Boundaries

The extent of this ecoregion is defined by the river drainages of the Chesapeake Bay. The ecoregion covers most of northern Virginia, the eastern extension of West Virginia, most of Maryland, part of southwestern Delaware, roughly the central one-third of Pennsylvania, and part of western New York.

Topography

The ecoregion includes the Appalachian Plateau and Ridge and Valley physiographic provinces in the western and northern portions of the ecoregion, the Piedmont Plateau in the south central portion, and the Atlantic Coastal Plain in the southeastern portion of the ecoregion. Elevation ranges from sea level to over 1400 m.

Freshwater habitats

The Chesapeake Bay represents the largest estuary in the United States, and its drainage includes a diversity of wetlands, marshes, riparian forests, rivers and streams.

Terrestrial habitats

The Chesapeake Bay ecoregion spans six terrestrial ecoregions that includes coastal forests and temperate broadleaf and mixed forests. Hemlock (Tsuga canadensis) and beech (Fagus grandifolia) once dominated the presettlement forests of the Allegheny Highlands, whereas massive tulip poplars (Liriodendron tulipifera), chestnuts (Castanea dentata), red spruce (Picea rubens), and oaks (Quercus spp.) once dominated the mid-elevations of the Appalachian/Blue Ridge forests. The Northeastern coastal forests are characterized by white oak (Quercus alba) and northern red oak (Q. rubra). Around the mouth of the Bay, Southeastern mixed forests and Mid-Atlantic coastal forests are the predominant vegetation types (Ricketts et al. 1999).

Description of endemic fishes

The only endemic is the Maryland darter (Etheostoma sellare), restricted to one small section of a stream in central Maryland.

Justification for delineation

Ecoregion boundaries are modified from Abell et al. (2000), which based its units on subregions defined by Maxwell et al. (1995).  Modifications to this ecoregion were made following recommendations from the Endangered Species Committee of the American Fisheries Society. The James River was moved from the Chesapeake Bay to the Appalachian Piedmont [157] based on a dissimilarity analysis that showed greater faunal similarities between the James and rivers south of it than those to the north and in the Chesapeake Bay ecoregion.