Cultivated Land Change Research Articles

Land Cover Changes and Their Driving Mechanisms in Central Asia from 2001 to 2017 Supported by Google Earth Engine

Limited research has been published on land changes and their driving mechanisms in Central Asia, but this area is an important ecologically sensitive area. Supported by Google Earth Engine (GEE), this study used Landsat satellite imagery and selected the random forest algorithm to perform land classification and obtain the annual land cover datasets of Central Asia from 2001 to 2017. Based on the temporal datasets, the distributions and dynamic trends of land cover were summarized, and the key factors driving land changes were analyzed. The results show that (1) the obtained land datasets are reliable and highly accurate, with an overall accuracy of 0.90 ± 0.01. (2) Grassland and bareland are the two most prominent land cover types, with area proportions of 45.0% and 32.9% in 2017, respectively. Over the past 17 years, bareland has displayed an overall reduction, decreasing by 2.6% overall. Natural vegetation (grassland, forest, and shrubland), cultivated land, water bodies and wetlands have displayed increasing trends at different rates. (3) The amount of precipitation and degree of drought are the driving factors that affect natural vegetation. The changes in cultivated land are mainly affected by precipitation and anthropogenic drivers. The effects of increasing urban populations and expanding industrial development are the factors driving the expansion of urban regions. The advantages and uncertainties arising from the land mapping and change detection method and the complexity of the driving mechanisms are also discussed.

Measuring urbanization-occupation and internal conversion of peri-urban cultivated land to determine changes in the peri-urban agriculture of the black soil region

Structural change in peri-urban cultivated land is an effective indicator of variations in the human-land relationship and can be used to evaluate the development of peri-urban agriculture (PUA) under the pressure of rapid urbanization. However, urbanization-occupation and internal conversion, two of the primary changes in peri-urban cultivated land, have rarely been comparatively studied, especially not in an area characterized by uniform and persistent agricultural structure. Therefore, the present paper selected Changchun City in the black soil region of northeast China as a representative case, and performed land use change and spatial cluster analyses to measure changes in rainfed land, paddy land, irrigated land and orchards in the peri-urban area throughout a period of rapid urbanization (1996–2015). The results indicate that irrigated land and orchards were mainly distributed within urban-adjacent areas, and paradoxically showed an evident decrease in quantity across time. The urbanization-occupied cultivated lands revealed an imbalance in the loss and gain of peri-urban cultivated land following rapid urbanization that favors grain production. Meanwhile, the results concerning internal conversion indicate a relatively strong conversion from non-staple food production to grain production. The cultivated lands converted for grain production in the peri-urban area were mostly located at the urban fringe and positively associated with the urbanization-occupied cultivated lands. However, the cultivated lands that were converted for the production of non-staple food were relatively small-scale, sparsely distributed and located far from the central urban area. Nevertheless, both types of internal conversion were gradually overshadowed by the ever-increasing urbanization. Our study revealed an impaired local supply of non-staple food and an overall reduction in the diversified use of peri-urban cultivated lands in the black soil region. These findings suggest that the current structure of peri-urban cultivated land in the black soil region of northeast China may well be insufficient for supporting sustainable PUA development.

Spatial Distribution of Global Cultivated Land and Its Variation between 2000 and 2010, from Both Agro-Ecological and Geopolitical Perspectives

Food security requires a thorough understanding of the spatial characteristics of cultivated land changes on a global scale. In particular, the spatial heterogeneity of global cultivated land changes needs to be evaluated with high spatial resolution data. This study aims to analyse the spatial distribution of global cultivated land and the characteristics of its variation, by using GlobeLand30 data for 2000 and 2010 with a 30-m spatial resolution. The cultivated land percentage and rate of cultivated land use change are calculated based on 18 agro-ecological zones (AEZs), 32 geopolitical and socioeconomic regions, and 283 world regions. The results show that (1) more cultivated land is located in regions under a temperate climate and moderate moisture conditions; (2) the percentage of cultivated land is related to the gross domestic product (GDP) and population, while increases and decreases in cultivated land are related to the rural population, policy encouragement, urbanization, and economic development; and (3) the percentage of cultivated land and rate of land use change within an AEZ vary greatly due to the different socioeconomic conditions, and the values within a geopolitical area also vary, due to different natural conditions.

