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Dune Plants: A Study in Adaptation

The native plants that grow closest to the ocean along the Jersey Shore have evolved to thrive in tough conditions – luckily for us.

Coastal dunes owe their existence to a small portfolio of plant species adapted to one of our area’s most extreme habitats. Wave action and wind will push sand ashore, but it’s the presence of these tough and hardy plant species that allow it to pile up and stay put.

What it is: Dune plants are a hearty bunch. 

If you’re asked to think of a dune, you’ll probably call to mind the grass-covered mounds you have to climb over — or hopefully through, on a designated path — to get to the ocean at your favorite beach. This “beach ridge” is called the foredune, and it's a tough place to live if you're a plant.

Salt in the air and the sand is toxic to plants – it inhibits their ability to take up water nutrients through roots and also sucks moisture from their leaves, dehydrating them from both ends.

And there’s not a lot of fresh water to begin with. Sand drains rainwater quickly, taking with it much of the scant available nutrients. Besides that, the substrate is generally unstable and prone to shifts, and vulnerable to steady wind and regular storms.

But dune plants have adapted to fill this narrow ecological niche. The species that move in first to colonize a raw mound of sand, called pioneer plants, tend to be sprawling, low-growing species that can hold onto water for some time.

A perfect example is the sea-beach amaranth. The plant has specially adapted stems called rhizomes that grow parallel to the ground, providing stability and allowing it to spread while also storing moisture and starch.

Sea-beach amaranth has a fascinating story of its own. It was first noted in the early 1800s on since-submerged Tucker’s Island, and was later recognized as an important part of beach ecology from New England to the Carolinas.

But despite being hardy enough to withstand coastal living, sea-beach amaranth is very sensitive to habitat disturbance by people. By 1913, it was gone from New Jersey and declining everywhere.

Interesting, then, that it was Monmouth County where the species reappeared. In 2000, it was found on newly replenished beaches in Sea Girt, and has since popped up on Sandy Hook, too.

The grasses in genus Ammophila – Marram grass, bentgrass and beach grass – are good examples of species that follow the pioneers, and are typical inhabitants of the dunes we’re used to seeing on our shores. 

These grasses send down stabilizing roots, which anchor the plant and the dune itself – the deep-growing roots help hold the sand in place. Ammophila species also have the ability to roll up their leaves when the air is full of salt spray, protecting their precious moisture.

Where to find it: New Jersey’s beaches are highly developed, and in many areas, the dunes have given way to boardwalks. But there are still beautiful stretches of dunes in their near-natural state. 

Sandy Hook’s beaches are a great example – there, you can see deep dunes in several stages of succession.

At Barnegat Lighthouse State Park on LBI’s north end, the relatively recent construction of a jetty has led to the buildup of sand. Park at 9th, 8th or 6th Street there and you can walk a sand path through nearly 2,000 feet of diverse beachfront habitat, including dunes.

Why bother: The Jersey Shore is famously overbuilt. People have made our beaches a summertime destination for generation after generation, and as a result, there are few stretches of oceanfront land that haven’t seen development.

In many places, the foredune is the last remaining vestige of natural maritime environment. We have good reasons to protect them. Without that ridge of sand, our coastal communities are far more vulnerable to storm damage and the natural shifting of sand by the tides. You could say that the hardy plant species that hold the dunes in place are responsible for making possible much of what we love about the Shore.

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