Windswept Bog Wetland Restoration Project

Since 2019, NCF's Department of Ecological Research, Stewardship and Restoration has been working with the Massachusetts Division of Ecological Restoration’s Cranberry Bog Program (DER) to plan a watershed-level wetland restoration project for its Windswept Bog property, located off Polpis Road in the northeastern portion of the island. Years of research, monitoring, engineering plan development, permitting, and grant writing came together in January 2024 when Phase 1 of the project initiated construction. NCF is extremely grateful to our project team members who worked so hard to get us to this stage: Jessica Cohn from DER and Michael Soares and Dr. Julianne Busa from Fuss & O’Neill, Inc. engineers. This project is funded by DER and generous grants from the Southern New England Estuary Program (SNEP) Watershed Implementation Program, the Richard K. Mellon Foundation, and the U.S. Fish & Wildlife Service National Coastal Wetlands Conservation Grant Program.

NCF contracted with SumCo Eco-Contracting, a firm that specializes in ecological and environmental improvement projects with experience restoring wetlands at other retired cranberry bogs elsewhere in Massachusetts, to accomplish the restoration construction work. The Windswept project is scheduled to take place over 2 years, with construction activities happening only during the winter dormant season (from November to mid-March) to avoid impacting rare plants, nesting birds and breeding wildlife on the property.

Phase 1 construction began in January 2024 and was completed in March 2024, with ~14.0 acres of former cranberry bog cells restored to hydrologically connected wetlands. Restoration of the remaining bog cells (~26.2 acres) began in November 2024 and will be completed by mid-March 2025. While the property is closed to the public during construction, visitors will be able to view the restored wetlands as they become re-vegetated over the coming growing season via walking trails and boardwalks once the site is re-opened.

Upon completion, this project will set a trajectory for natural recovery of ~40 total acres of retired cranberry bogs to diverse wetland habitats that enhance refugia for inland wildlife species, provide ecosystem services such as water quality improvement and flood storage, and increase coastal resilience by creating a pathway for eventual salt marsh migration.

Project Background

Windswept Bog, owned by Nantucket Conservation Foundation, Inc. (NCF), is located on Polpis Road in the northeastern portion of Nantucket Island, Massachusetts. Constructed and cultivated as a cranberry bog in the 1920’s, NCF acquired the property in 1980 and continued to operate the cranberry farm until 2018, with organic certification received in 2004. 

In 2019, NCF’s Board of Trustees decided to retire cranberry cultivation at Windswept Bog in order to pursue a watershed level wetland restoration project. The 231-acre property, which is contiguous with several thousand acres of protected conservation land in the Middle and Eastern Moors, contains 40 acres of former cranberry bog and 111 acres of natural wetlands. The site contains a popular trail system, which connects to a larger network around Stump Pond and into the Middle Moors.

The decision to abandon cranberry cultivation was based on two important factors: the many economic and climate-change related challenges facing this industry across the northeast and concerns about downstream water quality and nutrient loading within Polpis and Nantucket Harbor from the bogs and larger surrounding neighborhood. This restoration project does not include the Foundation’s Milestone Cranberry Bog operation, which is still being actively farmed for cranberries.

The Foundation’s Department of Ecological Research, Stewardship and Restoration worked with staff from the DER and Fuss & O’Neill to develop wetland restoration plans for the former bogs and surrounding areas at Windswept. Through its Cranberry Bog Program, MassDER works with local, state, and federal partners to provide technical services (such as engineering, design work, permitting and construction assistance), small grants, and project management and fundraising help to landowners interested in restoring wetlands on retired cranberry bogs. The Windswept Bog Wetland Restoration was selected as a Priority Project in 2020 by DER’s Cranberry Bog Program.

The former cranberry farm at Windswept Bog was divided into fourteen discrete bogs ranging in size from 0.7 to 8.4 acres. Each bog was separated by a 2- to 6-foot-high berm with water control structures built in to manage water levels for cranberry production. Primary legacy impacts on former cranberry farms such as Windswept include: (1) a sand fill layer placed over native wetland soils, (2) lateral and perimeter ditching, berms, and water control structures, and (3) physical simplification including channel straightening. The cumulative effect of these alterations was altered hydrology, dry soils in the upper bog platform, and a trajectory toward more upland plant species over time.

