Nantucket Barrier Beach and Wildlife Refuge: A New National Natural Landmark

Aerial view of the new Nantucket Barrier Beach and Wildlife Refuge NNL in Massachusetts.

Above Summit courtesy of The Trustees

The National Park Service is pleased to announce Nantucket Barrier Beach and Wildlife Refuge in Nantucket County, Massachusetts, has been named a National Natural Landmark (NNL). This special designation was made by Secretary of the Interior Deb Haaland and brings the total number of NNLs in the United States to 606.

Coatue's cuspate foreland (left shoreline) and cuspate spits (right shoreline).

Above Summit; courtesy of The Trustees

What Makes This Site Special

The Nantucket Barrier Beach and Wildlife Refuge is a unique coastal area that beautifully showcases two geological landforms: a world-class example of a rhythmic cuspate spit series and a large, well-developed, symmetrical cuspate foreland. The site, located on the northern extension of Nantucket Island 30 miles south of Cape Cod, is about 1,600 acres and is home to many different plants and animals.

Barrier Beach Forms Defined

Barrier beaches are made by waves, wind, and tides moving sand to form land that separates a small inland body of water (like a pond) from a larger one (like the ocean). 

Barrier spits are a type of long and narrow barrier beach that extends into the water from the mainland.  

Cuspate foreland refers to the curved part of a beach open to a large body of water (like the ocean) where there is no limitation to the distance traveled by wind and wave. 

Cuspate spits are curved projections of beach into an enclosed or semi-enclosed body of water where there is a limitation to the distance traveled by wind and waves.

Overview of some of the key geographic features at the new Nantucket Barrier Beach and Wildlife Refuge NNL site .

Google Earth

Formation of the Special Beach Forms

The barrier beach complex at the Nantucket Barrier Beach and Wildlife Refuge NNL formed over thousands of years, starting with deposits of glacial material some 23-24,000 years ago. As the ice melted and sea levels rose at the end of the last ice age, islands like Nantucket Island began to appear off the eastern shore of the US as areas of glacial deposits became separated from the mainland.

Sandy areas on the north side of Nantucket Island began to take shape as wind and wave action moved and deposited sand north/northwest, first connecting Nantucket Island to the 0.6-mile wide triangular Coskata Island. Sand movement and deposition continued north/northwest from Coskata building another 3.2-mile barrier spit out to Great Point.

A few thousand years ago as sea levels started to rise more slowly, sand moving south from Great Point began to form Coatue spit. This 6.5-mile barrier spit separates Nantucket Harbor from Nantucket Sound. These differing water body interfaces resulted in Coatue’s opposing shorelines being dramatically different from each other.

Coatue’s northwestern shore, open to Nantucket Sound where wind and wave action are not limited, is a long and sweeping cuspate foreland. Conversely, Coatue’s southeastern shore, constrained within Nantucket Harbor, features six curved sandy points that stick out into the harbor. When viewed from above, this series of concave sections of beach between these points resembles a serrated blade, like that of a bread knife.

While Coatue’s two opposing shorelines are both shaped by wind and wave action, there are three key coastal processes working together that specifically created and maintain the cuspate spit series on Coatue’s southeastern shore: 1) ample sand supply along a stable coast, 2) the harbor’s long axis alignment with seasonal wind and wave direction, and 3) a "Goldilocks" tidal amplitude – low enough to form barrier beaches, but high enough to erode spit tips. The cuspate spits within Nantucket Harbor are an interdependent, self-organized system in equilibrium. Thus, these three processes, in conjunction with the complex of barrier beach forms comprising the northern margin of Nantucket Island are vital. Loss or disruption of any of the supporting barrier beach features or processes will alter the appearance or existence of this rare coastal feature.

National Significance of Beach Forms

While the Nantucket Barrier Beach and Wildlife Refuge NNL is made up of a variety of barrier beach forms, the cuspate spit series is visually dramatic. This rhythmic series of symmetrical cuspate spits are easily the best organized and formed among any in the Atlantic Coastal Plain. They also persist in nearly pristine condition, maintaining their sweeping natural form. As the site is largely free from engineering and development, erosion and accretion along the shoreline are allowed to follow natural patterns and processes. And, cuspate spit series are globally rare!

Coatue’s cuspate foreland is another important feature. At nearly 6.5 miles in length, it represents the largest cuspate foreland in the Outer Lands portion of the Atlantic Coastal Plain. It is made further remarkable for its symmetry and continuity.

Dune and fringing marsh and Great Pond Lagoon.

N. Venti

A Home for Wildlife

This new NNL is not only geologically significant, the remarkable diversity of coastal features also provides vital habitat for many plant and animal species. Glacial outwash areas support old-growth oak forest, shoreline and beach deposits support eastern red cedar forests, ancient dune ridge uplands are vegetated with shrubs and tidal salt marshes, and even the sandy spits that jut out into Nantucket Harbor include saltwater tidal and brackish-water marshes.

Piping plover along the beach at Nantucket National Wildlife Refuge

Amanda Boyd/USFWS

This diversity of maritime plant communities and dune and beach complexes support rare plant species and provide rich uninterrupted habitat for a host of wildlife, including vital nesting sites for the piping plover, a federally listed threatened bird species.

Caretakers for this Special Place

All areas within the newly designated Nantucket Barrier Beach and Wildlife Refuge NNL are owned and managed by The Trustees of Reservations, Nantucket Conservation Foundation, and the U.S. Fish and Wildlife. These three organizations work collaboratively to manage and preserve the special natural features of this new NNL.

Diverse maritime ecosystems and beach and dune habitats adorn the Coatue spit with its sweeping shorelines.

Above Summit; courtesy of The Trustees

Why NNL Designation is Important

Nantucket Barrier Beach and Wildlife Refuge is a remarkable place that showcases the beauty and diversity of nature. This area is an outdoor laboratory where scientists can study natural coastal processes that are not found in many other places. It also provides a great opportunity for education about how barrier beaches form and function.

Designation as a National Natural Landmark provides recognition of its outstanding and significant features and encourages conservation efforts. This site joins hundreds of National Natural Landmarks located throughout the country that represent the Nation’s diverse biological and geological heritage.

Seals at Nantucket NWR.

Amanda Boyd/USFWS

Additional Resources to Learn More

Coskata-Coatue Wildlife Refuge, Nantucket, MA - The Trustees of Reservations

Coatue | Nantucket Conservation Foundation

Nantucket National Wildlife Refuge | U.S. Fish & Wildlife Service

Living Blue - Oceans, Coasts & Seashores (U.S. National Park Service)

National Natural Landmarks (U.S. National Park Service)

Special thanks to Dr. Nicholas L Venti, Certified Professional Geologist, who evaluated the site to determine national significance, and Drs. Christopher Hein, Virginia Institute of Marine Science, Robert Cook, Cape Cod National Seashore (retired), Zoe Hughes, Boston University, and Stephanie Stotts, University of Maryland Eastern Shore, who provided peer review.