Tha Aral sea: environmental impacts

During planning for a major expansion of irrigation in the Aral Sea basin, conducted in the 1950s and 1960s, it was predicted that this would reduce inflow to the sea and substantially reduce its size. At the time, a number of experts saw this as a worthwhile tradeoff: a cubic meter of river water used for irrigation would bring far more value than the same cubic meter delivered to the Aral Sea (6, 22-25). They based this calculation on a simple comparison of economic gains from irrigated agriculture against tangible economic benefits from the sea. Indeed, the ultimate shrinkage of the Aral to a residual brine lake as all its inflow was devoted to agriculture and other economic needs was viewed as both desirable and inevitable.

These experts largely dismissed the possibility of significant adverse environmental consequences accompanying recession. For example, some scientists claimed the sea had little or no impact on the climate of adjacent territory and, therefore, its shrinkage would not perceptibly alter meteorological conditions beyond the immediate shore zone (6). They also foresaw little threat of large quantities of salt blowing from the dried bottom and damaging agriculture in adjacent areas (22). This theory rested, in the first place, on the assumption that during the initial phases of the Aral's drying only calcium carbonate and calcium sulfate would be deposited on the former bottom. Although friable and subject to deflation, these salts have low plant toxicity. Second, it was assumed that the more harmful compounds, chiefly sodium sulfate and sodium chloride, which would be deposited as the sea continued to shrink and salinize, would not be blown off because of the formation of a durable crust of sodium chloride. Some optimists even suggested the dried bottom would be suitable for farming (22).

Although a small number of scientists warned of serious negative effects from the sea's desiccation, they were not heeded (14, 24). Time has proved the more cautious scientists not only correct but conservative in their predictions. A brief discussion of the most pronounced impacts follows.

Bottom exposure and salt and dust storms. The Aral contained an estimated 10 billion metric tons of salt in 1960, with sodium chloride (56%), magnesium sulfate (26%), and calcium sulfate (15%) the dominant compounds (22). As the sea shrank, enormous quantities of salts accumulated on its former bottom. This results from capillary uplift and subsequent evaporation of heavily mineralized ground water along the shore, seasonal level variations that promote evaporative deposition, and to winter storms that throw precipitated sulfates on the beaches (25-27).

Much of the 27,000 km2 of bottom exposed between 1960 and 1987 is salt-covered. In contrast to earlier predictions that were based on a faulty understanding of the geochemistry of a shrinking and salinizing Aral, not only have calcium sulfate and calcium carbonate deposited but sodium chloride, sodium sulfate, and magnesium chloride have as well (24). Because of the concentration of toxic salts in the upper layer, a friable and mobile surface, and lack of nutrients and fresh water, the former bottom is proving extremely resistant to natural and artificial revegetation (26, 28).

However, the most serious problem is the blowing of salt and dust from the dried bottom. There is as yet no evidence of the formation of a sodium chloride crust that would retard or prevent deflation (24). The largest plumes arise from the up to 100-km-wide dried stripe along the sea's northeastern and eastern coast and extend for 500 km (11, 25). Recent reports state traces of Aral salt have been found l000 km to the southeast of the sea in the fertile Fergana Valley, in Georgia on the Black Sea coast, and even along the arctic shore of the Soviet Union (29, 30).

Soviet scientists report major storms as beginning in 1975 when they were first detected on satellite imagery. Between 1975 and 1981, scientists confirmed 29 large storms from analysis of Meteor (a high-resolution weather satellite) images (11). During this period, up to ten major storms occurred in 1 year. Recent observations by Soviet cosmonauts indicate the frequency and magnitude of the storms is growing as the Aral recedes (31). Sixty percent of the observed storms moved in a southwest direction which carried them over the delta of the Amu Dar'ya, a region with major ecological and agricultural importance (11). Twenty-five percent traveled westward and passed over the Ust-Yurt plateau, which is used for livestock pasturing.

An estimated 43 million metric tons of salt annually are carried from the sea's dried bottom into adjacent areas and deposited as aerosols by rain and dew over 150,000 to 200,000 km2 (11, 13, 32). The dominant compound in the plumes is calcium sulfate but they also contain significant amounts of sodium chloride, sodium sulfate, magnesium sulfate, and calcium bicarbonate (33). Sodium chloride and sodium sulfate are especially toxic to plants, particularly during flowering. In spite of the expected increase in the area of former bottom, salt export is predicted to diminish slightly to 39 million metric tons per year by the year 2000 as a result of the exhaustion of deflatable materials, the leaching of salt into deeper layers, and through the process of diagenesis of the older surface (32).

Loss of biological productivity. As the sea has shallowed, shrunk, ant salinized, biological productivity has steeply declined. By the early 1980s, 20 of 24 native fish species disappeared and the commercial catch (48,000 metric tons in 1957) fell to zero (2, pp. 507-524; 13, 26). Major fish canneries at Aral'sk and Muynak, formerly ports but now some distance from the shore, have slashed their work force and barely survive on the processing of high cost fish brought from as far away as the Atlantic, Pacific, and Arctic oceans (29, 30, 34, 35). Both plants in 1988 will be switched to khozraschet (economic principles of management) and may be forced to close (30). Residual commercial fishing continues in lakes such as Sudoch'ye in the Amu Dar'ya Delta and in the two largest irrigation drainage water lakes that have formed (Sarykamysh and Aydarkul'). However, levels of pesticides and herbicides, from cottom field runoff, in fish taken from Sarykamysh and Aydarkul' are dangerously high, prompting a halt to commercial fishing in the former in 1987 (14, 29).

