Warming May Expand Locust Range
Rising temperatures could expand the area under threat from crop-devouring locusts by up to 25 percent in the coming decades, a new study found, as more places experience the cycles of drought and torrential rain that give rise to biblical swarms of the insects.
Desert locusts for millenniums have been the scourge of farmers across northern Africa, the Middle East and South Asia. They love hot, dry conditions, but need the occasional downpour to moisten the soil in which they incubate their eggs.
Human-caused warming is exposing new parts of the region to potential infestations, according to the study, which was published last month in the journal Science Advances.
“Given that these countries often serve as global breadbaskets and are already grappling with climate-driven extremes like droughts, floods and heat waves, the potential escalation of locust risks in these regions could exacerbate existing challenges,” said Xiaogang He, one of the study’s authors and an assistant professor of environmental engineering at the National University of Singapore.
Other scientists cautioned, however, that climate change is also affecting locusts in another way. As the planet warms, some of the areas where locusts live could become too hot and dry, leaving smaller territories in which they can multiply and congregate.
This might make it easier to use pesticides to stop outbreaks, said Christine N. Meynard, a researcher at the National Research Institute for Agriculture, Food and Environment in Montpellier, France, who was not involved in the new study.
Scientists have long understood that the insects’ lives are linked intimately with weather, climate and ecology. For long stretches of time, desert locusts stay out of sight in dry places. When it rains, their eggs flourish and so does the surrounding vegetation, giving hatchlings food. As the land dries out again, they convene where greenery remains, then take flight in swarms to search for more food, darkening skies and gobbling up crops.
In 2019, the worst locust infestations in a generation began descending on a stretch from East Africa to central India. The United Nations Food and Agriculture Organization and its partners worked to secure food supplies for tens of millions of people.
Dr. He and his colleagues used mathematical modeling to examine how climate factors shape the way locust invasions unfold across large areas. They found that the timing of seasonal rains can cause far-flung places to be at disproportionate risk of experiencing swarms at the same time. India and Morocco, for instance, are thousands of kilometers apart. And yet locust plagues are highly likely to be synchronized in the two countries, they found.
“Concurrent locust infestations have the potential to trigger widespread crop failures, jeopardizing global food security,” Dr. He said.
Based on how rainfall, temperatures, soil moisture and winds affect where locusts go, they also predicted how global warming might change the picture. They estimated that the pests’ total range could expand by 5 percent to 25 percent before 2100. Some places without locusts could start seeing them in the coming decades, including areas of Afghanistan, India, Iran and Turkmenistan.
A different species, the South American locust, plagues farms in Argentina, Bolivia, Brazil, Paraguay and Uruguay. Other research has predicted that warming will increase the range of that pest, too.
Heat and periodic downpours make ideal conditions.