Locust plagues may increase with global warming – 02/19/2024 – Environment

Rising temperatures could expand the area of ​​the world under threat from crop-eating locusts by up to 25% in the coming decades, a new study finds, as more places are subject to the cycles of drought and torrential rain that give rise to biblical swarms of the insects. .

Desert locusts have been a pest for farmers in North Africa, the Middle East and South Asia for millennia. They love hot, dry conditions, but need the occasional rain to moisten the soil where they incubate their eggs.

Human-caused warming is warming locust habitat and intensifying sporadic rains. This exposes new portions of the region to potential infestations, according to the study, published last Wednesday (14) in the journal Science Advances.

“Given that these countries often serve as global breadbaskets and are already dealing with climate extremes such as climate-driven droughts, floods and heatwaves, the potential escalation of locust risks in these regions could exacerbate existing challenges,” said Xiaogang He, a study author and assistant professor of civil and environmental engineering at the National University of Singapore.

Other scientists have warned, however, that climate change is also affecting locusts in another important way.

When they’re not congregating in their millions, devastating entire landscapes, these insects lead solitary, modest lives in arid zones. As the planet warms, some of these areas could become too hot and dry even for locusts, leaving smaller territories in which they could multiply and congregate.

That could make it easier to use pesticides to stop outbreaks before they turn into widespread pests, said Christine N. Meynard, a researcher at the National Research Institute for Agriculture, Food and the Environment in Montpellier, France.

“If you can focus on fewer areas” to combat locusts, “it’s much better,” said Meynard, who was not involved in the new study.

Locust invasions may be best known as a form of divine punishment, but scientists have long understood that insect lives are intimately linked to climate and ecology.

For long periods of time, desert locusts are scattered and out of sight in dry places, including the Sahara and Sahel in Africa and the Thar Desert in India and Pakistan. When it rains, their eggs bloom and so does the surrounding vegetation, giving the larvae plenty of food.

As the land dries out again, they begin to gather in places where vegetation remains. They then take off in swarms to look for more food, darkening the skies and devouring crops in some of the poorest places on the planet.

In 2019, the worst locust infestations in a generation began to spread across a swath of the globe from East Africa to central India. FAO (Food and Agriculture Organization of the United Nations) and its partner agencies carried out a vast operation to protect crops and livestock and guarantee food supplies for tens of millions of people.

Xiaogang He and his colleagues used mathematical modeling to examine how climate factors shape how locust invasions play out over large areas. They found that the timing of seasonal rains in the region can determine which distant places are at disproportionate risk of experiencing swarms at the same time.

India and Morocco, for example, are thousands of kilometers apart. And yet, locust plagues are highly likely to be synchronized in the two countries, the researchers concluded. Likewise for Pakistan and Algeria.

“Simultaneous locust infestations have the potential to trigger widespread crop failures, putting global food security at risk,” He said.

Based on what he and his colleagues determined about how rainfall, temperatures, soil moisture and winds affect locusts, they were also able to predict how global warming could change the picture.

They estimated that the insects’ total range could expand by 5% to 25% by 2100, depending on how much hotter the planet gets. Some places that don’t have grasshoppers today could start seeing them in the coming decades, the researchers pointed out. These places include areas of Afghanistan, India, Iran and Turkmenistan.

A different species, the South American grasshopper, ravages farms in Argentina, Bolivia, Brazil, Paraguay and Uruguay. Other research has predicted that global warming will also increase the geographic range of this pest.

In addition to climate and ecology, Meynard and other researchers see sociopolitical conditions as another important factor behind locust risks. In conflict-torn Yemen, for example, pest populations have grown unchecked in recent years, which may have worsened outbreaks in 2019 and 2020.

More stable countries have improved their locust monitoring and management, Meynard said. “There has been progress, for sure,” she said.