Mangroves: Not Your Average Tree

A healthy mangrove lagoon at Magens Bay, a protected nature preserve. (S. Pennington photo)
A healthy mangrove lagoon at Magens Bay, a protected nature preserve. (Source photo by Shaun Pennington)

This is the first in a series of stories on efforts to save and spread the territory’s mangrove trees.

When local scientists talk about the mangrove trees that once rimmed the territory’s shorelines, their passion is like that of a parent talking about a child.

There is a reason for that. Mangroves have served as nurseries for crucial marine life since the beginning of time. Sadly, huge swaths of the deep-rooted trees, which also prevent beach erosion, filter run off and non-point source pollution, have been lost to development.

Since mangroves provide a natural border between that land and sea, they occupy prime real estate and have fallen prey over the years to clear cutting for shore side development, both personal and commercial.

“They want to chop them down,” Howard Forbes Jr., marine science coordinator for the Virgin Islands Marine Advisory Service, told the Source recently. “But mangroves are not your average tree,” Forbes added.

Because of that the Virgin Islands Code specifically prohibits the cutting, pruning, removal and disturbance of mangroves, and requires that there be no net loss of wetland. Forbes said, often when permits are obtained to prune, cut or remove the trees, the terms include replacing the trees elsewhere. He feels replacing them one for one is not enough. “For every one, they should put back 10,” he said.

Mangled mangroves on St. Thomas's north side. (S. Pennington photo)
Mangled mangroves on St. Thomas’ north side. (Source photo by Shaun Pennington)

That does not seem unreasonable given what the loss of these natural sentinels has cost the environment and the community. The loss of the filter provided by mangroves allows pollution and sediment to smother and kill coral reefs and rob the hundreds, if not thousands of species that rely on them of their habitat. Livelihoods of fishermen are lost and tourism takes a hit from the deaths of the corals that have fed the territory in one way or another for decades or longer.

Wetlands specialist Kristin Grimes, assistant research professor at the University of the Virgin Islands, had even more to say on the possible futility of this kind of mitigation and true restoration. She is the person who knows about the difference, as she has been involved in several mangrove restoration projects scattered across the islands. First off, she was clear about the difference between mitigation and restoration. Each permit to cut or clear mangroves issued by the Department of Planning and Natural Resources carries specific directives, including replacing them she said. But DPNR has no centralized database for where the new seedlings or saplings have been planted.

Further, restoration involves years of follow-up to measure the effectiveness of the replanting. Most permits require three years of monitoring at most.
The reason this is important is that scientists still do not know if the newer growth has the same efficacy – most particularly in capturing and trapping carbon dioxide from the atmosphere – as the older trees that were lost in hurricanes in years past.

“Mangroves take CO2 and sequester it in their roots, locking it in below ground for thousands of years,” Grimes said.

According to, though mangroves make up less than two percent of marine environments, they account for 10 percent to 15 percent of carbon burial. The entry on Smithsonian says, “One study lists global mangrove carbon storage at 75 billion pounds of carbon per year.”

With panic about climate change starting to mount, the mangroves super carbon sucking power may be a factor in the sudden interest in the trees that Grimes is seeing.

“One of the things we’re learning,” she said in an interview, “is that the value of the mangroves and their importance to other systems can be magnificent.”

Even in small patches, she said.

Hurricane damaged mangroves struggle to survive in Hull Bay. (S. Pennington photo)
Hurricane-damaged mangroves struggle to survive in Hull Bay. (Source photo by Shaun Pennington)

Reducing storm surge, providing habitats for all kinds of fish and birds, along with the CO2 absorption are only a few of the connections the trees make with their neighbors on the earth.

And development is not their only enemy.

Hurricanes and other natural phenomenon also contribute to the demise of these fragile, critical environments.

The back-to-back Category 5 hurricanes of 2017 left thousands of pounds of debris entangled in the wetlands ecosystem. The large roots of the mangrove tree extend far out of the ground like skinny, alien legs and seem perfectly designed to catch flying or floating flotsam and jetsam.

Over the last two years in April, groups of volunteers have been enlisted to make their way into these mysterious, crooked forests to pull out mostly human made garbage that was blown into their midst.

The University of the Virgin Islands Center for Marine and Environmental Studies has received a $100,000 grant from the National Oceanic and Atmospheric Administration to continue cleaning up from hurricanes Irma and Maria. The work is expected to take place next spring and to develop a new marine debris action plan.

Part II – What was found in the last Great Mangrove Cleanups and what it means.

Print Friendly, PDF & Email