Glacial Rebound on Taashuyee (Mendenhall Wetlands)

Conserving wetlands and community access in Southeast Alaska through partnerships

Project supported by U.S. Fish and Wildlife Service and Southeast Alaska Land Trust

View of Mendenhall Wetlands

The Taayushee (Mendenhall Wetlands) are located in Juneau, Alaska. Juneau is home to the state capital and the largest city in southeast Alaska. The prominent features of this landscape include the Woosh eelʼóox̱ʼu héen, river that’s murky together (Mendenhall River) and Taashuyee, river- tide- or mudflats (Mendenhall Wetlands). The Alaska Department of Fish and Game (ADFG) manages these wetlands as part of the Mendenhall Wetlands State Game Refuge.

Ancestral Lands

Taashuyee, river- tide- or mudflats (Mendenhall Wetlands) are the ancestral lands of the Tlingit people, who lived in harmony with these lands for generations, and continue to steward them. The Tlingit are comprised of about 20 kwáan territories extending from Yakutat to Ketchikan. Áak’w Kwáan claims Taashuyee.

Unlike European place names mostly commemorating people, Lingít place names tell stories. How appropriate, then, for these names to usher-in our StoryMap.

Map of Juneau area with Lingit names.

Taashuyee (Mendenhall Wetlands)

Taashuyee (Mendenhall Wetlands)

The Taashuyee (Mendenhall Wetlands) are important beyond measure. Much of the wetland habitat on which many species depend on has been lost on a global scale. This means that these existing wetlands are critical for thousands of shorebirds and other wildlife as these wetlands are one of the few places that provide the necessary food and habitat that these animals need. Taashuyee are also a treasured recreation area for Juneau residents and visitors. Centrally located in the capital city, the Wetlands are a popular place for hiking, birding, hunting, and taking in the views.

Views across the Mendenhall Wetlands from the Marjory and Edgar Huizer Fishing Access Site on Douglas Island at high and low tides.

Due to their high ecological value, these wetlands have been designated as a globally recognized Important Bird Area by the National Audubon Society. The Refuge was created to preserve the highly productive estuarine wetlands and freshwater marshes, supporting large numbers of both migrating and resident bird populations.

A variety of birds that can be found on the Tayushee Mendenhall Wetlands.

Tour the Refuge

Home to countless species, culturally significant, and popular for recreation, take a tour of the Refuge and the unique wetlands within its boundaries.

Wigeon Ponds

These are lovely, naturally formed ponds near today’s extreme high tide. Wonderful habitat for geese, dabbling ducks, shorebirds, shorebirds, and western toads. During spring migration, Wigeon Ponds are one of the most exciting birder-destinations on Taashuyee. Wigeon Ponds are conserved by the Southeast Alaska Land Trust.

Fish Creek

Upper and Lower Fish Creek Estuaries provide important habitat for numerous duck species. During low tides, they will feed in the lower estuary and then travel to the upper estuary at high tides.

Airport Dike Trail

Used daily by walkers and nature enthusiasts, this security access doubles as our region’s most popular birding destination. From here, except on highest tides, forays launch southward into Taashuyee, the tideflats. Or, right from the trail, birders scan for resident and migrant birds at Otter Pond, Phalarope Slough, and Junk Car Slough.

Mouth of Woosh eelʼóox̱ʼu héen (Mendenhall River)

The mouth of Woosh eelʼóox̱ʼu héen (Mendenhall River) is one of the most important feeding locations for ducks and shorebirds on the wetlands. Observers have counted hundreds of birds especially in spring and fall migration.

Estuary of Til’héeni (Salmon Creek)

The estuary of Til’héeni, dog salmon stream, (Salmon Creek) is important for ducks, shorebirds and gulls. Gulls will dip for salmon eggs and feed on invertebrates in the rockweed. Bald Eagles also are found here, often feeding on salmon carcasses.

Spoil Islands

Spoil islands have been created by channel dredging throughout the area. On the plus side, they increase habitat diversity. On the minus side, along with dikes and other constructions, spoil islands impede tidal erosion. This has hastened the uplift of tidal lands above the influence of the tides.

Honsinger Wetlands

The Honsinger Wetlands conservation property is adjacent to the Mendenhall Wetlands State Game Refuge and the Miller-Honsinger dredge pond. The Honsinger Wetlands are conserved by the Southeast Alaska Land Trust and are an extension of the Mendenhall Wetlands.

