20世纪80年代以来全球耕地变化的基本特征及空间格局

本文基于全球1982-2011年土地利用/覆被的矢量数据,分析了20世纪80年代以来全球耕地变化的基本特征及空间格局。结果表明：① 20世纪80年代以来,全球耕地面积增加了528.768×10⁴ km²,增加速率为7.920×10⁴ km²/a,呈不显著增加趋势,全球耕地面积以20世纪80年代增速最快。20世纪80年代以来,北美洲、南美洲、大洋洲耕地面积呈显著增加趋势,分别增加了170.854×10⁴ km²、107.890×10⁴ km²、186.492×10⁴ km²,增加速率分别为7.236×10⁴ km²/a、2.780×10⁴ km²/a、3.758×10⁴ km²/a;亚洲、欧洲、非洲耕地面积为减少趋势,分别减少了23.769×10⁴ km²、4.035×10⁴ km²、86.76×10⁴ km²,减少速率分别为-5.641×10⁴ km²/a、-0.813×10⁴ km²/a、 -0.595×10⁴ km²/a。② 20世纪80年代以来,全球增加的耕地主要由草地、林地转化,分别占53.536%、26.148%。新增耕地面积主要分布在非洲南部及中部、澳大利亚东部和北部、南美洲东南部、美国的中部及阿拉斯加、加拿大中部、俄罗斯西部及芬兰北部、蒙古北部等区域。非洲南部的博茨瓦纳为全球耕地增加比例最高区域,增加了80%~90%。③ 20世纪80年代以来,全球耕地换化为其他用地共计1071.946×10⁴ km²,全球减少的耕地主要转化为了草地、林地,分别占比为57.482%、36.000%;全球减少耕地主要分布在非洲中部的苏丹南部、美国中南部、俄罗斯南部及欧洲南部的保加利亚、罗马尼亚、塞尔维亚和匈牙利等国,减少最大的区域为非洲南部,减少了60%。④ 各大洲耕地均表现出向高纬扩张的趋势,全球多数国家表现出新增耕地扩张而原有耕地减少的特点。

Spatiotemporal characteristics and patterns of the global cultivated land since the 1980s

Based on the global land use / cover data from 1982 to 2011(CG-LTDR), this paper analyzes the characteristics and spatial patterns of cultivated land change since the 1980s. The results are summarized as follows: (1) Since the 1980s, the world's arable land has increased by 528.768×10⁴ km² with a rate of 7.920×10⁴ km²/a, although the trend is not statistically significant. The world's arable land grew fastest in the 1980s. Areas of cultivated land in North America, South America and Oceania increased by 170. 854×10⁴ km², 107. 890×10⁴ km² and 186. 492×10⁴ km², respectively since the 1980s, showing significant trends with rates of 7.236×10⁴ km²/a, 2.780×10⁴ km²/a and 3.758×10⁴ km²/a, respectively. Areas in Asia, Europe and Africa decreased by 23.769×10⁴, 4.035×10⁴, 86.76×10⁴ km², with rates of -5.641×10⁴ km²/a, -0.813×10⁴ km²/a and -0. 595×10⁴ km²/a, respectively. Only Asia revealed a significant reduction trend. (2) Since the 1980s, the increased cultivated land in the world has been mainly converted from grasslands and forests, accounting for 53.536% and 26.148%, respectively. Newly cultivated land was mostly distributed in southern and central Africa, eastern and northern Australia, southeastern South America, central US, Alaska, central Canada, western Russia, northern Finland and northern Mongolia. Among these regions, Botswana in southern Africa has the highest proportion of increased arable land, an increase of 80%-90%. (3) Since the 1980s, a total of 1071.946×10⁴ km² of arable land has been converted to other types of land, mostly grasslands and forests that account for 57.482% and 36.000%, respectively. Global reduction of arable land was mainly found in southern and central Africa, central South America, southern Russia and southern Europe (Bulgaria, Romania, Serbia and Hungary). Among these regions, southern Africa experienced the highest reduction of 60%. (4) Cultivated lands in all continents had a trend of expanding to high latitudes, and most countries in the world are characterized by expansion of newly cultivated land and reduction of cultivated land in the earlier period.