Greenwich Beach

Most sand dunes are content to stay put, but the parabolic giants at Greenwich migrate inland at up to four metres per year, pushed by prevailing winds like slow-motion glaciers made of sand. These U-shaped behemoths, rare in North America, have been marching across this peninsula for millennia. To witness them, you traverse a 700-metre floating boardwalk over Bowley Pond, originally cedar, now polyethylene after the marsh claimed the first iteration in just two decades. The dunes, meanwhile, continue their patient conquest.

The original cedar boardwalk lasted twenty years before wind and salt spray took their toll, standard wear for wood sitting directly in tidal marsh. Its replacement, built from polyethylene, was chosen for durability rather than romance, though it does the same job: keeping hikers dry above cattails and red-winged blackbirds on the way to a dune system that has been doing this since long before anyone thought to build a walkway across it.