On the Problem of Anthropogenic Influence on Mammals of the Prepolar Ural Mountains

The eastern macroslope of the Prepolar Urals is inhabited by 40 mammalian species. Unique species diversity associated with a great variety of mountain landscapes is preserved in this relatively small area because of a low degree of anthropogenic impact. This study is an attempt to estimate the consequences of considerable intensification of human activity planned in connection with the exploitation of placer deposits. Previously, such work caused slight damage to terres- trial ecosystems because it affected the area of only 0.6--1.0 km 2 in each case. Nevertheless, these examples allow one to predict, to a certain extent, the trend of subsequent development of the anthropogenous pro- cesses in natural landscapes of the region. For a number of years, I studied the state of mam- malian populations in the regions of placer deposits, other mining enterprises, and wilderness areas. Large mammals. Route censuses of animals and their tracks were taken. Among large mammals, moose and bears prevail in the region (Flerov, 1933). On aver- age, one moose track and one bear track crossing the route were registered each 1.5 and 2 km, respectively. The tracks following along the route were not found on rock dumps of gold mines but occurred in river valleys not disturbed by mining. The tracks across the route were often near ravines joining the valley. The absence of differences between the results of censuses taken on rock dumps and in undisturbed areas is explained by the fact that the home ranges of these animals are con- centrated in ravines and on the slopes of mountain spurs. Bears in summer also occur in mountain tundras; they cross river valleys during daily migrations from one slope to another. Moose prefer forested slopes; hence, their routes across river valleys were mainly in the middle reaches, i.e., in the zone where gold placers are commonly located. Consequently, further develop- ment of gold mining in this region can have serious ecological consequences. The exploitation of large river valleys and neighboring tributaries of the same river system will result in the fragmentation of animal home ranges. In the summer and winter seasons, each individual range occupies 2.5-39.0 and 0.8-7.5 km 2, respectively (Filonov, 1993). Therefore, the loss of sev- eral parts of these ranges, even as small as i km 2 in area, will result in the substantial reduction of the total area inhabited by individual animals, and, conse- quently, in the decrease of animal abundance. Further development of mining in the Prepolar Urals will interfere with seasonal migrations of moose, preserved population of wild reindeer, and a number of rare (e.g., wolverine) and valuable commercial species (sable and marten). The point is that these migrations are generally directed from the plain to the mountains and back; hence, as mining is carried out on tributaries of large rivers flowing down from the main watershed, areas with depleted deposits in river valleys cut across the migration routes. As shown in some other regions of the Urals (Bukhmenov, 1975; Filonov, 1993), the gen- eral migration flow separates in such cases into discrete streams, traditional migration routes are displaced to new, less convenient locations, and the intensity of migration decreases. As a result, some animals winter under less favorable conditions, and their mortality increases.

An important role belongs to the effects of other industrial activities and anthropogenic factors associ- ated with mining, such as road construction, land clear- ing for house building, cutover and burned-out areas appearing in the forests, uncontrolled hunting, and anx- iety. Apparently, their adverse consequences will become even more serious with the expansion of min- ing industry. The road network will create additional barriers to animal migration; tree cutting and burning in large areas will bring about significant changes in food composition and supply of both herbivorous and pred- atory mammals, which lead to a short-term increase and subsequent decrease in animal abundance (Smirnov, 1987). Anxiety among animals will have the gravest consequences, making them migrate to the areas remote from the zone of industrial development and concentrate there. This primarily concerns herbiv- orous mammals. In the Prepolar Urals, where the productivity of ecosystems is relatively low, this process will soon result in the depletion of food resources and the consequent decrease in animal population size, as it occurred with wild reindeer. To date, the local popula- tions of large mammals have not been seriously affected by uncontrolled hunting. In the Man'ya River basin, for example, the estimated size of moose popu- lation is approximately 200 animals, commercial hunt- ing is virtually absent, and only two or three geologic field crews usually work in this region; as members of each crew shoot one or two moose per year, the total annual loss is only three to six animals, i.e., 1.5-3%. However, hunting pressure on these populations can rapidly exceed the allowable limit and result in their decline.

The aforementioned consequences of industrial development are equally unfavorable for representa- tives of the family Mustelidae. Small mustelids, such as weasels and ermines, have home ranges of several doz- ens of hectares (Danilov et al., 1979) but never inhabit the areas of rock dumps; hence, the appearance of each depleted mining site reduces the populations of these species by one or several individuals. Damage from mining is virtually irreversible, as the disturbed biogeo- cenoses will apparently recover for centuries (the areas of mines abandoned half a century ago are almost in the same state). Small mustelids face the risk of losing con- siderable proportions of their existing populations. This especially concerns ermines, which prefer floodplain biotopes. As to large mustelids, their home ranges cover dozens of square kilometers, and the effects of mining on these animals will be comparable to those on bears and ungulates.

