they continued breeding and started causing concerns. This might have been as far as the locusts got were it not for the fact that during October 2018, East Africa experienced unusually widespread and intense autumn rains, which were capped in December by a rare late season cyclone Pawan that made landfall in Somalia. These events triggered yet another spurt of reproductive activity.
In January 2020, the outbreak was affecting Ethiopia, Kenya, Eritrea, Djibouti, Somalia, and Burundi. The infestation "presents an unprecedented threat to food security and livelihoods in the Horn of Africa," according to the United Nations Food and Agriculture Organization (FAO). Rising sea surface temperatures (cf. the Indian Ocean Dipole) tip the scales in favor of circulation patterns like the one that set the stage for the desert locust outbreak. Keith Cressman, senior locust forecasting officer with the Food and Agriculture Organization said, he thinks, "we can assume there will be more locust outbreaks and upsurges in the Horn of Africa.” The situation was fueled by unusually heavy rains, causing a big concern in the Horn of Africa, where more than 24 million people are food insecure and 12 million people are internally displaced. Favourable conditions for the locusts prolonged the menace through January 2021.
Kenya On 28 December 2019, several large, immature swarms were first reported to have crossed into Kenya from Somalia, entering through the towns of Mandera and El Wak. Heavy rains over the preceding short rain season (October–December) created an environment conducive to locust breeding, and over the next two months the swarms spread and matured, infesting 21 counties by the end of February and reaching Kenya's borders with Uganda and Tanzania. By then, the plague was Kenya's worst locust outbreak in over seventy years, affecting approximately 70,000 hectares (172,973 acres) of land, and leading the country's agriculture minister to state that authorities were unprepared for an infestation of such scale. Over the next three months, particularly favourable rains caused locust swarms to migrate to the north-western counties of Kenya, and by mid-May, cumulative crop and pasture losses were estimated at between 5-15 percent in northern Kenya and 1-5 percent in south-eastern Kenya.
However, low levels of rainfall in May, in conjunction with both new and continued ground and aerial pest control initiatives, led the locust population, which had been stagnant over the preceding two months, to decline, with reduced average swarm sizes and a less widespread distribution of locusts, which were, by then, primarily resident in the north-western counties of Turkana and Marsabit. Continued low rainfall and the relative lack of greenery in north-western Kenya resulted in a progressive decline in both swarm size and overall population from June to September, resulting in reduced levels of locust maturation, which placed much of the remaining locust population in recession. As of October 2020, a few small (1–10 km2) swarms, slowly maturing at the border between the north-western counties of Baringo, Laikipia, and Samburu, were the only remaining gregarious locust populations in the country.
Somalia Somalia’s agriculture ministry called the outbreak a national emergency and major threat to the country’s fragile food security, saying the “uncommonly large” locust swarms are consuming huge amounts of crops. Combating the crisis wasn't expected to be easy, especially in Somalia, where parts of the country are in the grip of the al-Qaida-linked al-Shabab extremist group. Desert locusts were breeding in the regions of Galmudug (Mudug), Puntland, and Somaliland. Over the next six months, projections indicated that more than 100 000 hectares of land would have required direct control interventions in Somalia.
Eritrea In swarms the size of major cities, the locusts had also affected various parts of Eritrea. The military and general public had been deployed to combat the crisis according to Eritrea's Agricultural Ministry. In Eritrea, big swarms of immature adults that migrated from Ethiopia, were identified and controlled around Shieb, Gahtielay, Wengebo, and Beareze of the Northern Red Sea Coast. Moreover, the swarms of Tree Locust had been detected in Tserona, Mai-seraw, Quatit, and Digsa districts of Southern Eritrea.
Ethiopia The locusts also headed towards Ethiopia, Africa's second-most populous country, in that nation's worst outbreak in 25 years. Some residents were surprised to find the locusts inside their living rooms.
According to the Agriculture Ministry officials, the relatively few locusts that reached Ethiopia's capital Addis Ababa were “leftovers” from the “massive invasion” in the eastern and southern parts of the country. Spraying was conducted around the city to stop the outbreak from spreading elsewhere. Millions of people in this country already cope with the constant risk of drought or flooding,
The desert locust infestation in Ethiopia has deteriorated, despite ongoing ground and aerial control operations. Hoppers have fledged, and an increasing number of small immature and mature swarms have continued to devour crop and pasture fields in Tigray, Amhara, Oromia, and Somali regional states. In Amhara, some farms have registered nearly 100 percent loss of teff, a staple crop in Ethiopia. Moreover, eggs are hatching profusely and forming hopper bands in the Somali region, due to the heavy rainfall.
Despite major control and prevention operations, substantial crop losses had already occurred in the Amhara and Tigray regions of Ethiopia. The hopper bands (young locust populations moving together) had covered nearly 430 square kilometres and had consumed about 1.3 million metric tonnes of vegetation over a two-month period. The formation of bands continued in the rangelands of the Ethiopian Somali Region; and massive new swarms were expected to arrive from Yemen and Somalia. A swarm even forced an Ethiopian passenger plane off course in December.
Food ran out for the nearly 100,000 Eritrean refugees in Tigray, which was partially caused by the Tigran War.
Uganda The locusts headed toward Uganda and fragile South Sudan, where almost half the country faces hunger as it emerges from civil war. Uganda has not had such an outbreak since the 1960s and was already on alert. Uganda has not had to deal with a locust infestation since the ’60s so there was concern about the ability for experts on the ground to be able to deal with it without external support, That week, Uganda’s prime minister told agriculture authorities that “this is an emergency and all agencies must be on the alert,” the government-controlled New Vision newspaper reported.
South Sudan The locusts also headed towards South Sudan, where almost half the country faces hunger as it emerges from civil war. They have not had such an outbreak since the 1960s and was already on alert. In a country like South Sudan, where already 47% of the population is food insecure the crisis was expected to cause devastating consequences.
Djibouti