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The Arctic is by no means a uniform environment. Different
geological histories, warm and cold ocean currents, and local
weather patterns bring great ecological diversity to the scene.
From the permanent ice cover of the High Arctic to the boreal
forest of the subarctic, with the wide expanse of tundra in
between, the Arctic boasts a rich and varied array of habitats.
Tundra
 Arctic
tundra extends from the Arctic Basin in the north to the coniferous
treeline forests of the taiga further south. The region is
characterized by extremely low winter temperatures, sweeping
winds, little precipitation, poor nutrients, and short growing
seasons. In summer, thawing permafrost creates wetland conditions,
dotting the landscape with countless lakes, bogs, streams,
and meadows. Vegetation consists of mosses, lichens, grasses,
herbs and dwarf shrubs.
Tundra animal populations tend to vary greatly due to climate
and food conditions. Year round residents are adapted to handle
long, cold winters and to breed and raise young quickly in
the summer. Herbivorous mammals include: caribou, musk oxen,
lemmings, voles, arctic hares and ground squirrels. Carnivorous
mammal include: arctic foxes, wolves, and polar bears. Several
species of migratory birds (ravens, ducks, falcons, loons,
terns, snow geese, and gulls) arrive at the tundra regions
in summer to nest. Insect species thrive on the tundra, breeding
in the ubiquitous still water pools. Reptiles and amphibians
are few or absent.
Taiga or Subarctic
 The
Taiga or Subarctic Zone lies between the Arctic tundra to
the north and the closed canopy of the boreal forest to the
south. It is characterized by vast open forests of spruce
and birch that are home to a variety of bird and animal species.
Permafrost is only present in patches, and in summer the unfrozen
layer is generally thick.The trees closest to the treeline
or the edge of the tundra are likely to be low and stunted.
As temperature and snow conditions grow more favorable, treeline
vegetation is gradually replaced by the typical boreal forest
of spruce, pine, and fir. The scattered trees in these areas
let through enough light to support an understory vegetation
that is made up, depending on the amount of soil moisture,
of lichens, mosses, low brush, grass, herbs, and willows.
The taiga has a longer growing season than the tundra and
can support more wildlife. In addition to the reindeer/caribou
that migrate into the forest for winter, plant eaters include
rodents, hares, squirrels, moose, muskrat, and numerous bird
species. Predators include foxes, martens, minks, wolves,
wolverines, and lynx. People living on the tundra often use
the forest for protection in wintertime and for access to
firewood and fur-bearing animals.
Pack Ice  The
Arctic pack ice is a region of frigid winds, subzero temperatures,
limited sunlight, and endless expanses of ice-choked sea.
Six million square miles in extent, its edges are home to
several species of terrestrial and marine mammals, including
polar bears, arctic foxes, seals, walruses, and whales; and
sea birds such as guillemots, auks, and eiders. The sea ice
is also used as an important transportation route by caribou
and muskox and a traditional hunting ground for the Inuit.
Vegetation on the surface of the ice pack is limited at best.
However, cracks in the ice do provide growth surfaces for
ice algae which is a critical component to the marine food
chain. Also, the edge of the pack ice is a crucial zone for
many marine mammal species, such as seals, sea otters, sea
lions, and walruses, who will often haul themselves out of
the water and onto the ice to escape predators, to breed,
or simply to rest in the sun. These species, in turn, provide
food for polar bears, arctic foxes, and humans.
Lakes and Rivers
 High-Arctic
lakes are extremely poor in nutrients and often have very
few species in simple food webs. Lake ecology is governed
by ice-cover and the timing of the spring melt. In the High
Arctic, water temperatures rarely exceed a few degrees above
freezing. Surface water in Low-Arctic lakes may reach 70°F,
but the heat quickly dissipates in the fall. Depending on
latitude, snow cover, and the severity of the winter, ice
thickness typically ranges from three to ten feet. Productivity
in Arctic lakes is limited by low temperatures and also by
the lack of light and oxygen. Most of the nutrients come in
one short spurt during snowmelt.
Many Arctic rivers freeze solid during the winter, even if
they become warm in the summer. The water is often acidic
and rich in organic material from the surrounding landscape.
Because the ground has such a limited ability to store water,
the spring flood can be violent, undercutting the river bank
and causing extensive erosion along its path. Ice jams add
to the uneven flow and erosion.
Wetlands
 Wetlands
are typical of the Arctic tundra covering over 600,000 square
miles of landscape. The lack of oxygen in the waterlogged
soil of wetlands, along with cold ground temperatures delays
the decomposition of plant and animal matter and limits productivity.
Poor drainage of the underlying permafrost soils results in
a build-up of organic materials, such as peat and humic substances
which tend to color the water brown. The amount of water in
the ground also influences what will grow in a particular
wetland. The dominant plant species will in turn have a great
effect on the rest of the ecology.
There are five basic types of wetland: bogs, fens, swamps,
marshes, and shallow open water. Bogs and fens are the most
common.Bogs usually have a surface carpet of mosses, mainly
Sphagnum. The wet and acid peat that builds up due to poor
decomposition of Sphagnum also supports sedges and, in the
subarctic, trees. Emergent non-woody plants such as rushes,
reeds, and reed grasses are also common. Bacteria and fungi
feed on the roots and leaves of the plants, and in turn serve
as food for midge larvae.
Marine Systems
 The
highly productive Arctic marine environment is home to numerous
species of sea going mammals, shorebirds fish, shellfish,
crustaceans and other invertebrates. Arctic marine species
have adapted to the cold tempertures of the polar seas to
take advantage of the nutrient rich waters surrounding the
ice edges and continental shelves.
The Arctic marine food chain begins with plankton, which
provide the basis for all marine life in the north. Phytoplankton
(microscopic plant life) provides food for zooplankton (microscopic
animal life) which in turn, feeds the many species of fish,
shellfish, crustaceans and other invertebrates. A steady rain
of organic material sinks to the floor of the vast continental
shelves providing food for bottom dwellers. Arctic fish species
include: cod, char, salmon, capeline, herring, and halibut.
Walrus, sea lions, numerous species of seals and whales such
as belugas and narwhals all follow the ice-edge, taking advantage
of the ready access to food and (for the walrus and seals)
the availability of ice to haul-out on for sunning, mating
and raising pups. And at the very top of the food web is the
largest carnivore in the world -- the polar bear -- which
is as much at home swimming in the sea as it is lumbering
across hundreds of miles of pack ice.
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