Four Major Ecoregions (Distinct Environments) of North America

North America's terrestrial biomes are commonly classified into four major ecoregions:

1. Arctic Tundra

• Zone: North of treeline — Alaska (North Slope), Canadian Arctic Archipelago, northern Quebec/Labrador, Greenland.
• Climate: Polar (ET) — mean warmest month <10°C; permafrost continuous.
• Vegetation: Mosses, lichens, sedges, dwarf shrubs; no trees.
• Fauna: Caribou, muskox, Arctic fox, lemmings, polar bear (coastal), migratory birds.

2. Temperate Deciduous Forest

• Zone: Eastern US (New England to Georgia, west to Mississippi), southern Ontario/Quebec.
• Climate: Humid continental / subtropical — 4 distinct seasons, 75–150 cm precip.
• Vegetation: Broadleaf trees (oak, hickory, maple, beech) — shed leaves in autumn.
• Fauna: White-tailed deer, black bear, turkey, squirrels, salamanders, diverse songbirds.

3. Grasslands (Prairie / Great Plains)

• Zone: Central North America — rain shadow of Rockies; Texas to Alberta/Saskatchewan.
• Climate: Semi-arid to subhumid; hot summers, cold winters; fire-adapted.
• Vegetation: Tallgrass (east), mixed-grass (central), shortgrass (west) — deep-rooted perennials.
• Fauna: Bison (historically), pronghorn, prairie dogs, burrowing owl, badger, rattlesnakes.

4. Deserts

• Zone: Southwest US / Northwest Mexico — Mojave, Sonoran, Chihuahuan, Great Basin.
• Climate: Arid — <25 cm precip; extreme diurnal temp range.
• Vegetation: Xerophytes — cacti (saguaro, organ pipe), creosote, yucca, agave, ocotillo; ephemeral wildflowers.
• Fauna: Kangaroo rat, Gila monster, roadrunner, coyote, jackrabbit, sidewinder.

Important Nuances

• Boreal Forest (Taiga) — massive 5th region across Canada/Alaska (coniferous, subarctic).
• Mediterranean (Chaparral) — California, Baja (wet winter, dry summer).
• Temperate Rainforest — Pacific NW coast (redwood, cedar, hemlock).
• Montane / Alpine — vertical zonation on Rockies, Sierra, Cascades, Appalachians.

The "four" framework simplifies a continuum; ecologists recognize 15+ Level I ecoregions (CEC).