Millimeters That Matter: The Sea Level Rise Threshold Coastal Wetlands Can't Survive

0:00 Sea level rise. It's a term that we all hear and we're supposed to be afraid of it, but we don't really see it on a regular basis. It's really hard to believe somebody who's saying, hey, you know what? Sea level's rising and it's a real problem. And I'll be like, well, how much is it rising? And they're like, you know, a couple of millimeters every year. What? A couple of millimeters? That doesn't make sense. Why should I be worried about a couple of millimeters? And today's episode, we're going to talk about the effects of those couple of millimeters. per year increase and how that's increased over time, the rate of the those millimeters, how it's increased over time, and why we should be worried about it and how habitats are adapting to it in an era of climate change.

0:42 That's what we're gonna talking about on today's episode of the How to Protect the Ocean podcast. This is the podcast where you find out what you want to know about the ocean, ocean news, ocean updates, ocean science, ocean conservation, all these wonderful topics that we can talk about. I'm your host, Andrew Lewin. I'm a marine biologist and a science communicator. I love to talk about the ocean. I've made a my life's mission to be able to talk to you about things that happen in the ocean so that you can understand the people, like and get to know the people and the projects that they're working on to really find out, you know, how we're doing with ocean. And sometimes it's just to calm that ocean anxiety, sometimes and the climate anxiety, once we know. People are working on something and we can talk about it to our friends and family.

1:23 So that's what we're here to do. So hit that follow button on your favorite podcast app that you're listening to this to and and enjoy the show. So today we're going to be talking about sea level rise because sea level rise has an effect on coastal habitats. And all week we've been talking about coastal habitats, in particular mangroves and marshes. And you're probably wondering like why these two sp specific areas, these coastal habitats, is because We had Adam Langley, who's a who's a professor and he focuses on nutrients and he focuses on how habits, coastal habitats, in particular mangroves and and marshes in Florida and the southern East US perform and adapt to how things are happening with nutrients and how things are happening with the environment in terms and especially within sea level rise. And because you know these all these areas they They are able to adapt to their systems a lot of times, right? So the way these animals work is, or the way these habitats work is that they build up on their soil.

2:21 So a tree will grow, like say a mangrove tree or a marsh will grow. And then those plants eventually die. They go into the soil, they break down into the soil, they create more soil, and then that gets compacted on top of each other. And the soil just builds and builds and builds. And it'll solidify. that area the nutrients get get up taken into those those trees or the marshes and then everything else is kind of like packed in like this waterlogg soil because it's along the coastline and so they can handle the the salinity because that's what they're doing. Marshes are also called salt marshes and mangroves are known to be coastal coastal plants and coastal habitats that can handle this type of this type of environment and they will just build on top and on top of each other now with Rising seas, they will build that that rising sea will build millimeter by millimeter by millimeter. Now in 1990, the rate was around two and two point three millimeters per year.

3:15 That's how much the the sea was rising. Three decades later, now we're looking at about four and a half millimeters per year. So that's increasing the rate by almost double or more than double, or actually almost double. And so we're getting to a point where, at some point. the rate at which the soil is gonna pack on and these mangroves can keep up with sea level rise is going to get even and and the sea level is gonna take over. It's predicted by 2050, I believe, to go over the amount, the six point one millimeters of rate, which is more than what a mangrove and salt marshes can compact the soil, that that rate. The rate of sea level rise is going to outpace the rate of building up that soil. So they can't avoid sea level rise by going up.

3:59 So what do you do? There's another mechanism, the way these animals or the way these habitats will move, these plants will move. They will move horizontally. So if you can't move vertically, they'll move horizontally. And if they can't move vertically, they're eventually going to start dying in areas where this rate is going up. But where they can move is they can move vertically, they can move over. And I think that's where it it becomes a really important thing to look at because once you start moving over, now you you're like, well, how can they move over? How come they haven't moved over before? So mangroves and salt marshes have a limit, a latitudinal limit. It means they can only go to certain that they're usually in warmer environments. So when they go north, they're gonna die based on the freezes.

4:41 But as those freezes let up, those mangroves will continue to move forward. They're always trying to push. They're always trying to make way to build a bigger habitat. But they're they're limited by the amount like by the freezing that happens and by the weather. So if that temperature in a warmer environment is not going to kill them, then they're going to just continue to to move over. So I think there's a couple of things within here to really understand. i when we when we're talking about this stuff. You know, as I mentioned, we're looking at a tipping point of, roughly once once the sea level rise passes roughly 6.1 millimeters per year, mangroves generally can't build the soil that fast, Fast enough to keep up and keep their heads literally above water.