Understanding rural land use transition and regional consolidation implications in China

The changes in cultivated land and rural residential land and their interrelation are the most direct manifestation of land use transition in rural areas, which is an important basis to carry out rural land consolidation scientifically. This study constructs a conceptual model of rural land use transition and analyses the process characteristics and coupling relationship of land use transition between cultivated land and rural residential land in China in four periods from 1996 to 2016. Then, it puts forward response strategies for regional rural land consolidation. As the results show, an inverse trend between cultivated land and rural residential land, together with a certain degree of volatility demonstrated an inadequate transition in rural land use system. The types of cultivated land and rural residential land transition changed from single dominant to multiple equilibrium, but the main type of rural land use system in different stages was synchronous R negative linking. The spatial pattern of cultivated land and rural residential land transition is obviously unbalanced. The transition of rural land use system in the southeastern part of Hu Huanyong Line is active, where no transition model and process transition model play a dominant role. This area can be considered as priority for rural land consolidation in the future. Rural land consolidation should conform to the rules of land use transition, establish a multi-objective oriented regional differentiation strategy system, and promote the coordinated evolution of rural land use system.

Update of Cultivated Land Quality Grade Based on GIS—A Case Study of a County in Guangxi

The quality of cultivated land has an important influence on agricultural output, food security, sustainable development and the ability of using cultivated land resources. As the trend of cultivated land quality is getting more and more attention, in order to strengthen the management of cultivated land quality, improve the precision of cultivated land quality and other achievements, and maintain the current situation of cultivated land quality and other achievements. For this paper, taking A county of Guangxi Zhuang Autonomous Region as an example, with the support of GIS, the paper studies the grade and grade renewal of cultivated land by using the superposition method, studies the grade and grade change of regional cultivated land and its spatial distribution, grasps the status quo change of cultivated land and the grade and grade change of cultivated land caused by the quality construction of cultivated land in the year, and then provides scientific data for land use plan, land consolidation and cultivates land protection.

