青藏高原耕地面积时空变化特征及其驱动因子

Temporal and spatial patterns and driving factors of cultivated land change in Qinghai-Tibet Plateau

随着经济快速发展、城镇化进程加快以及人口基数不断增加,在城市用地不断向外扩张以及生态退耕措施的影响下,耕地面积呈逐年减小的趋势.这一现象加剧了农业发展与其他要素间的矛盾,对区域粮食安全也产生重要影响,因此,探讨耕地面积时空变化及其驱动机制对保障区域粮食安全具有现实意义.分析青藏高原地区1980年、1990年、2000年、2010年、2018年的耕地面积数据,结合户籍人口、地区生产总值(GDP)、粮食单产等统计年鉴资料解析影响其变化的主要驱动因子.结果表明:(1)青藏高原近40年耕地面积变化总体经历缓慢增加、显著增加和缓慢递减3个阶段,整个变化过程中耕地主要流失方向为林地和草地,分别占总流失面积的50.99%和32.02%,主要原因为退耕还林还草等政策的实施,其次为建设用地和水域增加.(2)耕地转为非耕地的地区主要集中在四川西部、云南西北部、青海东部,而耕地转入地区主要集中在青藏高原中部.以地市州来看,拉萨、海东、海西、阿坝、林芝等地区耕地面积变化特征以缓慢递增为主;西宁、黄南、甘孜、甘南等地区的耕地面积则呈缓慢递减的变化趋势.(3)主成分分析和结构方程模型结果显示影响耕地面积减少的主要驱动因素包括经济社会发展和粮食生产.其中经济和社会因素对耕地面积变化产生的影响为负值,社会因素产生的负影响最大,为-0.224,人口基数增长、建设用地扩张、土地利用转型要求以及二、三产业红利的吸引都会导致耕地面积减小.本研究揭示了青藏高原地区近40年耕地变化情况及流失方向,耕地面积波动主要受到经济社会因素以及政策因素的影响;上述结果可为今后国家粮食安全及当地生态环境可持续发展提供理论参考.(图7表8参45)

With rapid economic development, acceleration of urbanization, and continuous increase in population,the area of cultivated land has been decreasing year after year under the influence of the continuous outward expansion of urban land and measures of ecological restoration of farmland. This phenomenon has intensified the contradictions among many factors that have an important impact on regional food security. In this study,the cultivated land area data of Qinghai-Tibet Plateau from 1980, 1990, 2000, 2010, and 2018 were used to reveal the characteristics of the change in the cultivated land area of Qinghai-Tibet Plateau, which combines the registered population, gross domestic product(GDP), grain yield, and data from other statistical yearbooks to analyze the main environmental factors affecting cultivated land changes. The results were as follows:(1) The overall change in cultivated land area on Qinghai-Tibet Plateau over the past 40 years experienced three stages: first slowly increasing, then significantly increasing, and finally slowly decreasing. Throughout the changing process, arable land loss was mainly due to forest land loss and grassland loss, accounting for 50.99% and 32.02% of the total loss area, respectively. The underlying reason is mainly the implementation of ecological fallowing policies, for example, returning farmland to forest and grass, followed by constructed land and water areas;(2) The areas where cultivated land was converted to non-cultivated land were mainly concentrated in western Sichuan, northwestern Yunnan, and eastern Qinghai, while the areas where cultivated land was converted from others land types were mainly concentrated in the middle of Qinghai-Tibet Plateau.In terms of prefectures, the area of cultivated land for planting crops in Lhasa, Haidong, Haixi, Aba, Nyingchi,and other regions were mainly slowly increasing;In Xining, Huangnan, Ganzi, Gannan, and other regions, the area of arable land showed a slow decreasing trend;(3) The results based on principal component analysis and structural equation modeling showed that the main driving forces affecting the reduction of arable land included economic and social development and food production. Economic and social factors have a negative impact on the change in cultivated land area, with social factors carrying the largest negative impact(-0.224). This indicates that the growth of the population base, the expansion of construction land, the required transformation of land use, and the attractive benefits in secondary and tertiary industries will lead to a reduction in cultivated land area. This study revealed the change in cultivated land and the direction of loss in Qinghai-Tibet Plateau region over the past 40 years and analyzed the possible reasons that may affect the change in cultivated land area. It was concluded that its fluctuation is mainly influenced by economic, social, and policy factors,providing a theoretical reference for national food security and sustainable development of the local ecological environment in the future.