Warming temperatures are causing Arctic mosquito populations to thrive

Dartmouth College in Hanover, New Hampshire, has conducted a study found in the journal Proceedings of the Royal Society B: Biological Sciences that concluded warming temperatures in the Arctic are causing species of mosquitoes to grow faster and emerge earlier in the year. This is significantly increasing their populations and threatening many of the different organisms they feed on, including caribou and reindeer. 

According to researchers, the probability of Arctic mosquitoes surviving and reaching adulthood will increase by more than 50 percent if the Arctic temperatures rise at least 2 degrees Celsius. This impact is important to many ecosystems because changes in hatching timing can and will affect their role as pests to people and other mammals, as well as pollinators of tundra plants and as prey for other species, including migratory birds and beetles. 

Dartmouth researchers have developed a climate-population model for Arctic mosquitoes and their predators, which can be modified to fit any ecosystem in which the survival of the mosquitoes depends on their sensitivities to temperature changes. This model can predict the outcomes of different food chains in various ecosystems and can be used worldwide. 

The effect of warming temperatures on mosquito gestation
Mosquitoes have four stages of life: egg, larva, pupa and adult. Although each species of mosquito is unique, the Arctic mosquito tends to lay its eggs in small temporary ponds of standing water created by the snow melting during early spring. The first three stages of life are primarily aquatic and will last anywhere from five to 14 days. This is also the time that Arctic mosquitoes are the most vulnerable to predators. 

Climate change is having a direct impact on mosquito populations.

Climate change is having a direct impact on mosquito populations. 

Lauren Culler, a researcher at the Dickey Center's Institute for Arctic Studies at Dartmouth, recorded early spring temperatures in 2011 and 2012 on the west coast of Greenland, according to the Atlantic. Culler spent both summers determining population densities of Arctic mosquitoes and comparing them to past populations. Her results indicated that the mosquitoes where hatching as much as two weeks earlier, and the larva and pupal stages of development were shortened by approximately 10 percent for every 1-degree Celsius rise in temperature. The increasing temperatures are causing the different species of birds and beetles that prey on the Arctic mosquitoes during the larva and pupa stages to struggle. This is due to the period of time the mosquitoes are spending in the juvenile stages of development, which has decreased. A 2-degree Celsius increase predicts that the Arctic Mosquitoes' probability of surviving to adulthood will increase by 53 percent, and in turn, the population densities will also rise. 

Samples of Arctic mosquito eggs were gathered and brought to the Kangerlussuaq International Science Support building in Greenland where Culler and a team of scientists modeled Arctic tundra conditions while increasing the temperature slowly over many generations. The results showed that warmer standing water increased the rate of Arctic mosquito gestation and the growth and development through the larva and pupal stages took even less time. Local agencies in Arctic countries will need to work with water quality consultants as well as environmental experts to develop a plan to monitor the water supply if mosquito larva is increasing in bodies of water.

Arctic mosquito impact on caribou and the local ecosystems
Female mosquito reproductive success depends on finding a vertebrate organism as a blood source, which is often the caribou that graze in the Arctic Tundras of Scandinavia, Siberia, Alaska, northern Canada and Greenland. Unlike mosquitoes, caribou coordinate their life cycles with the sun and not seasonal temperature changes. Female calving occurs during late May and early June, and under normal conditions there is a lot of plant growth in May to support the pregnant caribou. Climate change has altered this, causing plants to bloom earlier in the year. This means that many of these plants are not available to the caribou that are becoming malnourished. As a result, fewer calves are being born, and fewer of them are surviving to adulthood. 

Arctic mosquito swarms are made up of hundreds of thousands to millions of insects, according to National Geographic.

"There aren't a lot of animals for them to eat in the Arctic, so when they finally find one, they are ferocious. They are relentless. They do not stop. They just keep going after you," said Culler.

The mosquito swarms can engulf a pregnant caribou until it stops eating and runs away or kill a juvenile caribou outright.

"Caribou have no defense against mosquitoes except to run," Culler said in the Atlantic.

When caribou are running they are not eating, which in turn will lead to less reproduction and less offspring. Previous studies show that when insect populations rise, the caribou and reindeer populations drop, and many of these populations are already in decline. 

Climate change is creating issues for a plethora of species, including mosquitoes as well as marine life.

Climate change is creating issues for a plethora of species, including mosquitoes as well as marine life.

Impact of Arctic mosquitoes on humans
Reiter (2001) in the journal Environmental Health Perspectives stated that of the 3,500 species of these insects, the largest populations of mosquitoes are found in the Arctic tundra, where extremely large numbers emerge in a single brood each summer from stagnant pools of melted snow that cover the permafrost. Mosquitoes are vectors to many different diseases, but the most common and one of the most dangerous is malaria. Temperature, rainfall, humidity and the duration of daylight all play a crucial role in the survival and transmission rate of mosquito-borne pathogens. 

Arctic mosquitoes are now hatching earlier and living longer then they have in the Arctic tundra, and many scientists as well as local agencies are concerned that these mosquitoes can and will cause a pandemic. Reiter (2001) in the journal Environmental Health Perspectives determined that caged mosquitoes can live for three to four months, but their median age in the field is about four to six days due to predators, disease and other hazards. Transmission models do exist for vectors and take into consideration the mosquito density per human, the average number of bites per day for each mosquito, the probability of a mosquito surviving through any one day and the pathogen incubation period in the insect, but the models do not consider the impact of the changing climate. 

There are not many organisms that live in the Arctic tundra, and those that do rely heavily on each other to maintain a balanced and stable food web. The changing climate is altering the Arctic ecosystems in ways that scientists are still struggling to predict. For over 4 billion years, the climate has changed; the temperature has risen and fallen slowly, allowing populations time to adapt. However, in the last 200 years the climate has changed at an accelerated rate, causing many organisms to become endangered or alter their way of life to survive.