Final answer:
The severe shrinkage of the Aral Sea over the past 40 years, losing four-fifths of its volume, is mainly due to human activities—specifically, massive irrigation projects that diverted the key rivers feeding the lake, which were initiated by the Soviet Union in the 1960s.
Step-by-step explanation:
The significant shrinkage of the Aral Sea, once the fourth largest lake on Earth, is primarily attributed to human activity specifically, extensive irrigation projects undertaken by the Soviet Union. In an effort to transform the desert region around the Aral Sea into agricultural lands, two major rivers that fed the sea, the Amu Darya and Syr Darya, were largely diverted for irrigation during the 1960s. Thus, the Aral Sea started to lose its main sources of water influx.
While climate change-related factors such as increasing temperatures, which contribute to the global meltwater volume and the expansion of water volume, have an effect on water bodies worldwide, these were not the primary contributors to the Aral Sea's shrinkage. Here, rather than a natural occurrence, it was man-made actions that had a more direct and substantial impact, leading to it losing four-fifths of its volume over a span of 40 years.
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