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1.
In this paper, we analyzed the spatial patterns of cultivated land change between 1982 and 2011 using global vector-based land use/land cover data. (1) Our analysis showed that the total global cultivated land area increased by 528.768×104 km2 with a rate of 7.920×104 km2/a, although this increasing trend was not significant. The global cultivated land increased fastest in the 1980s. Since the 1980s, the cultivated land area in North America, South America and Oceania increased by 170.854×104 km2, 107.890×104 km2, and 186.492×104 km2, respectively. In contrast, that in Asia, Europe and Africa decreased by 23.769×104 km2, 4.035×104 km2 and 86.76×104 km2, respectively. Furthermore, the cultivated land area in North America, South America and Oceania exhibited significant increasing trends of 7.236× 104 km2/a, 2.780×104 km2/a and 3.758×104 km2/a, respectively. On the other hand, that of Asia, Europe and Africa exhibited decreasing trend rates of–5.641×104 km2/a,–0.831×104 km2/a and–0.595×104 km2/a, respectively. Moreover, the decreasing trend in Asia was significant. (2) Since the 1980s, the increase in global cultivated lands was mainly due to converted grasslands and woodlands, which accounted for 53.536% and 26.148% of the total increase, respectively. The increase was found in southern and central Africa, eastern and northern Australia, southeastern South America, central US and Alaska, central Canada, western Russia, northern Finland and northern Mongolia. Among them, Botswana in southern Africa experienced an 80%–90% increase, making it the country with the highest increase worldwide. (3) Since the 1980s, the total area of cultivated lands converted to other types of land was 1071.946×104 km2. The reduction was mainly converted to grasslands and woodlands, which accounted for 57.482% and 36.000%, respectively. The reduction occurred mainly in southern Sudan in central Africa, southern and central US, southern Russia, and southern European countries including Bulgaria, Romania, Serbia and Hungary. The greatest reduction occurred in southern Africa with a 60% reduction. (4) The cultivated lands in all the continents analyzed exhibited a trend of expansion to high latitudes. Additionally, most countries displayed an expansion of newly increased cultivated lands and the reduction of the original cultivated lands.  相似文献   

2.
Swidden agriculture is by far the dominant land use system in the uplands of Southeast Asia (SEA), as well as other tropical regions, which plays an important role in the implementation of Reducing Emissions from Deforestation and Forest Degradation (REDD) of United Nations. To our knowledge, the long-term inter-annual area of newly burned plots (NBP) of swidden agriculture in mainland Southeast Asia is still not available, let alone in the whole tropics. With the strengthening regional geo-economic cooperation in SEA, swidden agriculture has experienced and/or is still experiencing extensive and drastic transformations into other diverse market-oriented land use types since the 1990s. In this study, high-level surface reflectance products of Landsat 4/5/7/8 family sensors including Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+) and Operational Land Imager (OLI) acquired in March, April and May of each year between 1988 and 2016 were firstly utilized to detect and monitor the extent and area of NBP of swidden agriculture with multiple thresholds of four commonly-used vegetation indices, namely the Normalized Difference Vegetation Index (NDVI), Normalized Difference Moisture Index (NDMI), Normalized Burn Ratio (NBR) and Soil Adjusted Vegetation Index (SAVI), in combination with local phenological features of swiddening and topographical data. The results showed that: (1) an annual average of 6.08×104 km2 of NBP of swidden agriculture, or 3.15% of the total land area of MSEA, were estimated in the past nearly three decades. (2) Annual NBP were primarily distributed in four major geomorphic units including the Central Range of Hills, Northern Mountainous Region, Western Myanmar Hills, and Annamite Chain. (3) A decadal average analysis indicated that the NBP of swidden agriculture opened year by year declined as a whole, especially after 2010, merely with an average of 5.23×104 km2. (4) The top ten provincial administrative units in Cambodia, Laos, Myanmar, Thailand and Vietnam, which consistently accounted for over 90% of the newly opened swiddens of each country, showed distinct fluctuations in using slash-and-burn practices in the last decades. The Landsat-based (30 m) reconstructed 29-year longitudinal updated maps (including extent and area) of the NBP of swidden agriculture may contribute to REDD and local livelihood related studies in Continental Southeast Asia. Our study further demonstrated that the multiple vegetative indices thresholds approach holds great potential in detecting swidden agriculture in tropical mountainous regions.  相似文献   

