Human impacts on the biodiversity of the Arctic

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Image via https://www.worldwildlife.org/places/arctic

This is Section 10.3 of the Arctic Climate Impact Assessment
Lead Author: Michael B. Usher; Contributing Authors:Terry V. Callaghan, Grant Gilchrist, Bill Heal, Glenn P. Juday, Harald Loeng, Magdalena A. K. Muir, Pål Prestrud

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[4] and Bernes[5], who included hydroelectricity generation as a major impact on freshwater systems.

Exploitation of populations (10.3.1)

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.

 Table 10.4. Percentage distribution of age classes of coniferous forests in countries with arctic territory[6]. The index, I, is the ratio of the percentage of trees over 80 years old to the percentage less than 40 years old, and so indicates the naturalness of the forests.

 

 0–40 yr

 41–80 yr

 81–100 yr

 >100 yr

  Index (I)

 Murmansk (Russia)

 31

 19

 5

 45

 1.61

 Norway

 33

 21

 13

 33

 1.39

 Finland

 32

 33

 13

 22

 1.09

 Karelia (Russia)

 40

 19

 17

 34

 1.02

 Sweden

 52

 22

 10

 16

 0.50

 

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[7]. 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[8]. Some subspecies of reindeer/caribou have also been close to extinction due to hunting pressure both in the European and North American Arctic[9]. Similarly, several goose populations have approached extinction due to hunting on the breeding and wintering grounds[10].

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).

caption Fig. 10.6. The reef-forming deep-sea coral, ''Lophelia pertusa'' (white coral, upper left hand corner), occurs on the continental shelf and shelf break off the northwest European coast. The red gorgonian, ''Paragorgia arborea'', occurs on these reefs. The brittle star, ''Gorgonocephalus caputmedusae'' (yellow, center), frequently occurs on top of the gorgonians to take advantage of stronger currents. (Photo: CAFF, 2001; reproduced with permission from CAFF, Iceland).

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[11]. 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[12]. 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[13].

caption Fig. 10.7. Fragments and larger pieces of dead coral, ''Lophelia pertusa'', from a trawling ground on the Norwegian continental shelf at a depth of about 190 m. The benthic communities have been severely disturbed and are virtually devoid of larger animals. (Photo: CAFF, 2001; reproduced with permission from CAFF, Iceland).

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[14]; (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[15]. 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[16].

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[17] went as far as to state that several fish stocks are just about eliminated. Hamre[18] 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[19]. 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.

Management of land and water (10.3.2)

Changes in both land and water use influence biodiversity in the Arctic. This is different to the situation in most of the more southern biomes where changes in land use predominate[20]. In the Arctic, the limited expansion of forestry and agriculture is likely to be restricted to particularly productive environments, although there is greater potential for aquaculture in the Arctic.

 Table 10.5. Extent of peatland [21]. The index, P, is the proportion of the total peatland not drained (the figure in the second column minus the sum of the figures in the third and fourth columns) to the total peatland area. Because different countries use different definitions for peatland, the data are not comparable between countries, although the values of P are comparable between countries.

 Country

 Total area of peatland (million hectares)

Area drained for forestry

 Area drained for agriculture

 'P''

 Iceland

 1.00

 small

 0.13

 0.86

 Karelia (Russia)

 5.40

 0.64

 0.09

 0.86

 Norway

 3.00

 0.41

 0.19

 0.80

 Sweden

 10.70

 1.50

 0.60

 0.80

 Finland

 10.40

 5.70

 0.60

 0.39

 

In the Arctic, the original change in land use might not be obvious and impacts may be progressive and long-lasting. Thus the gradual increase in grazing pressure, particularly by sheep, has resulted in the loss of sward diversity and eventual soil erosion. This was probably a contributory factor in the extinction of agricultural colonies in Greenland between AD 1350 and 1450. In Iceland, “desert” with unstable and eroding soils resulted from a combination of removal of the 25% forest cover and the introduction of sheep since settlement in the 9th century. Soil rehabilitation is now a priority, but is a long, slow process. Establishment of long-term grass swards has had some success, and planting birch (''Betula pubescens'') and native willows (''Salix lanata'' and ''S. phylicifolia'') is proving a successful conservation measure, using mycorrhizal inocula, for re-establishing species and habitat diversity of grasslands, shrublands, and woodlands that were lost through overgrazing[22][23] although non-native species can cause problems.

