FLORIDA MANGROVES
Hari Sreenivasan: This is the site of an outdoor laboratory on the banks of the
intracoastal waterway in northeast Florida. It’s part of a research project on
the interaction of climate change and coastal ecosystems. And getting here is
not easy.
Samantha
Chapman: That is not warm!
Hari Sreenivasan: That’s a little chilly.
It’s not so
coincidentally called the WETFEET project.
Samantha
Chapman: If you sink at all you wont go far...You won’t go… but
you can sink up to your waist sometimes.
Hari Sreenivasan: Samantha Chapman is an ecology professor at Villanova University
and the primary investigator on this project. I’m following her and her team
into this marsh where they’re studying the impact of climate change on a
tropical plant that’s been migrating further and further north: the mangrove.
Samantha
Chapman: We’re in this sort of
encroachment and spread phase where they’re moving northward and taking over
rather rapidly.
Hari Sreenivasan: There are three species of mangroves that grow in florida: white, black, and red. What they have in common is
an ability to grow with their roots submerged in salty water and soil. An
environment that kills many other plants. Mangroves grow around the world,
thriving in tropical conditions generally within a set distance of the equator.
But this spot in Florida, near St. Augustine, is north of that range.
Here in the Guana Tolomato Matanzas Research
Reserve, or GTM, mangroves are growing, in a region that was previously thought
to be too cold for them to permanently take root. Matt Hayes is post-doctoral
researcher at villanova.
Matt
Hayes: Historically they have
been up here before. So we know from looking at historical records from early
botanists and explorers they have spoken about seeing mangroves around here
even just north of here. But then once these cold snaps came that was enough to
kill them off and then they'd be pushed right back again further south of here.
Hari Sreenivasan: As climate change makes these cold snaps less frequent,
researchers are studying how permanently warmer temperatures will affect this
ecosystem.
Each of these chambers
is a glimpse into the future. By shielding it from the elements, the
temperature inside is a couple of degrees centigrade warmer. By doing this,
scientists can study what happens to the salt marsh and the mangrove in here at
these higher temperatures versus what’s outside.
Samantha
Chapman: What we see at least in
our first six months of data is that the mangroves seem to be growing faster in
the warming chambers.
Hari Sreenivasan: The WETFEET Project is a multi-year initiative, funded by the
National Science Foundation. Researchers pull water samples to measure data,
including salinity.
Samantha
Chapman: It’s kind of like
getting blood from a stone, right?
Hari Sreenivasan: They use bluetooth-connected sensors
to track environmental conditions like temperature and humidity; both inside
and outside of the chambers.
Is this
mangrove going to replace that marsh?
Samantha
Chapman:
Likely, yes. Unless there's a deep freeze, it's going to overtop the marsh and
as it does so it's going to shade out the marshes under it and it will just
take over.
Hari Sreenivasan: But a “take over” might not necessarily be a bad thing.
Mangroves are the foundation of an extremely productive coastal ecosystem in
their own right. To see the benefits that these plants provide, we traveled
more than 180 miles south to a research site near the coastal town of Ft.
Pierce. Here, it’s a more tropical environment, and a place where mangroves traditionally
thrive.
Ilka
“Candy” Feller: This
is solid mangrove. We have pretty much 100 percent cover of mangroves.
Hari Sreenivasan: Our guide is Candy Feller, an emeritus scientist at the
Smithsonian Environmental Research Center. She’s been studying mangroves for
more than three decades.
Ilka
“Candy” Feller: Mangroves
are known as a nursery of the sea so in Florida it's been shown that most of
the commercial fishes spend part or all of their their
lives in the mangroves so if you get rid of the mangroves and you've lost a
whole lot of your catch.
Hari Sreenivasan: In addition to anchoring a whole ecosystem, mangroves play an
important role in defending in shorelines from the sea. A 2017 study found that about 5.5 feet of mangroves can
reduce wave height by about 90 percent. By comparison, it takes 57 feet
of salt marsh to do the same.
In the 1980s, Florida
adopted its first rules to protect mangroves, but globally they are threatened
by agriculture and aquaculture, including shrimp farming, as well as coastal
development.
Ilka
“Candy” Feller: The
Achilles heel of mangroves is that they're occupying that part of the landscape
that people really covet.
Hari Sreenivasan: Researchers estimate that as much as a third of the world’s
mangrove habitat has been lost since 1980. But about 80 miles up the Florida
coast, Feller took us to an area that has seen a mangrove explosion in the last
15 years.
Merritt Island National
Wildlife Refuge - near NASA’s Kennedy Space Center - is home to hundreds of
bird species from Glossy Ibises to Great Blue Herons. It’s also part of what’s
known as the ecotone: part salt marsh, part mangrove environment.
Ilka
“Candy” Feller: I
remember the day when I was looking out there and it was just about as much
salt marshes as it was mangroves but it looks like
it's pretty much all mangroves now doesn't it?
Hari Sreenivasan: The transformation here has been so fast that an informational
sign is now completely out-of-date.
Ilka
“Candy” Feller: I
think this is extraordinary. This is what we're looking at here. It says the
marsh to the east is a grassland community. That is no longer a grassland
community. It’s a mangrove forest.
