Emergence of desert locust swarms during torrential rains after severe droughts exhibits implicit link between locust infestation and climate change. Indian Ocean Dipole (IOD), owing to temperature difference between eastern and western waters, during its negative phase creates floods in Australia and droughts in Africa. IOD transition from negative to positive phase creates drought in Australia and deluge in Africa [Ben 2019]. Rains cause vegetation growth enabling locust plague into gregarious swarms.
Locusts are common grasshoppers found in crops everywhere. These insects are usually solitary, but under certain circumstances become more abundant with change in their behavior and habits, gathering in swarm phase to become gregarious. Once locust swarm becomes migratory they attack crops, breed, multiply and wander randomly. Locust swarms originate in certain climate conditions in deserts and move to attack vegetation in plain agricultural regions. Farmers use pesticide sprays to reduce their strength else birds from remote regions get together to eat them naturally.
Scientists say that more study is needed to understand how far rising temperatures, more variable rainfall and shifting wind patterns caused by climate change will affect locust outbreaks. The FAO says that desert locust numbers can boom “if heavy rains fall in successive seasonal breeding areas”. Desert locusts swarming across the Horn of Africa have started laying eggs and the new generation of pests will aggravate what the United Nations says is “an unprecedented threat to food security and livelihoods” [Alister 2020]. “Desert Locusts present an extremely alarming and unprecedented threat to food security and livelihoods in the Horn of Africa,” [Josh 2020]. Ajit says, “Strengthened by climate change, the Indian Ocean Dipole has made Australia drier while countries such as Kenya, Somalia and Ethiopia become wetter and more hospitable to desert locusts.” Wildfires in Australia and deadly locust swarm in Africa are manifestation of climate change [Ajit 2020].
According to Antsey, “under suitable conditions of drought followed by rapid vegetation growth by rains, serotonin in locust brains triggers a dramatic set of changes leading to their abundant breeding, becoming gregarious and nomadic, 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.” [Antsey, 2009]. When local vegetation ends they move to nearby regions.
Sudan, Somalia and Kenya are affected by desert locusts during droughts in negative phase of IOD and inundating floods during positive phase of IOD. Severe drought followed by rainy season bolsters growth of vegetation that provokes locust to form swarm phase to attack crops collectively. Locusts and climate experts claim the climate change powers the swarms of desert locusts that have invaded eastern Africa, ravaging crops, decimating pasture and deepening a hunger crisis. Since June 2019, the fast-breeding locusts - already devouring huge swathes of Ethiopia, Kenya and Somalia - could grow by 500 times and move into Uganda and South Sudan. The hungry swarms threaten to exacerbate food insecurity in a region where up to 25 million people are reeling from three consecutive years of droughts and floods.
Normally there none or one to two cyclones in Africa, but in 2019 there were eight which led to emergence of insects into locust swarm infestation. The infestation from the Arabian Peninsula has also hit countries such as India and Pakistan, through Iran, with concern growing about new swarms forming in Eritrea, Saudi Arabia, Sudan and Yemen. Swarms sizing 40km by 60km devour crops on tens of thousands of hectares. Locust swarms emergence is linked with IOD and climate change [Nita 2020].
In January, swarming locusts emerged from the Red Sea coast of Sudan and Eritrea. Only a month later, they were already in Saudi Arabia and Iran. In March, they hit Pakistan’s southwestern Balochistan province. In May, they entered Sindh. Desert locust swarms attacked Baluchistan in March 2019. The swarms of locusts descended on Mastung, Dasht, Kund Mesori and Quetta areas of Balochistan in March 2019. Later the swarms of locusts attacked cotton fields in Khairpur, Sukkur, and Ghotki. Farmers had to bear huge losses due to crop loss in the attack. After leaving their trail of destruction in Sindh and Punjab, locust swarms again attacked crops in Kohlu district of Balochistan in December 2019 [Staff 2019]. Locust attacked many times in Sindh in 2019. In May 2019, the locust swarms attacked deserts of Thar, Nara, and Kohistan regions covering approximately 68,000 square kilometers area [Niamat 2019]. Swarms of locusts descended upon Malir, Korangi and New Town areas [Imran 2019].