caption Fig. 10.8. In Norwegian Finnmark the number of reindeer trebled between 1950 and 1989 resulting in extensive overgrazing of the vegetation. The ground to the left and above the fence had been overgrazed, while that to the right and in the foreground had been protected from grazing. Note the presence of shrubs and the green nature of the herbaceous ground cover[1]. (Reproduced with permission from Georg Bangjord, Statens Naturoppsyn, Norway).

Draining of peatlands, and other wetlands including marshes and salt marshes, has been widely undertaken to bring the land into productive use, mainly for forestry but to a limited extent also for agriculture. In general there is an inverse correlation between the extent of drainage and northerliness. Data for relatively small areas are not available, but national data are presented in Table 10.5. The index, P, gives an indication of how much of the national peatland has been drained, which in the most northerly areas is relatively small. Drainage has a major impact on biodiversity. Invariably most of the species characteristic of the wetland are lost, except where small populations survive in drainage ditches. The newly created habitats are more prone to invasion by non-native species, and soil erosion may become more problematic. Migratory bird species may lose nesting places, and the land cannot retain as much water as before and so runoff increases during and immediately after storms. Drainage therefore has a major effect on the functioning of ecosystems, as well as encouraging biodiversity loss, usually for very limited economic gains at a time when climate change is likely to increase both the risk and rate of desertification in the Arctic. Biodiversity conservation in the Arctic should recognize the importance of wetlands as functional ecosystems with their full biodiversity complement.

Overgrazing on the tundra can be severe; the subject has been reviewed by Hallanaro and Usher[24]. In Finland, there were around 120,000 reindeer at the start of the 20th century. This increased to around 420,000 animals by 1990, but subsequently declined to around 290,000 animals by 2000. The effects of overgrazing are clearly shown wherever areas of countryside are fenced off. Figure 10.8 shows an area of Norwegian Finnmark where the density of reindeer trebled between 1950 and 1989. Overgrazing eliminates ground cover by shrubs and dwarf shrubs, as well as reducing the cover of herbs, grasses, and lichens. A more detailed analysis of the area where this photograph was taken is shown in Fig. 10.9. Over the 23 years from 1973 to 1996, the area changed from one having around a sixth of the land being moderately to heavily grazed (with the remainder being slightly grazed), to one having around two-thirds being overgrazed, a little under a third being moderately to heavily grazed, and only a small proportion (probably less than 5%) being slightly grazed.

caption Fig. 10.9. Changes in grazing pressure in Finnmarksvidda, northern Norway, between 1973 and 1996. The increase in areas of lichen communities assessed as being overgrazed rises from none in 1973 to approximately two-thirds of the area in 1996[2]. (Reproduced with permission from The Nordic Council of Ministers, Denmark).

The long-term effects of overgrazing are unknown, but if it results in the elimination of key species, such as shrubs, the recovery of the overgrazed ecosystems will be very slow. If all the key plant species remain in the community, even at very low densities, and are able to re-grow and set seed after the grazing pressure is lifted, then recovery could be faster. Two factors are important – the intensity of the grazing pressure and the period of time over which it occurs. Experimental exclosures have shown that, once grazing pressure by large herbivores is lifted, the regrowth of shrubs and tree species can be remarkable. Outside the fence, willows are reduced to small plants, of no more than a couple of centimeters high and with a few horizontal branches of up to 20 cm. These plants have few leaves and generally do not flower. Inside the fence the willows grow to at least 40 cm high, and are full of flowers with abundant seed set (Fig. 10.10). It is unknown how long these dwarf, overgrazed plants can both survive and retain the ability to re-grow after the grazing pressure is reduced. There have been no studies on the associated invertebrate fauna of these willows. So, it also unknown whether the phytophagous insects and mites are able to survive such a “bottleneck” in the willow population, or for how long they can survive these restricted conditions.

caption Fig. 10.10. Whortle-leaved willow (''Salix myrsinites'') fruiting and growing in a grazing exclosure on limestone grassland that had been heavily overgrazed. After about 20 years without grazing by sheep or deer, this willow forms an understorey with other shrubs to a sparse woodland of birch (''Betula pubescens'') and rowan (''Sorbus aucuparia'') trees. (Photo: M.B. Usher, June 1998[3]).

