Here’s How Software Could Save Salt Marshes

Time may be running out for some coastal cities ... While sea level rise is squeezing salt marshes against higher, drier land and human infrastructure, it is likewise moving in on some oceanside neighborhoods.

But sea-level modeling tools hold hope for both.  By providing concrete pictures of what coastlines will look like under various climate change scenarios, the models are helping planners identify strategies for protecting saltmarsh habitat while managing existing coastal infrastructure and future development.

Coastal salt marshes — communities of plants and animals defined by the coming and going of ocean tides — form on sediment dropped from slowing river waters and incoming tides.  They provide a transition between dry land and ocean, protecting the coast from erosion, providing a home to a rich abundance of plant and animal life, filtering nutrients and other pollutants from runoff, and offering that critical band of Goldilocks habitat for the saltmarsh sparrow and other species that call the marshes home.

The maps give communities information they can use to not only plan for future urban infrastructure, but also make room within that infrastructure for saltmarsh habitat.  For thousands of years coastal marshes have kept pace with gradually rising oceans, growing vertically or retreating inland.  But the world has changed; the rate of sea level rise has doubled on the Northeast U.S. coastline since 1990, dams keep fresh sediment loads from the coast, and human structures such as roads and sea walls block inland migration.  As a result, those who seek to protect these unique ecosystems and the services they provide are looking for ways to help them overcome obstacles to migrating inland.

One promising approach involves cooperation between conservationists and city and state planners.  Using a coastal mapping tool originally developed for the U.S. Environmental Protection Agency called the Sea Level Affecting Marshes Model, or SLAMM, federal and state agencies and conservation organizations create maps showing where high tide will be as sea level rise increases.  The maps give communities information they can use to not only plan for future urban infrastructure, but also make room within that infrastructure for saltmarsh habitat.
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Marc Carullo, environmental analyst for the Massachusetts Office of Coastal Zone Management, says some communities in his area are excited about the model’s potential to help them proactively plan for coastal changes.  Currently, salt marshes help protect homes along the coast by decreasing water speed and turbulence and diffusing incoming waves.  “If we have large expanses of salt marsh becoming tidal flat, we’re going to lose ecosystem services and that could play a big role in how exposed that homeowner is to storm surge,” he says.  The visualizations SLAMM provides, he says, will help motivate communities to protect salt marshes and the services they provide.

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