Up until the early 1900s about three-quarters of Florida’s southern coast, from about Tampa Bay on the Gulf side around to The Indian River Lagoon on the Atlantic Ocean, was covered with, and protected by mangroves.
After coastal development took off in the 1900s hundreds of thousands of acres of mangroves were removed in urbanizing coastal regions. The Indian River Lagoon lost about 75% of its mangroves. About half were removed from Tampa Bay & Charlotte Harbor.
Development removed more than 70% in Naples Bay, as well as huge sections around Marco Island. Lee County’s mangroves fared a bit better, but about a quarter were removed.
Conservation efforts stepped in and saved places like Rookery Bay National Estuarine Research Reserve and the Ten Thousand Islands, and a state law called the Mangrove Trimming and Preservation Act took effect in 1996. It put restrictions on removing mangroves and how they’re trimmed.
Mangroves are so important for a wide variety of reasons, so we have a Mangroves 101 conversation to learn about them and the role they play in our coastal ecosystems, including providing storm protection and habitat for juvenile fish.
Guests:
Dr. Brian Bovard, Wetland Plant Ecologist in the Department of Ecology and Environmental Studies within the Water School at Florida Gulf Coast University and Associate Dean of Student and Faculty Affairs
Dr. Win Everham, Professor in the Department of Ecology & Environmental Studies at Florida Gulf Coast University and Program Coordinator, MA Environmental Studies
Click here to learn about the Living Lands Mosaic by Fort Myers artist, David Acevedo.
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Transcript created with Copilot. Please forgive any spelling errors or mistranslations.
Mike Kiniry
This is Gulf Coast Life. I'm Mike Kiniry. Thanks for joining us. Up until the early 1900s, about 3/4 of Florida's southern coast from Tampa Bay around to the Indian River Lagoon was covered with and protected by mangroves. Then coastal development took off in the early 1900s and hundreds of thousands of acres of mangroves were removed in urbanizing coastal regions. The Indian River Lagoon lost about 75% of its mangroves. About half were removed from Tampa Bay and Charlotte Harbor. Development removed more than 70% in Naples Bay, as well as a huge section around Marco Island. Lee County's mangroves fared a bit better, but about 1/4 of Lee County's mangroves were removed. Conservation efforts stepped in and saved places like Rookery Bay National Estuarine Research Reserve and the 10,000 Islands, and a state law called the Mangrove Trimming and Preservation Act took effect in 1996. It put restrictions on removing mangroves and how they're trimmed. Mangroves are important for many reasons, so today we're doing a Mangroves 101 show with Dr. Brian Bovard. He's a wetland plant ecologist in the Department of Ecology and Environmental Studies within the Water School at Florida Gulf Coast University. Thanks for being here, Dr. Bovard.
Dr. Brian Bovard
Thanks for having me.
Mike Kiniry
And Win Everham is a professor in the Department of Ecology and Environmental Studies at FGCU. Welcome back to
Dr. Win Everham
Thanks, Mike. It's always a pleasure.
Mike Kiniry
So I had an idea for doing this show several months ago, and I'd reached out to you, Win, because I always think of you in terms of mangroves. I hope you take that as a compliment. But when I think FGCU mangroves, I think Win Everham. And you said, but we got to get Brian Bovart on the show, too. So here we are. And as I researched this morning, I found a video from just a couple months ago featuring you that mentions Win about mangroves. So I guess I've got the two right people. And Sunday was National International Mangrove Day. Okay, so it's just one big, it's time to talk mangroves. So explain what a mangrove is, in simple terms, as if I was somebody who had no idea.
Dr. Brian Bovard
So mangroves are generally tree species, not always.
Mike Kiniry
Can be a shrub sometimes, right?
Dr. Brian Bovard
Sometimes they're ferns, sometimes there's actually a species of palm.
Mike Kiniry
Okay.
Dr. Brian Bovard
They cover about 15 different plant families and it's about 54 different species that are considered to be true mangrove species. And true mangrove species have special adaptations that allow them to survive along the coastline. So they have salt adaptations. Many of them can exclude salt at their roots, or they're able to take it up and then get it out of their system, usually through their leaves or through salt glands. They generally have some level of vivipary, which is just a nerdy term for being able to have live young.
Mike Kiniry
So their seeds- Those cool seed pods that they drop that look like torpedoes.
Dr. Brian Bovard
Yeah, so the red mangroves, they look like cigars or torpedoes. Those are germinated seeds on the tree. So our three species have varying levels of the ability to germinate on the mother tree.