Project Goals

The overall goals for this project include restoring wetland flow and connectivity, creating natural gradients between restored wetlands and surrounding uplands, maintaining or establishing valuable plant and wildlife habitats, perpetuating and enhancing public access, use and enjoyment of the Windswept Bog property, educating the public about the importance of restoration work, maintaining Stump Pond (a unique but human-made wetland created to serve as a reservoir for the cranberry operation back in the early 1900’s), and maximizing the restored wetland’s ability to filter excess nutrients to improve water quality in Polpis and Nantucket Harbors.

Since the early stages of this project, the Foundation’s ecology staff have been collecting information on pre, during, and post-restoration site conditions. This includes capturing and tagging spotted turtles on the property and tracking their movement patterns via radio telemetry, conducting water quality monitoring at multiple sites around the wetland, creating a comprehensive species list of plants on the property to document native, rare, unusual or invasive species, and conducting vegetation monitoring along transects and within plots to document plant community changes. Data loggers installed at numerous locations across the property provide understanding of changes to how surface water and groundwater flows through the site. Working with DER and Fuss & O'Neill, all this information was incorporated into the project's restoration design plans to minimize environmental and rare species impacts to the greatest extent possible.

Summary of the Restoration Design

Key features of the restoration design for Windswept Bog involve the following:

• Complete or partial removal of most berms to allow natural surface flow across the site and to restore hydrologic connections between bogs and adjacent wetlands to the greatest extent possible.
• Removal of water control structures located between the retired cranberry bogs. During cranberry production, water control structures were used to precisely manage water for draining and irrigation purposes.
• Excavation in select areas of bog cells to lower the ground surface elevation and establish semi-permanent and seasonally flooded wetlands that support wetland and/or aquatic vegetation.
• “Roughening” the surface of selected sections of bog. For retired cranberry bogs, roughening is the physical action that breaks apart the existing mat of cranberry plants and the underlying sanded surface. The goal is to expose native seed bank and peat deposits, as well as create microtopography to improve habitat diversity.
• Modification of drainage ditches located between the retired cranberry bogs or water reservoirs. These artificial, incised channels were constructed to convey water between bogs and reservoirs for cranberry farming and are not representative of natural flow paths found on the island. Drainage ditches are being restored as diffuse, vegetated flow paths that mimic the natural surface flow conditions typical on Nantucket.
• Filling or plugging the lateral and perimeter ditches located within the retired cranberry bogs to create diffuse, vegetated flow paths.
• Construction of a new flow path between Stump Pond and the downstream bog on the eastern side of the property to replace the water control structures proposed for removal. A permanent spillway transition is being constructed to maintain an adequate water level in Stump Pond.
• Reconfiguration of the trail system and access roads to allow for continued public use and provide land management equipment and emergency vehicle access. Since portions of existing trails are currently located on berms that are being removed, the restoration design includes a revised trail system that seeks to maintain public access for passive recreational opportunities throughout the site. The revised layout includes crossing structures, such as bog bridges or boardwalks, constructed at key locations where berm sections are removed.

What Will It Look Like?

Based on post-restoration vegetation response observed after Phase 1 completion at Windswept and at similar completed cranberry bog wetland restoration projects in southeastern Massachusetts, the initial vegetation communities that rapidly establish from the seed bank are dominated by graminoids (grass-like vegetation including grasses, sedges, and rushes). Over a longer time period, shrubs and small trees may become established. Small pools of open water and slow flow paths that increase the amount of time that water moves from the east side of the property to the west will allow wetland plants to uptake excess nutrients prior to existing the property at Polpis Road and heading downstream to Polpis Harbor.

We are extremely grateful to our partners at Mass DER for technical expertise and funding provided to support this project since its inception. Generous funding has also been provided by the Southern New England Estuary Program (SNEP) Watershed Implementation Program, the Richard K. Mellon Foundation, and the U.S. Fish & Wildlife Service National Coastal Wetlands Conservation Grant Program.