(Sphere) [Biosphere] (Earth) - zone of life
   (Biogeographic realm) Nearctic
     061 (Ecoregion complex) Sierra Madre Oriental and Occidental Pine-Oak Forests (Nearctic)
     069 (Ecoregion complex) Appalachian and Mixed Mesophytic Forests (Nearctic)
     072 (Ecoregion complex) Pacific Temperate Rainforests (Nearctic)
     073 (Terrestrial ecoregion) Klamath-Siskiyou Coniferous Forests (Nearctic)
     074 (Terrestrial ecoregion) Sierra Nevada Coniferous Forests (Nearctic)
     075 (Ecoregion complex) Southeastern Coniferous and Broadleaf Forests (Nearctic)
     081 (Ecoregion complex) Muskwa/Slave Lake Boreal Forests (Nearctic)
     082 (Ecoregion complex) Canadian Boreal Forests (Nearctic)
     094 (Ecoregion complex) Northern Prairie (Nearctic)
     113 (Ecoregion complex) Alaskan North Slope Coastal Tundra (Nearctic)
     114 (Terrestrial ecoregion) Canadian Low Arctic Tundra (Nearctic)
     121 (Ecoregion complex) California Chaparral and Woodlands (Nearctic)
     130 (Ecoregion complex) Sonoran-Baja Deserts (Nearctic)
     131 (Ecoregion complex) Chihuahuan-Tehuacán Deserts (Nearctic)
     145 (Freshwater ecoregion) Colorado River
     146 (Freshwater ecoregion) Lower Mississippi River
     151 (Freshwater ecoregion) Mississippi Piedmont Rivers and Streams
     175 (Freshwater ecoregion) Southeastern Rivers and Streams
     176 (Freshwater ecoregion) Pacific Coastal Rivers and Streams
     177 (Freshwater ecoregion) Gulf of Alaska Coastal Rivers and Streams
     194 (Freshwater ecoregion) Chihuahuan Freshwater