Mike Kiniry
Is it uncommon for a plant to be able to live in saltwater and do what mangroves do in terms of dealing with it?
Dr. Brian Bovard
Absolutely. And I think that that's why there's only about 54 species worldwide. And we've got three of them here.
Dr. Win Everham
If you think, Mike, old stories, some of them are in the Bible about if you want to destroy somebody's civilization, you salt the earth. make it impossible for them to grow their crops. If they were growing mangroves, wouldn't hurt them at all.
Mike Kiniry
Describe A mangrove when, paint a picture of somebody's driving around Southwest Florida, because there's lots of places where if you're heading out toward the beach or if you're heading down, like, you know, they're the dark green, bushy trees along the coast, basically, right?
Dr. Win Everham
That's about, that's all I was going to say. As I was sitting, listening to Brian, I was so glad. You really have to think about Brian when you say mangroves, right? The idea that there's a palm mangrove, I didn't know that. I think along any dense vegetation that you see right along the coast or even along the canals that are fed that have tidal influence, you're probably looking at mangroves.
Mike Kiniry
Are there any other things that would be in those places that would be sort of false mangroves to a passerby?
Dr. Win Everham
If you get far enough inland, I think I've seen Brazilian pepper.
Mike Kiniry
I was going to say Brazilian peppers kind of remind me of them, I think. But they wouldn't be where the salt water or brackish water, do they have to have salt water or I guess they could be in the estuaries? So can it be brackishy?
Dr. Brian Bovard
I don't know what their level of salt tolerance is. I bet it's pretty low. I think it's pretty low though.
Mike Kiniry
Oh, I meant mangroves. Mangroves, I mean, how far up into fresh water do mangroves get?
Dr. Brian Bovard
Mangroves can live in fresh water. The problem that they run up against when they're in more fresh systems is they're being competed with upland or terrestrial species that are better adapted and can grow faster than them.
Mike Kiniry
So here we've got three kinds of mangroves. Let me try to get this and you tell me if I've got it right. Red mangroves are the closest to the water. Black mangroves are kind of the intermediate mangroves. And then the white mangroves are the ones furthest from the water. Is that pretty much how it works?
Dr. Brian Bovard
That's the general textbook zonation. Here in Florida, we find them kind of interspersed, but you tend to see them dominating in those regions that you describe.
Dr. Win Everham
I still usually see reds right along the edge. But as soon as you get back behind that fringe of red mangroves, the forests in my experience get really interestingly complicated. And sometimes I've thought it's a legacy of past hurricanes or legacy of past changes in hydrology or sea level. But away from that edge, in many of the systems we work in, we'll see a mixture of reds and whites and blacks in difficult to understand ways.
Mike Kiniry
We talk about how they protect the shore from hurricanes and energy from tropical storms. Do those 3 each serve sort of overlapping purposes when it comes to that, or are they all just together one big protective layer?
Dr. Brian Bovard
I think of them as occupying very different parts of the landscape oftentimes. So as Wen described, you oftentimes have the red mangroves. They're really well adapted for the edges. of islands or river types of systems. So they're sort of outlining the bay. They tend to be a little bit less salt tolerant than say the black mangroves or the white mangroves that can deal with higher salinities. The black mangroves tend to be behind them and oftentimes there's a berm along the edge of rivers and islands that The red mangroves kind of line that berm and then it's kind of a depression behind it that ends up being what we refer to as a basin that holds water for a longer period of time. And as that water evaporates, the salts get concentrated. Those areas tend to be dominated by blacks. And then as you move upslope, you tend to pick up more and more of the white mangroves, which I think tend to be a little less flood tolerant. They like it a little bit drier, but can deal with relatively high salinities as well.
Dr. Win Everham
Isn't that weird though, Mike, that you would think the mangroves that can handle the high salinity would be the ones that are right against the sea?
Mike Kiniry
Reading my mind.
Dr. Win Everham
Yeah, but what happens is that you get storm surges or high tides that deposit water farther inland. And if it doesn't drain, then as it evaporates, it gets hypersaline from the evaporation, the salt is left behind. So the ones that are a little bit higher and a little bit farther in are the ones that really have to handle these episodes of extreme salt inundation.
Mike Kiniry
Did I get it about right in terms of where they were historically from maybe Tampa Bay to the Indian River Lagoon?
Dr. Win Everham
Yeah.
Mike Kiniry
As temperatures are warming, are they able to make it further north? Because I think frost must be a limiting factor.
