Between 2019 and 2021, swarms of desert locusts̨ swept across the Horn of Africa and East Africa. In response, the worst-affected countries, Kenya and Ethiopia, sprayed millions of hectares of cropland and pastures with chemical pesticides.
A new study now finds the chemical spraying coincided with a steep decline in honey production in Ethiopia. Co-author Elena Lazutkaite a specialist in sustainability and pest control, and her colleagues at the Berlin think tank TMG estimate that in Ethiopia, billions of honeybees died or abandoned their hives during this period. In their study in the journal Agronomy, they argue that use of synthetic pesticides was most likely to blame.
TMG is the nonprofit research arm of a consultancy co-founded by former top officials at the Food and Agriculture Organization and the U.N. Environment Programme.
Chemical control may work faster against pests, but it comes with a greater cost, Lazutkaite said. “If we consider the impact of wild pollinators and other non-target animals, the true costs of insecticide use could be in the realm of billions of U.S. dollars,” she said.
The FAO calls locusts a “dangerous migratory pest” because, in such colossal numbers, they can prove extremely destructive. An adult desert locust (Schistocerca gregaria) consumes as much as its own body weight in a day. The 2019-2021 infestations made food scarcer for 20 million people in the region.
S. gregaria isn’t always disruptive to human activities. This grasshopper species thrives in arid and semi-arid parts of Africa, the Middle East and Asia, stretching from West Africa to the Thar Desert in India. Usually, the insects are solitary. But if environmental conditions are favorable, particularly when heavy rains fall on normally dry areas, sparking a green spurt, it can cause locust numbers to explode. Driven by innate biological impulses, locusts form massive swarms that migrate long distances, sometimes thousands of kilometers, in a frenzied search for food.
In 2018, heavy rains, including from unusual cyclonic activity over the Arabian Peninsula, created the perfect storm. These abnormal conditions are likely to materialize more frequently due to climate change, lending urgency to calls to get locust control strategies right.
“With locust swarms as large as those involved in the 2020-21 upsurge, the only way to reduce their numbers is aerial and ground spraying with pesticides and biopesticides approved for that purpose,” the FAO said in a statement in response to Mongabay’s questions.
The FAO, responsible for keeping tabs on locust outbreaks, shipped more than 1 million liters (264,000 gallons) of “conventional insecticides” to the region. Ethiopia primarily used malathion and chlorpyrifos; Kenya deployed deltamethrin and fenitrothion. By contrast, Somalia, which also faced massive locust swarms, turned to the bioinsecticide Metarhizium acridum and the insect growth regulator (IGR) teflubenzuron that interferes with the development of insect exoskeletons. M. acridum is a fungus that selectively infects locusts and can prove fatal to them.
Robert A. Cheke at the University of Greenwich’s Natural Resources Institute in the U.K., which advised the Ugandan government during the latest outbreak, said countries tend to turn to conventional pesticides because they have more experience with them. “The M. acridum spraying involves a delay between the sprays and the deaths of the locusts, and they like to see immediate effects,” said Cheke, an ecologist who has researched locust outbreaks.
Lazutkaite said the lack of research data creates a false choice between cheap chemical agents versus pricier and slower-acting biocontrols. “If you look deeper, you realize chemical pesticides are not cheap,” she said.
Organophosphates act faster but also impact many non-target species. Chlorpyrifos and malathion, the control agents used in Ethiopia, pose the highest risk to honeybees. The chemicals were used continuously for two years, even during flowering and honey harvesting seasons, the researchers say. “Unfortunately, we don’t have enough data to show cause and effect,” Lazutkaite said.
She pointed out that there was no large-scale systematic monitoring of impacts following the chemical spraying campaign. The researchers relied on data on reduced honey production and beehive numbers to infer the impact on honeybee populations, along with evidence from the field of honeybee mortality and empty hives.
The study authors called for an inquiry into vanishing honeybees in Ethiopia and Kenya and other impacts on non-target organisms.
What is clear from official records is that along with the honeybees, honey disappeared too. Data from Ethiopia show honey production declined by nearly 80% between 2017-18 and 2021, translating into losses of $500 million. However, even this figure is conservative because there are cascading effects when pollinators go missing from ecosystems. Economic indicators don’t always capture damage to the larger ecosystem.
Addisu Bihonegn, a researcher and project coordinator at Bees for Development Ethiopia, is passionate about bees and keeps his own hives. He’s not a fan of chemical pesticides, but he’s no fan of locusts either, he told Mongabay over a call. Both harm honeybees, he said.
Locusts are aggressive in feeding on all the vegetative parts of the plants. They feast on flowering plants, eating into nectar and pollen reserves needed by bees.
Bihonegn and Lazutkaite said that in their experience, residents facing large locust swarms are keen to get rid of the swarms quickly.