Wigeon Ponds

These are lovely, naturally formed ponds near today’s extreme high tide. Wonderful habitat for geese, dabbling ducks, shorebirds, shorebirds, and western toads. During spring migration, Wigeon Ponds are one of the most exciting birder-destinations on Taashuyee. Wigeon Ponds are conserved by the Southeast Alaska Land Trust.

Fish Creek

Upper and Lower Fish Creek Estuaries provide important habitat for numerous duck species. During low tides, they will feed in the lower estuary and then travel to the upper estuary at high tides.

Airport Dike Trail

Used daily by walkers and nature enthusiasts, this security access doubles as our region’s most popular birding destination. From here, except on highest tides, forays launch southward into Taashuyee, the tideflats. Or, right from the trail, birders scan for resident and migrant birds at Otter Pond, Phalarope Slough, and Junk Car Slough.

Mouth of Woosh eelʼóox̱ʼu héen (Mendenhall River)

The mouth of Woosh eelʼóox̱ʼu héen (Mendenhall River) is one of the most important feeding locations for ducks and shorebirds on the wetlands. Observers have counted hundreds of birds especially in spring and fall migration.

Estuary of Til’héeni (Salmon Creek)

The estuary of Til’héeni, dog salmon stream, (Salmon Creek) is important for ducks, shorebirds and gulls. Gulls will dip for salmon eggs and feed on invertebrates in the rockweed. Bald Eagles also are found here, often feeding on salmon carcasses.

Spoil Islands

Spoil islands have been created by channel dredging throughout the area. On the plus side, they increase habitat diversity. On the minus side, along with dikes and other constructions, spoil islands impede tidal erosion. This has hastened the uplift of tidal lands above the influence of the tides.

Honsinger Wetlands

The Honsinger Wetlands conservation property is adjacent to the Mendenhall Wetlands State Game Refuge and the Miller-Honsinger dredge pond. The Honsinger Wetlands are conserved by the Southeast Alaska Land Trust and are an extension of the Mendenhall Wetlands.

What Makes Them Unique?

Not only are these wetlands of cultural, ecological, and recreational importance, they are also undergoing a unique geological process known as glacial rebound. Glacial rebound, also known as isostatic rebound, occurs where lands that had been weighted down by glaciers are expanding upwards and rapidly gaining in elevation as glaciers retreat. In the case of Taashuyee, Áak'w Kwáan Sít'i, Áak'w peoples' glacier (Mendenhall Glacier) is shrinking. The earth is now rebounding, like how a couch cushion that has been sat on regains its shape after a person stands up.

While sea invades land elsewhere worldwide, the opposite occurs here; land is advancing seaward.

Glacial Rebound

Glacial (or isostatic) rebound is measured using a term called uplift rate. Uplift rate is a measure of how much elevation an area gains each year. The uplift rates in Southeast Alaska are the fastest in the world and in Áak’w Aaní (Juneau area) they range from 0.33 inches per year to upwards of 0.50 inches per year.

The contours on this map show uplift in inches per year, based on Larsen et al (2005). Green dots mark the largest estuaries and uplift-meadow complexes (Carstensen, Armstrong and O'Clair 2014).

Uplift Rate

The area adjacent to the Woosh eelʼóox̱ʼu héen, Mendenhall River is experiencing approximately 0.5 inches of uplift per year. The area in red could move above the extreme high water line in the next 24 years (Carstensen 2021).

On Taashuyee (Mendenhall tidal flats), portions of the area are rising faster than sea level. Scientists can look at clues like old growth vegetation and identify the historic high tide line compared with where it is now and it has changed over 10 feet. Measurements indicate the uplift here is creating the equivalent of 8 acres per year of lands that are no longer covered by water at high tide (Carstensen & Pohl, 2021).

A Changing Landscape

The wetlands in the Taashuyee (Mendenhall tidal flats) are defined by the Extreme High Water Line. Many of these wetlands are well drained and only retain moisture due to the water coverage from extreme high tides. Once the uplift has moved them out of the tidal zone, they quickly transition into upland environments.

To see how this site has changed over time, click through this 6-part series of historical imagery centered over today’s airport.