Dr. Brian Bovard
Yeah, they're migrating N. There are conservation lands along the northern Gulf Coast that they're treating them almost like a quote unquote invasive species because it's impacting their ability to manage their migratory bird species that are using those areas.
Mike Kiniry
Interesting.
Dr. Brian Bovard
So they used to have salt marshes and now those salt marshes are being converted into mangroves as the mangroves are marching northward. And they've extended as far north as Georgia on the East Coast. So they're no longer just in Florida.
Dr. Win Everham
I think you're right, Mike, that it was the frost that was holding them south. When I first got down here in the mid 90s, we had a couple of colder winters that we just don't seem to have anymore. And I remember seeing mangroves, it looked as if they were burned. right at the water's edge, they were still green because I think they got like a little thermal protection from the water that didn't freeze. But then the air up above that got too cold and it killed the leaves. Didn't necessarily kill the trees, I don't know, but knocked them back. With our shifts in climate, those kinds of extreme cold events are getting rarer. And I think the mangroves are able to move up the coast and get established.
Dr. Brian Bovard
Yeah, some folks from the Smithsonian Institute have actually done some historical sleuthing where they've dug into old news articles going back to early 1800s. And they're finding records of periods where The mangroves had extended further north, north of St. Augustine, and then freeze events have pushed them further south. So yeah, interesting dynamics.
Dr. Win Everham
I think mangroves are wonderful. I imagine we'll talk about some of the benefits they give. One of the sound bites that I've been trying to use in the media is that if you protect mangroves, they'll protect you. know, you asked a couple of minutes ago. Whenever I think about that storm surge protection, what pops in my mind are the red mangroves with those prop roots. It just seems like they're building a fence to be able to hold back some of the head of the water. And I think there's really good evidence of their ability to minimize tidal storm surge and high waves inland if you've got an intact forest system. So I think of the idea of them moving N is good because we all need more protection in a changing world. But I understand how it can be viewed. You know, there are functional ecosystems along our coast as you go north that don't have mangroves. So mangroves moving into them is, you said, like exotics, right, Brian? I can see how they would see them that way. The world is in such a state of flux right now, you know, that with what we're doing to the atmosphere and how it's changing long-term climate and short-term weather is moving things around in complicated ways. And so I'm I think I'm good with mangroves moving N. One of the roles of mangroves is as they grow, they pull carbon out of the atmosphere. So I had this crazy insight one day of I wonder if we could go back historically to the times when temperatures rose sea level. In that case, carbon dioxide went up because as you heated the ocean, you released carbon dioxide. What's happening now is we're putting carbon dioxide into the atmosphere, which is making the planet hotter, which is releasing more carbon dioxide. You know, there's a feedback loop there. If mangroves spread out, they're going to pull carbon dioxide out of the atmosphere. So I wondered if that isn't, you know, hadn't been historically a way that the earth re-established balance.
Mike Kiniry
This is Gulf Coast Life. I'm talking today with Dr. Wynn Everham. He's a professor in the Department of Ecology and Environmental Studies at Florida Gulf Coast University. And Dr. Brian Bovard, he's a wetland plant ecologist in the Department of Ecology and Environmental Studies within the Water School at FGCU. We're talking about mangroves on the show today, what they are, where they are, where they used to be, and the various reasons they're so important. It did occur to me while thinking about this for today's conversation that because mangroves are so to being in the exact place where tropical systems meet the shore. We then decided to try to put our most valuable property in the same place that mangroves are most comfortable, and now we're spending a lot of money trying to prevent those properties from damaging ourselves. It just seems like a strange irony, and I had never really thought about it before.
Dr. Win Everham
I'm not sure I can add to that. I think you stated that very succinctly. Our coastlines are beautiful. We want them to continue to be beautiful. They're being challenged by storms, by sea level rise. Mangroves can help stabilize those shorelines. Mangroves can help protect us from those extreme storm surge events. So a smarter way of thinking about how we fit into the landscape rather than reshape the landscape to only our desires is finding the right balance with protecting mangroves.
Mike Kiniry
Can you talk some, Brian, about, they are nurseries, if you will, for offshore fish. So people who want to be anglers really rely on mangroves too.
Dr. Brian Bovard
Sure. I want to come back to your comment there. You know, I feel as a species, we like being close to the water, right? And we enjoy that view. Maybe the mangroves enjoy it as well. We're learning all sorts of things about how plants are able to perceive their environment. Maybe the mangroves like that view as well. But yeah, the mangroves are really providing this with lots of resources, including the aesthetics of the coastline, right? They're protecting our beaches. They're protecting the waterfront, our homes. They're providing us with the fisheries that they support, like snook, redfish, snappers.
