The area contains the only sizeable example of Connecticut River flood plain under preservation, exhibiting many successional stages including upland and flood plain forest, swamp, marsh, ponds, and meadows.
Unspoiled cold northern boreal sphagnum-heath bog occupying an old shallow glacial lake basin which demonstrates bog succession from the central open water pond to the surrounding spruce-fir forest.
This site contains three separate stands of undisturbed old growth red spruce on the northwest slopes of Mt. Greylock, the highest mountain in Massachusetts. These stands have been undisturbed for at least 150–180 years, and may be virgin. No other old growth red spruce stands are known in southern New England, while only a few comparable or better sites occur in northern New England.
The only known locality where the Muskeget beach vole is found, and southernmost station where the gray seal breeds. The area supports an enormous nesting population of herring gulls and black-backed gulls.
The largest freshwater cattail marsh in Massachusetts. The area preserves the habitat requirements of many bird species and serves as a breeding ground for the king rail and least bittern, rare species in the region.