Human impacts on the biodiversity of the Arctic
International Arctic Science Committee (Content Partner); Mark McGinley
(Topic Editor). 2007. "Human impacts on the biodiversity of the
Arctic." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland
(Washington, D.C.: Environmental Information Coalition, National
Council for Science and the Environment). Encyclopedia of Earth March 19, 2007.
The projected climatic changes in the Arctic, particularly the projected decrease in sea-ice extent and thickness, will result in increased accessibility to the open ocean and surrounding coastal areas.
This is very likely to make it easier to exploit marine and coastal
species, over a larger area and for a greater proportion of the year.
Decreased extent and thickness of sea ice and increased seawater temperatures will, however, also result in changes in the distribution, diversity,
and productivity of marine species in the Arctic and so will change the
environment for hunters and indigenous peoples. However, increased
traffic and physical disturbance caused by increased access to the
marine areas is likely to pose a more significant threat to biodiversity
than increased hunting pressure. On land, snow and ice cover in winter
enable access into remote areas by snowmobile and the establishment of
ice roads; however, in summer, transportation and movement become more
difficult. A shorter winter season and increased thawing of permafrost
in summer, potentially resulting from a warming climate, could reduce
hunting pressure in remote areas.
There are at least four types of pressure acting on marine, coastal, freshwater, and terrestrial habitats that affect both their conservation and biodiversity:
(1) issues relating to the exploitation of species, especially stocks
of fish, birds, and mammals, and to forests; (2) the means by which
land and water are managed, including the use of terrestrial ecosystems
for grazing domesticated
stock and aquatic ecosystems for aquaculture; (3) issues relating to
pollutants and their long-range transport to the Arctic; and (4)
development issues relating to industrial development and to the
opening up of the Arctic for recreational purposes. These factors were
discussed by Hallanaro and Pylvänäinen and Bernes, who included hydroelectricity generation as a major impact on freshwater systems.
Exploitation of populations
Exploitation and harvest of living resources have been shown to pose a threat to arctic biodiversity. Species like the Steller sea cow (Hydrodamalis gigas), in the Bering Sea, and the great auk (Pinguinus impennis),
in the North Atlantic, were hunted for food by early western explorers
and whalers, and became extinct in the 18th and 19th centuries,
respectively. Increasing demands
for whale products in Europe, and improvements to the ships and
harvesting methods intensified the exploitation of several arctic
baleen whale species from the 17th century onward. Over-exploitation
resulted in severely depleted populations of almost all the northern
baleen whale species, and few have recovered their pre-17th century
population sizes. For example, even though a few individuals have been
observed in recent years, the bowhead whale (Balaena mysticetus)
is still considered extinct in the North Atlantic. The Pacific
population is bigger, but still considered endangered. Both
subpopulations used to number in the tens of thousands. Many baleen
whales, feeding on zooplankton, were a natural part of the arctic
ecosystems 400 years ago. Their large biomass implies that they may
have been a “keystone” species in shaping the biodiversity of the Arctic Ocean.
Many populations of charismatic arctic species have been
over-exploited over the last few hundred years. The history of the
slaughter of walruses (Odobenus rosmarus) in the North Atlantic and Pacific is well documented.
The walrus survived because its range of distribution included
inaccessible areas, and the species is now expanding back into its
previous distributional range due to its protection and to a ban on
harvesting the animals in many areas. The International Polar Bear
Treaty (1973) protected the polar bear (Ursus maritimus) after several sub-populations became severely depleted due to hunting.
Some subspecies of reindeer/caribou have also been close to extinction
due to hunting pressure both in the European and North American Arctic. Similarly, several goose populations have approached extinction due to hunting on the breeding and wintering grounds.
There have also been effects on a number of tree species. Wood
has always been a valued commodity and since the first human
populations were able to fell trees and process the felled trunks,
forests have been cut for their timber. During the last few centuries,
systems of forest management
have developed to enable the forest to be regenerated more rapidly,
either naturally or artificially by planting young trees. The need to
exploit these forests for wood is demonstrated by the age structure of
the trees in national forest estates (Table 10.4). Natural (unmanaged)
forests have a large proportion of old trees compared to young trees,
whereas managed forests have a large proportion of younger trees (often
managed on rotations of 40 to 80 years). Table 10.4 appears to indicate
a positive correlation between northerliness and naturalness (indicated
by the index, I).
Since around the 1970s, modern management systems, improved control,
and changed attitudes have largely diminished threats from sports
hunting and harvesting for subsistence purposes. Most of the previously
overexploited populations are recovering or showing signs of recovery.
However, there are still examples where hunting is a problem. In
accordance with the International Polar Bear Treaty, local and
indigenous peoples are allowed to hunt polar bears. In Canada,
populations in some of the 14 management areas were over-exploited in
the 1990s, and hunting was stopped periodically in some of these areas.
Similarly, in Greenland, uncertainties about the number of polar bears
taken, and about their sex and age composition, have created concerns
about the sustainability of the current harvest.
In southwestern Greenland, seabird populations have been over-exploited
for a number of years by local peoples and the populations of
guillemots (Uria spp.) have decreased by more than 90% in this area.
Arctic and subarctic oceans, like the Barents, Bering, and Labrador
Seas, are among the most productive in the world, and so have been, and
are being, heavily exploited. For example, (1) commercial fish landings
in Canada decreased from 1.61 million tonnes in 1989 to 1.00 million
tonnes in 1998; (2) the five-fold decline in the cod (Gadus morhua)
stock in the Arctic Ocean between about 1945 and the early 1990s; and
(3) the huge decline (more than 20-fold) in the herring (Clupea harengus) stock in the Norwegian Sea. A report on the status of wildlife habitats in Canada stated that “Canadian fisheries are the most dramatic example of an industry that has had significant effects on the ocean’s habitats and ecosystems”.
Considerable natural annual variability in productivity, mainly
due to variations in the influx of cold and warm waters to the Arctic,
is a considerable challenge for fisheries management in the Arctic.
Collapses in fish populations caused by over-exploitation in years of
low productivity have occurred frequently and have resulted in negative
impacts on other marine species. The stocks of almost all the
commercially exploitable species in the Arctic have declined, and Bernes went as far as to state that several fish stocks are just about eliminated. Hamre
suggested that the relative occurrence of species at some trophic
levels has been displaced. Such changes in the few
commercially-valuable fish species can have tremendous impacts on the coastal communities which are dependent upon the fishing industry for their livelihoods.
Even though supporting information is scarce, it is likely that the
disappearance of the big baleen whales and the heavy exploitation (or
over-exploitation) of fish stocks over many years have changed the
original biodiversity and ecosystem processes of the subarctic oceans.
Heavy exploitation of benthic species, such as shrimps and
scallops, also affects other species in the benthic communities. Bottom
trawls damage species composition and so affect the food web. An example is the damage that can be caused to the cold water coral community. This coral reef
habitat, often in deep water near the edge of the continental shelf,
supports many other species such as gorgonians and brittle stars (Fig.
10.6). Passes over this community with a trawl leave only fragments of
dead coral that can support no other species (Fig. 10.7). It has been
estimated that, within commercial fishing grounds, all points on the sea floor are trawled at least twice per year.