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 mosquitos’ ranges moved toward the poles by 4.7 kilometers (2.9 miles) a year on average.
Mosquitos 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 mosquitos 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.
How climate change affects disease
Mosquitos are cold-blooded 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 millions of 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 mosquitos is affecting more than just humans. In Hawaii, native songbirds are succumbing to an avian form of malaria. As temperature rises, scientists expect mosquitos 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.