scientists have long warned The climate change would push species into new territories with the advance of disease-carrying mosquitoes their biggest concerns.
But this is not a theoretical future threat. mosquitoes that transmit malaria have been moving to warming regions in Africa for over a century, according to a new study.
Georgetown University biologist Colin Carlson and his colleagues used one of the most comprehensive datasets ever compiled by medical entomologists to track the spread of mosquitoes in Africa over 120 years.
The data allowed the researchers to estimate the range limits of 22 species anopheles Mosquitoes between 1898 and 2016. In that time, the world has warmed by at least 1.2 degrees Celsius, opening up new areas suitable for mosquitoes.
As a result, anopheles Mosquitoes have spread 4.7 kilometers (almost 3 miles) south each year and have risen 6.5 meters in height each year.
This is farther and faster than Estimates from a 2011 study who reported that terrestrial species were moving 1.7 kilometers poleward and 1.1 meters uphill annually — a rate that was about two to three times faster than previously thought.
In fact, this new study suggests that Africans anopheles Mosquitoes have moved so far that they are now found, on average, 500 kilometers (310 miles) closer to the South Pole and 700 meters (2,300 feet) further uphill than at the turn of the century.
According to Carlssonthis is some of the first “hard historical evidence” that mosquitoes are already on the move with rising temperatures – and have been for quite some time.
“This is exactly what we would expect if climate change helps these species reach colder parts of the continent.” says Carlson.
“Up to this point,” Carlson tells Science Alert, “most work on climate change and malaria has focused on the dynamics of malaria transmission itself. Here we take a step back and say that climate change could independently affect mosquitoes and mosquitoes.” before we even get to the malaria part of the story.”
Mosquitoes are fleeting: they can travel hundreds of kilometers overnight with wind currents. But these cold-blooded creatures are also sensitive to temperature fluctuations, humidity, and precipitation, so local climates dictate where they can survive.
Climate change is expected to not only expand the range of mosquitoes, but also increase the time they are in effect each year.
Note that this new study only tracked mosquitoes in the genus anophelessays Carlson other mosquito species are likely moving in a similar fashion, but only by collecting data can we begin to understand how far they can go.
“We tend to assume these shifts are happening all around us, but the evidence base is fairly limited.” says Carlson.
As for anopheles Mosquitoes, tracing their spread throughout history, could help explain the changing patterns of malaria transmission in the African region. It could also help clarify long-standing debates about why malaria cases have risen specifically in the East African highlands.
Some researchers have argued that the malaria resurgence in upland areas is better explained by expired control programs and growing drug resistancewhile others say rising temperatures are part of the powerful mix of factors that influence malaria transmission and we must recognize them.
“If [Anopheles] Mosquitoes are spreading in these areas for the first time,” Carlson arguedthen “it may help explain some recent changes in malaria transmission that have otherwise been difficult to attribute to climate.”
All of this information plays an important role in allocating health resources that researchers say should be directed to the edges of transmission zones, where health systems may not be adequately prepared to deal with the increasing risk of disease.
Of course it is not just malaria what we should worry about. This is what Carlson’s earlier research shows aedes Mosquitoes – which are carriers of Dengue, Chikungunya and Zika viruses – are also on the way.
In the worst case almost a billion people could be at risk of re-exposure virus transfer of aedes Mosquitoes as the planet heats up to add to that Billions more at risk from malaria.
However, less is known about the effects of climate change aedes mosquitoes than on anopheles Therefore, we can best manage the changing situation with increased surveillance to monitor disease outbreaks.
“We should look for species that are moving,” Carlson tells ScienceAlert, “and think about how we’re preparing for the health impacts of climate change.”
The research was published in biology letters.
