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Ecoregions of Delaware

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NameColor on Map
Virginian Barrier Islands and Coastal Marshes
Delmarva Uplands
Piedmont Uplands
Chesapeake Rolling Coastal Plain
Delaware River Terraces and Uplands

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About the Ecoregions of Delaware

Delaware is one of many states whose borders do not correspond well with ecological boundaries. The state contains a major border, the border between the Northern Piedmont and the Mid-Atlantic coastal plain, and a few more minor ones.

The climate is towards the cooler end of a humid subtropical climate, and has roughly equal precipitation year-round. There is only subtle climate variation throughout the state, with the south being slightly warmer and sunnier. The ecoregion boundaries in Delaware correspond to changes in topography and underlying geology, and also proximity to major bodies of water.

The northernmost part of the state is part of the Piedmont Uplands, a large region that mostly lives within Pennsylvania, Maryland, and Virginia; within Delaware, this is the most rugged, upland portion of the state. The southern border of this region in is well-defined, and marked by a fall line. This line roughly follows Kirkwood highway, or Delaware Route 2, for most of its length. Historically, the falls along this line were used to power mills, which explains the concentration of settlements along this border. Most of the state's population still lies along this border, which is not far north of the major east coast rail corridor and I-95.

The bulk of the state's area is located within the Delmarva Uplands, a mostly flat region with sandy soils, which also extends south and west through much of the portion of Maryland on the Delmarva Peninsula. The southernmost part of the state has a small region of coastline located within the Virginian Barrier Islands and Coastal Marshes, which extends south into North Carolina. This region is characterized by beaches, dunes, barrier islands, and coastal wetlands behind them. The climate here is moderated by the ocean and is slightly milder than that in the rest of the state.

A narrow portion of the state adjacent to the Delaware river and bay are part of the Delaware River Terraces and Uplands, a region that also includes the New Jersey side of the border, and extends north into Pennsylvania, about to Trenton, NJ. This region has abundant tidal wetlands along the estuary of the Delaware bay, the most significant being Bombay Hook National Wildlife Refuge.

A tiny portion of the Chesapeake Rolling Coastal Plain, mostly located within Maryland, also extends into the westernmost part of northern Delaware. This region, as with the Delmarva Uplands, is south of the fall line with the Piedmont, but tends to be more rugged than the Delmarva Uplands. The border of this region with the Delmarva Uplands is not well-defined and does not correspond exactly to differences in soil type. Delaware also has a peculiar local feature, Iron Hill, which is geologically part of the Piedmont, but geographically isolated from it and smaller than the scale at which ecoregions are defined, and thus included as part of the Chesapeake Rolling Coastal Plain in the ecoregion data and maps.


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.