By Judy Minot • Secretary; Co-Chair, Communications Committee
Most of us focus on large-scale effects of climate change: sea level rise, storms, droughts, floods, and fire. We don’t often consider how rising temperatures might affect populations of insects, ticks, and spiders, and how these may affect us. The mosquito is a case in point. It is an insect to be taken very seriously as temperatures warm.
Controlling the “World’s Deadliest Animal”
The Centers for Disease Control and Prevention labels the mosquito the “world’s deadliest animal.” For most NJ residents, mosquitoes are just an annoyance, but in the nation’s early history, mosquito-borne malaria and yellow fever outbreaks were common and deadly.
The salt marsh mosquito was once a burdensome pest in our state. Before 1912, most of the Jersey Shore and the Delaware Bay region were essentially uninhabitable because of the swarming, biting insects. Since the early 20th century, county mosquito control commissions have kept these populations in check, but sea level rise is making their work more difficult.
The control of the salt marsh mosquito is possible because these mosquitoes lay eggs only in specific places (in the mud above the water line), and only at specific times (determined by the moon and the tide). Mosquito specialists have amassed deep knowledge of the most “productive” breeding sites over many years. Crews visit these sites regularly to apply Bti, bacteria that are toxic to the larvae. They also dig ditches to reduce standing water in salt hay in the tidal creeks, where mosquitoes breed.
How Climate Change Complicates Mosquito Control
As sea level rises and breeding sites become wetter, mosquitoes move to higher, drier sites. According to Dina Fonseca, PhD, director of the Center for Vector Biology at Rutgers University, a rise in sea level of as little as ½ inch can make mosquitoes seek another place to lay eggs. Mosquito control teams must then locate these new sites, confirm the presence of larvae, and time the insecticide application, all of which takes time.
Another complication is warmer temperatures. The mosquito season that used to last from early June until the end of September now runs from May until mid-October, Fonseca said. Not only are budgets stretched over longer time periods, but also the season no longer fits the college vacation schedule, making hiring trickier.
Insects as Climate Change Indicators
Because they lay many eggs and mature quickly, insect populations can adapt and respond quickly to changes in temperature and humidity. More mosquitoes survive a warm winter, and they hatch earlier in a warmer spring, so changes in insect populations help indicate where and how much warming is taking place.
New Jersey’s 21 mosquito control programs are like “eyes” across the state. They keep tabs on how many and what species of mosquitoes are present at various places and times. According to Fonseca, southern mosquito species are moving northward into our state, including several that carry disease.
Non-native mosquitoes are also spreading due to warmer temperatures. The Asian tiger mosquito is an aggressively-biting, invasive species of mosquito first found in southern New Jersey in 1995. It is a potential carrier of encephalitis, dengue, yellow fever, and dog heartworm. These mosquitoes have made their way steadily north to higher elevations.
The Mosquito as Disease Vector
An insect may have to bite many times before transmitting a parasite from one host another. When insect numbers increase explosively, parasites like West Nile virus, Eastern equine encephalitis, and avian malaria are far more likely to be passed on.
So far, New Jersey has not seen major outbreaks of mosquito-borne diseases. It helps that we live in houses with screens and spend our time primarily indoors, in dry areas. But mosquito control teams are on the lookout, especially for mosquitoes like aedes aegypti, a species that is expanding its range north and carries Zika, dengue, yellow fever, and Chikungunya.
As we respond to the threat of climate change in our state, it’s important to keep as close an eye on these tiny invaders as on the biggest storms.
References
Deadliest animal: bit.ly/3ORyKSB
Tiger mosquito: bit.ly/3AKVU7e