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Changes in elevation cause shifts in vegetation and landscape characteristics. The intertidal zone is characterized by low marsh sedges that are regularly covered with water at high tides. Located just above the sedges are high marsh grasses that are only covered with water at extreme high tide events. The marshes are considered wetlands. Located at a higher elevation than the marshes are uplift meadows and spruce. Depending on soil composition and drainage, they may remain wetland or transition to upland habitat.

Below is an example of a typical Taashuyee uplift series showing changes in tree heights and shapes. This series is based on a 2013 LiDAR point cloud that shows vegetation structure in profile. As land rose, and highest tides dropped from 32- to 28- to today’s 21 feet, each vegetation belt advanced seaward.

Conserving Uplifted Lands

Land within the Refuge that is tidally influenced up to the mean high-tide level, is managed by the Alaska Department of Fish and Game (ADF&G) for its unique recreational and wildlife values. As post-glacial rebound lifts the outer edges of the Refuge beyond the reach of the tides, the Refuge boundary shrinks. When glacial rebound lifts this new land above the high tide line, landowners adjacent to the Refuge can go through a legal process to claim this new land as a part of their property. To ensure that these uplifted lands remain in their natural condition for habitat and recreation, the Southeast Alaska Land Trust (SEALT) sought partnerships with interested landowners through the Accreted Lands Project.

Conservation Partnerships

The Southeast Alaska Land Trust

The Southeast Alaska Land Trust works with willing landowners to conserve these unique, uplifted lands through conservation easements and land purchases. By partnering with landowners, the land trust seeks to ensure that these lands remain in their natural condition for habitat and recreation and to preserve the Refuge boundary. Since 2002, SEALT has been working with owners of accreted land adjacent to the Mendenhall Wetlands State Game Refuge (Refuge), in Juneau, to expand upon the established conservation area of the Refuge, maintain public access for recreational opportunities, safeguard important habitat for fish, birds, and other wildlife, and to preserve the Refuge boundary.

This map shows SEALT properties in and around the Refuge boundary. Total acreage of properties is 89.97 acres.

U.S. Fish and Wildlife Service

Through the  Coastal Program , the  U.S. Fish & Wildlife Service  (Service) partners with SEALT to conserve uplifted land adjacent to the Mendenhall Wetlands. SEALT’s long-standing partnership with the Coastal Program supports the goals of both SEALT and the Service through the conservation of valuable habitat and recreation opportunities for both wildlife and the public. 

The Coastal Program is one of the Service’s most effective resources for restoring and protecting fish and wildlife habitat on public and privately-owned lands. In Alaska, the Coastal Program focuses on the conservation and restoration of aquatic habitat and habitat connectivity for the benefit of federal trust species with a focus on Pacific salmon.

Alaska Department of Fish & Game

The  Alaska Department of Fish and Game  (ADFG) manages the Mendenhall Wetlands State Game Refuge for the protection of natural habitat and game populations, especially waterfowl, as well as to provide recreation. ADFG and SEALT have worked collaboratively to protect uplifted lands adjacent to the Refuge. 

"SEALT’s active perusal and purchase of uplifted lands helps to ensure that available parcels are identified, purchased and held in conservation for public use. SEALT has given lands to the state of Alaska which are currently available for public use and will eventually be incorporated into the Refuge." - Greg Albrecht, ADFG Habitat Biologist

Landowner Involvement

Wetland enthusiast Frank Rue lives on a parcel adjacent to the Refuge. When he found out his land was undergoing glacial rebound he worked closely with SEALT to be part of the uplifted lands project. He did this to ensure that the land was protected and reincorporated into the Refuge.

In this video, Frank sat down with USFWS’s Christy Cincotta and Kris Pacheco to share the story of why he got involved.  

Interview with landowner Frank Rue

The Work Continues

As Taayushee (Mendenhall Wetlands) change, the work continues to protect and preserve these lands for future generations through stewardship, management, and partnerships.

Special Thanks

Thank you to the tremendous assistance we received from Discovery Southeast naturalist Richard Carstensen; Krista Garrett, Amanda Pilley and staff at the Southeast Alaska Land Trust and landowner Frank Rue.

Gunalchéesh, for help with  Lingít place names,  to X̱'unei, Lance Twitchell, University of Alaska Southeast.

Richard Carstensen,  Juneau Nature 

Suggested Reading:

Credits

U.S. Fish and Wildlife Service

Wildlife Conservation