The W.G.A. is categorizing regions for wilderness guide specializations based on the Walter Biome classification system.

While more defined classifications are available, we feel that the following is sufficient for our purposes.
Boreal/ Nemoral
Walter VIII: Boreal
- Cold temperate with cool summers and long winters
- Evergreen, frost-hardy, needle-leaved forest (taiga)
Walter VI: Nemoral
- Moderate climate with winter freezing
- Frost-resistant, deciduous, temperate forest
Mediterranean/ Warm temperate
Walter IV: Mediterranean
- Winter rainy season and summer drought
- Sclerophyllous (drought-adapted), frost-sensitive shrublands and woodlands
Walter V: Warm temperate
- Occasional frost, often with summer rainfall maximum
- Temperate evergreen forest, somewhat frost-sensitive
Polar/ Arctic and Subalpine
Walter IX: Polar
- Very short, cool summers and long, very cold winters
- Low, evergreen vegetation, without trees, growing over permanently frozen soils
Equatorial/ Tropical
Walter I: Equatorial
- Always moist and lacking temperature seasonality
- Evergreen tropical rain forest
Walter II: Tropical
- Summer rainy season and cooler “winter” dry season
- Seasonal forest, scrub, or savanna
Continental/ Subtropical
Walter VII: Continental
- Arid, with warm or hot summers and cold winters
- Grasslands and temperate deserts
Walter III: Subtropical
- Highly seasonal, arid climate
- Desert vegetation with considerable exposed surface