Mike Kiniry
Little baby fish go and hide in there basically, right?
Dr. Brian Bovard
Yeah, their young spend part of their lifetime in the roots of those mangrove systems, feeding on the organisms that are there.
Dr. Win Everham
Hiding from predators.
Dr. Brian Bovard
Hiding from predators, yeah. So they really are kind of the foundation of our economy here when you think about it. not just the housing industry that you pointed out, but the fisheries or beaches and tourism industry.
Dr. Win Everham
So that process of growing in a wetland system pulls nutrients out of the water, settles the water down. So they're doing a lot. They're doing the water treatment that all wetlands do. And then the stuff that comes off of our land is cleaner if it goes through the mangroves. And as we've, I think I've said this to you before, Brian, as we've in our heads when we give these talks, got this list of things that mangroves do for us. I ran into Robert Gore, who is a faculty member at now FSW, wrote a book, Gulf of Mexico. I forget what year it was. And in his list, he included, Brian said aesthetics before. And he's right, I just never included it on my list. I would much rather look at a coastline that has mangroves than has riprap or seawall. It makes our coastlines more beautiful.
Mike Kiniry
That video on YouTube, you went into the impact of Ian on your, you have guys, you have like a test area or what do you call it?
Dr. Brian Bovard
Yeah, we have a long-term mangrove monitoring plot out in the Sarah Bay.
Mike Kiniry
Characterize, you know, Ian came, left a lot of stuff in the mangroves and including apparently sediment, which is causing some problems?
Dr. Brian Bovard
Right, yeah. So Hurricane Ian basically with the storm surge picked up a lot of sediment out of the bay and just dumped it onto portions of the mangrove forest that we're working in. And in some areas there was up to like 10 centimeters or so of sediment on the forest floor. that creates a problem for the mangroves because you and I, they need oxygen, right? And if you're suffocating them, that creates a problem. They've got to breathe too. And what we witnessed was over, I'd say, a period of maybe three to four months, the trees began to flush new leaves out and then they started dying. And our students would come back to the lab and be like, there's something going on with the trees in the middle of the plot. They're not looking too good. Yeah, and so what we witnessed over the span of a year was really a lot of death out there that was, it took them a while to succumb, but eventually that sediment really did take its toll on them because they couldn't get oxygen to the roots. If you kill the roots, you don't have a way to take up water and nutrients. the leaves suffered. They wilted in the summertime when it was really hot out. We had a really warm summer that summer after Ian, which kind of compounded things, I think. And so we lost trees out there that you couldn't even wrap your arm around. So they're like half a meter in diameter. So they've been around for a really long time.
Mike Kiniry
A mangrove that's a half meter in diameter. I don't think I could have imagined that a mangrove could be a half meter in diameter.
Dr. Win Everham
We'll take you out there.
Mike Kiniry
Apparently I need to see more mangroves deep into the stuff.
Dr. Win Everham
I think the national champion black mangrove is on Mount Key. I'm not sure if it's still alive, but when I got here, I remember I walked out there with **** Workman and it was, yeah. I think it might have took two of us to get our arms around it.
Mike Kiniry
So how's that area doing now? How long does it take mangroves to grow?
Dr. Win Everham
Before you answer that, though, I want to back up because I don't know who all is listening. People have this incomplete idea about plants and animals. The plants take in carbon dioxide and give off oxygen and animals take in oxygen and give off carbon dioxide. That's true, but it's incomplete. The plants, when they respire, when they do all the things, they also have to take in oxygen and give off CO2. It's just that they take in more CO2 than they give off because they create all their tissue. And so the net gain in the plants is carbon dioxide. That's how they pull it out, but they still need oxygen. And so most people will know if you want to kill your house plant, put too much water on it. And what you're really doing is drowning the roots. They can't get any oxygen exchange. So and I'd also like to again admit my short-term ignorance that when we first went out into our plot, remember that day? It was like less than 10 days after and we walked out and the entire plot was intact. And I suddenly realized, wow, when you put 10 feet of water into a forest or more, the wind can't blow the forest down. And so I think I had some good phrase like, I always knew that the mangroves protect us from storm surge. I never knew that the storm surge protected the mangroves from the hurricane wind. I thought, wow, what a cool insight. Turned out to be completely wrong.
Mike Kiniry
Well, it didn't protect him from the wind. It just didn't protect him from the storm.
