List of ecoregions in the United States (WWF)

The following is a list of ecoregions in the United States as identified by the World Wide Fund for Nature (WWF).

The United States is a megadiverse country with a high level of endemism across a wide variety of ecosystems.

The United States is unique among countries in that its terrestrial ecoregions span three biogeographic realms: the Nearctic, Neotropical, and Oceanian realms.

Alaska is the most biodiverse state with 15 ecoregions across three biomes in the same realm.

By contrast, Rhode Island is the least biodiverse with just one ecoregion—the Northeastern coastal forests—encompassing the entire state.

Ecoregions of North America, featuring the 50 United States , the District of Columbia and the five inhabited territories