Climate change ushers in the era of mosquitoes

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

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

There are few winners in the climate crisis, but scientists are pretty sure that among them are mosquitoes . This insect thrives in warm and humid places. Climate change is making heat waves more frequent and severe. However, so do hurricanes and floods. These phenomena leave many stagnant pools of water where most mosquitoes breed.

Rising temperatures allow mosquitoes to grow faster and live longer. In the past, they would die during the harsh winters in many places, but now they have a better chance of survival and have more time to grow populations. Heat also shortens the time it takes for the parasite or virus to mature inside the mosquito.

"The higher the temperature, the shorter that process. So mosquitoes not only live longer, but also have the ability to transmit disease earlier," said Oliver Brady, associate professor at the London School of Hygiene and Tropical Medicine. said.

Mosquitoes also derive other benefits from heat. As it gets hotter, more people tend to go out in the morning and late afternoon - golden times for mosquitoes.
High temperatures also prompt cities to increase the amount of green space for cooling, but can also provide ideal new breeding grounds for these bloodsucking insects.

In the US, the number of "mosquito days" - days with hot and humid conditions that mosquitoes love - has increased, according to analysis by the nonprofit research organization Climate Central. Researchers looked at 40 years of data at nearly 250 sites and found that more than 70 percent of them became more mosquito-friendly.

In sub-Saharan Africa, where malaria has had catastrophic consequences, climate change is helping mosquitoes to significantly expand their range. On average, the Anopheles mosquito that transmits malaria moves about 6.5 meters higher and nearly 5 kilometers farther south each year, according to Georgetown University.

That's the pace after climate change, said Colin Carlson, a biologist at Georgetown University, and that could have major consequences for areas that have never had malaria before and aren't ready to respond.

A worker sprays mosquito repellent Aedes aegypti 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 the worst outbreak of dengue fever ever recorded with about 150,000 infections and more than 250 deaths.

Experts say the unusually high rainfall and temperatures provide ideal conditions for mosquitoes. Scientists have not yet assessed exactly what role climate change plays in the outbreak, but Carlson says the connection seems pretty clear.

Currently, dengue fever is "knocking" on the door of Europe and America. "There will be an additional billion people living in the right weather conditions for dengue to spread, and most of them in temperate Western Europe, the United States and China," Carlson said.

However, the US and Europe are still unlikely to suffer large outbreaks, or have large numbers of deaths from the dengue virus. "The story of change in the future is actually more about a sharp increase in places where there is already an epidemic of dengue, it's going to get much worse," Brady said.

China and parts of India are particularly at risk, he pointed out. "It's a really scary situation because so many people live here and small changes can lead to disaster," he said.

Communities on the front lines of the climate crisis will always be hardest hit by mosquito-borne diseases, said Shannon LaDeau, a pathologist at the Cary Institute for Ecosystem Research.

The movement of these diseases to regions like the US and Europe can still come as a shock. "People living in temperate regions will face significant lifestyle changes because they've never had to worry about it before," LaDeau said.

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

The climate crisis doesn't just benefit mosquitoes. Some places can get too hot for them. "There is a threshold where, if exceeded, the chemicals in their bodies don't work anymore. The bad news is that these places can also be too hot for humans," LaDeau said.

Experts still have a lot of unknowns about how mosquitoes respond to the climate crisis. The relationship between climate change and disease is complex, says Gossner. According to Carlson, humans already know a lot about how temperature changes mosquito transmission, know a little about the speed at which mosquitoes move to new places and know very little about the growth of mosquito populations said. shared. Currently, scientists are working to develop tools to better assess the link between mosquito-borne diseases and climate change.