3.
Rubber plantation is the major land use type in Southeast Asia. Monitoring the spa- tial-temporal pattern of rubber plantation is significant for regional land resource development, eco-environmental protection, and maintaining border security. With remote sensing tech- nologies, we analyzed the rubber distribution pattern and spatial-temporal dynamic; with GIS and a newly proposed index of Planted Intensity （PI）, we further quantified the impacts and limits of topographical factors on rubber plantation in the border region of China, Laos and Myanmar （BRCLM） between 1980 and 2010. The results showed that： （1） As the dominant land use type in this border region, the acreage of rubber plantation was 6014 km2 in 2010, accounting for 8.17% of the total area. Viewing from the rubber plantation structure, the ratio of mature- （〉10 year） and young rubber plantation （〈 10 year） was 5：7. （2） From 1980 to 2010, rubber plantation expanded significantly in BRCLM, from 705 km2 to 6014 km2, nearly nine times. The distribution characteristics of rubber plantation varied from concentrated toward dispersed, from border inside to outside, and expanded further in all directions with Jinghong City as the center. （3） Restricted by the topographical factors, more than 4/5 proportion of rubber plantation concentrated in the appropriate elevation gradients between 600 and 1000 m, rarely occurred in elevations beyond 1200 m in BRCLM. Nearly 2/3 of rubber plantation concentrated on slopes of 8~-25~, rarely distributed on slopes above 35~. Rubber plantation was primarily distributed in south and east aspects, relatively few in north and west aspects. Rubber planted intensity displayed the similar distribution trend. （4） Comparative studies of rubber plantation in different countries showed that there was a remarkable increase in area at higher elevations and steeper slopes in China, while there were large appropriate topog- raphical gradients for rubber plantation in Laos and Myanmar which benefited China for rubber trans-boundary expansion. （5） Rubber plantation in BRCLM will definitely expend cross borders of China to the territories of Laos and Myanmar, and the continuous expansion in the border region of China will be inevitable.  相似文献   

4.
Land use/cover change is an important theme on the impacts of human activities on the earth systems and global environmental change. National land-use changes of China during 2010–2015 were acquired by the digital interpretation method using the high-resolution remotely sensed images, e.g. the Landsat 8 OLI, GF-2 remote sensing images. The spatiotemporal characteristics of land-use changes across China during 2010–2015 were revealed by the indexes of dynamic degree model, annual land-use changes ratio etc. The results indicated that the built-up land increased by 24.6×103 km2 while the cropland decreased by 4.9×103 km2, and the total area of woodland and grassland decreased by 16.4×103 km2. The spatial pattern of land-use changes in China during 2010–2015 was concordant with that of the period 2000–2010. Specially, new characteristics of land-use changes emerged in different regions of China in 2010–2015. The built-up land in eastern China expanded continually, and the total area of cropland decreased, both at decreasing rates. The rates of built-up land expansion and cropland shrinkage were accelerated in central China. The rates of built-up land expansion and cropland growth increased in western China, while the decreasing rate of woodland and grassland accelerated. In northeastern China, built-up land expansion slowed continually, and cropland area increased slightly accompanied by the conversions between paddy land and dry land. Besides, woodland and grassland area decreased in northeastern China. The characteristics of land-use changes in eastern China were essentially consistent with the spatial govern and control requirements of the optimal development zones and key development zones according to the Major Function-oriented Zones Planning implemented during the 12th Five-Year Plan (2011–2015). It was a serious challenge for the central government of China to effectively protect the reasonable layout of land use types dominated with the key ecological function zones and agricultural production zones in central and western China. Furthermore, the local governments should take effective measures to strengthen the management of territorial development in future.  相似文献   