Dr. Win Everham
But the stuff that Brian just said is really his work on our plot. So These delayed die-offs have been seen in a lot of systems and have often been tied to that hypersaline condition that comes from depositing farther inland the saltwater. And so we might have assumed that that's what ours was. I guess we did assume. But because of Brian's expertise in plant physiology, he really looked more closely at the plants, more closely at the rooting zone, more closely at the soil, and was really able to fill in that whole story of these fine particles getting down into the root zone and disrupting the oxygen exchange with the roots. And when I'm trying to tell this to people, anybody who was here after Ian, I don't know about you, Mike, if you had water in your house, once the water went out and it dried and you tried to take that sediment out, you had to wear a mask because the stuff was so small and dusty it came up. And that's that small dusty stuff that gets down into the roots and chokes the roots out, right? Now I forgot what you asked.
Mike Kiniry
Have they recovered?
Dr. Win Everham
Oh.
Mike Kiniry
I mean, because certainly over millennia, the big storms come, those sediments go, you know, it must be part of a broader cycle.
Dr. Brian Bovard
I was out there a couple of weeks ago, actually, and I walked through most of the plot. The individual trees, many of them died, right? So they'll never recover. They're dead. But I think the ecosystem as a whole is, it's doing a really good job of recovering now. I can remember going out there like maybe a year or so after and seeing a lot of young trees starting to come up around the periphery.
Dr. Win Everham
The whites came up really.
Dr. Brian Bovard
The interior was very dead and it seemed like, oh boy, it's going to take a really long time for this to recover. But if you go out there now, most of that plot has trees that are at least as tall as we are, if not maybe twice our height. They're growing fast now, so probably upwards of a meter a year. They're gonna be these thin pencils out there that you're not gonna be able to work your way through here in probably a year or two, but it'll be a dense canopy. And yeah, but the system's recovering now, it seems like.
Dr. Win Everham
If before this increasing frequency of storms that we're seeing now, if somebody had asked me how long does it take, I think 30 years would have popped in my head. And I think partly, Mike, that was just thinking that the average return time for a hurricane was closer to 40 years historically. And so just in the way I think about ecological systems and disruptions and recovery, the system has to be adapted to being able to recover before the next time it gets hammered. And if it doesn't have those adaptations, it doesn't persist. You know, it disappears from the landscape. But we're getting them more frequently than that. And what's your feeling, Brian? I still have a fear that they're coming too fast and that I completely agree with Brian that we can see great recovery. I'm just worried whether or not the recovery will be enough before the next storm hits. It's hard to say what recover means. If your forest had 40-year-old trees, then it takes 40 years to get 40-year-old trees again, except for the few that survive.
Dr. Brian Bovard
Yeah, it's gonna take a long time to replace those half meter wide trees, right? Like given, I guess, the current landscape of the climate, I think that maybe we never see trees that large on the plot that we're working on. I think that we've been lucky that since Ian we haven't had a hurricane yet to reset the system again. I think that had we seen something within a year or two, that could have been problematic. And I think the more frequent, the longer it's gonna take for these systems to actually become functional again.
Mike Kiniry
Let's hope we don't have another storm, but if we do, I guess a different opportunity to learn more about how things work.
Dr. Win Everham
Part of what we're doing now is that I think I speak for both of us. I'm not sure. We're ecologists. A lot of time the job of ecologists is to document change. Sometimes it means quantified degradation. And I think for me, the work on the mangroves just in the last five years has really shifted over from understanding disruption and recovery to restoration, trying to figure out the right ways, the right places, the right techniques to be able to help. Because my sense is that our fingerprints are on this increased frequency, increased intensity of cyclonic storms. And that if without our help, if they would drive mangroves off parts of our landscape, then it demands we accept responsibility. and we do something about.
Mike Kiniry
It. I hope that when people drive past dark green, bushy looking things along the coast, they'll have a better understanding in their head of what mangroves are. But we are unfortunately out of time.
Dr. Win Everham
No way.
Mike Kiniry
We are. Dr. Wynn Everham is professor in the Department of Ecology and Environmental Studies at FGCU. Thank you so much, Wynn.
Dr. Win Everham
Can we come back tomorrow? There's a lot more.
Mike Kiniry
To talk about for mangroves. We'll start a new mangrove series. Dr. Brian Bovard is a wetland and plant ecologist in the Department of Ecology and Environmental Studies within the Water School at FGCU. Thank you so much, Brian.
Dr. Brian Bovard
Thank you, Mike.
Dr. Win Everham
Thank you, Mike.