The arctic climate found in the north of Alaska contains many unique food
webs due to the long, dry winters and varied levels of sunlight. Due to its
extreme northerly position days vary from continuous darkness for 6 months
to continuous light for the remainder of the year. The harsh conditions
reduce the variety of organisms with 189 species of birds, 24 of land
mammals and 40 marine mammals. There are few plants, the unequal
distribution of sunlight forcing them to store energy during the summer,
building up reserves for the winter in total darkness. Most of the biomass
of a plant is stored underground where it is protected from the climate and
can be used later in the year. During this time algae blooms increase in
number, which provides food for zooplankton and small crustaceans such as
shrimp. Higher order consumers such as beluga and bowhead whales, seals and
birds feed on these organisms.
The main species found in the area include caribou, musk ox, arctic hare,
arctic fox, wolves and lemmings. Millions of geese, terns and gulls feed on
algae and shrimp during the summer. The food chain can not support these
all of these animals over winter, forcing birds, fish and marine mammals to
move south. Grizzly bears, marmots and squirrels store food over the summer
and hibernate during the cold winter months, while caribou, wolves, polar
bears and lemmings remain active. Snow geese, a common animal found in the
area, feed on grass shoots in the summer months. These food webs are very
fragile, with small changes having large effects on all animals in the
ecosystem. The secondary consumers, humans wolves and jaegers depend on
three main primary consumers of vegetation, microtine rodents, caribou and
ground squirrels. There are very few animals in the food web.
The diet of the animals varies over the year as different food sources
become available. In spring caribou feed on the growing buds and leaves of
the willow and the new grass and sedge shoots. Over summer plants grow
rapidly and the caribou eat large amounts to build up body fat. During
winter fungi and lichen are the main food source although they do not have
as much energy as grass shoots. The accumulated body fat provides extra
nutrients until the summer months. One wolf weighs 360 kg and needs 11 000
kg of prey to gain enough energy to survive. A wolf population would need
between 39 000 and 78 000 square kilometres to hunt in order to keep the
food web in balance.
Small mammals such as voles, lemmings and ground squirrels reproduce faster
than larger grazing animals and so require more food. The number of
lemmings reaches a maximum every 3 to 6 years. Between these times their
numbers drop to almost zero, having an important impact on the food
available for second order consumers. Although the lemmings destroy tundra
grasses and mosses when their population increases, they provide food for
foxes, weasels, owls, and jaegers. Their grazing and burrowing increases
the rate of decomposition and releases nutrients which increases plant
growth. The balance between the organisms in the food web is delicate and
easily disturbed.
There are more invertebrates than birds and mammals in this area. The
majority of these animals are nematodes, mites and springtails which eat
the slowly decaying plants, which can be anything from 1 to 200 years old.
They play an important role in decomposing the dead plant matter, releasing
more nutrients into soil.
How do humans influence the food web in this environment? The Inuit are
the native people of the Alaskan wilderness and have developed methods of
hunting that have a low impact on the food webs in the area. Sacred spaces
are set aside to allow animals to breed and recent conservation parks such
as the National Petroleum Reserve have been developed to protect endangered
species. With their food source protected they are able to eat 260 000 kg
of game a year, making hunting their main source of food The animals hunted
are mainly seals, whales, caribou and fish. One hundred grams of caribou
flesh gives 23.9 g of protein and 4.7 g of fat; for a Bowhead whale, 25.8 g
protein and 2.6 g of fat.
Numbers of animals in area hunted by the Inuit:
- Caribou - 75,000
- Moose - 1200
- Dall Sheep - 400
- Wolves - 300
- Grizzly bear - 450
- Fox - 2,500
Animals killed in the Inuit annual food harvest:
- Grizzly Bears - 14
- Polar Bear - 30
- Caribou - 150
- Moose - 27
- Dall Sheep - 45
- Bearded Seal - 600
- Hair Seal - 1,800
- Walrus - 200
- Beluga Whale - 20
- Bowhead Whale - 28
- Ducks, geese and cod are also hunted in large numbers.
The food webs found within the Alaskan wilderness are carefully kept in
balance by the Inuit so that they can continue to hunt their food. The
plant and animal life in the area has adapted to the harsh conditions,
creating a unique ecosystem.
