Saturday, December 5, 2020

Great news on the mangrove front

Expert opinion is this area can come back to life. Photo by Molly Kate Walsh

Expert opinion is this area can come back to life. Photo by Molly Kate Walsh

By Bob Olson

If you drive out State Road 92 near Stevens Landing you can see the fringe of a swath of destruction where 64 acres of mangroves have already drowned. More than 200 other acres are terminally ill.  From the air (see photograph) you can see the wide range of that destruction. The good news is that there are concerned citizens determined to save those mangroves, and permit applications have been filed. The group is aiming to have the permits by September 1st. The Stevens Landing die off will be the first area addressed. Experts predict that this dead space can become green in six months.

The problem of dying mangroves has been neglected for decades, and worsening each year. Our mangroves are the life blood of the ecosystem that surrounds Marco Island. Debbie Devore of the U.S. Fish and Wildlife Service (USFWS) has provided $50,000 from the USFWS Coastal Program to do a detailed study.  A plan developed under the auspices of Rookery Bay and overseen by Coastal Resources Group was performed by J.R. Evans Engineering. The result was a detailed topographical analysis and plan showing where natural flow exists. The plan was submitted

An aerial view of the mangrove die off Vintage Bay is seen along the top right. Photo by Craig Woodward

An aerial view of the mangrove die off Vintage Bay is seen along the top right. Photo by Craig Woodward

with the permit applications.

State Road 92 was built in the 1930’s with only a few culverts to move water under the road bed. The small diameter of those few culverts did not allow enough flowing water to support the natural mangrove fish hatcheries and tidal flow. Although the culverts are more than seventy years old, the engineering firm points out that they only have a fifty year life span.

Mangroves survive with the twice a day tidal flow being able to provide water and then allowing them to dry out. Mangroves can only be submerged in water 30% of the time, and then need to dry out the remaining time with the tidal flow. Hurricane Andrew hit in the early 1990’s and the mangroves drowned. Silt was produced, and toxic sulfur compounds built up killing the good plant life.

The federal government has authorized preliminary approval for a 75/25 grant from the Federal Government for approximately $600,000 to solve the problem long-term. It will need to raise locally approximately $160,000 to meet the 25% required matching funds and permitting costs.

The Fruit Farm Creek restoration project, as it is called, would install three new 48” culverts under

This photo shows little life in the area. Photo by Molly Kate Walsh

This photo shows little life in the area. Photo by Molly Kate Walsh

State Road 92 and open up the natural waterways along the south side of the road so that water and fish can migrate back and forth naturally with the tides. The technical term is called natural hydrologic restoration. If nothing is done, over 400 additional acres of mangroves would die in the next five years or so.

Expert opinion is that, within six months of the new culverts and drainage ditches being installed, the area would turn green again and the natural mangrove fish hatcheries would start to come back to life. The next job will be to keep the culverts and drainage ditches open so the tide can always flow.

The city council listened to a 20 minute presentation on the subject at its February 22nd meeting. The city website contains that presentation. www.cityofmarcois
land.com. Collier County Commissioner Donna Fila supports restoration efforts and has discussed similar restoration projects with extending out to State Road 41. We have a detailed slide presentation and aerial poster photographs. We would love to show them to you in your home or to meet with your club/ group. Please give us a call at 239-394-2000.

Working together this is a problem we can solve!

 

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