Ecological Divisions

When looking at a map of the entire North American continent, conservationists find it useful to divide the land into manageable "units" that are ecologically discreet in terms of climate, animal life, and plant species distribution -- anything that contributes to and determines the biodiversity of a given area. 

These units perform a second function, which is to help imperfect people speak a common language about the earth as we know it. When the scientific community, conservation groups, and concerned citizens meet to discuss planning and policy, it is very important that they understand which pieces of earth they are discussing -- and why. Ecological Divisions help each of these parties understand one another and keep the big picture in mind.

The following Ecological Division lines were created by modifying Ecoregions throughout the Western Hemisphere, which were established by The Nature Conservancy and World Wildlife Fund. North American examples include the Inter-Mountain Basins, the North American Warm Desert, the Western Great Plains, the Eastern Great Plains, the Laurentian and Acadian region, the Rocky Mountains, and the Atlantic and Gulf Coastal Plain

As you can see, these are big areas of the continent. And yet, even at this broad level, there are interesting demarcations. For example, a "Rocky Mountain" ecoregion is predominantly found within the Rocky Mountain Ecological Division. But so is the "Southern Rocky Mountain" ecoregion, though it is limited to southern portions of the broader Rocky Mountain Ecological Division. The reason is clear: though each of these ecoregions are home to different plants and animals -- biota -- they share enough broad biogeographic history to be studied as one Ecological Division unit. Now, that's keeping the big picture in mind. 

Ecological Divisions of the U.S.

  • Laurentian and Acadian

    Autumns are gorgeous and winters harsh in this region that extends in a broad arc from the northern Great Lakes through Pennsylvania's Allegheny highlands, upstate New York, northern New England, and adjacent parts of Canada.

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  • Central Interior and Appalachian

    The ancient Appalachians, rounded and folded by 300 million years of geologic history, have recovered over the past century, as has the rich wildlife they shelter.

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  • Gulf and Atlantic Coastal Plain

    Stretching from Cape Cod south through Florida and west to the Texas Gulf Coast, the Coastal Plain includes such prominent features as the Chesapeake Bay, long chains of Atlantic and Gulf barrier islands, and the lower Mississippi River with its fragile delta.

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  • Caribbean

    A vast rain-supplied wetland, the Caribbean Ecological Division that features the unique "river of grass" flow of the Everglades is threatened by rising population boom and demand for water.

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  • Eastern Great Plains

    Wheat, corn, and soy now dominate the gently rolling plains and deep black soils of the Eastern Great Plains, converting to agriculture a blanket of bluestem grasses and wildflowers that extended from east Texas to the Canadian border.

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  • Western Great Plains

    In these semiarid plains, evaporation usually exceeds precipitation, where drought, wildfire, and grazing help curb the spread of woodlands, yet create prairie potholes that serve as the continent's waterfowl factory.

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  • Madrean Semidesert

    Covering south Texas and a substantial part of northern Mexico, the Madrean Semidesert is a landscape of hot, dry scrublands where sparse grasses, cacti, and thorny shrubs such as mesquite are the dominant vegetation.

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  • Warm Desert

    The Warm Desert Ecological Division cuts a vast swath across the nation's southwestern quarter, yet our society has built upon it a series of boomtowns that call to mind the magnificent Anasazi culture that once thrived here and eventually collapsed about 700 years ago.

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  • Rocky Mountains

    Visitors to the Rocky Mountains Ecological Division have marveled at the jagged-peaked ranges separated by glacier-carved valleys that feature conifer-dominated forests and montane grasslands.

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  • Intermountain Basins

    This vast and topographically diverse space, bounded on the east by the Rockies and on the west by the Cascades and the Sierra Nevada, includes the dramatic red-rock canyons of the Colorado Plateau, the Great Salt Lake, thousands of square miles of sagebrush terrain, and some of the nation's greatest wilderness areas and national parks.

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  • Mediterranean California

    A Mediterranean-style climate, with rainy, mild winters and dry summers, coupled with an eclectic geologic history has produced a greater variety of plant and animal species in this region than anywhere else in the nation.

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  • North Pacific Maritime

    The Pacific Ocean's moderating influence and the high coastal mountains produce a damp climate with mild winters and cool summers ideal for coniferous forests of western red cedar, spruce, and giant Douglas fir, among the largest trees on Earth.

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  • Boreal

    The Boreal Ecological Division encompasses the interior of Alaska and stretches clear across the majority of sub-polar Canada, extending east to the north Atlantic coast. Think of the great northern conifers and long, difficult-to-survive winters.

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  • Arctic

    For thousands of years, the Arctic has been home to native peoples, who shared the treeless tundra of the continent's far-northern fringe with thriving flora and fauna, all of whom face heightened concerns for these fragile landscapes.

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  • Hawaiian Islands

    Ascending from the volcanic depths of the central Pacific, the evolutionary seclusion of Hawaii has crafted extraordinary creatures, including more than 30 species of honeycreeper, for instance, nearly half of which have disappeared.

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