| China's project of converting farmland to forest (grass) started in 2000 was a major ecological project with the largest investment, greatest policy guidance, widest involvement, and highest participation by the general public in China and even in the world. By 2008, the project had not only greatly changed the land use in the areas involved, but created obvious ecological effect as well.This paper studies the project implementation in Yiliang County, which is located in low mountainous basin and valley in northeast Yunnan, based on the county's land use status quo databases in 2000 and 2008 and by comprehensively integrating several technical methods such as GIS technology, field investigation, model simulation, and comprehensive analysis. It mainly contains the studies in the following four aspects: (1) analyzing the characteristics of land use change in Yiliang County from 2000 to 2008, especially the impact of the project implementation on land use change in Yiliang county; (4) quantitatively analyzing and evaluating the rational degree of land use change in Yiliang County during the said eight years based on the establishment of the concept of rational degree of land use changes, and its connotation, indexes, and estimation methods.The studies lead to the following major conclusions:1. Characteristics of land use change. During the eight-year period from 2000 to 2008, Yiliang County had generally experienced increase in farmland and construction land areas and decrease in unused land area. The land transformation had happened mainly among farmland, garden plot, woodland, and waste grassland, especially between farmland and woodland, woodland and waste grassland. While implementing the project of returning farmland to woodland, Yiliang County also destroys woodland for farming. From 2000 to 2008, some 27600.32 hm2 of farmland was returned to woodland, garden plot, and waste grassland (area of farmland returned to eco-friendly uses), of which, 25331.34hm2 was returned to woodland. In the same period, however, some 20198.37 hm2 of woodland was transformed into farmland. We should pay great attention to such phenomenon that while some farmland being returned to woodland, large amount of woodland is destroyed for farming. During the project of returning farmland to woodland in Yiliang County from 2000 to 2008, some 21814.92hm2 of the farmland on slopes of below 25°had been returned to woodland, accounting for 79.04% of the total returned farmland. The area of the returned farmland on steep slopes of over 25°accounted for 20.96% of the total returned farmland.2. Ecological effect of land use change. With the implementation of the project of returning farmland to woodland during the said eight years, the eco-system service value of the land in the county had been generally increased. However, because of the serious deforestation for farming, the forest coverage of the whole county decreased by 5554.87 hm2. In addition, As the areas of terraced field and terraced land had decreased by 1556.42 hm2 and 10684.19 hm2, respectively, the terraced rate of the farmland on slopes had growthed a little.3. Rational degree of land use change. During the said eight-year period, the rational degree (RD value) of the overall land use change in the whole county was merely 58.20% while the un-reasonable degree (UD value) was 41.80%. This indicates that the land use change is"moderately unreasonable."Among all the land varieties, farmland, woodland, and waste grassland had the largest changes. The eight-year project of returning farmland to woodland (grassland) had a reasonability degree of only 3.78%, but an un-reasonable degree of 80%. This means that the project is"highly unreasonable."The waste grassland was transformed mainly into woodland, which was caused largely by the forestation efforts in waste hills and closed mountains to match the"return of the farmland."The woodland was transformed mainly into farmland, which amounted to 12225.61 hm2 from 2000 to 2008. The woodland change is"moderately unreasonable". |
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