Geography of Uzbekistan Kazakhstan, also yielded about 60% of the total volume of Central Asia's emissions of harmful substances into the atmosphere. Because automobiles are relatively scarce, automotive exhaust is a problem only in Tashkent and Farghona. The reduction of water in Uzbekistan has resulted in soil degradation, and the spread of the salt from the evaporated Aral Sea has contaminated the surrounding soil. The soil has lost much of its water due to the increased surface irrigation. The irrigation of farmlands with water from the Aral Sea has resulted in increased salinization of the soil, causing the farmland to be less productive
Kazakhstan–Uzbekistan border sparsely populated and traverse largely desert areas, in stark contrast to the western third which is densely populated, containing some of the largest towns in Uzbekistan and southern Kazakhstan. The eastern-most section is mountainous and contains a series of national parks (Sayram-Ugam National Park and Aksu-Zhabagly Nature Reserve in Kazakhstan and Ugam-Chatkal National Park in Uzbekistan. Uzbekistan’s Jizzakh to Sirdaryo railway crosses through Kazakhstan briefly, a legacy of the Soviet era where infrastructure was built without regard to what were then internal boundaries. Russia had conquered Central Asia in the 19th century by annexing the formerly independent Khanates of Kokand