- Human impacts on the biodiversity of the Arctic
Pollution levels in the Arctic are generally lower than in temperate regions. Locally, however, pollution from mining, industrial smelters, military activities, and oil and gas development has caused serious harm or posed potential threats to plant and animal life. Long-range transport of pollutants from sources outside the Arctic, in the atmosphere, rivers, or ocean currents, is also of concern. Particular problems include nitrogen and phosphorus causing eutrophication (especially in the Baltic Sea), organic wastes from pulp mills creating an oxygen demand in the benthos, the effects of toxic metals (especially mercury), and bioaccumulation of organic compounds such as polychlorinated biphenyls (PCBs).
A recent report on the status of wildlife habitats in the Canadian Arctic listed four major classes of pollutant in the Arctic: mercury, PCBs, toxaphene, and chlorinated dioxins and furans (Table 10.6). Two main points are evident from Table 10.6: that pollutants are carried over long distances in the atmosphere and that pollutants accumulate in arctic food chains. Pollution is an international issue that needs to be resolved in a multi-national manner. However, wildlife is possibly more tolerant than might first appear because no arctic species are known to have become globally extinct due to pollution. However, the trends in pollutant uptake (see Table 10.6) are of concern.
Emissions of sulfur from industrial smelters and mining in the Russian Arctic have caused environmental disasters, killing vegetation and damaging freshwater ecosystems. These impacts have, however, been restricted to relatively small areas surrounding the sources. Long-range transport of sulfur and acid rain to the Arctic has reduced in recent years. The problems of acidification due to sulfur deposition are well known and ameliorative procedures have been established. Acidification results in lakes becoming clear and devoid of much of their characteristic wildlife, so causing considerable local loss of biodiversity. Data from well water in Sweden showed a north–south gradient in acidification, with fewest effects in the north. Liming the inflow waters of some lakes has seen a recovery or partial recovery in pH, the aquatic plant and animal communities, and recolonization and recovery of the fish populations. An analysis of Scandinavian rivers also showed a north–south gradient, with relatively few acidified rivers in the arctic areas.
Pollution is also a threat to the boreal forests. The problems of increased aerial deposition of nitrogen have been well documented, and result in both eutrophication and acidification. The acidifying effects of sulfur deposition tend to be least severe in the Arctic, owing to its distance from areas where sulfur oxide (SOx) gases are emitted. However, there are areas of the Arctic where the degree of acid deposition exceeds the soil’s capacity to deal with it, i.e., the critical load.
Levels of anthropogenic radionuclides in the Arctic are declining. Radionuclides in arctic food chains are derived from fallout from atmospheric nuclear tests, the Chernobyl accident in 1986, and from European reprocessing plants. Radiocesium is easily taken up by many plants, and in short food chains is transferred quickly to the top consumers and people, where it is concentrated. Radiocesium has been a problem in arctic food chains, but after atmospheric nuclear tests were stopped 40 years ago, and the effects of the Chernobyl accident have declined, the problem is diminishing. Hallanaro and Pylvänäinen discussed the effects of the nuclear tests in Novaya Zemla, Russia and the Chernobyl accident, and concluded that neither had “resulted in any evident changes in biodiversity”.
Oil pollution in the Arctic has locally caused acute mortality of wildlife and loss of biodiversity. Longterm ecological effects are also substantial: even 15 years after the Exxon Valdez accident in Alaska, toxic effects are still evident in the wildlife. A more acute form of pollution is due to major oil spills, although minor discharges are relatively common. Devastation of wildlife following an oil spill is obvious, with dead and dying oiled birds and the smothering of intertidal algae and invertebrate animals. The type of oil spilled, whether heavy or light fuel oil, determines the effects on the fish. Light oils that are partially miscible with seawater can kill many fish, even those that generally occur only at depth. Less sea ice resulting from a warming climate is likely to increase accessibility to oil, gas, and mineral resources, and to open the Arctic Ocean to transport between the Pacific and Atlantic Oceans. Such activities will increase the likelihood of accidental oil spills in the Arctic, increasing the risk of harm to biodiversity. A warmer climate may, however, make combating oil spills easier and increase the speed at which spilled oil decomposes.
With the possible exception of mercury, heavy metals are not considered a major contamination problem in the Arctic or to threaten biodiversity. The Arctic may, however, be an important sink in the global mercury cycle. Mercury is mainly transported into the Arctic by air and deposited on snow during spring; the recently discovered process involves ozone and is initiated by the returning sunlight. Mercury deposited on snow may become bioavailable and enter food chains, and in some areas of the Arctic levels of mercury in seabirds and marine mammals are increasing.
Persistent organic pollutants (POPs) are mainly transported to the Arctic by winds. Even though levels in the Arctic are generally lower than in temperate regions, several biological and physical processes, such as short food chains and rapid transfer and storage of lipids along the food chain, concentrate POPs in some species at some locations. AMAP concluded that “adverse effects have been observed in some of the most highly exposed or sensitive species in some areas of the Arctic”. Persistent organic pollutants have negative effects on the immune system of polar bears, glaucous gulls (Larus hyperboreus), and northern fur seals (Callorhinus ursinus), and peregrine falcons (Falco peregrinus) have suffered eggshell thinning. The ecological effects of POPs are unknown.
The direct effects of pollutants on trees are compounded by the effects of diseases and defoliating arthropods, and by interactions between all three. Across Europe, these have been codified into the assessment of crown defoliation and hence crown density. Each country prepares an annual report to allow the international situation to be assessed and trends determined. These assessments provide a measure of forest condition and changes in condition. These assessments are currently made in the main timber producing areas of Europe, but it would be of benefit to establish an international forest condition monitoring network across the boreal forests of the subarctic.
A warmer Arctic will probably increase the long-range transport of contaminants to the Arctic. Flow rates in the big Siberian rivers have increased by 15 to 20% since the mid-1980s (see Chapter 6) due to increased precipitation. Northerly winds are likely to increase in intensity with climatic warming, bringing more volatile compounds such as some POPs and mercury into the Arctic. Conservation action must aim to reduce the amounts of the pollutants resulting in chronic effects from entering arctic ecosystems, and to reduce the risk of accidents for pollutants resulting in acute effects.
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