Every summer growing up, my parents and I would pile into our Suburban with kayaks, beach toys and boogie boards and make the three-hour-long drive from Baltimore to the Jersey Shore.

As a kid, those three hours felt like an eternity. But I always knew we were close to the beach when my Dad would roll down all the windows and proclaim “Smell that?! That’s the salt marsh! Best smell in the world.”

To this day, the salt marsh is one of my favorite scents.

Now, the pungent aroma of the salt marsh might not be everyone’s cup of tea. But it is recognizable to many who travel to beaches throughout the United States. Today, we’re going to delve into the science behind these distinctive ecosystems.

What is a salt marsh?

Salt marshes are wetlands that are flooded with high tides and drained with low tides. They are found along coastlines in the United States and in other mid- and high-latitude countries (they’re not found as frequently in the tropics). There are more than 4.1 million acres of salt marsh in the United States found from the coast of the Bering Sea to the Florida Keys. Half of all the country’s salt marshes can be found along the Gulf of Mexico.

If you’ve ever seen a salt marsh up close, you know it’s made of thick, dark muck. The marshy soil is comprised of mud and peat, which is made of decaying plant matter. This decomposing organic matter combined with salt water flooding can make the soil hypoxic, meaning its oxygen levels are low. This results in its pungent and distinctive “rotten egg” smell.

Why are salt marshes important?

Salt marshes, like many wetlands, play an important role in healthy shorelines. They are crucial habitat for terrestrial and marine species, and provide a safe place to hide, find mates and raise young. Many commercially- and recreationally-important fish species live in salt marshes as juveniles, and many bird species take advantage of the high grasses in the marsh to feed and nest. According to NOAA, 75% of fisheries species use salt marshes for food, shelter or as a nursery, including popular seafood species like shrimp and blue crab.

Salt marshes protect more than just juvenile crustaceans—they protect people, too. They serve as a buffer between the land and ocean by absorbing wave energy during storms (similar to mangrove forests). They also trap sediment, help mitigate flooding in low-lying zones and filter nutrients and toxins out of runoff water. Essentially, they help reduce negative effects of ocean on the land, and land on the ocean—like a really helpful middle man.

They’re also important carbon sinks, meaning they take up and hold onto carbon that would otherwise be in the atmosphere. With the rapidly escalating effects of climate change, this function is more critical than ever!

Why are salt marshes in trouble?

Salt marshes love calm, low-lying coastal areas—and so do people. Historically, salt marshes have been lost to construction and development, resulting in a 25-50% decline in salt marshes worldwide. Increased nutrient runoff from fertilizers, farms and septic systems have led to increased nutrient levels in marshes, which throws the ecosystem off balance. Additionally, other pollution from industrial runoff and herbicides introduce toxins into the marsh, which can hurt or even kill wildlife. To top it off, other factors like overfishing of top predators and introduction of invasive species can further hurt the salt marsh ecosystem.

Fortunately, there are conservation programs worldwide to help protect and restore salt marshes. One way you can help is by supporting policies that protect wetlands, including salt marshes. By advocating for these critical ecosystems, you’re helping our ocean, its wildlife and all of us who depend on it!