Locust Swarms: Will We Listen to Nature’s Warnings?

The COVID-19 pandemic has wreaked havoc all over the world, everywhere from the U.S. Sunbelt region, with rapidly growing cases, to Italy, which has since recovered after being one of the hardest-hit countries. The pandemic has already taken such a physical and mental toll, yet developing countries in East Africa, like Somalia, are simultaneously battling an equally destructive plague: locust swarms.  

Locusts are defined as informal groupings of grasshoppers that swarm. Through erratic outbreaks of locust breeding and generation, swarms with as many as 80 million locusts descend upon a region and threaten the livelihood and food security of millions of people. With a voracious appetite, a locust can eat its weight in plants each day and quickly spread to neighboring regions with its ability to fly up to 90 miles within 24 hours. To put this into perspective, a swarm the size of Paris can eat the same amount of food in one day as half the population of France. 

These locust plagues have long terrorized populations all over the world since Biblical times. From 942 to 944 A.D., locusts invaded the Yellow River Basin of China, demolishing crops and creating a great famine that starved 1/10th of the total population in the area (Fei & Zhou, 2016). It is said that the largest swarm ever recorded took place in the U.S. plains states in the 1870s. In 2013, half of Madagascar was infested by flying swarms, threatening 60% of the country’s rice production (Africa Research Bulletin, 2013). 

Today, the desert locust outbreak (Schistocerca gregaria) covers most of East Africa, the Arabian peninsula, and is quickly spreading to parts of Southwest Asia. These plagues compound an already dire situation in countries like Somalia and Yemen, whose internal conflicts, widespread poverty, and corruption prevent adequate locust control. Even before the pandemic, 30 million people in West Africa were in urgent need of food assistance, and the World Food Program estimates that more than 13 million will face food insecurity with the added socioeconomic impact of COVID-19. 

Why is this happening now?

How do we get menacing swarms of locusts from solitary hoppers? The answer is in the climate. Desert locusts only lay their eggs in moist soil to prevent them from drying out, so when the desert receives some heavy rain, locusts rapidly breed and can lay up to 1,000 eggs per square meter of soil. In May 2018, unexpected heavy rainfall from rare sequential cyclones created pools of water in deserts across the Horn of Africa. These cyclones, spawned by changes in the Indian Ocean Dipole, which is the difference in sea surface temperatures between Arabian Sea and eastern Indian Ocean, have continued to come and go for the last two years, creating abnormally long periods of breeding for locusts. With each generation of locusts, the population exponentially increases about 20-fold. 

Normally solitary animals due to frequent cannibalism, these locusts are suddenly crowded in areas of moist vegetation, leading to release of serotonin in their brains and a subsequent physical transformation into a “gregarious phenotype”. These locusts change from tan to a bright yellow and black color and develop an immense appetite. Even their brains grow 30% larger (Ott & Rogers, 2010) and their leg muscles increase in volume by 17% (Rogers et al, 2016) . According to researchers at the Max Planck Institute, almost as soon as these gregarious locusts are born, they begin to move collectively to search for food and to avoid being attacked by their own species. Those that don’t move with the group risk survival and this constant, ordered motion continues in the air, thus creating swarms. 

Though cyclones descending upon East Africa were considered rare a few years ago, a warming planet means warmer seas to spawn more cyclones, and consequently, more locust infestations. In a study by the Centre for Southern Hemisphere Oceans Research (CSHOR), researchers found that if the global temperature increases by just 1.5 degrees Celsius, the incidence of the cyclones created by changes in the Indian Ocean Dipole could double (Cai et al, 2018). Essentially, if we don’t quickly find sustainable solutions to slow global warming, locust plagues may be a new pandemic that is here to stay. 

What’s being done right now to stop these infestations?

Currently, the most efficient method to tackle these locust swarms is to spray pesticides from aircrafts, but with extremely harmful impacts to human and livestock health as well as disruptions to the natural ecosystem, it is nowhere close to the final solution. In addition, large-scale operations are not cheap; the 2003-2005 desert locust plague in Africa cost $450 million USD to stop and $2.5 billion USD in crop damage. While biopesticides, based on the fungus M.acridum and a pheromone PAN, have been gaining traction in the global fight, lockdowns orders arising from COVID-19 measures have caused increases in shipping delays and prices. Further downstream with agricultural production, access to fertilizers, seeds, and livestock fodder have been limited due to import bans, and the closing of markets to reduce risk of transmission has meant that less produce and livestock is making it to the public.

Researchers of the Global Locust Initiative at Arizona State University are some of the key players trying to develop sustainable solutions to the infestations. The director of the initiative, Dr. Arianne Cease, and her lab have focused on reforming agricultural practices. They’ve found that locusts have carbohydrate-heavy diets, and sustainable farming practices using organic soil matter and nitrogen can produce plants with low carbohydrate content that are not attractive to locusts (Word et al, 2019). Another preventive management system used by Australia involves modifying the habitat with the aim of conserving natural enemies of locusts like parasitic insects, birds, lizards, and desert foxes. To fight the imminently approaching 400 billion locusts from the India-Pakistan border, China enlisted 100,000 ducks to be sent to Pakistan later this year.

Other groups, like the Food and Agriculture Organization of the United Nations (FAO), are focusing on stopping swarms before they wreak havoc. Using data from previous infestations, the FAO can predict and project where locusts might head over a month ahead of time and subsequently alert countries to mobilize their forces. In collaboration with NASA and the European Space Agency, FAO is examining satellite images to locate and monitor areas of moist soil and vegetation where locust outbreaks may begin. As of July, FAO has prepared an emergency action plan for at-risk regions in East Africa creating 32 surveillance teams with locust monitoring technologies and helicopters and drones ready to deploy pesticides. Though well-equipped, locust upsurges are still highly variable, and the rapidly worsening climate crisis may mean locusts are not going anywhere anytime soon. 

If the one million animals threatened with extinction or the Australian bushfires that devastated an estimated 46 million acres and almost 3,000 homes won’t galvanize our world into action, will locusts? 

Works Cited:

Africa Research Bulletin. MADAGASCAR: Locust Plague. Afr Res Bull Econ, 50: 19910B-19910C (2013). doi:10.1111/j.1467-6346.2013.05078.x

Cai, W., Wang, G., Gan, B. et al. Stabilised frequency of extreme positive Indian Ocean Dipole under 1.5 °C warming. Nat Commun 9, 1419 (2018). doi: 10.1038/s41467-018-03789-6

Jie Fei and Jie Zhou. The drought and locust plague of 942-944 AD in the Yellow River Basin, China. Quaternary International, 394: 115-122 (2016). https://doi-org.turing.library.northwestern.edu/10.1016/j.quaint.2014.11.053

Ott SR, Rogers SM. Gregarious desert locusts have substantially larger brains with altered proportions compared with the solitarious phase. Proc Biol Sci. 277(1697):3087-3096 (2010). doi:10.1098/rspb.2010.0694 

Rogers, S. M., Riley, J., Brighton, C., Sutton, G. P., Cullen, D. A. and Burrows, M. Increased muscular volume and cuticular specialisations enhance jump velocity in solitarious compared with gregarious desert locusts, Schistocerca gregaria. J. Exp. Biol. 219, 635-648 (2016). doi:10.1242/jeb.134445

Sci. Total Environ., 663: 632-643 (2019). 10.1016/j.scitotenv.2019.01.313

Word, M.L., Hall, S.J., Robinson, B.E., Manneh, B., Beye, A., Cease, A.J. Soil-targeted interventions could alleviate locust and grasshopper pest pressure in West Africa