Man’s deadliest enemy. Photo: Joel Sartore, National Geographic
After the floods, famines and forced migrations that global warming is predicted to bring about, the spread of mosquitoes may seem like adding insult to injury. Mosquitoes, however, remain our deadliest animal adversary, killing an estimated 100 million humans worldwide.
But it gets worse.
A recent study by an international team of scientists, published in Nature Microbiology, provides forecasts for how and where mosquitoes will spread under various climate change conditions. Long story short, none of these conditions involve a ‘no-spread’ option.
The team, from the UK, the US and Belgium, focused on two key disease-spreading mosquito species: Aedes aegypti and Aedes albopictus. They first used historical data from over 3,000 locations in Europe and North America about the mosquitoes distributions to analyse how fast and into which habitats each species spread.
They found that A. aegypti tends to spread over long distances, while A. albopictus‘s spread has been more localized. Within the U.S., A. aegypti spread north at a relatively constant rate, about 150 miles per year. A. albopictus spread most quickly between 1990 and 1995; its advance has since slowed to about 37 miles per year. In Europe, A. albopictus has spread faster, advancing about 62 miles per year increasing to 93 miles per year in the past five years.
The group’s models predict that A. aegypti will spread mostly within its current tropical range, but will also spread through warming temperate places in the U.S. and China, reaching as far north as Chicago and Shanghai, roughly by 2050. In central southern United States and Eastern Europe, which climate models predict will become more arid, A. aegypti is expected to decline.
In contrast, A. albopictus is predicted spread widely across Europe, reaching large areas of France and Germany over the next 30 years. The group also predicts that A. albopictus will establish toeholds the northern U.S. and the highland regions of South America and East Africa in that timeframe.
At the moment, human activity drives the greatest spread of mosquitoes, through simple things like leaving standing water untended and more complex things like rapidly rising ran populations. For the next 5-15 years, the group’s models predict human activity to remain the dominant factor in mosquito spread. After this, however, a warming climate looks likely to take over.
With this new work, we can start to anticipate how the transmission of diseases like dengue and Zika might be influenced by a variety of environmental changes,” says Simon I. Hay, director of Geospatial Science at IHME and Professor of Health Metrics Sciences at the University of Washington. “Incorporating this information into future scenarios of risk can help policymakers predict health impacts and help guide strategies to limit the spread of these mosquito species, an essential step to reduce the disease burden.”