NORTH CAROLINA (QUEEN CITY NEWS) – “The reason I find them so interesting is because they’re that frontier of change, and so they’re so responsive to things that we humans do,” reflects Himmelstein.
These coastal wetlands are crucial to the food we eat, the homes we build, and the storms we survive, “whether it modifies the coastline or affects the way sea levels are rising, they’re some of the first environments to respond to that.”
But marshes are changing faster now than ever before, “it is all-natural, these things have happened in the past, but the rate at which we’re seeing them happen is what’s alarming a lot of us in the climate science field.”
Joshua Himmelstein is a Ph.D. student in coastal geology at UNC’s Institute of Marine Sciences. He’s tracking the movement of marshes, “while we have a new growth of salt marshes in the upland, we have erosion further out closer to the waterways.”
He explains that the movement triggered by sea-level rise, “we see about 4 mm a year in sea-level rise. Even though it sounds like a pretty small amount, that little incremental amount of water level rise is reaching higher and higher areas that were once used to being covered in fresh water, rain maybe, that are now seeing salt water, changing the ecosystem.”
These marshes often protect our homes and the homes of sea critters we depend on; he explains, “depending on how much is removed and how much is created, it might change things like the amount of carbon that’s drawn down or the amount of species that can depend on that landscape.”
So to find answers, we venture into these moving marshes that look beautiful but, “there are some bacteria, they use anaerobic respiration. These bacteria can only make energy when there’s no oxygen…and one of the byproducts is sulfur,” that’s science talk for smells like rotten eggs.
Saltwater marshes are the frontier of sea-level rise. As sea-levels rise and storms become more intense, salt water makes it farther inland. The extra salt leaves skeletons left behind; dead trees now called a ghost forest show where that salt water is killing the trees.
Any greenery left behind them is the next victim of the sea-level rise and salt water intrusion.
To figure out when and where this transition happened, they cut deep into the soil to pull out a core that reveals a slice of history.
It may not look like it, but this core is filled with information. It gives them a 3D look at our coast, “normally, we just have satellite imagery, or imagery from drones, or a map that somebody drew 200 years ago, but this allows us to integrate over time as well,” compares Himmelstein. Himmelstein explains, “When you look at it is kind of like mud, and it’s uninteresting, but here we see sea-level rise.”
Since marshes grow vertically by compressing on top of each other, the older sediment is compressed back towards the bottom, and the newer, fresher soil is on top. So, the soil tells its own story of its past, but as it migrates inland to follow the salt water, it also gives us a taste of the future.
Himmelstein predicts, “You’ll see them moving into areas that used to be our backyards, our football pitch, and our agricultural land. We just drove by a farm, and I’m sure in 50 years that’s going to be a salt marsh.”
While some marsh grows inland, coastal erosion, storm surge, and fast tidal rises erode marshes closer to the water. Himmelstein explains, “that’s why folks are interested in measuring how much new marsh is being created versus how much old marsh is being eroded at one edge.”
These cores also show us where carbon is stored; marshes can be more efficient at the job than rainforests; he explains, “you can see roots all the way down, even though these are many years old, they still haven’t broken totally down. They stay there, so that’s just carbon that’s being stored in the soil.”
But what seeps in doesn’t always stay there; Himmelstein points out, “now if that marsh is eroded, all that carbon is released back into the waterways and eventually the atmosphere.”
These cores tell us that marshes are good at keeping pace with sea-level rise, but only to an extent; too much water suffocates the marshy grass. Himmelstein predicts, “there’s a chance that when you look at the net change, there’s actually a loss in salt marsh area because the amount of erosion is greater than the amount of encroachment.”
So back in the lab, Himmelstein takes his cores and cuts them into little slices that he freeze-dries and stores. He cuts them layer by layer, one centimeter at a time, 100 slices in total.
He suits up and puts chemistry to work. Each centimeter can then be tested to figure out its age. So far, the cores have told us that there was a transition in the marsh, just not when. Himmelstein asks if “the rate of this marsh growth, is it faster or slower than sea-level rise?”
And by using the past, we can forecast the future; he predicts, “if it’s slower, we’re going to lose that marsh it’s going to drown if it’s faster than marsh will stay as a marsh until it can no longer because sea-level rise is just too fast.”
“There are places where marshes and other habitats are being squeezed between all this structure we built and the water that’s rising,” Dr. Joel Fodrie is a marine ecologist at UNC. He predicts, “It’s going to change the dynamic in those places and probably cost us these coastal habitats.”
He and Himmelstein align conservation is vital, “we know a lot about the ecosystems, and now it’s about what can we do, where can we direct money, where can we as concerned citizens start to focus our efforts?” asks Himmelstein.
In order to conserve the benefits we need to reap from these marshes, like coastal protection, wildlife habitat, and carbon storage, we need to protect the land it lives on.
A study done by Climate Central ranks North Carolina as one of the most vulnerable, forecasting more than an 80% loss in marshes if we keep developing the land as we are now. But the study shows we can prevent many of those losses with some conservation.
This interactive map lets you get to those changes county by county. You can change the pollution pathway to best and worst-case scenarios to better understand the impact we could have, both good and bad, on our coast.
“The bumper sticker says ‘no wetlands, no seafood,’ and there’s a lot of truth in that,” Dr. Fodrie explains that our marshes act as nurseries for all the baby shrimp, crabs, and seafood we love. He adds, “So even if you want to catch a big fish that lives miles offshore when that fish was a baby fish, it might be in these marshes.”
As these critters chase salt, they’re also running into other obstacles like land development, poor water quality, and warming ocean temperatures. Dr. Fodrie explains, “It’s not just warmer, it’s sea-level rise, it’s ocean acidity, it’s storminess, it’s changes in the seasonal timing of things.”
Simply put, it’s not simple. These are complex changes happening in our ocean ecosystems, “all of those are syndromes of climate change, and so trying to unravel this mystery. It does take time,” he explains.
We can’t fight off these changes, Dr. Fodrie acknowledges, “we’re going to keep adapting, that’s our best hope is to keep adapting and find new solutions, these new mouse traps.”
The marshes will move with or without us, Himmelstein predicts, “they might change in the area, there might be half as many marshes in 1,000 years as there are today, or there might be twice as many. The jury is still out; a lot of it depends on things we choose to do at the coast,” because in the end, it’s our home too.