5:26 And NASA's own sea level data shows that the global rate has already reached four and a half millimeters per year and is and it continues to climb. So it's gonna get there. We're actually closer than we ever have been, than we were in the 90s. And of course, the second method is to is for the marsh or mangrove to move. So it's to shift landward as this as the shoreline behind it floods. So the the idea is that as this kind of grows, as the sea level kind of overtakes those mangroves, they're going to move in and they're going to move out. Or they're going to move over. So it really just depends on what how what like what's built behind them to allow them to move and where they can go in the future. And I think that's interesting.

6:06 the Blackwater National Wildlife Refuge is in in Maryland, which is just around Chesapeake Bay, has lost more than 4,000 acres of marshland, nearly half of its historic wetland since it was established in the the projections are pointing to as much as three feet of sea level rise in Chesapeake Bay by 2100, which is to be honest, it's not that far off. We're already in 2026. You know, it seems far off, but it's actually not that far off to get to that level. It's enough to submerge almost all the refugees remaining tidal marsh if nothing changes. Now, this doesn't really necessarily mean that it's not going to adapt, These habitats have adapted for you know hundreds of thousands of years. And so in 2013, refuge biologists Matt Wilbeck and colleagues published the Blackwater 2100 strategy.

6:51 And it's built on it on one insight that marshes have always survived rising seas by moving inland. So away from the coast and moving inland. So as those the rising seas get higher and higher along the coastline, the marshes are going to get taken over, but they're also going to move inland, towards more towards inland. And they've always survived that way. So what they're what the managers were thinking during this Blackwater Hunter strategy is like, how do we make sure that they can actually move inland? It's been developed. There's there's a lot of development that's been going on since there. So they're gonna have to make sure that they can make way and clear the way for this movement to happen, and not have like not move in towards a fixed line, And so the plan identified the migration corridors.

7:31 So they were gonna have specific c corridors, so roughly 2,300 potential acres along the Nanticoke River and roughly 3,600 potential acres along the Corsi Creek. And that started using like conservation easements to keep that land open. Paying landowners and farm and mostly farmers 40 to 60% of the property value to keep it undeveloped rather than converting it. So just part of their land, maybe not all their land. And the thing is that like it's worked. About 812 acres are protected along Corsi Creek and roughly 2,300 acres along the Nanacoke, which is what they wanted. And with about 5,000 acres still unprotected.

8:12 So they still have some work to do in certain areas. So it's not necessarily a finished story. It's not a victory right now. And scientists and conservation managers are still involved in that marsh migration because that migration might not always outpace the current state of sea level rise. and there may not be always like these willing landowners to sell what they want, or those landowners may need to develop that land at some point in time. You know, they may be forced to do so. So it's a real working model and it's proof that like if you give wetlands room to move, that works. But it's something like the community, can actually plan around and fund and not just hope for. So it's one of these things where it's like, yes, these animals these these habitats, I keep calling the animals, these habitats can build up.

8:56 And they are a place for refuge for a lot of other animals in the sea as well as on land. So having that buildup is great. But if it outpa if that sea level rise outpaces the buildup, which it's going to at some point, then and some point sooner than later, then it's gonna move vertically. And that move is gonna go move towards inland. So it's up to managers and people who are looking after the coast to not develop it with hard concrete pads or like a what they call hardlining coastal areas. You gotta keep those soft, you gotta keep those green so that these these habitats can move inward. and move around and they can get away from the sea level rise, which is happening more than often than not.

9:36 And for sea level rise, you just don't know like people often say, like, how does work? Part of it is melting sea ice that that raises the water. The other part is that it's so warm, the water expands and it has to has nowhere to go. So it goes up. And yes, it might seem like it's small in millimeters, but it's having an impact right now as we speak on marshes, on mangroves and other coastal habitats. We just use those two as examples. but if you want more information, you can go to the interview I did on Monday in Monday's episode and and and listen to that because that's where Adam Langley talks all about it, gives you more detail. And I think it's important to understand that seal of rise is a problem. It's a threat, even if it's millimeters, and we need to have we need to do better with that.

10:18 So that's it for today's episode. if you have any questions or comments, you can hit me up on either Spotify has a comment section, or you can go to the show notes. I have all my socials in there. I want to thank you so much for joining me on today's episode of the How to Protect the Ocean podcast. I'm your host, Andrew, and have a great day. We'll talk to you next time in happy conservation.