A new vision of West Coast estuaries — and their losses

By Laura Brophy, Estuary Technical Group Director, March 2018

In October 2017, ETG Director Laura Brophy and collaborators at the Pacific Marine and Estuarine Fish Habitat Partnership (PMEP) finished new maps of current and historical tidal wetlands for the entire U.S. West Coast. The mapping methods -- originally developed by ETG in collaboration with Oregon's Coastal Management Program -- use LIDAR data (ground elevations) and water level models from NOAA. These methods provide a much more accurate picture of the original extent of our estuaries, compared to past maps. This groundbreaking work places PMEP, as well as the Institute for Applied Ecology, in a national leadership role for estuarine resource management.

With these new maps in hand, the PMEP team then created a comprehensive analysis of tidal wetland losses on the West Coast. Across 55 of the largest West Coast estuaries – which contain 97% of West Coast historic tidal wetland area -- 85% of tidal wetlands have been lost, totaling over 300,000 hectares. This shows the huge impact people have had on our coastal resources over the last century.

Tidal wetland losses have accrued over time as a result of human activities. Many tidal wetlands were diked beginning in the early 1900s, and development has continued since then. Until now, no one knew the magnitude of losses of these valued ecosystems across the West Coast. 

Map showing retained (green) versus lost (tan) tidal wetlands in the Nestucca Bay Estuary

Bar chart showing retained (green) versus lost (tan) tidal wetlands in the Nestucca Bay Estuary

Vicinity map for the Nestucca Bay Estuary

These tidal wetlands provide many valued ecosystem services. They serve to reduce flooding, and even reduce global warming by storing carbon in their soils ("blue carbon"). They filter water and provide hunting, fishing, and recreation areas for people. They are also home to a diverse array of creatures that depend on these wetlands to support their growth and reproduction. Salmon and other fish and shellfish need the deep, narrow channels in tidal wetlands for shelter from predators and from rapid river flows. Young salmon especially depend on tidal wetlands as a safe and rich environment to feed, grow, and adjust to ocean salinity during their migration to the sea. Birds - from ducks and geese to sandpipers and snipe - feed on the abundant invertebrate life in tidal wetlands, and mammals like raccoons, elk, deer, and bear find these wetlands provide bountiful food sources including fish, shellfish, succulent plants, and dense stands of grass and sedge.

With the new, accurate maps created by IAE and PMEP, we now have an expanded vision of our estuaries, past and present. The maps give us solid, useful information on our estuaries' historical extent and how it has changed due to human activities. With this important information, we can now do a better job planning for protection of the remaining tidal wetlands - and restoration of those wetlands that have been lost - to help the people, fish and wildlife that depend on them. To bring back these treasured habitats, IAE works with many other groups on tidal wetland restoration projects across the Pacific Northwest. We’ve helped restore thousands of acres and measure the results, building back our legacy of tidal wetlands for future generations.

Laura Brophy surveys tidal channels in high marsh, Siletz River estuary of Oregon

Tide gauge and salinity logger installation: Goose Point

Measuring soil accretion in a tidal wetland

Tidal wetlands provide many recreational opportunities.

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