东南诸河流域1990-2015年土地利用时空变化特征及驱动机制

PDF HTML阅读 XML下载 导出引用 引用提醒 东南诸河流域1990-2015年土地利用时空变化特征及驱动机制 DOI: 10.5846/stxb201810102187 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金地区基金项目（31660233）；国家自然科学基金项目（51711520317） Spatial and temporal variability characteristics and driving mechanisms of land use in the Southeastern River Basin from 1990 to 2015 Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土地利用/覆被变化作为影响全球环境变化的重要因素，是人类活动最直接的反映，其驱动力分析能够很好地揭示人类活动对土地资源的影响机制。运用ArcGIS空间分析和SPSS主成分分析等方法，从整个东南诸河流域片区的尺度上，研究了包含中国台湾地区在内的1990-2015年间的土地利用时空变化特征，并探究其主要驱动机制。研究结果为：（1）全流域各土地类型面积占比为：林地 > 耕地 > 草地 > 城乡建设用地 > 水域 > 未利用土地，林地与耕地的空间分布特征均为"北聚南散，北多南少"，城乡建设用地集中分布在经济较为发达的台湾海峡两岸沿海地区以及流域大陆北部靠近长江三角洲的地区。（2）全流域土地类型的面积变化量为：城乡建设用地 > 耕地 > 草地 > 林地 > 水域 > 未利用土地。流域土地利用综合动态度为0.68%，整体用地类型转化程度先降低再增加，并以城乡建设用地和耕地为主要变化类型。流域南部各市的土地利用变化较北部剧烈，台湾地区主要土地利用变化类型为耕地和城乡建设用地。（3）大陆地区城乡建设用地变化的主要驱动力为人口数量及结构、城市化和社会经济发展，台湾地区在此基础上增加了社会工农产业结构调整因素。大陆耕地变化的主要驱动力为人口数量及结构、城市化水平和社会工农产业结构，社会工农产业结构和农业生产水平是台湾地区耕地变化的主要驱动力。本研究为东南诸河流域土地资源规划管理提供科学依据，为自然流域尺度的土地利用变化及其驱动机制研究提供可靠实例。 Abstract:Land use change, an important factor affecting global environmental change, is one of the most crucial human activities. Research on land use change is critical to reveal the mechanism of impacts of human activities on land resources. In this study, we used the ArcGIS spatial analysis function and the SPSS principal components method to analyze the spatial and temporal changes of land use in the Southeastern River Basin (including Taiwan) from 1990 to 2015 and explore the possible driving mechanisms. The main results are as follows:(1) From 1990 to 2015, the proportions of different land types throughout the basin was forest land > farmland > grassland > urban and rural construction land > water area > unused land. Forest and cultivated land largely gather on the north of the basin, while they are more scattered and less in the south. Urban and rural construction land is concentrated in the coastal areas of Taiwan province, where the economy is relatively well developed, as well as in the northern basin near the Yangtze River Delta. (2) The comprehensive dynamic degree of land use in the basin is 0.68%, and the degree of conversion of overall land use type first declined and then increased from 1990 to 2015. Most changes occurred on urban and rural construction lands and cultivated land. Land usage change in the southern region of the basin is more intense than that in the north. The main type of land use change in Taiwan province was cultivated land and urban and rural construction land. The comparison of changes in the area of land types in the basin is:urban and rural construction land > cultivated land > grassland > forest land > water area > unused land. The most significant increases in urban and rural construction comes from cultivated land. Hence, the increases in cultivated land begins with forest land and then gradually transitions to urban and rural construction land. There is a certain degree of synergy between the intensity of urban land use and cultivated land. The latter has maintained a large degree of change and dominates the changing structure of each period. The average annual dynamics of other construction land in the past 25 years was 17.30%, showing clear growth trends. (3) The main driving forces behind urban and rural construction land usage changes in mainland China are population quantity and structure, urbanization level, and level of social and economic development. On this basis, Taiwan province has increased the social industrial and agricultural industrial structure adjustment factors. Additionally, the main driving forces behind changes in cultivated land in mainland China are population size and structure, urbanization level, and social and agricultural industrial structures. In Taiwan province, the social and agricultural industrial structures and agricultural production levels are the main forces driving changes in cultivated land. In this study, we analyzed the spatial and temporal variability and driving mechanisms of land use changes in the southeastern river basins. This study provides theoretical support for the rational planning for land resources in the region, and provides baseline data support for the comprehensive management of resources and the environment at the basin-wide scale. 参考文献 相似文献 引证文献

Cultivated-land change in Mu Us Sandy Land of China before and after the first-stage grain-for-green policy

Cultivated-land change in Mu Us Sandy Land of China before and after the first-stage grain-for-green policy

Institutional transition and implementation path for cultivated land protection in highly urbanized regions: A case study of Shenzhen, China

Cultivated land is a key resource and environmental factor for human survival and development, and internationally, special protection is generally imposed on cultivated land. China conducts the most stringent cultivated land protection system worldwide, but the restraint mechanism of rigid control with pure administration cannot change the continuous decreasing trend in the acreage and quality of cultivated land. Shenzhen, which is the city with the fastest economic growth in China and a highly urbanized area with a non-agricultural population, has very serious issues regarding cultivated land encroachment, spatially fragmented distribution, and land abandonment, which has rendered cultivated land protection extremely difficult. In this article, the present cultivated land protection situation in China and other countries is summarized, and the acreage change, spatial distribution, and land abandonment of cultivated land in Shenzhen are summarized and analyzed. Then, we propose an institutional framework for the transition of cultivated land protection in Shenzhen, which includes spatial optimization, management innovation, and safeguard systems. The implementation path to the transition of cultivated land protection includes a basic farmland reformation project, spatial usage control and zoning of cultivated land, tender and bid management for cultivated land leasing, and management innovation for facility agricultural land. The pros and cons of how non-agricultural populations impact cultivated land protection and the compound benefits, including the political, ecological, cultural, and technical aspects, of cultivated land protection in highly urbanized areas are discussed. This article notes the potential risks in management innovation in facility agricultural land. The proposed institutional framework for the transition of cultivated land protection and its implementation paths provide a reference for cultivated land protection and utilization in highly urbanized areas and suburbs with a heavy contradiction between economic growth and cultivated land protection in developing countries.