Although the vascular plants are the most obvious, it is the lichen component of arctic habitats that can be most affected by overgrazing. In areas with reindeer husbandry, the lichen cover has generally thinned on the winter grazing grounds. In the most severely impacted areas the lichens have been almost completely grazed out of the plant communities, or have been trampled, exposing bare ground which is then subject to erosion. Lichens, which are capable of surviving the harshest of environmental conditions, are frequently the most important photosynthetically active organisms in tundra ecosystems. Albeit slow-growing, many lichen species only thrive at low temperatures, and there is concern that if climate change results in a reduction in the number of lichen species or individuals, there could be a massive release of CO2 to the atmosphere[25]. The combination of very low growth rates, overgrazing by domesticated or wild mammals and birds, and climate change indicates that large areas of the Arctic are susceptible to huge habitat changes in the future. Potentially, the lichen cover could be replaced by bare ground, with the risk of erosion by wind and running water, or by species that are currently not native to the Arctic.

Forests provide shelter during the coldest months of the year, and some of the mammals that feed on the tundra in summer migrate to the forests in winter. Pressure on herbaceous ground vegetation, especially on the lichens, can be severe. This is likely to be more of a problem in managed forests where the trees are grown closer together, less light reaches the forest floor, and the herbaceous and lichen layer is thus sparser. Overgrazing of the forest floor vegetation, including the young regeneration of tree species, is a problem in some areas and a potential problem in all other areas. Overgrazing, however, may not just result from agricultural and forestry land use; it may also result from successful conservation practices. For example, the population of the lesser snow goose (''Chen caerulescens'') in northern Canada rose from 2.6 million in 1990 to 6 million in 2000 as a result of protection. In summer, the geese feed intensively on the extensive coastal salt marshes (of western Hudson Bay), but large areas are now overgrazed, the salinity of the marshes is increasing, and vegetation has deteriorated. These examples demonstrate the potential fragility of ecosystems in which the food web is dominated by a few key species – a situation not uncommon in the Arctic.

The introduction of species into species-poor northern ecosystems is a disturbance which can have major impacts on the existing flora and fauna. The impact of introduced foxes and rats on seabird populations on arctic islands is particularly strong. A similar situation also occurs when new species are introduced into isolated freshwater ecosystems or when conditions change within a lake. For example, opossum shrimps (''Mysis relicta'') were introduced into dammed lakes in the mountains of Sweden and Norway by electric companies to enhance prey for burbot (''Lota lota'') and brown trout (''Salmo trutta''). Unexpectedly, the shrimps ate the zooplankton that was a food source for Arctic char (''Salvelinus alpinus'') and whitefish (''Coregonus lavaretus''), leading to an overall decline in fish production. Arctic char provide many interesting insights into arctic species. The resident population in Thingvallavatn, Iceland, was isolated from the sea 9600 years ago by a volcanic eruption, and became trapped within the lake. There are now four distinct forms that, although closely related genetically, are very different with respect to morphology, habitat, and diet. The Arctic has been described as a “theatre of evolution” as the few resident species capitalize on those resources that are not contested by other species. This encourages genetic diversification, a feature that is strongly shown by the Arctic char, a genetically diverse species and the only freshwater fish inhabiting high-arctic waters[26].

The subtle and sensitive interactions within food webs are illustrated by an experiment at Toolik Lake LTER (Long Term Ecological Research) site in Alaska. Lake trout (''Salvelinus namaycush'') play a key role controlling populations of zooplankton (''Daphnia'' spp.), snails (''Lymnaea elodes''), and slimy sculpin (''Cottus cognatus''). To test the hypothesis that predation by lake trout controls populations of slimy sculpin, all large trout were removed from the lake. Instead of freeing slimy sculpin from predation, the population of burbot rapidly expanded and burbot became an effective predator, restricting slimy sculpin to rocky littoral habitats, and allowing the density of its prey, chironomid larvae, to remain high. This is an example of changes in “topdown” control of populations by predators, contrasting with “bottom-up” control in which lower trophic levels are affected by changes in nutrient or contaminant loading[27] (see also Chapter 8).

