Why mangroves are so important for our ecosystem & coastal living

This is Gulf Coast Life I’m Mike Kiniry. Thanks for joining us. Up until the early 1900s, about three quarters of Florida 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 a quarter of Lee county's mangroves were removed. Conservation efforts stepped in and saved places like Rookery Bay National Estuarine Research Reserve in 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 Doctor 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, Doctor Bovard.. Thanks for having me. And Win Everham is a professor in the Department of Ecology and Environmental Studies at FGCU welcome back to the show Win. Thanks, Mike. It's always a pleasure. So I had an idea for doing this show several months ago, and I had reached out to you when and 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 whenever him and you said but we got to get Brian Bovard on the show to. So here we are. And as I researched this morning, I found a video from just a couple of months ago featuring you that mentions win about mangroves. So I guess I've got the two right people. Yeah, I hope so. And Sunday was National. International Day. Okay, so it's just one big one. It's time to talk mangroves. So explain what a mangrove is in simple terms, as if I was somebody who had no idea. So mangroves are generally. Tree species. Not always. That can be a shrub. Sometimes. Sometimes they're ferns. Sometimes there's actually a species of palm okay. So okay. They cover about 15 different plant families and are 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. There are generally have some level of viviparous, which is just a nerdy term for being able to have live young. So their seeds. Those cool seed pods that they drop that look like torpedoes. 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. Is it uncommon for a plant to be able to live in saltwater and do what mangroves do in terms of dealing with it? Absolutely. So, and I think that that's why there's only about 54 species worldwide. And we've got three of them here. So 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. You make it impossible for them to grow their crops. If they were growing, mangroves wouldn't hurt them at all. Describe a mangrove. When paint a picture of somebody 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 they're the dark green, bushy trees along the coast, basically. Right? That's about all I was going to say. 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. Right. Yeah. 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. Are there any other things that would be in those places that would be sort of false mangroves to a passerby? If you get far enough inland? I think I've seen Brazilian pepper. I was going to say Brazilian peppers kind of remind me of them, I think. Yeah, but they wouldn't be where the saltwater or brackish water do they have to have saltwater or I guess they could be in the estuary. So can it be brackish? Why. I. I don't know what their level of salt tolerance. I bet. It's pretty low. I think it's pretty. Low though. Oh, I meant mangroves. Mangroves. I mean, how far up into fresh water do mangroves get? Mangroves can live in freshwater. Oh okay. Problem that they run up against when they're in more fresh systems as they're being competed with upland or terrestrial species that are better adapted and can grow faster than them. 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? 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. I've still usually see reds right along the edge, but as soon as you get back behind that fringe or red mangroves, the force, 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. We talk about how they protect the shore from hurricanes and energy from tropical storms. Do those three each serve sort of overlapping purposes when it comes to that, or are they all just together, one big protective layer? I think of them as occupying very different parts of the landscape oftentimes. So as when describe, you oftentimes have the red mangroves that are really well adapted for the edges of islands or river types of system. 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 up slope, 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. Isn't that weird though, Mike, that you would think the mangroves that could handle the highest salinity would be the ones that are right against the sea. Read my mind. But what 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 hyper, 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 of extreme salt in India. Did I get it about right in terms of where they were historically, maybe Tampa Bay to the Indian River lagoon? Yeah. As the as temperatures are warming, are they able to make it further north because I think frost must be a limiting factor. Yeah. They're migrating north. There are conservation lands along the northern Gulf Coast that they're 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. Interesting. 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 there are no longer just in in Florida. What I think I think mangroves are wonderful. Imagine we'll talk about some of the benefits they give. One of the soundbites that I've been trying to use in the media is if you protect mangroves, I'll protect you. You know, you asked a couple of minutes ago, I whenever I think about that storm surge protection, what pops up my mind to 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 the head of the water, you know, and I think there's really good evidence of their ability to minimize title storm surge and high waves inland if you've got an intact for system. So I think of the idea of them moving north 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, they would see them that way. The world is in such a state of flux right now, you know, with what we're doing to the atmosphere and how it's changing. Long term climate and short term weather is is moving things around in, in complicated ways. And so I'm, I'm, I think I'm good with mangroves moving north mangroves one of the roles of mangroves is as they grow they pull carving out of the atmosphere. So I had this 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. I mentioned that Mangrove Trimming and Preservation Act that took effect in 1996. Can you give the basics on like what it