The red comes from iron oxide in the sandstone, laid down in sediments roughly 250 million years ago when this part of the world was a semi-arid plain. Glaciers carved the coastline into its present form, and now the sea continues the work. Winter storms drive waves against the soft cliffs with enough force to undercut them, sending slabs of red rock crashing to the beach below. The park experiences severe coastal erosion -- the shoreline retreats measurably each year, and the cliffs that look permanent from a summer beach blanket are anything but. This is a landscape actively remaking itself, the red sand redistributed by currents into the beaches and dunes that define the park's character. At Greenwich, on the park's eastern extension added in 1998, parabolic dunes -- U-shaped formations pushed inland by prevailing winds -- rank among the most distinctive dune systems in North America.

In late spring, sections of the park's beaches close to human traffic. Rope barriers go up, signs warn of fines, and Parks Canada staff patrol the perimeters. The reason weighs less than two ounces: the piping plover, a small shorebird the color of dry sand that nests directly on the beach in shallow scrapes. Fewer than 8,000 piping plovers remain in the world, and PEI National Park is one of their critical nesting habitats, designated as a Canadian Important Bird Area. The plovers are nearly invisible against the sand -- their camouflage is exquisite, which is precisely the problem. Beachgoers can step on a nest without ever seeing it. Beyond the plovers, the park supports over 300 species of birds, from great blue herons stalking the wetlands to bald eagles circling the cliffs, and mammals including red foxes, coyotes, beavers, and mink moving through the marshes and forests behind the dunes.

Green Gables Heritage Place sits within the park's boundaries, and the literary connection runs deeper than a single farmhouse. Montgomery grew up in Cavendish, surrounded by the landscapes the park now protects -- the red-cliffed beaches, the birch-lined lanes, the ponds she renamed with a novelist's flair. The Lake of Shining Waters, Lovers' Lane, the Haunted Wood: these are real places within or adjacent to the park, and visitors walk them today on maintained trails that follow the routes Montgomery knew as a girl in the 1880s and 1890s. Cavendish Beach, the park's most popular stretch of sand, draws crowds in summer who come for the swimming and stay for the views -- the red cliffs rising on either side, the dunes rolling behind, and the Gulf stretching north toward a horizon that looks like the edge of the world.

The tension at the heart of PEI National Park is the tension between preservation and disappearance. The coastline the park was created to protect is eroding. Climate change intensifies winter storms, and rising sea levels accelerate the process. The dunes that shelter the wetlands behind them are fragile -- a single breach can flood a freshwater pond with saltwater, transforming its ecology overnight. Parks Canada manages this with a light touch: boardwalks keep feet off the dunes, beach closures protect nesting birds, and the interpretive programs emphasize the dynamic nature of the coast rather than pretending it is static. Part of the Jezero crater on Mars was informally named after the park -- an unlikely tribute, but perhaps a fitting one. Both landscapes are shaped by forces larger than human intervention, beautiful precisely because they are unfinished.