and finer material. When water saturates the upper surface, bogs and ponds may
form, providing moisture for plants that are able to resist the cold climate, such
as low shrubs, sedges, mosses, liverworts, grasses, approximately 400 varieties
of flowers, and lichen. All plants are adapted to sweeping winds and
disturbances of the soil. Protected by snow during the winter, plants are short
and are found in clumped distribution patterns to resist cold temperatures. They
can carry out photosynthesis at low temperatures and low light intensities. Most
plants reproduce by budding and division rather than sexually by flowering.
Food webs are simple and are characterized by low biodiversity. Animals are
adapted and highly specialized for long, cold winters and to breed and raise
young quickly in the summer. Mammals and birds also have additional
insulation from fat. Many animals hibernate or migrate south during the winter
because food is not abundant.
Animals include herbivorous mammals, such as lemmings, voles, caribou,
Arctic hares, and squirrels. Carnivorous animals include Arctic foxes, wolves,
and polar bears. Migratory birds include ravens, falcons, loons, sandpipers, terns,
snow birds, and various species of gulls. Insects include mosquitoes, flies,
moths, grasshoppers, and bees. Reptiles and amphibians are few or absent
because of the extremely cold temperatures. Fish include cod, salmon, and trout.
Alpine Tundra
The alpine tundras are located on mountains throughout the world at high
altitude where trees cannot grow. The growing season is approximately 180
days. The nighttime temperature is usually below freezing. Unlike the Arctic
tundra, the soil in the alpine tundra is well drained. Plants are very similar to
those of the Arctic tundra and include grasses, dwarf trees, and small-leafed
shrubs. Animals living in the alpine tundra include mountain goats, sheep, elk,
birds, beetles, grasshoppers, and butterflies.
Major Environmental Threats
■ Melting permafrost, as a result of global warming, is radically changing
the biome and what species are able to live there.
■ Ozone depletion at the North and South Poles means stronger ultraviolet
rays that harm wildlife; with some restrictions on ozone-depleting
chemicals, this problem is diminishing to some extent.
■ Air pollution contaminates lichen, a significant food source for many
animals.