The boreal forest is the largest forested biome on Earth, covering 17 million km2 of the Northern Hemisphere, and accounting for approximately one third of Earth's total forest area.

In Alaska, the boreal forest occupies some 60-70% of the land area, with tundra and coastal coniferous forest making up the remainder. Approximately 32% of the Interior Alaska boreal ecoregion is forested, of which >60% is dominated by black spruce (Picea mariana). The remainder is a complex mosaic of grasslands, shrublands, bog and fen meadows, shrub and sedge tundra, and open water, with rock outcrops, snow and ice at high elevations.