Human Eradication of Mosquitoes, San Francisco, and the Destruction of the Indian River Lagoon

Mosquitos were a great nuisance to early pioneers and were often swarming by the thousands. (Public internet photo, 2014)
Mosquitos were a great nuisance to early Florida pioneers, often swarming by the thousands. Mosquito impoundments  created to control their breeding have destroyed over 40,000 acres of important salt marsh habitat along the IRL. (Public internet photo, 2014.)

So there Ed and I were, in San Francisco, for my 50th birthday, and although we had a fantastic trip, everything I looked at that had to do with water, I saw through my “Indian River Lagoon” muck colored sunglasses…

Map showing former tidal marsh area of San Francisco Bay; restored marsh; and beach with water quality warning., (Photos Thurlow-Lippisch, 2014.)

Photos: Water quality sign San Francisco Bay; restored tidal marsh at Chrissy Field; map showing former natural tidal marsh area of San Francisco Bay compared to today.”  (Photos Thurlow-Lippisch, 2014.)



On our first day, we decided to rent bicycles and ride over the Golden Gate Bridge as my sister Jenny and her husband Mike had recently done the same. It was great fun, and once I got my legs moving, we first explored a nearby area that is being restored and redeveloped around Chrissy Air Field.

There were educational signs discussing the importance of salt marsh habitat and a map showing how much marsh had been lost in the development of the San Francisco Bay area. The main focus was on the “restored” marsh in front of us that had been a dump for the military and filled in with sediment  from the bottom of the bay.

From the 1800s through around 1960 marshes were considered “unhealthy.”  But in time it was realized that marshes contributed greatly to environmental health and were critical for good water quality, wildlife habitat, and linked to clean drinking water.

Reading the signs I said to Ed: “Wow! Look Ed,  see that NOTICE sign for the bay’s water quality and bacteria levels.? Just like home!” Ed smirked, more interested in the old airfield that still took up a good portion of Chrissy Marsh.

So we rode our bikes over the Golden Gate Bridge and as I was struggling to breathe and not collide with on coming bicyclists, I thought about salt marshes in my own home town, and how they were destroyed not by a dump, filled in to become an air field, but mostly by mosquito impoundments.

Ed and my bicycle ride over the Golden Gate Bridge, 2014.

Ed and my bicycle ride over the Golden Gate Bridge, 2014.

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Before and after the turn of the 19th century, Florida was full of mosquitos and even in the 1960s when I was living in Stuart, they were ferocious. I remember being at the bus stop in in middle school and running in place the entire time so they couldn’t bite my legs. There were positives as well, like the social event of riding my bike with my friends behind the mosquito truck with its billowing cloud of pesticide spray that came to visit every few evenings during the summer. 🙂

Today it is well accepted in scientific circles that the most extensive impacts of Florida’s salt marshes have been associated with mosquito control programs which continue to be in great demand  in Florida today. Some of the highest densities of  mosquitoes ever recorded in the continental US occurred right here in south Florida before mosquito control.

To alleviate this issue and encourage development in Florida, salt marsh impoundments were constructed as a government management technique to decrease mosquito populations by continually flooding impounded areas of marsh. Around 1930, thousands acres of wetland marshes along the Indian River Lagoon were flooded to keep misquotes from hatching as salt marsh mosquitoes lay their eggs just above the edge of the water level in these areas. By flooding the impounded marshes, mosquito managers could flood the impoundments and drown the eggs.

Smithsonian/IRL: (

Today there are 192 impoundments along Florida’s east coast. A large percentage of these impoundments are in IRL as the IRL takes up 40 % of Florida’s east coast.  These impoundments  are separated from the lagoon by dikes built  around a designated area so it can be filled with water via a pump systems. Over 40,000 acres…


Filling these areas with water has had a  huge ramifications on wildlife in the lagoon as the dikes cut off juvenile fish and other critters from their needed protective mangrove/seagrass areas and habitat. Over time, this habit disconnect and loss has led to the extinction the dusky seaside sparrow in the 1987 and much lower and less healthy fish populations.

Also, in some cases the impoundments did not work, or were not well managed, and became breeding grounds for mosquitoes. Drowned native vegetation suffered, especially noticeable is the loss of the giant black mangroves, whose breathing, tubular root systems were drowned killing these ancient trees and leaving them as sentinels of death within the system.

Things have gotten better. As the destruction of salt marshlands and the negative effects on the IRL became more apparent, in the 1980s and 90s some mosquito managers started altering their practices by managing chosen sites with the RIM or “Rotational Impoundment Management Plan.” The RIM program is a seasonal rather than yearly control method, promotes flushing of impounded areas, uses fewer pesticides, focuses on water quality improvements and the promotes restoration of native vegetation.

These improved management strategies have helped lessen the isolation of fish species from their habitat; have allotted benefits to animals,  trees, and vegetation; and improved water quality for tiny and important marsh critters, the base of the food chain.  Nonetheless, the “tidal  exchanges” of the impoundments are limited and not what nature intended.

While fighting for the IRL, we must remember to fight on all fronts and continued improvements of mosquito impoundments should not  be forgotten!

So in conclusion, I loved visiting California. There were too many people but great beautiful, protected National Parks.

I am really enjoying  being home, especially in my own bed. And right away,  on the first night back, I had a wildlife visitor welcoming me home, the familiar sound in the darkness of a mosquito buzzing around my ear!


IFAS/UF/ Mosquito Management/RIM: (

Florida Gulf Coast University/Florida Coastal Salt Marshes: (

4 thoughts on “Human Eradication of Mosquitoes, San Francisco, and the Destruction of the Indian River Lagoon

  1. I didn’t know about the mosquito impoundments! I clearly recall running behind the pesticide truck though. It’s crazy when policy follows superstition like the marshes being “unhealthy”. Great article Jacqui.

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