Climate Change, as warned by scientists, push many species into new territories. And the latest threat is that disease carrying mosquitoes are finding new territories, which increases the risk of spreading of diseases to new horizons. In a new study, researchers found that Malaria spreading mosquitoes have been moving into warming areas for over a century in Africa.
THE DATA AND FINDINGS
The researchers from Georgetown University biologist under Colin Carlson used one of the most comprehensive datasets ever compiled by medical entomologists to track the outer reaches of mosquito distribution in Africa over 120 years. They estimated the range limits of 22 species of Anopheles mosquitoes between 1898 and 2016. In that time, the world has warmed by at least 1.2 degrees Celsius, opening new areas suitable to mosquitoes.
As a result, Anopheles mosquitoes have spread southward by 4.7 kilometres (nearly 3 miles) every year, and risen 6.5 meters in elevation each year.
However, a 2011 study noted that terrestrial species were moving poleward by 1.7 kilometres a year and up slope by 1.1 meters each year – a rate that was, at that time, roughly two to three times faster than previously thought.
The scientists said that African Anopheles mosquitoes moved so far that, on average, they are now found 500 kilometres (310 miles) closer to the south pole and 700 meters (2,300 feet) farther uphill than they were at the turn of the 20th century.
Carlson noted that it was the first “hard historical evidence” that mosquitoes are already on the move with rising temperatures – and have been for quite from time. “This is exactly what we would expect to see if climate change is helping these species reach colder parts of the continent,” says Carlson.
SENSITIVE TO CHANGES
Though mosquitoes can travel hundreds of kilometres overnight with wind currents, they are much sensitive to temperature changes, humidity, and rainfall. It’s expected that climate change will not only expand the range of mosquitoes but also lengthen the time each year when they are out in force.
Noting that this new study only tracked mosquitoes in the genus Anopheles, Carlson says other mosquito species are probably moving in a similar way, but only by collecting data can we begin to understand just how far they may go.
“We tend to assume that these shifts are happening all around us, but the evidence base is fairly limited,” says Carlson.
As for Anopheles mosquitoes, retracing their spread through history could help to explain shifting patterns of malaria transmission in the African region. It could also help clarify long-standing debates over why malaria cases have risen in highland east Africa, specifically.
NOT JUST MALARIA
Carlson’s past research shows that it is not just malaria carrying mosquitoes are on the move but Aedes mosquitoes – which are vectors for dengue, chikungunya, and Zika viruses – are also on the move. However, Less is known about the impact of climate change on Aedes mosquito than on Anopheles so we best get to grips with how the situation is changing – with increased surveillance to monitor for disease outbreaks.
The research has been published in Biology Letters.