Hari Sreenivasan: The changes look just as dramatic from above. Researchers measure
the expansion of mangroves using satellite images, and in this region alone
mangrove cover increased by nearly
70 percent from 2003 to 2010.
Samantha
Chapman: They are really flexible
like snorkels too.
Hari Sreenivasan: Back at the WETFEET Project, about two hours up the coast,
researchers bring us to another site where mangroves are encroaching on salt
marsh.
Samantha
Chapman: Here’s the little root
that sticks out.
Hari Sreenivasan: This is a mangrove propagule, the plant’s seedling.
Samantha
Chapman: And then it
essentially lifts up its head and then it pops out its first two real leaves.
Hari Sreenivasan: It’s not just the growth of mangroves popping up in this salt
marsh that researchers are studying. They are also measuring a hidden benefit
of mangroves that’s trapped in the ground beneath them.
The mud that I’m
standing in, this really dark stuff, that is thousands
of years worth of carbon that’s been captured and
locked in by this salt marsh. Now as these mangroves work their way up the
coast researchers are trying to figure out how that affects the rate at which
that carbon is stored.
Samantha Chapman: These
wetlands are like little strips and so by area they're not the biggest carbon
stores, but they can take up carbon really quickly and lock it away.
Hari Sreenivasan: As mangroves grow they
absorb carbon dioxide and other climate change-causing greenhouse gases from
the atmosphere. These elements are converted by the mangroves to organic matter
and trapped in the soil below. This stored carbon is known as blue carbon, and
by growing quickly and decomposing slowly, mangroves store more of it, on a per
area basis, than any other type of forest on earth.
Samantha Chapman: I think this system is one in which we're seeing some hope. The
vegetation, the plants are adapting to climate change. They are moving into a
place where they couldn't be before because it's warmer and that may, and
that’s what we are trying to figure out, end up helping us with issues like
carbon storage and sea level rise.
Hari Sreenivasan: But the transition from grassy salt marsh to bushy mangrove is not
seen as beneficial by everyone.
Nikki
Dix: It's not that either one
is better than the other, it's just how is it going to change
Hari Sreenivasan: Nikki Dix is the research director at GTM, and a scientist working
on the WETFEET Project.
Do the people that live
around here understand the difference between an invasive species and what a
mangrove is, what a mangrove does?
Nikki
Dix: Yes, some do some don't.
So we try to educate people the best we can. When people are not used to seeing
mangroves out their backyard they're used to this nice flat marsh view. And
then you start getting trees blocking your view. They immediately think oh it's
an invasive we've got to cut it down.
Danny
Lippi: You can't touch it.
People don't like that. They don't like being told no especially people that
can afford to live on the water.
Hari Sreenivasan: To “touch” a mangrove in Florida, you usually need the help of
someone like Danny Lippi. He’s an arborist near where the WETFEET Project is
underway and he’s licensed by the state to trim mangroves.
Hari Sreenivasan: He recently trimmed these mangroves from around 12 feet down to 8
feet, after a months-long regulatory process. The penalty for removing or
improperly pruning a mangrove is up to 5,000 dollars per plant.
Danny
Lippi: Every once in a while
you'll get a pretty good client that understands the benefits. But I'd say most
of my clients don't care about any of that. They just want to have a view this
plants in their way and the state says that they can't remove it when they want
to.
Hari Sreenivasan: Our final stop with Candy Feller was nearly 40 miles north of the
WETFEET Project on Amelia Island, near the border with Georgia. She’s brought
us to the northernmost known mangrove on the eastern seaboard.
Ilka
“Candy” Feller: That
tree got there, about 15 years ago. We
think that it probably arrived during or after the 2004 hurricanes.
Hari Sreenivasan: Researchers believe the plants’ northern march
is spurred by extreme weather events like hurricanes physically spreading
mangrove propagules. That push from a hurricane, combined with no significant
freezes, means this plant has been able to take root.
Ilka
“Candy” Feller: The
predictions are that we're going to have less intense and fewer freezes. We're
going to have more and more intense hurricanes, which means that mangroves who
can be pushed further and further up the coast. So these become like a sentinel
of, a biological sentinel of the effects of climate change.
Hari Sreenivasan: Back at the GTM reserve, there are more than 72,000 acres of
protected land, including almost 40 miles of coast. as climate change
continues, researchers believe this ecosystem will see more and more mangroves.
It’s an encroachment that could permanently change this landscape in ways that
researchers are racing to understand.
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TIMECODE |
LOWER THIRD |
1 |
02:09 |
GTM RESEARCH RESERVE, FL HARI SREENIVASAN @HARI |
2 |
02:49 |
SAMANTHA CHAPMAN VILLANOVA UNIVERSITY |
3 |
04:18 |
ILKA “CANDY” FELLER SMITHSONIAN ENVIRONMENTAL RESEARCH CENTER |
4 |
06:59 |
SAMANTHA CHAPMAN VILLANOVA UNIVERSITY |
5 |
07:44 |
NIKKI DIX RESEARCH DIRECTOR, GTM RESEARCH RESERVE |
6 |
|
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