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Climate change may make it easier for mosquitoes to spread malaria

As temperatures rise, such insects have crept farther from the equator in Africa, according to a new study

Nyakaka Yomlat is tested for malaria in Old Fangak, South Sudan, in 2021. (Adrienne Surprenant for The Washington Post)
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As temperatures rise, many tropical species once confined to the warmest parts of the globe are expected to climb to higher altitudes and creep farther from the equator.

That already may be happening with mosquitoes carrying malaria, one of the world’s most devastating diseases and one that already kills more than 600,000 people a year. Evidence shows the insects are flapping their tiny wings to new locales in Africa, according to a new study.

Using data dating back to 1898, a team of Georgetown University researchers found the limits of the malaria mosquitoes’ ranges moved away from the equator by 4.7 kilometers (2.9 miles) a year on average over the past century.

Mosquitoes did some mountain climbing, too, with species gaining an average of 6.5 meters (21.3 feet) in elevation annually on the continent during the same time period, according to a paper published Tuesday in Biology Letters.

Colin Carlson, a biologist at Georgetown who led the paper, said he needs more data to draw a direct link between the spread of malaria mosquitoes and rising temperatures.

“But what we can say is a lot of these species are moving in the direction and at the speed that looks like a climate change impact,” he said.

The deadliest impacts of climate change won’t just come from floods, droughts and other disasters. According to top U.N. climate scientists, some of the worst consequences will come from disease.

Few if any diseases have beset humanity as severely or for as long as malaria. The pathogen is ancient, so old it may have infected the dinosaurs. During human history, it may be responsible for killing half of all people who have ever died, according to one estimate.

Many studies have predicted the spread of disease due to climate change in the future. But this study suggests that was already happening in Africa in the 20th century, according to Sadie Ryan, an associate professor of medical geography at the University of Florida not involved in the research.

“They managed to leverage this massive dataset over space and time,” Ryan said.

“We don’t need to keep making fancy models to say, maybe it’s happening,” she added.

How climate change affects disease

Mosquitoes are coldblooded creatures that function best at balmy temperatures. Since the Industrial Revolution, humans have warmed Earth more than 1 degree Celsius on average.

With climate change poised to upend habitats and push plants and animals to new locales, pathogens are on the move, too. In North America, for instance, the tick responsible for Lyme disease is already reaching north in Canada.

The spread of mosquitoes is affecting more than just humans. In Hawaii, native songbirds are succumbing to an avian form of malaria. As temperature rises, scientists expect mosquitoes to spread higher into the islands’ mountains until the birds have nowhere else to go.

The most recent study in Africa has limitations, Carlson said.

His team, for example, relied on a century’s worth of mosquito observations from many researchers in Africa to make its conclusions. Over the decades, mosquito hunters may have changed the way they looked for the insects in the wild.

And he and his colleagues did not yet connect the malaria mosquitoes’ movement directly to temperatures or studied whether more people are falling ill from the disease as a result. They just looked at how the range of mosquito species changed over time.

“There’s a ton more work for us to do,” Carlson said.

Still, the early findings don’t bode well for the global fight against malaria.

Today, governments and philanthropists spend billions of dollars annually on bed nets, insecticides and a medicine called quinine to prevent infection and blunt malarial fever and other symptoms. Yet funding is still short of international goals.

More on climate change

Understanding our climate: Global warming is a real phenomenon, and weather disasters are undeniably linked to it. As temperatures rise, heat waves are more often sweeping the globe — and parts of the world are becoming too hot to survive.

What can be done? The Post is tracking a variety of climate solutions, as well as the Biden administration’s actions on environmental issues. It can feel overwhelming facing the impacts of climate change, but there are ways to cope with climate anxiety.

Inventive solutions: Some people have built off-the-grid homes from trash to stand up to a changing climate. As seas rise, others are exploring how to harness marine energy.

What about your role in climate change? Our climate coach Michael J. Coren is answering questions about environmental choices in our everyday lives. Submit yours here. You can also sign up for our Climate Coach newsletter.