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Port Susan Bay holds some of the finest estuarine habitat in Puget Sound. The Stillaguamish River spills into the bay, mixing freshwater and saltwater to create extensive estuarine marshes.

The marshes support abundant invertebrate life which, in turn, feed hundreds of thousands of shorebirds, including dunlins, western sandpipers, and Wrangel Island snow geese. Port Susan Bay and adjacent Skagit Bay are important stops for migratory birds traveling along the Pacific Flyway.

Port Susan Bay also faces challenges. Levees along the Stillaguamish River have disconnected it from floodplain wetlands which used to moderate river flows to the estuary by storing winter rainwater and releasing it slowly over the course of the year.

A sea dike, built in the 1950s to create more farmland, directs much of the river and its sediment load away from the historic estuary, leading to erosion of the tidal marsh. And now, our changing global climate brings new threats to the estuary.

Roger Fuller, an estuarine ecologist for the Conservancy, talks about using Port Susan Bay as a laboratory for studying climate change.

Nature.org:

Roger Fuller:

After the Conservancy bought the preserve, we did a general habitat survey and map, and looked at historical photos to see how the estuary is changing. It has become clear that it’s not static, and it appears to be declining in productivity and value for most of the animal and plant species that thrive there. For example, the tidal marsh zone, which is sort of like the "bread basket" for the whole estuary ecosystem, has been gradually disappearing.

Nature.org:

Roger Fuller:

Well, of course we humans have had the biggest impact by converting natural habitat to other land uses and changing some of the key processes that feed the estuary. But, one of the factors we knew was out there was climate change. That’s also what we had the least information and knowledge about. That led us to develop a project to evaluate how climate change is affecting the estuary. A lot of the big questions have to do with the interplay of climate change effects?how does sea-level rise interact with changes in river flow; how does increased storm intensity interact with sea-level rise. We also wanted to look at how these changes will interact with existing human constraints like the dike system. The dike system changes where fresh water and sediment go, how long fresh water spends in the estuary, how much large wood is in the estuary, what kind and how much habitat is possible. And, obviously, dikes prevent habitats from moving inland as seas rise. All those things affect the resiliency and health of the estuary, and its ability to adapt to a changing climate.

Nature.org:

Roger Fuller:

I think that we are in for some really big challenges, that we have the ability to respond to those challenges and adapt what we do on the ground to make systems like these estuaries resilient to those changes. But that’ll require some big changes in how we as society choose to use and take care of the lands and waters on which we depend, and perhaps the biggest challenge ahead will be whether we have the political will and social adaptability to make those changes.