OUR CHANGING ENVIRONMENT: the Aral Sea, Central Asia

The destruction of the Aral Sea ecosystem has been sudden and severe. Beginning in the 1960s, agricultural demands deprived this large Central Asian salt lake of enough water to sustain itself, and it has shrunk rapidly. Uzbekistan, Kazakhstan, and other Central Asian states used this water to grow cotton and other export crops, in the face of widespread environmental consequences, including fisheries loss, water and soil contamination, and dangerous levels of polluted airborne sediments.

The Aral Sea is one of the greatest environmental catastrophes ever recorded. Humans have made use of the waters of the Aral basin for thousands of years, borrowing from its two major rivers: the Amu Darya, which flows into the Aral Sea from the south; and the Syr Darya, which reaches the sea at its north end. The Kara Kum Canal opened in 1956, diverting large amounts of water from the Amu Darya into the desert of Turkmenistan, and millions of hectares of land came under irrigation after 1960. While the sea had been receiving about 50 km³ of water per year in 1965, by the early 1980s this had fallen to zero. As the Aral shrank, its salinity increased, and by the early 1980s commercially useful fish had been eliminated, shutting down an industry that had employed 60 000.

Photo above shows an abandoned fishing boat in what was once the Aral Sea. Satellite images below show how the sea shrank between 1973 and 1999

The declining sea level lowered the water table in the region, destroying many oases near its shores. Over-irrigation caused salt build-up in many agricultural areas. By the beginning of the 1990s, the surface area of the Aral had shrunk by nearly half, and its volume was down by 75 per cent. Winds picked up sediments laced with salts and pesticides, with devastating health consequences for surrounding regions (see also box).

Landsat data: USGS/EROS Data Center Compilation: UNEP GRID Sioux Falls Photo: UNEP, Topham Picturepoint