Climate change ushers in the age of mosquitoes

Rising temperatures create favorable conditions for mosquitoes to breed, develop and transmit diseases in places where they could not live before.

An Anopheles stephensi mosquito, which can carry malaria, feeds on human blood. Photo: James Gathany/CDC/Handout/Reuters

There are few winners in the climate crisis, but scientists are pretty sure that mosquitoes are among them, CNN reported on June 29. The insects thrive in warm, humid places. Climate change is making heat waves more frequent and severe. But so are storms and floods. These events leave behind stagnant water, where most mosquitoes breed.

Rising temperatures allow mosquitoes to develop faster and live longer. They would have died in harsh winters in many places before, but now they have a better chance of surviving and have more time to build up their populations. Heat also shortens the time it takes for parasites or viruses to mature inside mosquitoes.

“The higher the temperature, the shorter that period. So not only do mosquitoes live longer, they are also able to transmit disease earlier,” said Oliver Brady, associate professor at the London School of Hygiene and Tropical Medicine.

Mosquitoes also benefit from heat in other ways. As the weather gets hotter, more people tend to be outdoors in the morning and late afternoon — prime breeding times for mosquitoes.
High temperatures are also prompting cities to increase green space for cooling, but could also provide ideal new breeding grounds for these blood-sucking insects.

In the US, the number of “mosquito days” — days with warm, humid conditions that mosquitoes love — has increased, according to an analysis by the nonprofit research organization Climate Central. Researchers looked at 40 years of data from nearly 250 locations and found that more than 70% of them have become more mosquito-friendly.

In sub-Saharan Africa, where malaria has taken a devastating toll, climate change is helping mosquitoes expand their range dramatically. On average, the Anopheles mosquitoes that transmit malaria are moving about 21 feet higher and nearly 3 miles farther south each year, according to Georgetown University.

That's the speed at which climate change is happening, and it could have major consequences for areas that have never had malaria before and aren't prepared to deal with it, said Colin Carlson, a biologist at Georgetown University.

A worker sprays insecticide against Aedes aegypti mosquitoes to prevent the spread of dengue fever in a neighborhood in Piura, northern Peru, June 11, 2023. Photo: Ernesto Benavides/AFP/Getty

Dengue fever, another potentially deadly disease, could also increase as the world warms. Peru is grappling with its worst dengue outbreak on record, with about 150,000 cases and more than 250 deaths.

Experts say unusually high temperatures and rainfall have created ideal conditions for mosquitoes. Scientists have yet to assess the exact role climate change has played in the outbreak, but Carlson said the connection seems pretty clear.

Now, dengue is "knocking on the doors" of Europe and the United States. "There will be another billion people living in climates suitable for dengue to spread, and most of them will be in temperate Western Europe, the United States and China," Carlson said.

However, the US and Europe are still unlikely to experience large outbreaks or large numbers of deaths from dengue. “The story of future change is actually more about a surge in places where dengue is already endemic, and the disease will get much worse,” Brady said.

China and parts of India are particularly at risk, he pointed out. “It’s a really scary situation because there are so many people living there and small changes can be catastrophic,” he said.

Communities that are on the front lines of the climate crisis will always be hardest hit by mosquito-borne diseases, according to Shannon LaDeau, a disease ecologist at the Cary Institute of Ecosystem Studies.

The migration of these diseases to areas like the US and Europe could still come as a shock. “People living in temperate zones will face a significant change in their lifestyle because they have never had to worry about it before,” LaDeau said.

Mosquito eggs float next to a dead mosquito on the water surface in a trap set by Louisville Metro Health and Wellness in Louisville, Kentucky, on August 25, 2021. Photo: Jon Cherry/Getty

The climate crisis isn't just a boon for mosquitoes. Some places could become too hot for them. "There's a threshold beyond which their body chemistry stops working. The bad news is that these places could also become too hot for humans," LaDeau said.

Experts still have a lot to learn about how mosquitoes will respond to the climate crisis. The relationship between climate change and disease is complex, Gossner said. Carlson said we know a lot about how temperature changes the ability of mosquitoes to transmit disease, a little about how quickly mosquitoes can move to new places, and little about how mosquito populations grow overall. Scientists are now working to develop tools to better assess the link between mosquito-borne disease and climate change.

Thu Thao (According to CNN )

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