By Dr. Robert Thorson
Nourishing beaches with sand to keep the tourists happy is like nourishing your body with food. It’s a temporary fix. Before you know it, the ocean is hungry again.
And the ocean has been particularly hungry this year. Four powerful nor’easters slammed the New England coast this winter. Waves exceeded 40 feet, communities were flooded, sea walls crumbled, clam shacks were destroyed and beaches were stripped of so much sand that once-buried shipwrecks appeared on the Maine coast. Two of these storms caused the highest and third-highest tidal surges in Boston since good record-keeping began in 1825.
During the past century, wave power was intensified by planetary warming. Local sea levels are rising faster than expected, due to irreversible meltdown of the Greenland and West Antarctic ice sheets and to downward flexing of the Earth’s crust.
Within the next few thousand years, interglacial sea levels will likely rise 15 to 20 feet above present heights. New England’s strong, rocky mainland will survive, but much of Cape Cod and the Islands will disappear, one storm-bite at a time. This “inevitable loss of this fragile land to the sea” was predicted decades ago by Robert Oldale, a highly respected U.S. Geological Survey geologist and former colleague.
His prediction was for Sarah Dinwoodey, a then ninth-grade student who had asked him what the future would bring. Oldale’s response began with before-and-after photographs of Billingsgate Island, the so-called “Atlantis” of Cape Cod.
When the Pilgrims arrived in 1620, they saw a peninsula extending southward into Cape Cod Bay from the mainland west of Wellfleet. Thanks to storm erosion, that peninsula became a 60-acre island supporting a 30-house community of fishermen and whalers. By 1855, the island had been cut in half and the original lighthouse destroyed. A higher, stronger, replacement lighthouse was built of bricks, supported by massive granite stones and armored by 1,000 feet of sea wall.
That, too, was gobbled up one storm at a time until 1915, when the entire island disappeared. Today, ruins decorate a sandy shoal.
The story of Billingsgate Island at the century scale is a microcosm for the story of Cape Cod during the past few thousand years and for the next few thousand to come. The basic story is simple. Rising seas cause coastal erosion, which provides sand for beaches, which grow and shrink as they are reshaped by currents before being inevitably lost to the sea. Oldale correctly put a positive spin on shoreline erosion: “Sand is the very life blood of Cape Cod. How then, can we consider erosion, the process that supplies this sand, anything but a benefit to the Cape?”
Private and municipal landowners plug their ears to this inconvenient truth. Logically and legally, they armor their shores against coastal erosion. The barriers they erect capture sand as the current flows past and starve down-drift beaches of sand. Unhappy tourists, tourist-dependent-businesses and interior residents then complain to municipal officials, as they did last year in Chatham, Mass. Last November, the town responded by appropriating $750,000 to dredge 50,000 cubic yards of offshore sand and haul it back up to the public beaches at Cockle Cove and Harding Beach. This is enough wet sand to bury Cape Cod’s entire, year-round human population of about 200,000 residents twice over.
I’m OK with armoring and nourishing managed beaches in the short term as a compromise between private and public property rights. But as storms get stronger and as sea levels higher, beach nourishment is a progressively losing strategy. Given the severe erosion associated with this year’s back-to-back-to-back-to-back-to-back-to- back nor’easters, I wonder if Chatham will move ahead with its plans.
If the Cape were to become a national park, I would advocate removing all coastal defenses against erosion. The resulting beaches might become as wildly beautiful as when described in Henry Thoreau’s book “Cape Cod” (1862) and Henry Beston’s “Outermost House” (1928), relative to Robert Finch’s “The Outer Beach” (2017). The earlier books describe larger, more magnificent beaches than the ones we see today.
Sometime in the distant future, the Bay State will lose its outer Cape, and thus its namesake bay. Though I’m already grieving the human losses, I’m comforted by knowing that this is just the way the geological cookie crumbles.