A Mangrove Misunderstanding: Silent Guardians of the Coast

June 6, 2022

By Leif Johnson

I pull, the mud pulls back. For a brief moment we seem to reach an impasse with neither side willing to budge, but like an older brother, poised and ready to release when you’re at your most vulnerable, the mud swiftly releases its grip on my boot sending me headlong into a tangle of mangrove roots.

Having grown up with an older brother whose main goal in life was to harass me, I feel like I should’ve seen that one coming and as I stagger to my feet the trees seem to sway with laughter just as he would have.

Read just about anything on mangrove forests and you’ll quickly learn how incredibly important these ecosystems are to all forms of life around them. However, it’s precisely the way they deliver this litany of benefits that can make them such a nightmare to walk through. These forests are the ultimate test to your depth of field, troubling even the most nimble of us, and oftentimes, while I myself stumble about; I entertain visions of James Bond attempting a “high speed” chase through here.

Raccoon in mangroves

The roots and branches of these red mangroves spread out at awkward angles, arcing through the air and bracing the trees like stilts and buttresses in the muddy ground. Sometimes referred to as “walking trees” these modified branches weave a dense mat that helps to stabilize the soil, aerate, and prop the trees up. Hence the name “prop roots”.

Using these roots to prop me up after my rough start to the day, I make my way over to our work site. Placing your foot down here is like placing a puzzle piece; you rotate it every which way before putting it down, searching for the best fit. When finally I arrive at the site, the trees still sway in the wind, sunlight splintering through their canopies in disco ball fashion. The shimmering lacework of spider webs glint and wave on a breeze that carries the sound of distant Naples traffic.

Bits of trash lie scattered about: grocery bags, water bottles, and sand castle implements, all wafted in on the tides.

The patch of forest we’re standing in is known as the Clam Bay Natural Resource Protection Area, and it’s one of the few remaining stretches of a chain of mangrove bays that used to skirt this entire coastline. Over the years, as people flocked to the shores of Southwest Florida, many of the bays were developed on, their waters drained and mangroves ripped out. Though some forests may have been lucky enough to escape this fate, all of them have been altered and Clam Bay is no exception with its boundaries now boxed in by condos and hotels.

The remaining habitat that exists here consists of three bays: Upper, Inner and Outer Clam Bay. All are connected to Clam pass by sinuous lines of wandering creeks. Like lungs to a throat, the bays breathe in and out each day, slowly filling and emptying to the rhythm of the tides, life here hinging on a faraway moon.

The Conservancy of Southwest Florida has been monitoring this system since 1999 making it one of the longest-running mangrove studies in the state. Over the decades, with multiple monitoring plots scattered throughout, we’ve worked to gain an understanding of how the forest is faring.

Our work is much like your annual physical at the doctor’s; only our patients are trees. Having worked to assess the health of these plots for nearly two decades the trees are now old acquaintances and each year we return to check in on them. We measure how tall they are, how wide they are and check to see if there are any abnormal growths or discolorations occurring. Every tree and propagule (baby mangrove) over 32 centimeters tall is tagged and measured within 6 meters of a center pole.

With the sun rising ever higher overhead, we go about our work, yelling measurements, ID numbers, and distances back and forth. The occasional kayaker floats by, peering through the trees in bewilderment while the tide creeps in like growing grass, unnoticed until you’re ankle deep in water.

City sounds pierce the silence, filling the spaces between branches with the shrieks of sirens and drone of traffic. It’s now an impossible task to escape these invasive reminders, but, here and there, a brief lull can set in and for the slightest moment in time a primal silence seems to peel away the decades. For a second the rush of traffic is washed over by the sound of nearby waves, the rustle of the wind and songs of birds retain their rightful place among the leaves and in that instant, everything seems right.

It’s those times I enjoy most, enveloped in a world that, aside from the trash, remains indistinguishable from hundreds of years ago. That these moments still exist brings me peace and empowers me to work harder to protect them and by the time the last number is called and our patients are all accounted for, the sun is fast closing in on the western horizon.