Locust Swarm Infestation in India/Pakistan
After Baluchistan and Sindh provinces of Pakistan the locust swarms attacked three border districts Banaskantha, Patan and Kutch in Gujrat India. The locusts, known as tiddis locally, have wreaked havoc on standing crops of castor, cumin, jatropha, cotton, and potato, and fodder grass in around 20 talukas. Originally, the locusts emerged in February this year from Sudan and Eritrea on Africa’s Red Sea Coast and travelled through Saudi Arabia and Iran to enter Pakistan, where they invaded the Sindh province and from there they moved into Rajasthan and Gujarat [Mahesh 2019].
Locust attacked South Punjab in September 2019 and parts of central Punjab in January 2020. Locust attack in Punjab is likely to cause huge losses [Editor 2020]. Swarms of yellow locusts that have since March been devastating crops in Pakistan’s southwestern and southern provinces of Balochistan and Sindh, have entered southern Punjab’s Cholistan desert as officials scramble to contain the risk to the country’s cotton cash crop [Raja 2019[. The Khyber Pakhtunkhwa government on Wednesday declared emergency to control spread of locust in nine southern districts of the province following the entry of large swarms of pest to Dera Ismail Khan district. Mr Saadullah said the rising temperate was likely to cause more damage to crops in the area. He urged the government to tackle the issue to ‘save poor farmers from starvation’ saying the locust has caused havoc in several districts of Punjab [Manzoor 2020].
Locust attacks were common before 1959, which decreased significantly after 1960s. Latest attack occurred in 1990s in subcontinent. Locust swarms can travel 38 to 100km in one day in search of vegetation and food crops. The 50 swarms which invaded Kenya in early 1954 were estimated from the air reconnaissance observations and probably to within about 10 %, to cover a total area of approximately 1000 km2 to 1300 km2 (Rainey I954), with the biggest single swarm covering 200 km2. Farmers controlled locust by spraying insecticides. “Somali Republic and neighboring areas of Ethiopia during June-September 1960, which was treated with some 175 tons of concentrated insecticide from the air, in the largest-scale campaign ever undertaken in this area. The results were illustrated by detailed assessments of dead locusts following the application of 38 tons of concentrated insecticide against a single swarm over a period of six days, which demonstrated a corresponding kill of some 20000 tons of locusts; it was cautiously concluded that 'this campaign seems to have caused a considerable set-back to the development of the locust plague.” [Rainey 1979].
The traditional means of locust control are based on the use of insecticides from the ground or the air, but other methods using biological control are proving effective. Beating drums, throwing flames and fire crackers protect crops yet not very effective. “By the 1950s, the organochloride dieldrin was found to be an extremely effective insecticide, but it was later banned from use in most countries because of its persistence in the environment and its bioaccumulation in the food chain.” [Kral 1997].
To control the locust the hoppers are targeted early by applying water-based, contact pesticides using tractor-based sprayers, and where possible, spraying concentrated insecticide solutions from aircraft over the insects or the vegetation on which they feed is preferable. The use of ultralow-volume spraying of contact pesticides from aircraft in overlapping swathes is effective against nomadic bands and can be used to treat large areas of land swiftly. Other modern technologies used for planning locust control include GPS, GIS tools, and satellite imagery, and computers provide rapid data management and analysis [Ceccato 2014]. A biological pesticide was used to control locust control in Tanzania in 2009 to treat around 10,000 hectares in the Iku-Katavi National Park infested with adult locusts. The ultimate goal in locust control is the use of preventive and proactive methods that disrupt the environment to the least possible extent. Aerial spray, however, affects several living species.
Locust have been used as food historically. Locusts are mentioned in Torah, Bible and Quran. It is halal food and African, Arabs and some Asian eat locusts. Agriculture Minister Sindh province, after failing to cope with locust attack, advised public to make Biryani of locust insects and eat.
Locust swarms have historically been attacking various regions of Africa, Middle East and Asia. However, the emergence of locust swarms occurs in specific weather conditions. Severe drought followed by rains is the optimum time for their emergence in Africa. Once the locust swarms rise they multiply their number over time. Climate change might have created the favorable environment for their emergence in Africa, Middle East and then spreading to Iran and Pakistan is routine tactics.
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