It is one of the largest intact temperate rainforests remaining in the world — a landscape of extraordinary biological diversity and productivity that has been shaped by the specific combination of North Pacific maritime climate, complex island and fjord topography, and the ecological dynamics of the temperate rainforest system.

The Sitka spruce and western hemlock that dominate the forest canopy; the understory of mosses, ferns, and shrubs; the salmon streams threaded through the landscape; the rocky coastlines and inter-tidal zones — all of these are components of an integrated ecological system of remarkable richness.

The ecological productivity of the Tongass landscape is not simply a modern phenomenon.

The basic ecological structure of the temperate rainforest of southeastern Alaska — the salmon runs, the marine productivity, the forest system — has been present in something close to its current form since the early Holocene.

The specific species composition of the forest has changed somewhat as climate has shifted and as succession has proceeded from the early post-glacial pioneering communities to the climax forest of today.