A relatively low population density of large mam- mals is characteristic of the entire Prepolar Urals (Fle- rov, 1933; Laptev, 1958; Berdyugin, 1997), and its gradual decrease under the effects of anthropogenic factors can rapidly bring many species to the point of extinction. Therefore, instead of developing the mining industry in this region, it would be expedient to orga- nize there a specially protected area (e.g., national park) providing for the conservation of the entire com- plex of natural conditions, including the species diver- sity of mammals. This measure will also prevent pollu- tion of the rivers that provide spawning grounds for valuable fish species.

Small mammals. The species of this group (rodents and shrews), owing to their great abundance and diver- sity, play an important role in the processes occurring in natural communities. Differing from each other in biological requirements, they perform different func- tions in the communities and can promote their devel- opment in one direction or another, depending on exist- ing conditions.

The material on small mammals was collected in the main types of their habitats, both natural (27 types) and anthropogenically transformed to a greater or lesser extent (11 types). The results of this investigation are shown in the table.

In the Prepolar Urals, this animal group is repre- sented by ten species, two of which occur only in their natural habitats and are absent from anthropogenically transformed biotopes. A decrease in species diversity indicates degradation of animal communities. On the other hand, water voles appeared in the same areas. The occurrence of this species in the mountains provides evidence that human activities resulted in the expansion of river segments with a slow current and loose soils on the banks. This also follows from the fact that the abun- dance and proportion of root voles--rodents character- ized by a similar mode of life increased in the com- munities of anthropogenically transformed habitats (Berdyugin, 1985). The expansion of such landscape elements in the mountains can have grave conse- quences, as strong spring and rain floods, which are common in this zone, inevitably wash the soil away and denude the banks.

In general, the structure of rodent communities in natural habitats is characterized by the following fea- tures. The total number of rodents is relatively low: this is evidence that the productivity of both rodent commu- nities and biocenoses of the Prepolar Ural Mountains as a whole is also low. The northern red-backed vole is the dominant species accounting for almost half the total number of rodents in the communities. The large- toothed red-backed vole, a specific mountain species in the Urals, is subdominant. Three species--bank, field, and Middendorff voles--are common and fairly numerous components of the communities. Other spe- cies are relatively rare. In anthropogenically trans- formed habitats, the species ratio changes substantially: the proportions of the dominant species and large- toothed red-backed voles decrease, whereas those of bank voles (more typical for the southern taiga) and Middendorff voles (inhabitants of open tundra areas) increase. Changes in the proportion of root voles in rodent communities were considered above.

All distinctive features of rodent communities in the anthropogenically transformed habitats indicate that these areas are losing the landscape pattern characteris- tic of the Prepolar Urals, i.e., coniferous forests are replaced by deciduous ones, treeless areas increase in size, and the structure of the herbaceous layer changes. In addition, the system of slowly flowing streams is formed (see above). Thus, landscape formations char- acteristic of plains and atypical for highlands appear in the mountain area. They are extremely insecure under conditions of the mountain relief and cannot provide for its stabilization. These events in their natural course can lead to a general landscape crisis (Makunina, 1974).

The survey of areas exposed to less destructive anthropogenic influences several decades ago showed that changes in plant and rodent communities are gen- erally interconnected. When the cessation of mining is followed by the development of birch, mixed conifer- ous-birch, and, at later stages, birch--coniferous herba- ceous forest communities, bank voles become domi- nant in the rodent community, and field voles increase in number. Rodents can be abundant in such forest bio- cenoses. Because of certain ecological peculiarities (primarily those of feeding), these species interfere with the reverse transformation of biocenoses into their initial state, i.e., the state of equilibrium under given environmental conditions. When anthropogenic effects result in predominant development of herbaceous asso- ciations, rodent communities are characterized by increasing proportions of field voles and, in mountain tundras, Middendorff's, bank, or gray-sided-backed voles. The ecological effect of this phenomenon is the same as in the previous case. Disturbed sites are often occupied by plant communities with a weakly devel- oped herbaceous-moss layer and low productivity (even by local criteria). They are usually inhabited by northern red-backed voles, but the density of these ani- mals is extremely low. Finally, the variant closely resembling the situation on fresh rock dumps was observed in the areas where the plant cover and soils were largely (but incompletely) destroyed in the course of mining. The recovery of the biota in this case is com- plicated and proceeds extremely slowly. For example, a site of the sedge-moss tundra exposed to such an impact more than 50 years ago is still uninhabited by rodents.

To date, the biotic complex has been completely destroyed in relatively small areas. However, further development of gold mining and the resulting expan- sion of such areas in the Prepolar Urals may have grave consequences, up to the point of ecological disaster.

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