5.
Unplanned urban growth, particularly in developing countries has led to changes in land use/land cover (LULC). Numerous Indian cities face problems of unplanned LULC change due to nominal or non-existent planning efforts compounded by rapid urban population growth. The Guwahati Metropolitan Area (GMA) is one such urban centre. The present study assesses the trajectories of LULC change using Landsat imageries acquired in 1976, 1989, 2002 and 2015. Natural and semi natural vegetated area and artificial and natural water bodies decreased while built-up areas, cultivated and managed areas, and natural and semi natural non-vegetated areas increased. The built-up area increased from 23.9 in 1976 to 115.1 km2 in 2015 becoming the dominant land cover class accounting for 41.8% of the total geographical area. During this period, natural and semi natural vegetated land were reduced by 88.9 km2 at an annual rate of 2.2 km2. Over the years there was an increasing trend of built-up land and cultivated and managed areas in the peripheral areas of the city while natural and semi natural vegetated land diminished. Consequently, as in many other developing countries, there is an urgent need for the governmental authorities and other stakeholders to implement effective urban planning policies.  相似文献   

6.
基于遥感和GIS的中国20世纪90年代毁林开荒状况分析   总被引：10，自引：0，他引：10  
毁林开荒过程是一种林地变为耕地的土地利用变化过程,可以通过遥感和GIS技术对这一过程进行监测。本文通过覆盖全国的TM影像数据,对20世纪90年代林地转为耕地的面积及其空间分布进行分析,从而对全国毁林开荒过程进行遥感监测。结果表明,该时期有17630km2的林地被开垦为耕地。不同面积等级的开垦过程在不同流域分布也不同:面积小于10hm2和介于10～100hm2的被开垦林地较广泛地分布于各大流域;而面积介于100～1000hm2的被开垦林地主要分布于松辽流域、黑龙江流域和东北东部流域、长江流域、珠江流域和云南省所在流域;大于1000hm2的被开垦林地则几乎全部分布于松辽流域、黑龙江流域和东北东部流域。坡度大于3°的毁林开荒地面积占总面积的295%;对土壤侵蚀背景的分析表明,土壤侵蚀强度以微度和轻度为主  相似文献   

7.
We initially estimated the cropland area at county level using local historical documents for the Songnen Plain (SNP) in the 1910s and 1930s. We then allocated this cropland area to grid cells with a size of 1 km × 1 km, using a range of cultivation possibilities from high to low; this was based on topography and minimum distances to rivers, settlements, and traffic lines. Cropland areas for the 1950s were obtained from the Land Use Map of Northeast China, and map vectorization was performed with ArcGIS technology. Cropland areas for the 1970s, 1980s, 1990s, 2000s, and 2010s were retrieved from Landsat images. We found that the cropland areas were 4.92 × 104 km2 and 7.60 × 104 km2, accounting for 22.8% and 35.2% of the total area of the SNP in the 1910s and 1930s, respectively, which increased to 13.14 × 104 km2, accounting for 60.9% in the 2010s. The cropland increased at a rate of 1.18 × 104 km2 per decade from the 1910s to 1970s while it was merely 0.285 × 104 km2 per decade from the 1970s to 2010s. From the 1910s to 1930s, new cultivation mainly occurred in the central SNP while, from the 1930s to 1970s, it was mainly over the western and northern parts. This spatially explicit reconstruction could be offered as primary data for studying the effects of changes in human-induced land cover based on climate change over the last century.  相似文献   

8.
基于GIS 的中国人居环境指数模型的建立与应用   总被引：39，自引：5，他引：34  
封志明  唐焰  杨艳昭  张丹 《地理学报》2008,63(12):1327-1336
以1km×1km 栅格为基本单元, 选取地形、气候、水文、植被等自然因子, 构建了基 于人居环境指数的中国人居环境自然适宜性评价模型, 运用GIS 技术, 定量评价了中国不同 地区的人居环境自然适宜性, 揭示了中国人居环境的自然格局与地域特征。研究表明： 中国 人居环境指数整体呈现由东南沿海向西北内陆递减的趋势; 人居环境指数与人口密度显著相 关, 二者的对数曲线拟合度R2 值高达0.87, 人居环境指数可以综合反映区域人居环境的自然 适宜程度。中国人居环境自然适宜性评价结果显示, 中国人居环境适宜地区430.47×104 km2 , 接近国土面积的45%, 相应人口占全国的96.56%, 其中3/4 以上的人口集聚在约占1/4 人居 环境高度适宜和比较适宜地区; 中国人居环境临界适宜地区225.11×104 km2 , 占国土面积的 23.45%, 相应人口4112 万, 占全国的3.24%, 人口密度每平方公里18 人, 是中国人居环境 适宜与否的过渡地区; 中国人居环境不适宜地区304.42×104 km2, 人口249 万, 不到全国的 0.2%, 人口密度每平方公里不足1 人, 大片地区沦为“无人区”。  相似文献   

