How to understand the changing shape of our fragile coastal landscape.

Photo by Terry Pommett

Photo by Terry Pommett

Erosion has been unkind to Cape Cod and the Islands. Over the last seven years, we have witnessed houses swept off beaches or left teetering on the edge of cliffs. On Nantucket, Sankaty Head Lighthouse and the old ‘Sconset summer homes had to be moved back from the edge of eroding hundred-foot bluffs. By 2008, Chatham was losing 10 feet off the end of North Beach every day when the inlet migrated north. North Beach Island eroded at the rate of 80 feet a year, threatening a dozen camps owned by private homeowners and the Cape Cod National Seashore. The east side of Martha’s Vineyard lost about a foot of beach every day and a troublesome new break opened into Katama Bay, disrupting the Chappaquiddick ferry on the Vineyard.

Then, in November of last year, it seemed as if someone had flipped a switch. The weather turned unseasonably mild, temperatures rose above 60 degrees, and lilacs and forsythia started blooming in December. Snowy owls started appearing frequently on Cape Cod. There was no snow, few storms, and, compared to previous years, little erosion.

And here is the irony: Scientists can predict that Cape Cod is going to wash away in about 5,000 years, that the Cape will lose about a thousand acres to erosion in 200 years, and when we should expect a hundred-year storm, but they can’t tell a homeowner if he can stay in his barrier beach camp for another season or if it makes sense to build a seawall to protect his oceanfront house for another 20 years.

This is because erosion doesn’t proceed in a nice linear fashion according to sea level rise. The pattern is different: seven-year stretches of severe erosion follow seven-year stretches of mild erosion. And we saw this global process shift dramatically at the end of 2011.