Short Wave - The Mighty Mangrove

Episode Date: October 15, 2021

Along certain coastlines near the equator, you can find a tree with superpowers. Mangroves provide a safe haven for a whole ecosystem of animals. They also fight climate change by storing tons of carbon, thanks to a spectacular above-ground network of tangled roots. Ecologist Alex Moore talks to guest host Maria Godoy about how mighty this tree is, and why it is under threat. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Today, we're going to talk about a swamp creature, a gnarled thing that lives partially submerged in saltwater and mud. But this creature isn't scary. It's actually quite beautiful. It's a mangrove tree, and it's got some pretty cool superpowers. For starters, it grows on coastlines in salty waters that would kiss. most other trees, but not the mighty mangrove.

They are able to effectively excrete the salt out of their cells. So they're like sweating salt? Yeah, effectively they are. You can find really cool pictures online of the leaves that just have these little like salt crystals on the surface of the leaves. Wow. Alex Moore studies these salt sweating trees in American Samoa. Around the world, mangroves only grow close to the equator. They love tropical and subtropical coastlines in places like Indonesia, Mozambique, and Brazil.

In the U.S., they're in Florida. In many of these places, mangroves are under threat, which should alarm everyone because these trees have another critical superpower. They suck carbon dioxide out of the atmosphere and trap it in soil and sediment. They're wicked good at it. By some estimates, mangroves can store five times more carbon than forests on land. And the secret to the superpower lies in mangrove's most eye-catching feature, something most trees keep underground. Their roots. They have like a relatively thin trunk.

And then off of those trunks, you have sort of this network of smaller root systems that you can see above ground that are called prop roots. Yeah, like these gnarly roots almost like something from Lord of the Rings. Yeah. These so-called prop roots form a dense tangled network. They look almost like giant nests. And in a certain way, they are because a lot of species grow up in the protection of the mangrove forest. Alex says mangrove forests are almost like a city. Lots of animals live in them, fish, turtles, birds, even crocodiles and sharks.

So you can have a mangrove tree that is maybe just like an apartment building, and then you can have the mangrove ecosystem that is really more of the city that is made up of a lot of these different kinds of buildings. And these mangrove ecosystems, they have a big role to play in protecting the people and animal that live by them. So today on the show, we talk about the marvels of mangroves, the critical role they play in fighting climate change and what's threatening them. I'm Maria Godoy. You're listening to Shortwave from NPR.

Alex Moore is a postdoctoral researcher at Princeton University. They've dedicated their whole career to studying mangroves. And Alex thinks mangroves are underappreciated superheroes of the environment. They just don't get the attention that, say, a coral reef or a tropical rainforest does. I think one reason that they tend to be less well-known is because they're not really thought of as places that are super hospitable for people. There can be a really tricky system to navigate and physically, you tend to have a lot of different species that are actually quite dangerous. They seem dangerous. Dangerous, why?

Well, I mean, dangerous just in terms of any number of ways, actually. So, like, one is that the sort of platform that you're walking on across these spaces is not super solid and stable. Then if you are a person who is prone to spraining your ankles, that is very likely to occur. Right here. If you want to walk in those areas. But other things are just, like, they harbor lots of different kinds of species that are actually quite dangerous. Okay, so they're like complex superheroes like Batman, you know. They have tricky backstories.

Right. It's like floods and climate change, but they hang out with sharks and reptiles. But not all the residents of that mangrove apartment building are shady. These trees also provide shelter for fish, crab, snails, and other animals. So you have these habitats that tend to act as refuges for species to come into. When they're vulnerable, they tend to grow in those spaces for long periods of time and then move out of those spaces when they become bigger. Sharks nurse in these habitats as well.

So there's lots of different things that happen across the mangrove system. Okay, so you have like crabs and sharks and fish coming and, And sort of growing up in these mangroves because they're protected by these giant gnarly roots. And then once they're big enough to fend for themselves, they leave. Yep, that's exactly what happens. That's cool. Okay, so it's like a protective city. It's like school.

It's a, you know, they grow up and they learn to be strong and then they leave. I like that. But mangroves, they're not just protecting animals, right? They're also protecting people from floods. How does that work? So the prop roots of these mangrove trees, will basically slow down waves that come across these coastal regions. And it's called wave attenuation.

And so that wave speed, wave velocity, all of those things decrease as they come across these mangrove systems. And as they lose that energy, they then are less likely to damage and impact communities that live near or just beyond mangrove spaces. Is it just because the roots are so big? They're essentially forming like a wall like sandbags do for some places? Yeah. In very much a very similar way. So it's because they're big, but it's also because these trees tend to grow in really dense numbers. So because they have so many of them within a small area, they're also really working together to really cause that attenuation that then helps prevent damage that you might see along the coastlines due to tropical storms or other flooding incidents.