9.
中亚土地资源开发与利用分析   总被引：3，自引：1，他引：2  
中亚地区土地资源开发与利用研究信息资料有限,研究深度无法满足亚欧内陆干旱区社会经济可持续发展的科学要求。采用欧空局（ESA）GlobCover 2 2005年的全球陆地覆盖数据集资料和世界粮农组织（FAO）统计资料,较为系统分析了1992-2009年中亚土地资源开发与利用及其变化趋势。研究表明：（1）中亚耕地面积及作物产量呈先迅速下降后缓慢上升的趋势,耕地面积由1992年的43.1×104 km2（比例10.9%）下降到2000年的29.8×104 km2（比例7.58%）,然后上升至2009年的31.6×104 km2（比例8.04%）,但仍未恢复到1990年代初的水平;（2）林地与草地面积变化不明显,但草地载畜量变化显著。其中哈萨克斯坦2009年草地载畜量（6.25×107标准羊单位）仅为1992年草地载畜量（9.91×107标准羊单位）的63.1%;土库曼斯坦2009年草地载畜量为2.96×107标准羊单位,是1992年草地载畜量（1.04×107标准羊单位）的3倍左右;乌兹别克斯坦、塔吉克斯坦和吉尔吉斯斯坦草地载畜量均有不同程度的增加;（3）中亚地区土地资源生产潜力巨大,但在土地利用过程中出现了农田土壤侵蚀、土壤盐渍化和过渡放牧等生态问题,如何有效治理与防治上述问题,对中亚地区土地资源可持续利用和生态保护具有重要意义。  相似文献   

10.
The karst critical zone is an essential component of the carbon (C) pool, constituting the global C cycle. It is referred to as one of the “residual land sink” that remains largely indeterminate. Karst area (2.2×107 km2) comprises 15% of the world’s land area, and karst area comprises 3.44×106 km2 of area in China. Due to the complexity of karst structure and its considerable heterogeneity, C sequestration rate estimations contain large inaccuracies, especially in relation to the different methods used in calculations. Therefore, we reevaluated rock weathering-related C sink estimations in China (approximately 4.74 Tg C yr–1), which we calibrated from previous studies. Additionally, we stipulated that more comprehensive research on rock-soil-biology-atmosphere continuum C migration is essential to better understand C conversion mechanisms based on uncertainty analyses of C sink estimations. Moreover, we stressed that a collective confirmation of chemical methods and simulated models through a combined research effort could at least partially eliminate such uncertainty. Furthermore, integrated C cycling research need a long-term observation of the carbon flux of multi-interfaces. The enhanced capacity of ecosystem C and soil C pools remains an effective way of increasing C sink. Karst ecosystem health and security is crucial to human social development, accordingly, it is critical that we understand thresholds or potential C sink capacities in karst critical zones now and in the future.  相似文献   

11.
江汉平原土地利用的时空变化及其驱动因素分析   总被引：31，自引：4，他引：27  
采用遥感、GIS一体化技术,利用1989～1990、1995～1996和1999～2000年获取的三期陆地资源卫星图像,对江汉平原土地利用10年变化和以1995～1996年为界的前后两个5年变化的时空特征进行了分析,并探讨了变化的驱动因素。结果表明,该区的土地利用在不同的时间及空间尺度上有明显不同的特点。10年间,耕地减少近5万hm2,其中,前5年的减少量占多数,达6783%。各类建设用地总计增加了156万hm2,其中,前5年的增加量是后5年的2倍。水域面积在10年间增加了达到354万hm2,后5年的增幅不到前期的1/2。土地利用变化最快的区域均处于工业经济较发达、城市化较快的地区如武汉、仙桃,变化最慢的区域在监利、松滋、天门等地。政策、社会经济与科技因素对土地利用随时间尺度的变化有决定性的影响。  相似文献   

12.
中国西北水资源利用及生态环境安全   总被引：1，自引：1，他引：0  
1 Introduction In the 21st century, water resources will become the international and strategic resource instead of petroleum (Kang et al., 1994a, b). At present, the freshwater resources crisis all over the world has made people aware that although water…  相似文献   