Disturbance resulting from management in marine ecosystems has not been widely studied, other than by observing the impacts of trawling on seabed fauna and habitats (Figs. 10.6 and 10.7) and preliminary consideration of the potential impacts of invasive species through aquaculture, ballast water, and warming[28]. Impacts of trawling are not particularly apparent in shallow waters where sediments are soft and organisms are adapted to living in habitats that are repeatedly disturbed by wave action. In deeper waters, undisturbed by storms and tides, large structural biota have developed, such as corals and sponges, and which provide habitats for other organisms. These relatively long-lived, physically fragile communities are particularly vulnerable to disturbance and are not adapted to cope with mechanical damage or the deposition of sediment disturbed by trawls.

Fish farming also affects marine ecosystems. This can be local due to the deposition of unused food and fish feces on the seabed or lake floor near the cages in which the fish are farmed. Such deposits are poor substrates for many marine organisms, and bacterial mats frequently develop. There can also be polluting effects over wider areas due to the use of veterinary products. Over a wider area still, escaped fish can interbreed with native fish stocks, thereby having a genetic effect. Thus, commercial fishing and fish farming can have adverse effects on arctic biodiversity. Sustainable management practices may be difficult to develop, but their introduction and implementation are essential if the fishery industries are to persist into the future.

There is a particular need to assess the potential problems faced by migratory fauna. The challenges met by migratory species are illustrated by the incredible dispersion of shorebirds to wintering grounds in all continents (Fig. 10.4). Recent evidence on waders from the East Atlantic flyway compares the population trends in seven long-distance migrant species that breed in the high Arctic with 14 species that have relatively short migrations from their breeding grounds in the subarctic. The long-distance migrants all show recent population declines and are very dependent on the Wadden Sea on the Netherlands coast as a stopover feeding ground. The waders with shorter migrations are much less dependent on the Wadden Sea and show stable or increasing populations. The emerging hypothesis is that waders with long migrations are critically dependent on key stopover sites for rapid refueling. For the Wadden Sea, although the extent available has not changed, the quality of resources available has declined through expansion of shellfish fisheries[29].

There is evidence of a similar impact on migratory waders at two other sites. In Delaware Bay, a critical spring staging area in eastern North America, the impact is again due to over-exploitation of food resources by people. Similarly, the requirements of people and waders are in conflict in South Korea where a 33 km seawall at Saemangeum has resulted in the loss of 40,000 hectares of estuarine tidal flats and shallows. This site is the most important staging area on the East Asian Australasian Flyway, hosting at least 2 million waders of 36 species during their northward migration. At least 25,000 people are also dependent on this wetland system.

Thus, there are many forms of physical and biological disturbance in the Arctic (as well as in southern regions used by arctic species during migration). Such disturbances arise directly or indirectly from human intervention and the management of land and water. Although deliberate intervention can generate unexpected consequences, there is no doubt that conservation management is essential if the biodiversity of the Arctic is to be protected. In particular, implementation of international agreements, such as the Convention on the Conservation of Migratory Species of Wild Animals (also known as the Bonn Convention) and the Ramsar Convention on Wetlands, is increasingly urgent as a means to protect wetland and coastal areas.

Pollution (10.3.3)

Pollution levels in the Arctic are generally lower than in temperate regions[30]. 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[31][32]. 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).

Table 10.6. Major groups of pollutants in freshwater ecosystems and species in the Canadian Arctic[33].

