By Yun Son
The year 2020 has been one of the most chaotic and challenging years in the past few decades. Globally, many governments are presently facing numerous catastrophic disasters, notably the COVID-19 pandemic, multiple economic recessions and social-conflict crises. Among this flurry of problems is an issue that has managed to go fairly unnoticed, and which primarily terrifies entomophobes: locust swarms. Deep down however, locust swarms constitute a much larger issue.
Locusts (Acrididae), especially desert locusts (Schistocerca gregaria), are insects related to and resembling grasshoppers. In size, they are comparable to a paper clip and have robust hind legs that allow them to hop around. Much like a common grasshopper, under ordinary circumstances most locusts display solitary behaviours, but at other times, locusts can behave irregularly and form swarms. Swarm behaviour, or swarming, refers to the gregarious behaviour particularly observed in insects such as bees and termites. Animals exhibiting this kind of behaviour form societies, clusters and communities; acting in a collective way, and often migrating as a whole towards the same direction. (Microsoft Academic, n.d.) Locust swarms are in many ways impressive. One single swarm can be as big as 80 million locusts. A typical desert locust can travel at speeds of up to 19 kilometres per hour and can even fly nonstop for a considerable duration of time. (National Geographic, n.d.)
Under especially arid conditions, such as droughts, solitary locusts group together in small areas where they can find plants to feed on. This swift change in lifestyle causes a release of serotonin in the central nervous systems of locusts, consequently causing them to manifest more sociable behaviours, an increase in their appetite and rapidity of their movements. Once the aridity ends and starts to rain, vegetation grows more abundantly, giving locusts the perfect conditions to reproduce and form even larger crowds. At this point, locusts are undergoing what is called the gregarious phase which refers to the complete change in lifestyle, from a solitary structure to the forming of groups. During this period, locusts experience a massive change in their physique: their brains grow in size, their endurance rises, and they can alter their form and colour. (National Geographic, n.d.)
In recent years, the frequency of locust swarms has alarmingly increased. The reason behind this upsurge is none other than climate change. According to Keith Cressman, senior locust forecasting officer at the FAO (Food and Agriculture Organisation of the United Nations), climate change has impacted and changed the dynamics of pest control and reproduction of locusts. Furthermore, climate change has induced the number of cyclones to increase, creating the perfect conditions and environment for locusts to reproduce. Importantly, human activities contribute to global warming. Recent research shows that anthropogenic global warming may have amplified patterns of warming and cooling in the Indian Ocean. This phenomenon is called the Indian Ocean Dipole (IOD) and often referred to as the Indian Niño. As the IOD intensifies, the frequency of tropical storms and heavy rains could increase as well, which would allow locust swarms to further thrive. In the past 3 years, the number of cyclones in the Indian ocean have noticeably surged, leading to an unprecedented number and intensity of rainfalls in Somalia, Yemen and Saudi Arabia (Khan, 2020).
Since the ancient times, locusts have threatened and scared humanity. Their existence has been recorded on the tombs of ancient Egyptians, in Homer’s Iliad, in the Bible and the Quran. They have always been a symbol of plague and calamity. Locust plagues have destructive impacts on crops and agriculture, which often results in famine. Regions of Africa and Southwest Asia are particularly at risk of plagues. Countries, including Uganda and Kenya, have been reporting devastating waves of locusts since 2019, each wave 20 times worse than the last(Okiror, 2020). Some farmers in Pakistan have lost up to 50% of their cotton crops. Large locust swarms, if spread out, could in theory could cover up to a fifth of Earth’s land surface. It is also important to know that one locust eats a mass of plants equivalent to its own body mass a day, meaning that a swarm would in average consume 423 million pounds of plants a day; In one day, a swarm as large as Paris consumes the same mass of plants that half the population of France would consume in a day. (National Geographic, n.d.)
To sum up, climate change and abnormal environmental conditions have allowed more and more locust attacks to occur, growing both in size and in intensity each year. In consequence, we are now experiencing great famine. This increase in locust swarms should be taken as a warning and bear in mind that these abnormalities and catastrophes are to a large extent man made. Consequently, there is a global responsibility to invest in efforts and research to limit the exposure of crops to locust swarms, and reduce the impact they have on vulnerable communities.
National Geographic. (n.d.) Locusts. Available from: https://www.nationalgeographic.com/animals/invertebrates/group/locusts/ [Accessed 24th August 2020]
Microsoft Academic. (n.d.) Swarm behaviour. Available from: https://academic.microsoft.com/topic/181335050/publication/search?q=Swarm%20behaviour&qe=And(Composite(F.FId%253D181335050)%252CTy%253D%270%27)&f=&orderBy=0 [Accessed 24th August 2020]
Khan, R. S. (2020) Record locust swarms hint at what’s to come with climate change. Eos. Available from: https://eos.org/articles/record-locust-swarms-hint-at-whats-to-come-with-climate-change [Accessed 24th August 2020]
Okiror, S. (2020) Second wave of locusts in east Africa said to be 20 times worst. The Guardian. Available from: https://www.theguardian.com/global-development/2020/apr/13/second-wave-of-locusts-in-east-africa-said-to-be-20-times-worse [Accessed 25th August 2020]
BBC News. (2020) China may send ducks to battle Pakistan’s locust swarms. Available from: https://www.bbc.com/news/world-asia-china-51658145 [Accessed 25th August 2020]