13.
中国海洋油气资源开发与国家石油安全战略对策   总被引：17，自引：3，他引：14  
石油是中国能源安全的核心问题,随着我国石油供应对外依赖程度的增大,石油安全问题越来越突出,将会成为我国21世纪经济、社会可持续发展面临的一个重要问题。我国是海洋油气资源丰富的国家,广阔的海域中分布着近100×104km2的含油沉积盆地,近海石油资源量为240×108t,天然气资源量为140×1012m3。海洋油气资源的开发利用,将能部分解决我国油气资源进口数量。本文讨论了解决石油安全的四种模式,对我国油气安全的国际和国内条件进行了分析,提出了解决我国油气安全的战略对策。  相似文献   

14.
西北地区的退耕规模、粮食响应及政策建议   总被引：19，自引：0，他引：19  
退耕还林(草)是西北地区生态环境建设的重大举措,但退耕必然会对的粮食生产带来直接影响。基于全国土地利用详查的分县数据,研究认为:(1)按照法律规定,大于25度的陡坡耕地必须无条件地退耕。仅此一项,西北地区就必须退耕153.6×104hm2,占现有耕地的9.2%,粮食减产为71.2×104t,占1996年粮食产量的2.2%,对全区人均粮食占有量的影响很小;(2)在保证人均耕地0.1hm2前提下对大于15度的坡耕地退耕,则退耕面积可达347.8×104hm2,超过现有耕地的1/5;对应的粮食减产为234.5×104t,是1996年粮食产量的7.3%,甘肃、陕西和青海的粮食减产比例都在1/10左右,退耕带来的直接粮食减产效应是显而易见的。最后针对西北地区的退耕规模及其粮食响应,提出了两条政策建议  相似文献   

15.
In order to advance land use and land cover change (LUCC) research in Nepal, it is essential to reconstruct both the spatiotemporal distribution of agricultural land cover as well as scenarios that can explain these changes at the national and regional levels. Because of rapid population growth, the status of agricultural land in Nepal has changed markedly over the last 100 years. Historical data is used in this study, encompassing soils, populations, climatic variables, and topography. Data were revised to a series of 30 m grid cells utilized for agricultural land suitability and allocation models and were analyzed using a suite of advanced geographical tools. Our reconstructions for the spatiotemporal distribution of agricultural land in Nepal reveal an increasing trend between 1910 and 2010 (from 151.2 × 102 km2 to 438.8 × 102 km2). This expanded rate of increase in agricultural land has varied between different eco, physiographic, and altitudinal regions of the country, significantly driven by population changes and policies over the period of this investigation. The historical dataset presented in this paper fills an existing gap in studies of agricultural land change and can be applied to other carbon cycle and climate modeling studies, as well as to impact assessments of agricultural land change in Nepal.  相似文献   

16.
There exists great potential of rural land consolidation in China due to the aggravated hollowed villages against the background of rapid rural-urban transformation. The paper aims to investigate the potential of rural land consolidation within four urbanization scenarios: Complete urbanization, Semi-urbanization, Urbanization in batches and prospective urbanization in 2020. Research findings show that, (1) the potentials of rural land consolidation in complete and semi-urbanization are 809.89×104 hm2 and 699.19×104 hm2 respectively while rural consolidation rates are 50.70% and 43.77%. As for the urbanization in batches and urbanization in 2020, the potentials are 757.89×104 hm2 and 992.16×104 hm2. (2) Beside Tibet and Ningxia, rural consolidation rates in most provinces are between 40% and 60%, and the land increase rates are between 3% and 12%. Significant correlation between potential of rural land consolidation and the degree of hollowed villages is also found. (3) Evident differences of potential of rural land consolidation exist across provinces. Rural consolidation rates in the East and Central provinces are higher than that in the West provinces. Villages in the developed areas have higher consolidation rates than those in the less developed areas, and villages in the plain areas tend to have higher consolidation rates than those in the mountainous areas.  相似文献   

