粮食国际贸易对我国水土资源利用的影响分析

Impacts of International Grain Trade on Utilization of Water and Cultivated Land

为满足国内粮食需求,粮食贸易成为弥补我国粮食缺口,缓解水土资源短缺的重要手段。近年来我国粮食进出口在数量和结构上均发生了较大变化,基于此本文定量计算了2000年以来我国以粮食贸易为载体进口的虚拟水量及耕地使用量。计算结果表明:2000年以来由于我国大豆进口量持续增长,我国以粮食为载体的虚拟水净进口量及土地替代使用量持续上升,2004年达到峰值,分别为1 244×108m3和1 580×104hm2,在进口虚拟水中径流性水资源为498×108m3,是当年全国总用水量的9%,农业总用水量的13.9%;从区域看,东南、华南、华北是粮食贸易的受益地区,粮食贸易有效的缓解了这些地区水土资源供应紧张的局面,而对中西部欠发达地区的影响相对较少。

Water and cuhivated land are basic factors of agricultural production. In recent years, water shortage and land degradation have become constraints on China＇s socioeconomic development. To meet domestic demand, grain trade has become an important means of filling the gap between supply and demand, and can also be considered an effective method for reducing pressure on water and land use. However, grain trade is a sensitive topic as China accounts for a large share of global food production and consumption. Changes in its net trade could affect markets and grain prices worldwide. Since 2000, grain imports and exports have changed substantially in both quantity and type. This paper attempts to analyze the change and its impacts on water and land use and put them in the regional context. The concepts of virtual water and equivalent cultivated area help us to calculate the water flows and land exchange based on grain transfer between China and other nations. The virtual water flows can be divided into two parts, green water and blue water, to correspond with the existing statistical system for comparison and analysis. The results indicate that grain imports have kept increasing since 2000 due to fluctuations in domestic grain production and growth in cooking oil consumption. Virtual water and land imports also grew with the jump in soybean imports. This peaked in 2004 with a virtual water net inflow of 124 billion m^3 , of which 49.8 billion m^3 was blue water, accounting for 9% of national water use and 13.9% of national agricultural water use. Meanwhile the net imported grain was equivalent to a grain-planted area of 25 million ha and a cultivated area of 15.8 million ha, which accounted for 24.6% and 12.2% of national grain-planting area and national cultivated area respectively. From a regional perspective, the regions in developed areas such as the southeast, south-central and north-central regions were the recipients, with virtual water inflows and imported cultivated land to these areas accounting for more than 90% of the national total. Meanwhile, the less-developed regions in central and western China seldom benefited from grain trade in terms of water and land use. This situation will probably not change in the near future, as the northeast and Huang-Huai-Hai regions are national breadbaskets, and their importance in this role is further strengthened by the central government due to fluctuations in grain production. Nevertheless, highly efficient agriculture is imperative, as a fundamental way to solve the mismatch between land and water distribution. Grain trade can be utilized as a supplement to supply national food demand. However, the issue of how to keep grain trade in a pluralistic structure in terms of grain type should receive more attention, as cost and risk will intensify if a specific type of grain is more dependent on the international market for supply.