Marshes to Mudflats: Climate Change Effects Along Coastal Estuaries in the Pacific Northwest

Over 50% of commercial and recreationally important fish species depend on coastal wetlands. In the Pacific Northwest, coastal wetlands, where the ocean meets the land, are highly productive areas that support a wealth of wildlife species from salmon to ducks. The tidal marshes, mudflats, and shallow bays of coastal estuaries link marine, freshwater, and terrestrial habitats and provide economic and recreational benefits to local communities. However, wetlands in this region and elsewhere are threatened by sea-level rise and other climate-related changes. According to a USFWS and NOAA report, between 2004 and 2009, 80,000 acres of wetland were lost on average each year, which is a significant increase from the previous six years.



While we know that these coastal ecosystems are already changing, we know comparatively less about how these areas might continue to change over the next 50 to 100 years. The goal of this project was to provide scientific information that will support long-term coastal planning and conservation efforts in the face of changing climate conditions. Researchers looked at the effects of sea-level rise on nine tidal marshes in Washington and Oregon. They compiled data on coastal terrain, tidal flooding, vegetation, and how quickly sediments accumulate, to assess how sea-level rise may alter these ecosystems in the future. Researchers found that factors such as elevation, sediments, and rate of sea-level rise can all affect marsh resilience. Importantly, researchers found that while most of the tidal marsh study sites will be able to persist in the face of sea-level rise over the next 50-70 years, sea-level rise could eventually outpace the growth of marshes and drown most high and mid-elevation marsh habitats by 2110.