17.
Estimates of the physical boundary conditions on sediment source and sink regions and the flux between them provide insights into the evolution of topography and associated sedimentary basins. We present a regional‐scale, Plio‐Quaternary to recent sediment budget analysis of the Grande, Parapeti and Pilcomayo drainages of the central Andean fold‐thrust belt and related deposits in the Chaco foreland of southern Bolivia (18–23°S). We constrain source‐sink dimensions, fluxes and their errors with topographic maps, satellite imagery, a hydrologically conditioned digital elevation model, reconstructions of the San Juan del Oro (SJDO) erosion surface, foreland sediment isopachs and estimated denudation rates. Modern drainages range from 7453 to 86 798 km2 for a total source area of 153 632 km2. Palaeo‐drainage areas range from 9336 to 52 620 km2 and total 100 706 km2, suggesting basin source area growth of ～50% since ～10 Ma. About 2.4–3.1 × 104 km3 were excavated from below the SJDO surface since ～3 Ma. The modern foredeep is 132 080 km2 with fluvial megafan areas and volumes ranging from 6142 to 22 511 km2 and from 1511 to 3332 km3, respectively. Since Emborozú Formation deposition beginning 2.1 ± 0.2 Ma, the foreland has a fill of ～6.4 × 104 km3. The volume and rate of deposition require that at least ～40–60% of additional sediment be supplied beyond that incised from below the SJDO. The data also place a lower limit of ≥0.2 mm year?1 (perhaps ≥0.4 mm year?1) on the time‐ and space‐averaged source area denudation rate since ～2–3 Ma. These rates are within the median range measured for the Neogene, but are up to 2 orders of magnitude higher than some observations, as well as analytic solutions for basin topography and stratigraphy using a two‐dimensional mathematical model of foreland basin evolution. Source‐to‐sink sediment budget analyses and associated interpretations must explicitly and quantitatively reconcile all available area, volume and rate observations because of their inherent imprecision and the potential for magnification when they are convolved.  相似文献   

18.
陕西省土地利用动态变化分析   总被引：29，自引：0，他引：29  
李团胜 《地理研究》2004,23(2):157-164
基于陕西省 1 991～2 0 0 1年土地利用现状年度变更调查数据 ,分析了陕西省 1 991年初到2 0 0 1年末的土地利用动态变化。在这 1 1年间陕西省土地利用变化较大 ,其中以园地变化最大。城市用地、农村居民点及交通用地增长较快。从地区来看 ,杨凌土地利用最活跃 ,汉中土地利用最不活跃。土地利用程度最大的是杨凌 ,最小的是商洛。渭南、西安和杨凌的土地利用程度提高了 ,其余各地土地利用程度减小了。土地利用变化存在明显的地域差异 ,陕北、陕南以生态退耕还林还草为主 ,关中以结构调整为主。政策因素、自然因素、经济杠杆的调节及人口因素是陕西省土地利用变化的主要原因。  相似文献   

19.
东北松嫩平原生态系统服务价值损失的的估算   总被引：2，自引：0，他引：2  
1IntroductionEcosystems around the globe create and maintain an environment suitable for the continuation of human life. Ecosystems supply goods such as timber, pharmaceuticals, and seafood, and so provide services including purification of air and water,…  相似文献   

20.
“一带一路”贸易网络与全球贸易网络的拓扑关系   总被引：5，自引：0，他引：5  
宋周莺  车姝韵  杨宇 《地理科学进展》2017,36(11):1340-1348
共建“一带一路”倡议致力于建设开放型经济、确保自由包容性贸易。本文基于社区发现法、拓扑网络可视化等方法,对比分析“一带一路”贸易网络与全球贸易网络的拓扑关系,明确其贸易在全球的地位,以期为“一带一路”自由包容性贸易体系建设提供科学支撑。研究发现：①全球贸易网络可以识别出5个组团,其核心节点分别是中国、美国、德—荷—法—英等欧洲发达国家、俄罗斯、印度—阿联酋。②“一带一路”沿线可以识别出3个主组团及2个次组团,其中,亚欧大组团以中国为核心、俄罗斯为次核心,南亚—西亚组团以印度、阿联酋、沙特阿拉伯为核心。③在全球贸易网络中,大部分沿线国家仍被中国、俄罗斯、印度—阿联酋等核心节点所吸引,且与“一带一路”沿线的贸易联系较强;中东欧国家主要被德—荷—法—英等西欧国家核心节点所吸引,是“一带一路”低渗透国家;部分东南亚国家虽然被吸纳到以中国为核心的亚澳—南非组团,但与“一带一路”贸易联系还需加强。  相似文献   

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