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Crop Diversification in the Asia-Pacific region - United Nations in ...

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soybean us<strong>in</strong>g paddy fields should contribute to <strong>the</strong> conservation of <strong>the</strong> rice-based farm<strong>in</strong>gsystem.4.3 Environmental Externalities of Japan's Paddy Fields Farm<strong>in</strong>gLocated <strong>in</strong> <strong>the</strong> <strong>Asia</strong>n monsoon zone, Japan has an annual precipitation of 1,800 mm,almost twice as high as <strong>the</strong> world average. The country is confronted with <strong>the</strong> substantialrisks of flood and water shortage ma<strong>in</strong>ly because of <strong>the</strong> relatively steep river gradientscaused by <strong>the</strong> mounta<strong>in</strong> range of 2,000 - 3,000 m elevation runn<strong>in</strong>g through <strong>the</strong> centre of <strong>the</strong>ma<strong>in</strong> island, and seasonal torrential ra<strong>in</strong>falls such as <strong>the</strong> summer ra<strong>in</strong>y season and typhoons,as well as <strong>the</strong> strong water demand required to supply <strong>the</strong> 124 million population liv<strong>in</strong>g <strong>in</strong> asmall country.Aga<strong>in</strong>st such a background, paddy field farm<strong>in</strong>g has been built up as a key systemthat plays a major role not only <strong>in</strong> food production but also to mitigate <strong>the</strong> severegeographical and climatic conditions and preserve <strong>the</strong> environment which has prevailedthroughout <strong>the</strong> country's history of more than 2,000 years.While <strong>the</strong>re are more than 2,200 years of climatic background <strong>in</strong> <strong>the</strong> country's longhistory, it has been widely recognized by <strong>the</strong> public, that, without mak<strong>in</strong>g major demands onnatural resources, paddy fields are highly effective <strong>in</strong> prevent<strong>in</strong>g floods and foster<strong>in</strong>g waterresources (as effective as dams). In addition, <strong>the</strong> terraced paddy fields are highly effectiveaga<strong>in</strong>st soil erosion on <strong>the</strong> steep hillsides.Farm areas which are composed of paddy fields provide landscape, sightsee<strong>in</strong>g andrecreational sites. Fur<strong>the</strong>rmore, paddy fields also provide a circulat<strong>in</strong>g soil system and purifyNO 2 and SO 2 <strong>in</strong> <strong>the</strong> air.Moreover, <strong>in</strong> contrast to uplands, paddy field farm<strong>in</strong>g is <strong>in</strong> l<strong>in</strong>e with susta<strong>in</strong>ableagriculture. As proven through centuries of practice, it is free from <strong>the</strong> damage result<strong>in</strong>gfrom repeated cultivation and accumulation of sal<strong>in</strong>ity and is less harmful <strong>in</strong> terms of groundwater contam<strong>in</strong>ation. Accord<strong>in</strong>g to calculations by <strong>the</strong> substitutive cost method (Table 3), <strong>the</strong>total value of environmental externalities provided by paddy fields is estimated to reach4,600 billion Yen (this is approximately US$45 billion at <strong>the</strong> exchange rate as per May 31,2000).55

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