Mosquitoes were detected in Iceland for the first time this month, resulting in the country losing its status as one of the only places in the world without them. The findings were confirmed by the country’s national science institute on Monday.
This follows record-breaking heat this past summer, which has sped up glacial melting in the country.
When were mosquitoes detected in Iceland?
On October 16, insect enthusiast Bjorn Hjaltason posted on a Facebook group Skordýr og Nytjadýr Á Íslandi (Insects in Iceland) that he had spotted mosquitoes in Kjos at dusk that day.
He said he had caught some using a red wine ribbon, a trap using sweetened wine as bait to attract insects. Kjos is a glacial valley 52km (32 miles) northeast of the Icelandic capital, Reykjavik.
Hjaltason sent the mosquitoes to the Natural Science Institute of Iceland, where entomologist Matthias Alfredsson confirmed they were indeed mosquitoes.
Which type of mosquitoes have been found?
Alfredsson identified the mosquitoes as belonging to the Culiseta annulata species. This cold-resistant species is native to the Palearctic, which refers to Europe, North Africa and most of Asia north of the Himalayas. The Culiseta annulata are not known to carry disease but are generally considered a nuisance.
“It has adapted to a rather cold climate, surviving the winter as an adult and then staying in shelter, such as outbuildings and basements. The fly stings but is not considered dangerous to humans as it does not carry any known infections in these areas,” a news release published by the Natural Science Institute on Tuesday stated.
Mosquito species that are well adapted to cooler conditions and can survive winters as eggs or larvae do not tend to carry disease.
“Their development is slower, their active season shorter and most tropical diseases cannot complete their life cycle before cold weather sets in,” British entomologist Luke Tilley from the Royal Entomological Society told Al Jazeera. “Cooler regions, therefore, tend to have mosquitoes but with lower disease risk.”
Why did Iceland not have any mosquitoes before?
There are more than 3,500 species of mosquitoes around the globe, and they can be found in most parts of the world, bar a very few, including Antarctica.
Mosquitoes breed in shallow, stagnant bodies of water, which Iceland has in abundance. Despite having many marshes and ponds, however, it has never had a native mosquito population.
This is because mosquitoes are cold-blooded, which means they thrive in warmer environments. Male mosquitoes also feed on flowers, which thrive in warmer temperatures.
“Warmer air and water speed up their growth, feeding and reproduction and also allow disease‑causing organisms inside them to develop more quickly. Longer warm seasons mean more generations of mosquitoes each year, and changes in rainfall can create new pools and puddles for breeding,” Tilley said.
Iceland is generally cold throughout the year. Its average temperature varies from minus 1 degree Celsius (30 degrees Fahrenheit) in the winter to 11C (52F) in the warmest months.
Mosquitoes lay their eggs during cold weather, and when the water thaws, the larvae hatch from the eggs. In Iceland, however, water typically freezes and thaws several times a year, making the landscape generally inhospitable for mosquitoes.
Before mosquitoes were spotted this month, the closest they had come to Iceland was in the 1980s when biologist Gisli Mar Gislason spotted one inside his aeroplane that had arrived at Keflavík International Airport from Greenland. The mosquito is preserved at the Icelandic Institute of Natural History.
Gislason told Al Jazeera that more mosquito species are in warm climates than cold, and the greatest diversity of mosquitoes is seen in tropical areas.
“There is one species in Greenland, Aedes nigripes. It is a high Arctic species, and their density is controlled by the abundance of hosts, [such as] muskoxen, Arctic foxes, reindeers, polar bears and humans.”
Why are mosquitoes appearing in Iceland now?
In a statement, the Natural Science Institute said it is unclear how this particular mosquito species came to be in Iceland. However, it added: “It is likely that it was transported by freight. It is uncertain whether it has settled here permanently, but everything indicates that it can survive in Icelandic conditions.”
A growing number of new insect species are being observed in Iceland due to a warming climate and increased transportation, the institute said.
The country is warming at an unprecedented rate. In May, Iceland and neighbouring Greenland experienced record-breaking heat due to a persistent weather pattern that brought unusually warm air from the south. In May, temperatures recorded in Iceland were 13 degrees Celsius (23.4 degrees Fahrenheit) warmer than the 1990-2020 average – 10 times higher than the average warming of 1.3 degrees Celsius (2.3 degrees Fahrenheit) across the world as a whole.
The country’s glaciers have been rapidly melting and are projected to lose about half their volume by 2100, the country’s Vatnajokull National Park website said.
Increasingly, “cooler climates can support mosquito development and survival. They can adapt to cooler temperatures up to a certain temperature below which they cannot survive. It depends which mosquito species,” Yaw Afrane, a professor of Medical Microbiology at the University of Ghana, told Al Jazeera.
Are mosquitoes making new appearances in other parts of the world as well?
Yes. Warming temperatures are changing how mosquitoes behave in many parts of the world.
As the planet warms, “vector-borne diseases will move to areas that have been free of them as the climate will be more permissive to disease vectors,” Afrane said.
The World Health Organization has identified an increase in insect-borne disease as one of the biggest health threats to humans associated with climate change.
“Warmer conditions can allow mosquitoes and the pathogens they carry to survive in new regions, extending the potential range of diseases such as dengue, chikungunya and West Nile virus,” Tilley said.
“International travel, trade and changes in land use also play a part. The key is careful monitoring and preparedness to prevent local transmission.”
In September 2023, the United Kingdom found the eggs of Aedes aegypti mosquitoes in the country for the first time near Heathrow Airport. Then in August 2024, four Aedes albopictus eggs were found at a motorway service station in Kent. No further specimens were found on investigation.
The Aedes aegypti is responsible for the spread of diseases such as dengue, chikungunya and Zika. Aedes albopictus can also transmit diseases such as dengue and chikungunya.
European countries have reported increasing cases of mosquito-borne illnesses recently. Last year, Italy had more than 200 local dengue cases. France and Spain also reported cases of the disease. This year, France has recorded 500 cases of chikungunya.
Warmer countries that already have high rates of mosquito-borne illnesses are seeing a surge in numbers. In September, Bangladesh recorded the largest single-day rise in both deaths and hospital admissions from dengue fever when 12 people died and 740 new people were hospitalised in just 24 hours.
Besides increasing temperatures, heavy rainfall can also allow mosquitoes to thrive. The rain flushes mosquito eggs, larvae and pupae from areas where they breed to new areas. If rainwater does not drain away properly, it leaves pools of shallow, stagnant water, the ideal breeding grounds for mosquitoes.
Tilley explained that besides the spread of disease, changing mosquito populations can also create shifts in the ecosystem. “More mosquitoes can benefit their predators such as bats, dragonflies and birds, but disease in wildlife may also rise,” he said.
“A mosquito in a new area will be a prey for predators like fish, waterfowl and insect-eating insects. There is, therefore, more diversity of food for these predators,” Gislason told Al Jazeera, adding that it is difficult to predict accurately what will happen if a mosquito enters a new area. He said, however, that major changes in aquatic ecosystems in Iceland have not been observed yet.
Tilley said these shifts in mosquito behaviour also allow insect scientists to study climate change patterns, noting, “Insects like mosquitoes are valuable indicators of environmental change, helping insect scientists track how ecosystems respond to a warming climate.”