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

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Sea level rise. It's a term that we all
hear and we're supposed to be afraid of
it,

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but we don't really see it on a regular
basis.

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It's really hard to believe somebody who's
saying,

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hey, you know what? Sea level's rising and
it's a real problem.

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And I'll be like, well, how much is it
rising?

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And they're like, you know, a couple of
millimeters every year.

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What? A couple of millimeters?

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That doesn't make sense. Why should I be
worried about a couple of millimeters?

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And today's episode, we're going to talk
about the effects of those couple

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of millimeters.

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per year increase and how that's increased
over time,

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the rate of the those millimeters,

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how it's increased over time, and why we
should be worried about it

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and how habitats are adapting to it in an
era of climate change.

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That's what we're gonna talking about on
today's episode of the How

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to Protect the Ocean podcast. This is the
podcast where you find out what

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you want to know about the ocean,

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ocean news, ocean updates, ocean science,

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ocean conservation, all these wonderful
topics that we can talk about.

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I'm your host, Andrew Lewin. I'm a marine
biologist and a science communicator.

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I love to talk about the ocean.

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I've made a my life's mission to be able
to talk to you about things that happen

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in the ocean so that you can understand
the people,

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like and get to know the people and the
projects that they're working

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on to really find out, you know,

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how we're doing with ocean. And sometimes
it's just to calm that ocean anxiety,

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sometimes and the climate anxiety,

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once we know.

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People are working on something and we can
talk about it to our friends and family.

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So that's what we're here to do.

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So hit that follow button on your favorite
podcast app that you're listening

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to this to and and enjoy the show.

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So today we're going to be talking about
sea level rise because sea level rise

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has an effect on coastal habitats.

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And all week we've been talking about
coastal habitats,

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in particular mangroves and marshes.

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And you're probably wondering like why
these two sp specific areas,

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these coastal habitats, is because

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We had Adam Langley, who's a who's a
professor and he focuses on nutrients

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and he focuses on how habits, coastal
habitats,

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in particular mangroves and and marshes in
Florida and the southern East

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US perform and adapt to how things are
happening with nutrients and

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how things are happening with the
environment in terms and especially within

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sea level rise. And because you know these
all these areas they

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They are able to adapt to their systems a
lot of times,

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right? So the way these animals work is,

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or the way these habitats work is that
they build up on their soil.

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So a tree will grow, like say a mangrove
tree or a marsh will grow.

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And then those plants eventually die.

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They go into the soil, they break down
into the soil,

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they create more soil, and then that gets
compacted on top of each other.

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And the soil just builds and builds and
builds.

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And it'll solidify.

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that area the nutrients get get up taken
into those those trees or

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the marshes and then everything else is
kind of like packed in like this waterlogg

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soil because it's along the coastline and
so they can handle

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the the salinity because that's what
they're doing.

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Marshes are also called salt marshes and
mangroves are known to

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be coastal coastal plants and coastal
habitats that can handle this type

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of this type of environment and they will
just build on top and on top

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of each other now with

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Rising seas, they will build that that
rising sea will build millimeter

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by millimeter by millimeter. Now in 1990,

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the rate was around two and two point
three millimeters per year.

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That's how much the the sea was rising.

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Three decades later, now we're looking at
about four and a half millimeters

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per year. So that's increasing the rate by
almost double or more than double,

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or actually almost double. And so we're
getting to a point where,

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at some point.

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the rate at which the soil is gonna pack
on and these mangroves can keep

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up with sea level rise is going to get
even and and the sea level

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is gonna take over. It's predicted by
2050,

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I believe, to go over the amount,

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the six point one millimeters of rate,

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which is more than what a mangrove and
salt marshes can compact the soil,

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that that rate.

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The rate of sea level rise is going to
outpace the rate of building up that soil.

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So they can't avoid sea level rise by
going up.

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So what do you do? There's another
mechanism,

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the way these animals or the way these
habitats will move,

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these plants will move. They will move
horizontally.

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So if you can't move vertically,

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they'll move horizontally. And if they
can't move vertically,

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they're eventually going to start dying in
areas where this rate is going up.

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But where they can move is they can move
vertically,

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they can move over.

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And I think that's where it it becomes a
really important thing to look

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at because once you start moving over,

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now you you're like, well, how can they
move over?

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How come they haven't moved over before?

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So mangroves and salt marshes have a
limit,

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a latitudinal limit. It means they can
only go to certain that they're usually

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in warmer environments. So when they go
north,

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they're gonna die based on the freezes.

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But as those freezes let up,

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those mangroves will continue to move
forward.

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They're always trying to push.

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They're always trying to make way to build
a bigger habitat.

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But they're they're limited by the amount
like by the freezing that happens

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and by the weather. So if that temperature
in a warmer environment is

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not going to kill them, then they're going
to just continue to to move over.

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So I think there's a couple of things
within here to really understand.

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i when we when we're talking about this
stuff.

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You know, as I mentioned, we're looking at
a tipping point of,

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roughly once once the sea level rise
passes roughly 6.1 millimeters per year,

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mangroves generally can't build the soil
that fast,

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Fast enough to keep up and keep their
heads literally above water.

