Association of State Wetland Managers - Protecting the Nation's Wetlands.

The Wetland Wanderer: She Who Dances with Mosquitoes: A Restless Night Spent Exploring the Relationship between Wetlands and Mosquitoes

by Brenda Zollitsch

There are many reasons I might not sleep well on any given night, but the most annoying is surely a visit from a single, bloodthirsty, whining mosquito.  Such was my lot two weeks ago when I was staying at a coastal hotel in Boothbay, Maine and shared my room with one…single…mosquito.  Not only was its insidious whine like nails on a chalkboard, it also occasionally lit on my face in the dark silence and I could feel it walking across my skin.  As the night went on, I could imagine it chortling at my plight through its tiny, vile proboscis.  We joke in Maine that the mosquito is our state “bird.”  Surely if you are visiting our state this summer you too have had the joy of “dancing with mosquitoes”.

As I lay in the dark, trying not to wake my children but occasionally mosq1slapping myself in the face in a futile attempt to rid myself of my night visitor, I thought about the relationship between the mosquito and wetlands.  Can you tell what I do for a living?  As I awaited my next opportunity to vanquish my foe, I did some research on my iPhone.  Despite my circumstances, I found out a variety of interesting and remarkably useful facts and/or findings about mosquitoes and their relationship with wetlands:

  • There are an estimated 70 quadrillion mosquitoes in the world on any given day.
  • There are more than 3,500 species of mosquitoes worldwide.  Approximately 40 species live in the State of Maine. A few of them rarely or never bite humans.
  • Some species of mosquitoes lay their eggs in pools of stagnant water.  Especially-attractive locations include old tires, puddles, pots and cans left lying around, as well as birdbaths and swimming pools —places where water lies still and provides no ecosystem checks and balances.
  • Mosquitoes spend their first 10 days in water, as water is necessary for mosquito eggs to hatch into “wigglers” (larval stage mosquitoes).  Wigglers feed on organic matter in stagnant water before they turn into pupae, their last phase before changing into adult mosquitoes.
  • Mosquitoes have lots and lots of predators throughout their life cycle — birds, bats, fish, and other invertebrates, especially dragonflies.
  • Mosquitoes can be vectors for some very scary diseases, such as malaria, West Nile Virus and Eastern Equine Encephalitis.  Mosquitoes kill approximately 725,000 people every year according to the World Health Organization (nearly twice as many as our next deadliest foe: ourselves).
  • However, not all species of mosquitoes carry these diseases .  In many cases, mosquitoes that commonly carry West Nile Virus are not those that live in and around wetlands, but rather ones that both breed in stagnant water that has collected in a variety of containers and frequently feed on birds and a variety of mammals, which facilitates the transmission of these arboviruses to humans[1].
  • Other problematic breeding areas can include Combined Sewer Overflows and failed bioretention systems can actually increase mosquito populations and should be addressed to reduce the presence of mosquitoes and potential associated disease risk.
  • The presence of a healthy wetland generally does not increase the risk of people getting those diseases.  While mosquitoes do generally breed in small pools or large bodies of shallow, stagnant water, a healthy wetland is more likely to reduce the mosquito population than increase it.
  • Filled or partially filled wetlands can be a big threat as well.  Unfortunately, sometimes wetlands are filled as an effort to reduce mosquito populations.  Studies have found that this can actually have the unintended consequence of increasing mosquito populations.
  • A healthy wetland can actually reduce the mosquito population.

mosq3It’s the last bullet that spurred me to write this blog.  Over time, people have blamed wetlands for the spread of mosquitoes.  Mosquitoes have been part of the public relations challenge for wetlands throughout human history.  Wetlands have long been thought of as mosquito-breeding nuisances[2] and drained to protect nearby populations from disease.

However, when a natural wetland is drained, it may still be able to trap enough water after a heavy rain to breed mosquitoes..   Although adult mosquitoes have a very short life cycle (from four days to a month), the eggs they lay can remain dormant for more than a year, hatching when flooded with water. Because of this, a drained or degraded wetland area may actually produce more mosquitoes than it did when it was a healthy, functioning wetland.” 

Flying in the face of popular perception, healthy natural or restored wetlands can actually reduce mosquito density because of the wetland’s associated large number of mosquito eating predators . In the words of wetland restoration expert Tom Biebighauser of the Wetland Restoration and Training Center, when there is a healthy wetland, “the mosquitoes check in, but they don’t check out.”

Considering that we have never existed as a species WITHOUT mosquitoes[3], one would think we would have figured this out by now.  Unfortunately, we have made many a misstep in the management of BOTH mosquitoes and wetlands, and the two together over time — whether filling wetlands, applying damaging pest management techniques or working to eradicate the insect altogether.

In closing, here are some of the key ways we can work to address mosquito issues, while still supporting healthy wetlands:

  • Stop the filling and degradation of wetlands.  A healthy wetland can do much more to reduce mosquito populations than one that has been altered and no longer supports a healthy ecosystem.
  • Support additional research into the role of wetland restoration and other land management techniques in controlling mosquitoes.
  • Support balanced consideration of wetlands ecosystem health and mosquito control when considering management options.  Broad-scale chemical control harms wildlife and does not provide long-term solutions.  Modern mosquito control agents can cause significant negative impacts to non-target species.
  • Use GIS to identify and target treatment of hot spots where mosquito production is a real problem
  • mosq5Generate site-specific knowledge  of wetland areas and conduct monitoring and assessment to determine whether mosquito populations are a problem and target specific spot control, leaving the majority of the habitat untreated.
  • Develop conservation plans that include the conservation and protection of the natural predators of mosquitoes.
  • At your home or business:
    • Get rid of unused tires and other water-trapping containers that are stored outdoors and throw out (or at least turn over) containers that can trap water and serve as mosquito breeding areas.
    • Remove leaves and sticks that might trap water in your roof gutters.
    • Cover trash and drill holes in recycling containers to allow water to drain away.
    • Store boats and kayaks upside down.
    • Change the water in plastic wading pools and bird baths weekly.

Once my mosquito had whined off into the dawn full of its hard-fought meal, I sat there with the sunrise, watching one of my favorite shows, Sherlock on PBS.  Like Sherlock and Moriarty, humans and mosquitoes have had a complicated history full of intriguing twists and turns.  We are a long way from solving the case, but in the meantime research and practice provide a well-documented trail of clues that can demystify the myth that mosquito control requires the destruction of wetlands.

For more information:

  • To learn more about ecologically sound management of mosquitoes in wetlands, go here.
  • To learn about mosquitoes in Maine, wing your way to Maine’s Mosquito webpage.
  • To understand the relationship between healthy wetlands and mosquito populations, go here.
  • For more interesting facts about mosquitoes, go here.

[1] In Maine, this group includes three of the more common WNV vectors, Aedes japonicus, Culex pipiens and C. restuans as well as other possible vectors – C. salinarus and Aedes triseriatus.

[2] Gardner (2011). Lawyers, swamps and money: U.S. Wetland Law, Policy and Politics.  Island Press.

[3] Mosquitoes have been around since the Jurassic Period, making them about 210 million years old.

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