There are very few winners in the climate crisis, but scientists are pretty sure there’s going to be at least one: Mosquitoes.

 

These insects – annoying at best, deadly at worst – thrive in warmth and humidity. As climate change ushers in more frequent and more severe heat waves, as well as storms and floods that leave behind pools of stagnant water in which most breed, it’s boom time for mosquitoes.

 

For the first time in decades, the US Centers for Disease Control and Prevention is warning of several locally acquired cases of malaria in the United States – news that has thrust mosquitoes into the spotlight. While it’s too soon to know whether these specific cases are connected to climate change, scientists have been warning that malaria could become more common in the US as temperatures rise there.

 

It has raised fresh concerns about mosquitoes pushing into regions they have not been in for generations – or ever – and what that might mean for the spread of the deadly diseases they transmit.

 

Rising temperatures allow mosquitoes to grow faster and live longer. Whereas before they would die out during harsh winters in many places, now they have a greater shot at surviving and more time to build up their populations. Heat also speeds up the time it takes for a parasite or virus to mature inside a mosquito.

 

“The hotter the temperature gets, the shorter that process becomes. So not only are these mosquitoes living longer, but they’re potentially becoming infectious sooner,” said Oliver Brady, an associate professor at the London School of Hygiene and Tropical Medicine.

 

They gain other benefits from heat, too. When it’s hotter, more people tend to be outside in the morning and late in the afternoon – prime time for mosquitoes.

 

Heat is also pushing cities to increase their amount of green space, which has a vital cooling effect but could also provide ideal new breeding grounds for the blood-sucking insects.

 

In the US, the number of “mosquito days” – those with the hot and humid conditions they love – has increased across the country, according to a recent analysis from Climate Central, a nonprofit research group.

 

Researchers looked at data spanning more than four decades in nearly 250 locations and found that more than 70% of them had become more hospitable to mosquitoes.

 

While most of the approximately 200 mosquito species in the US are harmless, there are about a dozen which can pass on diseases to humans, including chikungunya, dengue, zika and West Nile viruses.