Tundra

The tundra is a treeless polar desert found in the high latitudes in the polar regions, primarily in Alaska, Canada, Russia, Greenland, Iceland, and Scandinavia, as well as sub-Antarctic islands. The region's long, dry winters feature months of total darkness and extremely frigid temperatures.

Structurally, the Tundra is a treeless expanse that supports communities of sedges and heaths as well as dwarf shrubs. Vegetation is generally scattered, although it can be patchy reflecting changes in soil and moisture gradients. Most precipitation falls in the form of snow during the winter while soils tend to be acidic and saturated with water where not frozen.

Tundra ecoregions were selected primarily because of extraordinary seasonal concentrations of breeding waterfowl and shorebirds, as well as caribou. Relatively intact tundra ecoregions were chosen, wherever possible. Some tundra ecoregions such as Chukotsky are distinctive in that they display an appreciable level of regional plant endemism.

Biodiversity Patterns
Species typically have widespread distributions, except for some herbaceous plants; low alpha diversity, low beta diversity.

Minimum Requirements
Vast natural habitats are required to allow many species to track patchy resources that vary in location from one year to the next (e.g., lemming irruptions), the presence of varied habitats and associated resources is critical for the survival of many vagile vertebrates; migration corridors for large vertebrates must remain intact to allow large-scale seasonal movements (e.g., caribou).

Sensitivity to Disturbance
Groundcover and surface water flow is highly sensitive to disturbance with very poor resiliency; many vertebrates highly sensitive to the presence of humans or to low intensity hunting; polar ecosystems are particulary sensitive to changes in climatic parameters associated with global climate change; toxins and other compounds tend to sequester and break down only slowly in polar ecosystems.