does, what it prevents, what people have to do if they want to try to have property with a mangrove? I'm not sure I have all the details on that permit. You know, people would remove mangroves with no control, you know, before we started to recognize their value. So people are still able to trim back mangroves. It's my understanding that's related to maintaining their view field from their homes. But it's a trimming back rather than a removal, and you have to go through a permitting process to do that. So I feel like that's potentially a really good example of the kind of balance that we need, you know, making sure that human needs are met but not met in a way that's short term, that doesn't consider the long term implications of what we're doing. It did occur to me, while thinking about this for today's conversation, that because mangroves are so suited 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 our, you know, it just seems like a strange irony. I had never really thought about it before. I'm not sure I can add to that. I am sure you know, stated that very successfully. Yeah. Yeah, it's. Really are 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. Can you talk some Brian about, you know, they are nurseries, if you will, for offshore fish. So people who want to be anglers really rely on mangroves too. Sure. I want to come back to your comment there. 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 esthetics of the coastline right there, protecting our beaches there, protecting the waterfront or homes. They're providing us with the fisheries that they support, like snook, redfish, snappers. Little baby fish. Go and hide in there basically, right? Yeah. They're young spin part of their lifetime in the roots of those mangroves systems, feeding on the organisms that are there and. Hiding for predators. 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 are beaches and tourism industry. 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 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 was a faculty member at now FSU, wrote a book, Gulf of Mexico. I forget what year it was, and in his list he included Brian said before and I he's right. I just never included 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. That video on the 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. Yeah. We have a long term mangrove monitoring popped out Sarah Bay. Characterize you know Ian came left a lot of stuff in the mangroves including apparently sediment which is causing some problems. 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 forests that were working in. And in some areas there were there was up to like ten centimeters or so of sediment on the forest floor. That creates a problem for the mangroves because like 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 3 to 4 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, oh, 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. Really. That's a half meter in diameter. Yeah. I don't think I could have imagined that a mangrove could be a half meter in diameter. We'll take. You out there. Apparently, I need to see more mangroves deep into the stuff. 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 Dick Workman, and it was. Yeah, they go by, took two of us to get arms around it. So how is that area doing now? How long does it take mangroves to grow? Before you answer that though, I want to back up because I don't know who I was listening. People have this incomplete idea about plants and animals that 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 aspire, when they do all the things that 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, 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 that can't get any oxygen exchange. So what? What? 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's like less than ten days after, and we walked out and the entire plot was intact and and I suddenly realized, wow, when you put ten feet of water into a forest. Or more 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 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. Well. From the wind did. It just didn't protect him from the storm. But the stuff that Brian just said is really his work on our plot. So these 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, you know, 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 and what I'm trying to tell this to people, anybody was here after he and I don't know about you, Mike. If you 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. I want to back up and get that now. I forgot what you asked. Brian. Have they recovered? Oh. I mean, because certainly over the millennia, the big storms come, those sediments go. You know, it must be part of a broader cycle. 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 their 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. The whites came up really. 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 going to be these thin pencils out there that you're not going to be able to work your way through here, and probably a year or two, but it'll be a dense canopy. And. Yeah, but the system is recovering now. It seems like. 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, understood 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. So if you were going to put a number on that, it's hard to say what recover means, right? You know, 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 survived. So yeah, it's going to take a long time to replace those half meter wide trees, right? Like. Yeah, a real long time. Dr. Win Everham is professor in the Department of Ecology and Environmental Studies at FGCU. Thank you so much. When can we come back? Tomorrow. There's a lot. More to talk about. We'll. We'll start a new mangrove series. Doctor Brian Bovard is a wetland plant in the Department of Ecology and Environmental Studies within the water school at FGCU. Thank you so much, Brian. Thank you Mike. Thank you Mike. If you missed any of the show, you can always hear all of our episodes in their entirety on our website. Our show today was produced by yours truly, with audio production from Matt Krause and video production from David Oquendo. For now, thanks for listening. I'm Mike Kiniry. This is WGCU-FM Fort Myers 90.1 WMKO Marco Island 91.7 FM. And for Southwest Florida.