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Environmental problems of Northern Eurasia

Deforestation and Degradation of Forests

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Impacts of Air Pollution and Nuclear Fallout

Around many industrial cities, forest damage attributed to air pollution (particularly oxides of sulphur) has been a concern since the early 1980s. Two regions, where forests (including forest-tundra) are threatened, stand out: the Kola and the Taymyr peninsulas. Both regions accommodate important mineral resources and large nickel and copper smelters, ranking among the world's largest, produce massive emissions of sulphur dioxide (SO2) and heavy metals. The destruction of vegetation occurs as a direct result of plant responses to air pollution and acidification and is also facilitated by indirect factors such as declining soil and water quality. Soil erosion, developing in the areas of severe damage to vegetation, contributes to the degradation of forests and wildfires have a greater effect on weaker stands. Damage to the highly sensitive and slowly developing subarctic forests, which play important ecological and climate protection roles, is a serious problem for Russia and, in the case of the Kola peninsula, for Scandinavian countries as well (Gytarsky et al., 1995; Alekseev, 1995; Nojd et al., 1996).

The impacts of air pollution on forests of the Kola peninsula and Fennoscandia are the best researched. These forests are composed mainly of pine, spruce, and birch. The most severe damage occurs around the mining towns of Nikel, Monchegorsk, and Zapolyarny, which at the end of the 1980s emitted more SO2 than Finland, Sweden, and Norway combined (Tuovinen et al., 1993). Tall stacks (up to 200 m high in Monchegorsk) facilitate transportation of pollutants over long distances and both modelling and observations suggest that the Kola smelters have a detrimental effect on air quality over a distance of 200 km (Tuovinen et al., 1993). Areas of strong impact around Nikel and Monchegorsk occupy 300 km2 and 190 km2 and areas of average impact cover 1260 km2 and 460 km2, respectively. The SO2 concentrations of 40-70 mg m3 averaged over the vegetative period correspond to the areas of damage (Hydromet-eorological Service, 1997; Mikkola, 1996). The critical ambient SO2 concentration for potential detrimental effects has been estimated as approximately 20 mg m3. This threshold is exceeded over areas greater than 7700 km2 around Nikel, 1400 km2 of this being Norwegian territory. Critical for the acidification value of sulphur deposition, which with respect to the Arctic ecosystems is as low as 0.3 g m 2a-1, is exceeded over 150 000 km2, 19 000 of this belongs to Norway (Tuovinen et al., 1993).

Detailed descriptions and classifications of damage to vegetation have been published by Kryuchkov (1993) and Alekseev (1995). Three broad classes of impact are identified. Average impact implies that pollution influences health, productivity, structure, and composition of vegetation. Defoliation occurs and changes are observed in the reproductive phase of pine in which the number of normally developed seeds per cone and the number of seeds with embryos decreases to 10-20 per cent compared with the healthy trees. Lichens are damaged and sensitive lichen species are eliminated while tolerant dwarf shrubs sustain growth (Alekseev, 1995). Ecological effects in the areas of strong damage involve dieback of trees, deformation of tree crowns and defoliation, disappearance of lichen cover, damage to undergrowth, and reduction of seed-containing embryos to under 6 per cent in comparison with unpolluted sites. In the most severely impacted localities, tree stands disappear and only single damaged or dying trees occur and, simultaneously with declining vegetation, soil organic layers are destroyed and mineral horizons become exposed (Alekseev, 1995).

Research on effects of pollution on tree growth has shown that there is a divergence between the affected and healthy areas (Nojd and Reams, 1996; Nojd et al., 1996). Usually, tree growth is not considered a sensitive indicator of pollution effects because it is primarily controlled by interannual variability in summer temperatures. However, the removal of the influence of climatic variability on the growth of plants has shown that while there was no difference in growth between the now damaged and healthy areas prior to 1939 when Monchegorsk (the oldest mining complex) began operating, since the 1960s a divergence in growth rates has been observed. The early 1960s were characterized by slow growth in response to lower summer temperatures, followed by a recovery in the 1970s and 1980s in the unaffected areas. In contrast, a negative trend has occurred in the areas of average damage since the 1960s and in the areas of little damage since the 1980s.

With respect to radioactive contamination of forests, two areas have been impacted: the southern Urals and areas affected by the Chernobyl accident (Chapter 19). An explosion at a military nuclear facility in the Chelyabinsk oblast in 1957 followed by the severe droughts of 1967 and 1972, which allowed scattering of radioactive material from dried-out contaminated lakes, formed the so-called Eastern Urals Radioactive Trail which extends eastwards of Chelyabinsk and covers a territory of 20 000 km2, most of which is forest land (Monroe, 1992). The releases during the Chernobyl accident contaminated about 125 000 km2 of land in Belarus, the Ukraine, and Russia. About 73 000 km2 of this area are forests which were workplaces and recreation areas, and whose products were a supplementary source of food for the local population (NBA, 1995). Because of the high filtering characteristics of trees, deposition was often higher in forests than in agricultural land. Pine forests located in proximity to Chernobyl were affected particularly badly. An area of about 375 ha was so severely contaminated that trees and the top 10-15 cm layer of soil had to be removed in order to reduce land contamination and prevent the dispersion of radioactive materials through possible forest fires (NBA, 1995). Cost-benefit analysis for forest clean-up suggested, however, that complete removal of the organic layer, which is the most promising clean-up policy, is too expensive for application across wider areas (Linkov et al., 1997). Assuming that forest ecosystems are characterized by increased soil-to-plant transfer of radionuclides, there is a possibility of exposure for individuals whose diet depends on forest products or who are employed in forest-based industries (NEA, 1995).

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