So we're talking about flood protection, which is obviously important to the communities that live close to mangroves. But mangroves actually have a big role to play globally in protecting everyone. And I've actually heard them called super trees. Do you think they deserve that title? I mean, I think they do. And so if we're talking about things at sort of a global scale, I think one of the most important and maybe underrated functions that mangrove systems perform is they do a lot of carbon sequestration.

So they take a lot of that carbon dioxide that's in the atmosphere and it becomes a part of the bodies of the trees because they use that carbon to build their tree structures. And then over time, when their leaves fall, and land within the soil, they then get buried in the soil. So basically, these trees are sucking the carbon dioxide out of the atmosphere and trapping it. Yes. So these ecosystems, they store a lot of carbon in amounts that are disproportionate to the size of these ecosystems.

And so this is one of the ways that people are thinking on a global scale of how we can try to mitigate climate change. So we need more mangroves. We definitely need more mangroves. In fact, many scientists say mangroves are a critical tool in the fight against climate change, but they don't seem to be a big part of the conversation for most people. And sadly, mangroves continue to disappear, which is pretty bad news because when they're cut down, they release that carbon they've been storing into the atmosphere. So among the biggest threats to mangroves currently are mostly human-induced.

The biggest one these days is really land conversion. So the majority of mangrove losses that we see across the globe are due to converting what once was a mangrove into usually aquaculture spaces. So fish farming and shrimp farming, that kind of thing? Yeah, so those are really, really big. And then the other one is actually climate change itself. One of the things that tends to be the most significant negative impact across these systems is sea level rise. These systems, even though they are well adapted to these wet, conditions, they can't keep up with the pace. So basically they can, they're adapted to like salty

water, but they're not adapt. The waters are rising too fast. Right. The waters are rising too fast. And, and, you know, insofar as you can be adapted to having salt within your system that you are able to excrete, if you can't get oxygen, you can't grow. So let's talk about your research in American Samoa. What are you hoping to learn scientifically about the mangrove ecosystem there? So I am, interested in going into these mangrove habitats and trying to understand what different animals play different roles within that environment. And so in order to do that, I basically set up cages across these landscapes and the cages prevent certain species from accessing areas of this environment. And so I can measure how healthy is this space with some of these species present

and now comparing it to the health of the space when these species are absent to see what happens. Okay, so we want to see how these animals, like, what are they doing to the city? How are they really contributing to it? And will the mangrove fall apart if you take them out? My hope is that it doesn't, but the reality is that it would be good for us to know because the world is changing. And so we should be aware of what the impacts of those changes might be. Okay. But so we're talking about mangroves, but you're not just studying trees. You're actually also studying the people who live around them. You're interviewing them. What does that work look like?

My goal has always been to understand the system in terms of all of the parts that are really important to it. All environments are influenced by the communities of people that live within them and live near them. And I think it's important to make sure we include these people in the work that we're doing. And so in my work, that looks like meeting with community members who live around these mangrove spaces to understand how do they value these ecosystems, how do they use these ecosystems, what are their thoughts? about how they are being managed or how they should be managed. And the goal in all of these conversations is really to build up a clear understanding of how people feel and to see if the ways that they value the systems, if the ways that they traditionally use those systems can be helpful and included in the ways that we manage and restore them.

So not only thinking about the science in terms of how we can serve and restore, but also thinking about the social and cultural values and uses that could also be really helpful in informing our restoration and concertary. practice. Has it changed your outlook as a scientist at all? I mean, I think that a lot of times when you come into a community as a researcher, there's a lot of trepidation because they have maybe had previous negative experiences with people who say that they do conservation. One thing that can make these kinds of things really challenging is sort of the scale, right? So climate change is sort of a big scale, longer term effort,

whereas trying to find space to build a house for your family is quite immediate. So you have to be thinking about what are the trade-offs across the different kinds of approaches and choices you might be making. And so I think that I would say what I have learned the most is less about what it means to do the science and more about what it means to sort of be a scientist as like a person communicating with other people and just trying to, you know, find where you have overlapping values, overlapping interests and the ways that you can help each other. And I don't think that's something we are taught to do as scientists, but I think it's really important to do as people engaging in work with other community members. Alex, thank you for this really truly fascinating

conversation about Mangroves. Absolutely. It was my pleasure. This episode was produced by Burley McCoy, edited by Sarah Saracen, and fact-checked by Indy Kara and Margaret Serino. The audio engineer was Josh Newell. I'm Maria Godoy. Thanks for for listening.