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And NASA's own sea level data shows that
the global rate has already reached four

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and a half millimeters per year and is and
it continues to climb.

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So it's gonna get there. We're actually
closer than

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we ever have been, than we were in the
90s.

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And of course, the second method is to is
for the marsh or mangrove to move.

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So it's to shift landward as this as the
shoreline behind it floods.

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So the the idea is that as this kind of
grows,

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as the sea level kind of overtakes those
mangroves,

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they're going to move in and they're going
to move out.

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Or they're going to move over.

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So it really just depends on what how what
like what's built behind them

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to allow them to move and where they can
go

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in the future. And I think that's
interesting.

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the Blackwater National Wildlife Refuge is
in in Maryland,

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which is just around Chesapeake Bay,

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has lost more than 4,000 acres of
marshland,

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nearly half of its historic wetland since
it was established in

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the the projections are pointing to as
much as three feet of sea level rise

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in Chesapeake Bay by 2100, which is to be
honest,

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it's not that far off. We're already in
2026.

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You know, it seems far off, but it's
actually not that far off to get to that
level.

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It's enough to submerge almost all the
refugees remaining tidal marsh

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if nothing changes. Now, this doesn't
really necessarily mean that it's

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not going to adapt, These habitats have
adapted for you know hundreds

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of thousands of years. And so in 2013,

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refuge biologists Matt Wilbeck and
colleagues published

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the Blackwater 2100 strategy.

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And it's built on it on one insight that
marshes have always survived rising seas

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by moving inland. So away from the coast
and moving inland.

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So as those the rising seas get higher and
higher along the coastline,

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the marshes are going to get taken over,

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but they're also going to move inland,

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towards more towards inland. And they've
always survived that way.

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So what they're what the managers were
thinking during this Blackwater Hunter

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strategy is like, how do we make sure that
they can actually move inland?

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It's been developed. There's there's a lot
of development that's been going

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on since there.

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So they're gonna have to make sure that
they can make way and clear the

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way for this movement to happen,

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and not have like not move in towards a
fixed line,

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And so the plan identified the migration
corridors.

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So they were gonna have specific c
corridors,

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so roughly 2,300 potential acres along the
Nanticoke River

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and roughly 3,600 potential acres along
the Corsi Creek.

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And that started using like conservation
easements to keep that land open.

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Paying landowners and farm and mostly
farmers 40 to 60% of the property value

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to keep it undeveloped rather than
converting it.

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So just part of their land, maybe not all
their land.

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And the thing is that like it's worked.

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About 812 acres are protected along Corsi
Creek and roughly 2,300 acres along

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the Nanacoke, which is what they wanted.

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And with about 5,000 acres still
unprotected.

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So they still have some work to do in
certain areas.

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So it's not necessarily a finished story.

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It's not a victory right now. And
scientists and conservation managers

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are still involved in that marsh migration
because that migration might

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not always outpace the current state of
sea level rise.

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and there may not be always like these
willing landowners to sell what they want,

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or those landowners may need to develop
that land at some point in time.

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You know, they may be forced to do so.

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So it's a real working model and it's
proof that like if you give wetlands room

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to move, that works. But it's something
like the community,

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can actually plan around and fund and not
just hope for.

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So it's one of these things where it's
like,

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yes, these animals these these habitats,

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I keep calling the animals, these habitats
can build up.

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And they are a place for refuge for a lot
of other animals in the sea as well

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as on land.

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So having that buildup is great.

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But if it outpa if that sea level rise
outpaces the buildup,

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which it's going to at some point,

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then and some point sooner than later,

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then it's gonna move vertically.

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And that move is gonna go move towards
inland.

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So it's up to managers and people who are
looking after the coast to

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not develop it with hard concrete pads or
like a what they call hardlining coastal

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areas. You gotta keep those soft,

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you gotta keep those green so that these
these habitats can move inward.

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and move around and they can get away from
the sea level rise,

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which is happening more than often than
not.

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And for sea level rise, you just don't
know like people often say,

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like, how does work? Part of it is melting
sea ice that that raises the water.

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The other part is that it's so warm,

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the water expands and it has to has
nowhere to go.

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So it goes up. And yes, it might seem like
it's small in millimeters,

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but it's having an impact right now as we
speak on marshes,

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on mangroves and other coastal habitats.

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We just use those two as examples.

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but if you want more information,

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you can go to the interview I did on
Monday in Monday's episode and

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and and listen to that because that's
where Adam Langley talks all about it,

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gives you more detail. And I think it's
important to understand that seal

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of rise is a problem. It's a threat,

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even if it's millimeters, and we need to
have we need to do better with that.

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So that's it for today's episode.

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if you have any questions or comments,

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you can hit me up on either Spotify has a
comment section,

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or you can go to the show notes.

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I have all my socials in there.

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I want to thank you so much for joining me
on today's episode of the

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How to Protect the Ocean podcast.

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I'm your host, Andrew, and have a great
day.

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We'll talk to you next time in happy
conservation.