Mercury

  • mercury is the most important metal in arctic lakes from a toxicological viewpoint
  • observations show, and models confirm, that about a third of the total mercury that enters a high-arctic lake is retained in the sediments, around half is exported downstream, and the rest is lost to the atmosphere
  • mercury concentrations consistently exceed guideline limits in fish for subsistence consumption or commercial sale
  • mercury concentrations in fish tend to increase with increasing fish size

PCBs

  • subarctic lakes first show PCB concentrations in the (±10 years)
  • high-arctic lakes show no significant PCB concentrations until the 1960s (±10 years)
  • PCB concentrations in fish tend to increase with increasing fish size

Toxaphene

  • toxaphene is the major organochlorine contaminant in all fish analyzed
  • highest toxaphene levels are generally seen in fish that are strictly piscivorous
  • toxaphene concentrations in fish tend to increase with increasing fish size |- | '''Chlorinated dioxins and furans'''
  • chlorinated dioxins and furans are found in fishes from some Yukon lakes
  • levels of chlorinated dioxins and furans in fish throughout the Canadian Arctic are low compared to levels in fish obtained either near bleached Kraft mills or in the lower Great Lakes |}

 

A recent report on the status of wildlife habitats in the Canadian Arctic[34] 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[35]. 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[36]. 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[37] 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[38] 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[39], 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[40].

Levels of anthropogenic radionuclides in the Arctic are declining[41]. 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[42] 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[43]. 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[44]. 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[45]. The Arctic may, however, be an important sink in the global mercury cycle[46]. 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[47]. 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[48] 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[49]. 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.

Development pressures (10.3.4)

Biodiversity in the Arctic is affected by pervasive, small-scale, and long-lasting physical disturbance and habitat fragmentation as a side-effect of industrial and urban developments and recreation. Such disturbances, often caused by buildings, vehicles, or pedestrians, can alter vegetation, fauna, and soil conditions in localized areas. A combination of these “patches” can result in a landscape-level mosaic, in effect a series of “new” ecosystems with distinctive, long-term, biodiversity characteristics. These are becoming more widespread in the Arctic and in some cases can, through enhanced productivity and vegetation quality, act as “polar oases” having a wide influence on local food webs.

Forbes et al.[50] reviewed patch dynamics generated by anthropogenic disturbance, based on re-examination of more than 3000 plots at 19 sites in the high and low arctic regions of Alaska, Canada, Greenland, and Russia. These plots were established from 1928 onward and resurveyed at varying intervals, often with detailed soil as well as vegetation observations. Although these patches have mostly experienced low-intensity and small-scale disturbances, “none but the smallest and wettest patches on level ground recovered unassisted to something approaching their original state in the medium term (20–75 years)”. Forbes et al.[51] concluded that “in terms of conservation, anthropogenic patch dynamics appear as a force to be reckoned with when plans are made for even highly circumscribed and ostensibly mitigative land use in the more productive landscapes of the increasingly accessible Arctic”.

Development in the marine environment of the Arctic is currently very limited. However, a recent report on the status of wildlife habitats in the Canadian Arctic[52] stated that “the Arctic landscapes and seascapes are subject to…oil and gas and mining developments [which] continue to expand”. Muir’s[53] analysis of coastal and offshore development concluded that pressures on the marine environment are bound to increase. There will be further exploration for oil and gas. If substantial finds are made under the arctic seas then development is likely to take place. While most known oil reserves are currently on land, offshore exploration, such as that west of the Fylla Banks 150 km northwest of Nuuk in Greenland[54], will continue to have local impacts on the seabed. Muir[55] also predicted that marine navigation and transport are likely to increase in response to both economic development and as the ice-free season extends as a result of climate change, with the consequent infrastructure developments.

Recreational use of arctic land by people, largely from outside the Arctic, is increasing. Although hikers and their associated trails potentially present few problems, this is not the case for the infrastructure associated with development and for off-road vehicles. Potential problems with trails are associated with vegetation loss along and beside the trail. This leads to erosion of the skeletal soils by wind, frost, or water. There is current discussion about the use of trekking poles[56] and whether, by making small holes in the ground that can fill with water, followed by freeze–thaw cycles, they increase the potential for erosion.

Use of off-road vehicles has increased with their greater accessibility. They can also exert greater environmental pressures than trampling by people. As a result various laws and regulations have been introduced to reduce or eliminate the damage that they cause. In Russia, off-road vehicles are frequently heavy, such as caterpillar tractors. Although it is forbidden to use these in treeless areas in summer, violations are thought to be common. Norway has prohibited off-road driving throughout the year, although different rules apply to snowmobiles. Use of the latter is becoming more frequent, with 10–11 per thousand of the population owning them in Iceland and Norway by the late 1990s; this increases to 17 in Finland, 22 in Sweden, and 366 in Svalbard. The Fennoscandian countries have established special snowmobile routes to concentrate this traffic and so prevent more widespread damage and disturbance to snow-covered habitats.

