The Aral Sea Basin

There has been much concern in the past decade about recent changes to the Aral Sea and its environs (see, for example, Micklin 1991, Glantz et al. 1992). Without exception, this concern has focussed upon the disadvantages of these changes. Outside the scientific literature, claims have even been made that recent changes will result (or have resulted) in the destruction of a unique lake and the development of a lifeless, poisonous inland sea (e.g. Ellis 1990). Setting such extreme claims aside, there is no doubt that there is considerable cause for concern. Nevertheless, recent changes within the Aral Sea need to be placed in perspective and considered in relation to limnological changes to large, permanent salt lakes elsewhere, as well as to past changes in the lake itself. Further, the limited extent to which the lake was scientifically distinctive needs to be recognized.

The flora of the Amu Dar’ya delta and the nature of its changes following recent anthropogenic desertification is one of the most thoroughly studied research topics concerning problems of the Aral Sea. Numerous publications and dissertations (Bachiev 1985, Bachiev et al. 1989; Kabulov 1990, Maylun 1964, Mamutov 1990, Novikova 1992, Treshkin, 1990 and others) indicate the nature of the transformation of the tugai communities, document the process as one of degradation, and predict their demise and replacement by solonchak desert (Figure 1). Until the second half of the 1980s, predicted changes have indeed occurred, but processes of vegetation transformation under the impact of environmental aridity continues and has not yet been described. Here, I am concerned not with vegetation degradation but with the processes of formation of stable desert communities. Apart from rapid increases in repetitive inundation of the delta, commencing in the mid-1980s and generally regarded in a positive light, there has also been further environmental destabilization of the delta, and this has led to degradation of the vegetation. In this connection, the present work aims to assess the current dynamic state and likely changes in the vegetation in the near and distant future.

In 1983, high mortality and deformity rates were found for waterbirds at the Kesterson National Wildlife Refuge in the San Joaquin Valley (Figure 1, index map). The cause of these phenomena was found to be high selenium concentrations in the drainwater from recently reclaimed farmland that feeds the refuge (Ohlendorf et al. 1986). The source of the selenium was weathering of marine shale on the west side of the valley (Presser and Barnes 1984). In response to concerns about similar irrigation-induced problems in other parts of the western United States, the US Department of the Interior began the National Irrigation Water Quality Program (NIWQP) in 1986.