The table below provides a summary of the general wetland types mapped by the National Wetlands Inventory for the Boston Harbor Islands. Most wetlands are of the marine or estuarine type; there are few freshwater wetlands.
Marine Intertidal Wetlands
Marine intertidal wetlands are the predominant coastal wetland type found in both the Outer Harbor Islands (Great Brewster Island, Middle Brewster Island, Outer Brewster Island, Calf Island, Little Calf Island, and Green Island) and along the eastern exposures of Deer Island and Lovells Island. These habitats are exposed to the waves and currents of the open ocean (Massachusetts Bay) with the water regimes being determined primarily by the ebb and flow of the tides. Classes of marine intertidal wetlands within the national park area include rocky shore, aquatic bed and unconsolidated marine intertidal wetlands.
Estuarine Intertidal Wetlands
Estuarine intertidal wetlands are the predominant wetland type in the shoreline habitats of the majority of the Inner Harbor, Quincy Bay and Hingham Harbor areas within the Boston Harbor Islands national park area. These include the shorelines of Bumpkin Island, Button Island, Gallops Island, Georges Island, Grape Island, Hangman Island, Long Island, Moon Island, Nut Island, Peddocks Island, Raccoon Island, Ragged Island, Rainsford Island, Sarah Island, Sheep Island, Slate Island, Spectacle Island, Thompson Island, and World’s End, as well as the western shores of both Deer Island and Lovells Island. Estuarine wetlands may also be found in low-lying areas adjacent to the shoreline which may be partially or fully enclosed by land, but have regular or sporadic access to tidally influenced harbor water. These habitats include low-lying regions on Thompson Island, Spectacle Island, Deer Island, Long Island, Moon Island, Peddocks Island, Sheep Island, World’s End and Calf Island. Classes of estuarine intertidal wetlands within the national park area include unconsolidated, emergent, aquatic bed and rocky shore estuarine intertidal wetlands.
While most of the estuarine intertidal wetlands fringing the properties of the national park area are quite small in extent, the estuarine intertidal wetlands found at World’s End comprise the northern edge of a larger system, the Weir River Area of Critical Environmental Concern (ACEC). It is regionally significant both for its size and its importance in providing a relatively undisturbed marshland wildlife habitat.
Similarly, two additional ACECs, and part of a third ACEC, are located in the general proximity of the national park area: Weymouth Back River; Neponset River Estuary; and Rumney Marshes. While the ACECs are located almost entirely outside of the boundary of the national park area they are biologically connected and the habitats they provide are of great significance to the overall ecological health of the entire Boston Harbor area.
Palustrine (Freshwater) Wetlands
Palustrine wetlands occur in areas where the salinity due to ocean derived salts is less than 0.5 parts per thousand. Within the national park area these are limited to a few small areas freshwater marsh and/or small ponds located on Deer Island, Thompson Island, World’s End, Long Island, Lovells Island and Great Brewster Island. While small in area, these freshwater resources may be of significant biological value. For example, Ice Pond, a small, shallow pond located at World’s End is the only surface freshwater source in the reservation and functions as a woodland vernal pool which could be of biological significance during the reproductive cycles of resident amphibian and/or reptile populations.
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Palustrine
Wetlands
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Estuarine
Subtidal
Wetlands
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Estuarine
Intertidal
Wetlands
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Marine
Intertidal
Wetlands
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Bumpkin Island
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|
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X
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|
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Button Island
|
|
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X
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|
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Calf Island
|
|
|
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X
|
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Deer Island
|
X
|
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X |
X
|
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Gallops Island
|
|
|
X |
|
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George’s Island
|
|
|
X
|
|
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Grape Island
|
X
|
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X
|
|
|
Great Brewster
|
X
|
|
|
X
|
|
Green Island
|
|
|
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X
|
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Hangman Island
|
|
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X |
|
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Langlee Island
|
|
|
X |
|
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Little Brewster
|
|
|
|
|
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Little Calf Island
|
|
|
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X
|
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Long Island
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X
|
|
X |
|
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Lovells’ Island
|
X
|
|
X |
X |
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Middle Brewster I.
|
|
|
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X
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Moon Island
|
|
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X |
|
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Nut Island
|
|
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X
|
|
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Outer Brewster I.
|
|
|
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X
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Peddocks’ Island
|
|
X
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X
|
|
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Raccoon Island
|
|
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X
|
|
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Ragged Island
|
|
|
X |
|
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Rainsford Island
|
|
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X
|
|
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Sarah Island
|
|
|
X |
|
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Sheep Island
|
|
|
X |
|
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Slate Island
|
|
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X
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|
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Spectacle Island
|
|
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X |
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Thompson Island
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X
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|
X
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|
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Webb State Park
|
|
|
X
|
|
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World’s End
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X
|
|
X
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