Implications of infrastructure development and habitat fragmentation, especially the construction of linear features such as roads and pipelines, are less clearly understood. However, Nellemann et al.’s research[57] gave some indications about effects on reindeer. Reindeer generally retreat to more than 4 km from new roads, power lines, dams, and cabins. The population density dropped to 36% of its pre-development density in summer and 8% in winter. In areas further than 4 km from developments, population density increased by more than 200%, which could result in overgrazing of these increasingly small “isolated” areas. If reindeer, easily able to walk across a road, behaviorally prefer to avoid roads, what are the effects of such developments on smaller animals, vertebrates and invertebrates, that are less capable of crossing such obstacles? This indicates that arctic habitats must be of large extent if they are to preserve the range of species associated with such habitats. How large should habitats be? Two developments 8 km apart, on the basis of Nellemann et al.’s research[58], can only accommodate 8% of the wild reindeer density (using winter data), and so developments will have to be more distant from each other if there is not to be undue pressure on the reindeer population and the habitats into which they move. Nellemann et al.’s conclusion[59] was that the impacts of development in the Arctic extend for 4 to 10 km from the infrastructure. So, two developments separated by 20 km may leave no land unimpacted. Developments must therefore be carefully planned, widely separated, and without the fragmentation of habitats by roads, trails, power lines, or holiday cabins.

As well as potential impacts from development, habitats will change with a changing climate. An example of where this is important for tourism is in the Denali National Park, the most visited national park in Alaska. Bus tours provide the main visitor experience by providing viewing of wildlife and scenery along the park road. The Denali park road begins in boreal forest at the park headquarters and extends through treeline into broad expanses of tundra offering long vistas. Climate-driven changes in the position of forest versus tundra would have significant effects on the park by changing the suitability of certain areas for these experiences. A treegrowth model for the park has been developed based on landscape characteristics most likely to support trees with positive growth responses to warming versus landscapes most likely to support trees with negative responses[60].The results were projected into the 21st century using data from the five general circulation models climate scenarios used in the ACIA analysis. The scenarios project climates that will cause dieback of white spruce at low elevations and treeline advance and infilling at high elevations. The net effect of tree changes is projected to be a forest increase of about 50% along the road corridor, thus decreasing the possibility for viewing scenery and wildlife at one of the most important tourist sites in Alaska. The maps of potential forest dieback and expansion should be useful for future planning.

Developments have two important implications for conservation, and both can potentially be implemented a priori. First, what regulations are needed to reduce environmental risks? A study for the Hudson Bay area of Canada[61] provided possible mechanisms for safeguarding local communities, biodiversity, and the environment, while not totally restricting development. Second, how can competing interests be reconciled? Muir[62] advocated forms of integrated management, although stating that such “approaches to integrated management which reconcile economic and conservation values will be complex and consultative”. There is a need for biodiversity conservation interests to form an integral part of any consultations over the use of the marine, coastal, freshwater, and terrestrial resources of the Arctic.

 

Chapter 10: Principles of Conserving the Arctic’s Biodiversity
10.1 Introduction
10.2 Conservation of arctic ecosystems and species
    10.2.1 Marine environments
    10.2.2 Freshwater environments
    10.2.3 Environments north of the treeline
    10.2.4 Arctic boreal forest environments    
    10.2.5 Human-modified habitats
    10.2.6 Conservation of arctic species
    10.2.7 Incorporating traditional knowledge
    10.2.8 Implications for biodiversity conservation
10.3 Human impacts on the biodiversity of the Arctic
10.4 Effects of climate change on the biodiversity of the Arctic
10.5 Managing biodiversity conservation in a changing environment

caption Image Source: Wikimedia Commons

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Glossary

Citation

Committee, I. (2014). Human impacts on the biodiversity of the Arctic. Retrieved from http://www.eoearth.org/view/article/153595

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