HomeMy WebLinkAboutSubmittal-Elvis Cruz-Mangrove facts sheetSubmitted inter the pubiic
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Mangrove Facts for Miami City Commission City clerk
Item RE-4 Thursday, April 27, 2023
By: Elvis Cruz 631 NE 57 Street Miami, Florida 33137 (305) 754-1420 ElvisCruz@mac.com
Several falsehoods are being promoted by mangrove enthusiasts with little regard for the
negative impact to the public's enjoyment of the public waterfront in public parks. The worst
example is the falsehood that a row of mangroves along a shoreline can stop hurricane storm
surge. Mangroves cannot defy the laws of physics; they cannot hold back a wall of water being
pushed by 100-plus mile an hour hurricane force winds. Here is the truth:
Storm surge: An April 13, 2022 Miami Herald article quoted three scientists on the
ineffectiveness a narrow shoreline planting of mangroves for decreasing storm surge.
https://www.miamiherald.com/news/local/environment/article259496044.html
1. Peter Sheng, a University of Florida researcher who's studied the protective value of
mangroves in Florida, said they're an incredible tool when used correctly. In places like Cutler
Bay, huge swaths of mangroves provide a barrier between the 10-foot-plus waves from
hurricanes and populated areas. "If you have a narrow urban mangrove planter, it doesn't cut
it," he said. "Three meters of mangrove does nothing. It's a token for the look. If you want to
dissipate waves, you need at least 100 meters."
2. Rik Gijsman, a coastal engineer and researcher at the University of Twente in the
Netherlands... Gijsman said studies consistently show that to cut huge waves down to size takes
a lot of mangroves, an Everglades -sized amount of mangroves.
"Mangroves will never provide full safety for real storm surges," he said. "To really attenuate
the waves you need kilometers of them."
3. Yuepeng Li, a Florida International University researcher who's published multiple papers
attempting to quantify exactly how much protection mangroves offer...
...it takes about half a mile worth of mangroves to lop off even one foot of storm surge.
"Even one mile of mangroves, I don't think it will significantly decrease the surge," Li said.
Pictures from the State of Florida clearly show shoreline mangroves get destroyed by
hurricanes. See slide number 10: https://nmsfloridakeys.blob.core.windows.net/floridakevs-
prod/media/dots/20181016-fwcm angrove. pdf
The often quoted Nature Conservancy study on mangrove flood risk reduction benefits:
https://www.nature.org/content/dam/tnc/nature/en/documents/Mangrove Report digital FI
NAL.pdf On page 7: In hurricanes Charley and Wilma, mangroves reduced flood height only
4.2 to 9.4 centimeters per kilometer of mangrove forest width. That's an insignificant
reduction. On page 11: In Miami Dade there were only $1,400 in benefits per hectare of
mangroves. A hectare is 107,639 square feet, so that's $566 per acre. But what is the dollar
value of the public waterfront we would give up?
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Fish nursery: The larger the area mangroves cover over water, the more fish can be produced.
But living shoreline plans in Miami parks have shown the mangroves on land, so they can't
function as fish habitat. it is unlikely that DERM would give permission to plant mangroves in
the water, especially if it's too deep.
Rip rap (limestone boulders) placed in front of a seawall diminishes wave action and
creates a living shoreline, with many nooks and crannies. Also, concrete moldings can be
applied to seawalls to incubate oysters and other marine life. We need not block our parks'
waterfront to help the environment.
Oysters: Oysters are a viable solution, real science. Oysters clean the water. If you want to
filter water, you have to put the water filters in the water, not on the shoreline.
Fish kill misconception: Miami's fish kill of August 2020 was reported to have been caused by
five factors: 1. high water temperature, 2. leaking sewer mains under the bay, 3. fertilizer, 4.
septic tanks, 5. storm sewers. The main source ofpollution was from the Little River.
Note that nothing planted on the shoreline would change any of those factors.
The fish kill proved we already have a large fish population. 27,640 counted, 56 species.
Alternative locations for planting mangroves: 2.88 miles of shoreline along the Julia Tuttle
causeway, 1 mile along the 79 Street causeway, and several islands in the bay.
Carbon sequestration: The amount of carbon that would be sequestered by mangroves along
the shoreline in a City park is extremely insignificant, less than one car's production.
One acre of mangrove forest can store about 1,450 pounds of carbon per year.
(https://oceans j4edu/ocean-life/plats-algae/mangroves) •
Doing the math: Since there are 5.5 pounds of carbon in a gallon of gasoline, 1,450
pounds of carbon = 2.63 gallons of gasoline sequestered per acre per year. By comparison, the
average car uses 330 gallons of gasoline per year. (10,000 miles per year at 30 mpg. Many cars
are driven more miles and get less mileage.)
But the US burns 360 million gallons of gasoline per day. That's aside from jet fuel,
diesel, coal, natural gas and propane.
Morningside Park already has 2.5 acres of mangroves inside the park. There are more linear
feet of living shoreline inside the park, with the canal, the tidal basin, the island and drainage
ditch, than the bayfront shoreline of the park.
In Summary: Mangroves provide benefits when they cover a large area, but not when planted
as a narrow shoreline strip. Mangrove enthusiasts place little value on protecting the public's
enjoyment, access and views of the waterfront. Proposed living shorelines in Miami parks are
ornamental environmentalism, providing little benefit but a large detriment to the public's
enjoyment. Better alternatives exist, like seawalls with rip -rap and oyster reefs.
If anyone has any doubt about anything I've said or written, please challenge me. 1 would be
happy to meet and go over the scientific facts and impacts / benefits to the public.
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