In the fading light, we pack up our gear and head out, high stepping and ducking our way out of the dense latticework of roots and branches. As we stumble through the mud I almost get the sense that we’re not supposed to be here, as if these forests are too delicate for the cumbersome gait of humans, but these are resilient places and I can’t help admiring the hardiness of the plants that call them home. They fill a tough niche, or role, in the environment, bridging the gap between terrestrial and marine habitats.

The bravest of the land plants, adrenaline junkies of a sort, these trees dare to venture out into the seas, pushing the limits for all plant kind.

If you’ve spent any time around mangroves you know they have a distinct smell. It’s true, and out here my brain never quite knows what to make of that smell. It’s clean, but dirty, all at the same time; like a T-shirt that got the “quick wash” cycle when it needed the “heavily soiled” one. This pungent odor is the smell of hydrogen sulfide, often referred to as the “rotten eggs gas” and can become more intense during the spring and summer months. Hydrogen sulfide is produced in these forests by anaerobic bacteria as they break down organic matter (detritus) in the soil. Mangroves produce massive amounts of detritus — up to one kilogram per square meter every year — which, as it breaks down uses up a lot of the oxygen in the water, hence the anaerobic (without oxygen) bacteria. The breaking down of detritus releases nutrients back to the forests and out to the open ocean on the backs of the tides, making this ecosystem a crucial source of naturally occurring nutrients to the coast.

Unfortunately, though this smell is the product of an incredibly important ecological function, it is often thought of as offensive to humans, which has been a prime factor in shaping how people initially viewed and in some cases still view mangroves today. Couple this odor with an abundance of bugs, mud, navigation hazards, and the fact that they occupy prime coastal real estate and you have what some might call, an enemy of the state, or just a worthless swamp. All of this has inevitably led to mangroves being undervalued and consequently destroyed, “approximately 50% of the world’s mangrove forests have disappeared over the past 50 years.”

“Previous research by Valiela indicated mangroves are being destroyed more than twice as quickly as the well-publicized destruction of tropical rain forests.”

Luckily though, many people didn’t agree with this view of mangroves, and in recent decades, scientists have dared to look deeper into their function and role. Through their research we now know them to be a vitally important piece to life on the coast.

“To keep every cog and wheel is the first precaution of intelligent tinkering.” — Aldo Leopold

Not only do these forests provide massive amounts of nutrients to the ocean and stabilize soil with their roots, they also build soil by trapping it, creating new land. They act as crucial nursery habitat for nearly all of our sport and commercial fish in Southwest Florida. They break down wave height by 13–66% over 100 meters and reduce storm surge by 5–50 centimeters over a kilometer, combat erosion, promote biodiversity, sequester more CO2 per hectare than the rainforest, and help improve water quality by filtering and trapping sediments. All of which culminates in “at least US$ 1.6 billion each year in ecosystem services.”

These forests are the ultimate multitaskers and if any of us worked as hard as they did we would have a cloud of bugs following us and smell pretty bad too.

Motoring home at the end of the day, weaving through shallow waters, the mangroves loom stoically overhead, casting long shadows as they stand guard over the bay and all those who call it home.

These trees can’t speak. They can’t vote and hence they can’t defend themselves in our man-made world. They’re like magicians who can’t reveal their secrets, leaving it up to us to decipher them, to look deeper and connect the dots, to create a culture that appreciates and values these incredible places before it is too late.

Try to out muscle nature and we risk falling on our face, just as I did, but work with it and we can build a better world than we ever thought possible.

So breathe in that “rotten egg” smell and know that you wouldn’t be visiting this place if it weren’t for the forests that produce it. Call it a love/ hate relationship if you wish, but just know that in this part of the world, all lines lead through the mangroves. Florida would certainly not be what it is today without the bugs, heat, and swamps that are so often labeled as a minus on the pro con chart of the region. From the beaches, fishing, diving, abundance of wildlife and the health of an entire coastline, mangroves are the guardians of what Florida and the tropics represent in the minds of people all around the world and like them, we need to give a bit more than we take, both for our own sake and all those who will come after us.