发展生物能源引发的土地利用问题

在经济发展不断增加对能源的需求和国际上减少温室气体排放的压力下,生物能源得到了各国政府的大力扶持并取得了快速发展。全球燃料乙醇生产总量1975年为5.68×108L,2000年增加到170×108L,2007年迅速增加到511×108L。生物柴油也自2000年的约9.1×108L迅速增加到2007年的132×108L。生物能源的迅速发展带来了关于其对粮食安全影响的激烈争论。论文从剖析近年来关于生物能源发展对粮食安全的影响入手,系统分析了耕地在生物能源生产及其效应研究中的重要作用、近年来生物能源发展占用耕地面积、对土地利用变化的影响及其对农户耕地利用决策行为的影响机制。研究发现:①土地作为生物能源生产的主要资源投入类型,是其对粮食安全产生影响的最重要媒介;②近年来生物能源占用耕地面积呈不断增加趋势,2004年,全球生物能源占地1 400×104hm2,约为全球耕地总面积(140 583×104hm2)的1%,到2007年,占地4 221.7×104hm2,相当于2004年的3.05倍,据保守估计到2030年,将占地5 300×104hm2;③发展生物能源直接带来林地、草地和农用地等土地利用类型之间,以及不同农作物类型之间的土地利用冲突,并带来土地利用方式的显著变化;④从农户尺度看,相对于粮食作物,能源作物具备较高的经济收益,根据对广西武鸣县的农户调查得出,2009年木薯纯收益为11 123.04元/hm2、甘蔗为12 138.36元/hm2,远远高于稻谷(6 984.04元/hm2)、玉米(5 104.61元/hm2)、花生(2 851.36元/hm2),收益上的比较优势是其播种面积不断增加的根本原因。

Land Use Changes Caused by Biofuel Production

Influenced by increasing thirst for energy to fuel fast growing economy and pressure of reducing greenhouse gas emissions, biofuel production expanded rapidly these years. The total bio-ethanol production increased from 5.68×10⁸ L in 1975 to 170×10⁸ L in 2000 and to 511×10⁸ L in 2007. The biodiesel increased from 9.1×10⁸ L in 2000 to 132×10⁸ L in 2007. The rapid increase of biofuel aroused hot debates on its effect on food security. This paper analyzed the debates of biofuel production, area of land used for biofuel production, its impact on land use changes and the international mechanism of farmers’ land use decisions. Results show that as one of the main input of biofuel production, land use change is the medium of its influence on food security, environment and other social dimensions. Secondly, the arable land used for biofuel production has been increased rapidly these years. In 2004, there was 1400×10⁴hm² of arable land used for biofuel production, accounted for 1% of the total arable land (140583×10⁴hm²). In 2007, figure increased to 4221.7×10⁴hm². It is projected that fuel crops’ sown area may account for 15%-20% of the total sown area in some countries in the near future. Fuel crops will become one of the main crops. Thirdly, extension of the sown area of fuel crops caused remarkable land use changes. Large area of forest, grassland and unused land was converted to agricultural land. In the internal planting structure, food crops were converted into fuel crops. Fourthly, household is the basic decision maker of land use changes. Attracted by higher income, famers are more inclined to plant crops that have more net income. From the input-output comparison of main food and fuel crops in Guangxi, net income of fuel crops is much higher than food crops. In 2009, the net income of cassava was 11123.04 yuan/hm² and sugarcane 12138.36 yuan/hm², more than rice (6984.04 yuan/hm²), maize (5104.61 yuan/hm²) and peanut (2851.36 yuan/hm²). This is the basic reason for the increase sown area of fuel crops. Finally, the paper proposed that further studies were needed to be done on the quantitative analysis of the competition of biofuel crops and food crops, the internal mechanism of farmers’ land use decisions, the impact of biofuel production on future land use changes in the process of urbanization.