Tim Johnson

MA - New Maps Track Receding Wetlands on Island

Some 3,500 acres of salt marshes on Martha's Vineyard serve as natural storm buffers and support vital ecosystems.

By the year 2070, salt marshes on Martha’s Vineyard are expected to decrease by nearly 200 acres as sea levels rise, forcing shorelines and floodplains inland and threatening homes and vital ecosystems that have existed for generations.

That’s roughly the equivalent of losing half of East Chop — or six Camp Grounds worth of gingerbread cottages.

The Martha’s Vineyard Commission has been working with the state Coastal Zone Management (CZM) agency to map the expected changes at locations across the Island — from Squibnocket Pond to Sunset Lake — so Vineyarders can better visualize and understand the impacts of wetland migration in their own backyards.

Using data from CZM’s Sea Level Affecting Marsh Migration (SLAMM) model, commission special projects planner Dan Doyle and cartographer Chris Seidel have put together about a half-dozen story maps through GIS technology that illustrate how the Island’s wetlands are expected to evolve and migrate inland over the next 50 years.

The maps, now available online and made possible by a 2019 Edey Foundation grant, paint a picture of an Island with 125 miles of rapidly-changing shoreline and coastal ecosystems that will be transformed as marshlands recede and regularly flooded wetlands take their place, testing crucial services and infrastructure such as the Martha’s Vineyard Hospital and Dukes County avenue, among others.

The SLAMM model bases its predictions on an expected 4.5-foot linear increase in sea levels over the next 80 years. Although it does not account for existing infrastructure, it does use existing topographic conditions, including current ecosystems and shorelines, to assess habitat change.

Read more.