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Ecoregions of Virginia

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About the Ecoregions of Virginia

Virginia can be divided into 27 ecoregions. The state's borders correspond poorly to ecoregions, and all of these regions extend outside borders of the state. The state's southern border cuts perpendicularly across many ecoregions, and even the northwestern border, which loosely follows the ridges of the Appalachian mountains, is irregular and cuts across the regions in many places. The state also includes the southern tip of the Delmarva peninsula, and parts of the northeastern border of the state on the mainland also cut across ecoregion boundaries.

Most of the state has a humid subtropical climate with four well-defined seasons. The coastal parts of the state have the mildest climate, and the Chesapeake bay also moderates the climate. Although precipitation is fairly equally distributed throughout the year, there is a slight seasonality, with a wet season peaking in summer; this effect is strongest closer to the coast. In the inland parts of the state, high elevations have a cooler climate with high precipitation, similar in many respects to the climate in coastal New England.

Broadly, Virginia can be divided into three large-scale ecoregions: the Appalachians along the northwest border of the state, the Southeastern USA Plains running through the central portion of the state and covering most of the state, and the Middle Atlantic Coastal Plain in the southeastern corner of the state as well as the portion of the state on the Delmarva peninsula. The border of the coastal plain is well-defined and marked by a fall line. The large, central part of the state can be further divided into the large and interior Piedmont region, the Northern Piedmont in the north, and the Southeastern Plains to the east.

The Coastal Plain can be subdivided into 5 regions. The Virginian Barrier Islands and Coastal Marshes directly border the ocean and consist of sandy barrier islands and coastal marshes; this region is found in portions of Virginia both north and south of the Chesapeake bay. On the Delmarva peninsula, just inland from this region lies a narrow strip of the Delmarva Uplands, a relatively flat, upland area with sandy soils. Directly west of this, and also south of the bay, directly inland from the barrier islands, lie the Chesapeake-Pamlico Lowlands and Tidal Marshes, which extend to surround the Chesapeake bay on both shores. Along the southern border of the state, extending into North Carolina, is a small area of Swamps and Peatlands. West of this, also extending into NC, is a much larger area of Mid-Atlantic Flatwoods.

The central portion of the state is divided into 7 regions. The Southeastern plains consist of the Rolling Coastal Plain, covering most of this portion of the state, and in the far north, a small portion of the Chesapeake Rolling Coastal Plain. The relatively large Piedmont region consists mostly of the Northern Outer Piedmont in the east, and northwest of this, the Northern Inner Piedmont. These two regions are interspersed with three small areas of Triassic Basins. The Northern Piedmont is divided into the Piedmont Uplands, a hilly upland region that makes up most of this section of the state, the smaller, more low-lying Triassic Lowlands, and, interspersed throughout that region, the rugged, irregularly-shaped ridges of the Trap Rock and Conglomerate Uplands.

The Appalachians are the most ecologically diverse part of the state, contributing 15 of the state's ecoregions. Broadly, the portions in Virginia can be divided into three sections: the Blue Ridge in the southeasternmost portion of the mountains, the Ridge and Valley just inland from that, and past that, a small section of the Central Appalachians that cuts through the westernmost part of the state.

The Blue Ridge is divided into five sections. The north is divided into the broader Northern Igneous Ridges to the east, and the much narrower Northern Sedimentary and Metasedimentary Ridges to the west. In the south, it is divided into a fairly narrow section of the Southern Crystalline Ridges and Mountains in the east, a region that becomes much broader farther south, outside the state, the New River Plateau, and the Southern Sedimentary Ridges.

The Ridge and Valley system has the greatest ecoregion diversity, with 8 total regions. Broadly this region is divided into northern and southern sections, corresponding to changes in climate and forest type. In the north, the subregions are the Northern Limestone/Dolomite Valleys, the Northern Shale Valleys, the Northern Sandstone Ridges, and the Northern Dissected Ridges and Knobs. In the south, these same regions have their counterparts, the Southern Limestone/Dolomite Valleys and Low Rolling Hills, Southern Shale Valleys, Southern Sandstone Ridges, and the Southern Dissected Ridges and Knobs.

The portion of the Central Appalachians in Virginia mostly consists of the Dissected Appalachian Plateau but there is a narrow slice of the Cumberland Mountain Thrust Block contained within the state as well. These two regions are high in plant biodiversity, owing to their large presence of the biodiverse mixed mesophytic forests, but they are also threatened by extensive coal mining, including strip mining and mountaintop removal.

References

1. Woods, A.J, Omernik, J.M., Brown, D.D. "Level III and IV Ecoregions of Delaware, Maryland, Pennsylvania, Virginia, and West Virginia", U.S. Environmental Protection Agency: National Health and Environmental Effects Research Laboratory, Corvallis, OR (1999) Web.