Employment directly and indirectly related to the Aral fishery, reportedly 60,000 in the 1950s, has disappeared (36). The demise of commercial fishing and other adverse consequences of the sea's drying has led to an exodus from Aral'sk and Muynak whereas many former fishing villages have been completely abandoned (30, 34). During recent years, more than 40,000 have left the districts of Kzyl-Orda Oblast that abut the Aral on the east and northeast (30).

Deterioration of deltaic ecosystems. The shrinking of the Aral along with the greatly diminished flow of the Syr Dar'ya and Amu Dar'ya has had particularly devastating effects on these rivers' deltas (11, 13, 14, 26, 37). Prior to 1960, these oases surrounded by desert not only possessed great ecological value because of the richness of their flora and fauna but provided a natural feed base for livestock, spawning grounds for commercial fish, reeds harvested for industry, and opportunities for commercial hunting and trapping. Deltaic environments deteriorated as river flow diminished and sea level fell, leading to the drying or entrenchment of distributary and even main channels, the cessation of spring inundation of floodplains, and the shrinking or disappearance of lakes. Between 1960 and 1974, the area of natural lakes in the Syr Dar'ya Delta decreased from 500 km2 to several tens of square kilometers, whereas in the Amu Dar'ya Delta from the 1960s until 1980, 11 of the 25 largest lakes disappeared and all but 4 of the remainder significantly receded (38, 39).

Native plant communities have degraded and disappeared. Tugay forests, composed of dense stands of phreatophytes mixed with shrubs and tall grasses fringing delta arms and channels to a depth of several kilometers, have particularly suffered. The expanse of Tugay in the Amu Dar'ya Delta, estimated at 13,000 km2 in the l950s, had been halved by 1980 (37). The major cause of deltaic vegetation impoverishment has been the 3 to 8 m drop of ground water along with the end of floodplain inundation.

Degradation of vegetational complexes and drops in the water table have initiated desertification in both deltas. Satellite imagery and photography from manned spacecraft indicate that desert is spreading rapidly (11) . Livestock raising has also suffered considerable damage because of a decline in yields and a reduction of suitable areas. In the Amu Dar'ya Delta between 1960 and 1980 the area of hayfields and pastures decreased by 81% and yields fell by more than 50% (26).

Habitat deterioration has harmed delta fauna, which once included muskrat, wild boar, deer, jackal, many kinds of birds, and even a few tigers. At one time 173 animal species lived around the Aral, mainly in the deltas; 38 have survived (26, 30). Commercial hunting and trapping have largely disappeared. The harvest of muskrat skins in the Amu Dar'ya Delta has fallen to 2,500 per year from 650,000 in 1960 (14)

Climate changes. Earlier claims to the contrary notwithstanding, research over the past two decades has established that the Aral affects temperature and moisture conditions in an adjacent stripe estimated to be 50 to 80 km wide on its north, east, and west shores and 200 to 300 km wide to the south and southwest (13, 26, 40). With contraction, the sea's influence on climate has substantially diminished. Summers have become warmer, winters cooler, spring frosts later, and fall frosts earlier, the growing season has shortened, humidity has lowered, and there has been an overall trend toward greater continentality. The most noticeable changes have occurred in the Amu Dar'ya Delta. At Kungrad, now located about 100 km south of the Aral, comparison of the period 1935 to 1960 with that of 1960 to 1981 indicates that relative humidity diminished substantially, the average May temperature rose 3 to 3.2 degrees Celsius, and the average October temperature decreased 0.7 to 1.5 degrees Celsius (l3). The growing season in the northern Amu Dar'ya Delta has been reduced an average of 10 days, forcing cotton plantations to switch to rice growing (14, 26).

Ground-water depression. The drop in the level of the Aral has been accompanied by a reduction of the pressure and flow of artesian wells and a decline of the water table all around the sea (13). Soviet scientists have estimated that a 15-m sea level drop, likely by the early 1990s, could reduce ground-water levels by 7 to 12 m in the coastal zone and affect the water table 80 to 170 km inland (41). The sinking water table has had significant adverse impacts outside the Amu Dar'ya and Syr Dar'ya deltas, drying wells and springs and degrading natural plant communities, pastures, and hayfields.

Water supply and health concerns. The reduction of river flow, salinization and pollution of what is left, and lowering of groundwater levels has caused drinking water supply problems for communities around the sea. Problems are especially acute in the more heavily populated deltas (13, 26). To provide a reliable, safe water supply to Nukus (1987 population of 152,000) in the Amu Dar'ya Delta, a 200-km pipeline costing 200 million rubles (officially a ruble is about publication.60) is under construction from the upstream Tyuyamuyun Reservoir. The declining quality of drinking water is cited as the main factor increasing intestinal illnesses, particularly among children, and throat cancer incidence in the lower reaches of the Amu Dar'ya and Syr Dar'ya (26, 34, 35). There is fear of epidemics because of the deterioration of the quality of the water supply and the increasing rodent population (8, 35). Desert animals who use the Aral Sea as a drinking source have died from its greatly increased mineral content (26).

Economic losses. There are no accurate figures on damages associated with the Aral's recession. Soviet scientists and economists have attempted to estimate the costs of the more tangible consequences. A 1979 study concluded that aggregate damages within the Uzbek Republic, which has suffered the greatest harm, totaled 5.4 to 5.7 billion rubles (42). A 1983 evaluation concluded that annual damages in the lower course of the Amu Dar'ya were 92.6 million rubles with the following distribution: agriculture, 42%; fisheries, 31%; hunting and trapping, 13%; river and sea transport, 8%; and living and working conditions, 6% (26). A recent popular article listed, without elaborating, a figure of 1.5 to 2 billion rubles as the annual losses for the entire Aral Sea region (14).