He says mismanagement of the antiquated irrigation system has made efficient farming much more difficult.

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Because much of the loss to insects and diseases occurs after the plants are fully grown, the use of genetically engineered varieties that have higher post-harvest yields means that the farming (and irrigation) of fewer plants can produce the same total amount of food.

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But human factors have also played their part, with over-grazing, over-farming, misuse of irrigation and the unsustainable demands of a growing population all contributing to environmental degradation.

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In Soviet times, Tajikistan like other Central Asian republics, particularly Uzbekistan and Turkmenistan used to take far too much water from the Amu Darya and Syr Darya rivers for grandiose irrigation schemes, mainly for cotton farming.

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Alternative livelihoods such as ecotourism and fish farming could provide an alternative to intensive crop farming, while better management of crops and irrigation and the adoption of alternative energy sources such as solar power would all contribute to environmental sustainability.

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Miranda ranks high among Venezuelan states in agricultural and pastoral production, and government irrigation projects have resulted in the expansion of its large-scale farming and in the diversification of its agriculture.

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In the countryside the men have the backbreaking work of farming without mechanisation: again, fuel is dear, and many powered irrigation systems have broken down.

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"Dry farming" is labor intensive, but in the American West, plentiful, cheap water for irrigation is a distant memory.

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The ADB's figure for farming is not much higher, with only about 6% of Africa's cultivated land under irrigation.

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