Bihonegn described the damage from locusts as “unimaginable.” “The devastation of locusts is out of the control of communities, and they are forced to use chemicals. They want to eradicate the locusts quickly before they cause huge damage,” he said.
Risks exist both to humans and animals, but these can be managed if proper protocols are followed, according to the FAO. “Spraying is applied to locust infestations only — inhabited areas, beehives, game parks, and grazing animals are carefully avoided,” the agency said in its statement, adding that “well-trained, properly equipped teams” carry out the spraying using the minimal dose of pesticide needed to be effective.
However, TMG researchers said the pesticide campaign was marred by the reliance on “inexperienced agents.” Where monitoring did take place, there was evidence of overdosing and of precautionary measures being ignored.
The group also raised questions about the European Union financing, via the FAO, the procurement of chemical agents banned in the EU.
“These are chemicals that we wouldn’t put on our soil,” said Lazutkaite, who is based in Berlin, citing the example of chlorpyrifos. The EU phased out chlorpyrifos in 2020 over concerns that it caused brain damage in children and unborn babies. In 2021, the U.S. banned its use. A proposal to list chlorpyrifos as a persistent organic pollutant under the Stockholm Convention is under consideration.
Opposition to these chemical agents is part of a global movement away from synthetic pesticide use detrimental to the environment and human health. Currently, China and the U.S. are the biggest exporters of chemical pesticides, but six of the top 10 exporters in 2020 were European countries, according to U.N. trade data. The other two are India and Israel.
An investigation by Greenpeace and Swiss NGO Public Eye found that European companies export pesticides banned in the EU to countries with weaker regulations. Most of these exports originate from Belgium and Denmark and are destined for low- and middle-income nations across the globe, including in Africa.
Advocates for alternative strategies like integrated pest management say it’s possible to prepare for locust upsurges before they reach threatening proportions. This means “detecting breeding grounds and controlling locusts at the hopper stage before we have a swarm size of Luxembourg,” Lazutkaite said. Hoppers are newly hatched locusts that have not yet grown wings.
Lazutkaite said early-warning systems and early action were part of the answer. The TMG researchers also recommended ditching organophosphates for a wholesome strategy relying on biopesticides and encouraging birds that prey on locusts.
The experience of Somalia shows that biopesticides are gaining traction as alternatives. Green Muscle, a formulation of M. acridum, has been around for more than two decades. It was used in Tanzania in 2009 in Iku-Katavi National Park, keeping the safety of the park’s wild residents in mind. But the 2019-2021 outbreak was the first time it was deployed on such a large scale, covering around 230,000 hectares (568,000 acres) in the Horn of Africa.
Bihonegn said biopesticides work better when there’s a program to monitor locust upsurges, before large swarms form and begin to migrate. An agency responsible for issuing early warnings does, in fact, exist: the Desert Locust Control Organization for Eastern Africa. But it’s critically underfunded. Mounting an early and coordinated response involves more than the choice of control agent. Practical difficulties range from the humdrum, like lack of funding, to the formidable, like poor access to remote and strife-torn regions.
Northern Ethiopia was in the grip of a civil war from late 2020 to November 2022. Somalia marked three decades of civil strife in 2021. Yemen, located on the Arabian Peninsula where the swarms initially arose, has been grappling with a years-long civil war.
The surveillance of locust swarms and breeding areas often relies on remote-sensing data, but countries need to validate that data through site visits. Teams must be adequately trained before the locust swarms emerge. There isn’t a lot of incentive to keep control squads ready and on standby when there are no locust swarms in sight, Cheke said.
Mullié, W. C., Prakash, A., Müller, A., & Lazutkaite, E. (2023). Insecticide use against desert locust in the Horn of Africa 2019–2021 reveals a pressing need for change. Agronomy, 13(3), 819. doi:10.3390/agronomy13030819
Kamga, S. F., Ndjomatchoua, F. T., Guimapi, R. A., Klingen, I., Tchawoua, C., Hjelkrem, A. R., … Kakmeni, F. M. (2022). The effect of climate variability in the efficacy of the entomopathogenic fungus Metarhizium acridum against the desert locust Schistocerca gregaria. Scientific Reports, 12(1). doi:10.1038/s41598-022-11424-0
Vosshall, L. B. (2020). Catching plague locusts with their own scent. Nature, 584, 528-530. doi:10.1038/d41586-020-02264-x
Roussi, A. (2020). Why gigantic locust swarms are challenging governments and researchers. Nature, 579(7799), 330-331. doi:10.1038/d41586-020-00725-x
This article by Malavika Vyawahare was first published by Mongabay.com on 1 May 2023. Lead Image: The desert locust thrives in arid and semi-arid parts of Africa, the Middle East and Asia, stretching from West Africa to the Thar Desert in India. Image by Paul Korecky via Wikimedia Commons (CC BY-SA 2.0).
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