Science & Environment
1:08 pm
Tue May 27, 2014

Salt Marshes the Unsung Heroes of our Coasts

Credit Dan K / Flickr

Ask not what salt marshes can do for you (they're already doing plenty, and paying dearly for it), but what you can do for salt marshes.

When it comes to the coast, beaches always seem to get top billing, while salt marshes get pretty soundly ignored. There's no annually updated Top Ten Salt Marshes list, no marsh-centric travel guides. Salt marshes have a reputation for being smelly and muddy, places to be avoided, or worse, filled in.

In reality, though, wetlands are unsung heroes. They filter the water – and the air, for that matter - sucking up nutrients and pollutants from gound water, as well as carbon dioxide from the atmosphere. They shelter the young of countless marine animals, and protect our homes from storms. It's hard to put a dollar figure on these so-called ecosystem services, but the Massachusetts Division of Ecologial Restoration estimates healthy marshes could be worth millions.

They can also be really fun places to explore, as any marsh enthusiast can tell you. I went on my first "marsh muck" sometime in middle school and was instantly converted into a life-long marsh lover. Radio producer Rob Rosenthal says he grew up playing in a Cape Cod salt marsh, and may well have salt marsh in his blood.

And then there's John Teal, renowned marsh ecologist, scientist emeritus at Woods Hole Oceanographic Institution, and author of the book Life and Death of the Salt Marsh. Seen through Teal's eyes, marshes are places of beauty and abundance, full of natural and human history.

But we have not been kind to our wetlands. While we’ve largely forsaken our history of “reclaiming” them, as the practice of filling them in was euphemistically called, human activities continue to impinge on the health and integrity of salt marshes. Coastal development, invasive species, climate change and nutrient-laden run-off are among the myriad threats.

In fact, the functions that make marshes valuable can be exactly what makes them vulnerable. Marsh grasses presented with excess nitrogen in the soil (from septic systems, or lawn and farm fertilizers) don't bother to make the vast root networks that hold marshes together, and soil microbes actually eat away at the structure. The top-heavy grasses fall over, making it impossible for all but a lucky few to gather sunlight and photosynthesize. A marsh in this state isn't the rich, productive ecosystem it once was. It is a crippled marsh, susceptible to drowning and incapable of performing its usual duties as a safe haven for juvenile ocean animals or as a storm barrier for human abutters. 

Linda Deegan, Senior Scientist with the Ecosystems Center at MBL, and James Rassman, Acting Manager and Stewardship Coordinator for Waquoit Bay National Estuarine Research Reserve, say they increasingly see marshes - from New Jersey to Massachusetts - that are showing signs of significant impairment. And even those in the best of shape are hard pressed to keep their heads (excuse the anthropomorphism) above water as the pace of sea level rise accelerates.

Nick Wildman, Priority Projects Coordinator with the Massachusetts Division of Ecological Restoration, makes it his job to try to help marshes that have been disabled by human activities recover. It's impossible to remove all the stressors facing most marshes; nutrient loading and climate change are beyond his purview. But sometimes, he says, just removing a dam or widening the inlet that feeds a marsh can provide enough of a boost to enable a marsh to cope with those other stressors on its own.

Those cases are becoming rarer, though, and Wildman says the size of marshes where restoration is feasible is shrinking as a result of human development. Still, Wildman, Rassman, and Deegan all say they are cautiously optimistic that attitudes toward marshes are changing and there is still time to preserve our coastal wetlands.