Small UAV based multi-viewpoint image registration for monitoring cultivated land changes in mountainous terrain

ABSTRACTLand degradation, soil erosion, and illegal occupation in the mountainous terrain of southern China have severely reduced the amount of cultivatable land. The use of small unmanned aerial vehicles (UAVs, aka drones) equipped with various types of cameras is considered to be a flexible and low-cost platform for monitoring cultivated land changes. However, image pairs of the same scene taken from different viewpoints often contain discontinuous rotated images with illuminated variations. To address these problems, a novel small UAV based multi-viewpoint image registration method for monitoring cultivated land changes in mountainous terrain is proposed. First, a mixed feature descriptor (MFD) is defined for measuring global and local discrepancies between two datapoint sets, and a deterministic annealing scheme is employed to control the balance of the MFD. Second, the mixed feature finite mixture model (MFMM) is formulated to be the estimation of mixture densities. Finally, the double geometric constraints for -minimizing estimate based energy optimization is formulated in order to calculate a reasonable position in a reproducing kernel Hilbert space. Extensive experiments on UAV images with different viewpoints are conducted. Experimental results show that our method provides better performances in most cases after comparing with six state-of-the-art methods.

Cultivated land change in the Belt and Road Initiative region

The Belt and Road Initiative (BRI)–a development strategy proposed by China – provides unprecedented opportunities for multi-dimensional communication and cooperation across Asia, Africa and Europe. In this study, we analyse the spatio-temporal changes in cultivated land in the BRI countries (64 in total) to better understand the land use status of China along with its periphery for targeting specific collaboration. We apply FAO statistics and GlobeLand30 (the world’s finest land cover data at a 30-m resolution), and develop three indicator groups (namely quantity, conversion, and utilization degree) for the analysis. The results show that cultivated land area in the BRI region increased 3.73×104 km2 between 2000 and 2010. The increased cultivated land was mainly found in Central and Eastern Europe and Southeast Asia, while the decreased cultivated land was mostly concentrated in China. Russia ranks first with an increase of 1.59×104 km2 cultivated land area, followed by Hungary (0.66×104 km2) and India (0.57×104 km2). China decreased 1.95×104 km2 cultivated land area, followed by Bangladesh (–0.22×104 km2) and Thailand (–0.22×104 km2). Cultivated land was mainly transferred to/from forest, grassland, artificial surfaces and bare land, and transfer types in different regions have different characteristics: while large amount of cultivated land in China was converted to artificial surfaces, considerable forest was converted to cultivated land in Southeast Asia. The increase of multi-cropping index dominated the region except the Central and Eastern Europe, while the increase of fragmentation index was prevailing in the region except for a few South Asian countries. Our results indicate that the negative consequence of cultivated land loss in China might be underestimated by the domestic- focused studies, as none of its close neighbours experienced such obvious cultivated land losses. Nevertheless, the increased cultivated land area in Southeast Asia and the extensive cultivated land use in Ukraine and Russia imply that the regional food production would be greatly improved if China’ “Go Out policy” would help those countries to intensify their cultivated land use.

Measuring the Cultivated Land Use Efficiency of the Main Grain-Producing Areas in China under the Constraints of Carbon Emissions and Agricultural Nonpoint Source Pollution

The carbon emissions and agricultural nonpoint source pollution constraints were incorporated into the input–output index system, and the epsilon-based measure (EBM) super efficiency model and global Malmquist–Luenberger (GML) index were used to measure the cultivated land use efficiency and changes in the total factor productivity (TFP) of cultivated land use in the main grain-producing areas in China from 1993–2016. The results indicate that: (1) from 1993 to 2016, the cultivated land use efficiency in the main grain-producing areas in China showed a tendency to fluctuate and increase, with obvious stage characteristics; however, the overall level was not high. (2) There is a significant difference in the cultivated land use efficiency under the constraints of carbon emissions and nonpoint source pollution in the main grain-producing areas in the different provinces, and low-efficiency provinces have higher input redundancy and undesired output redundancy than high-efficiency provinces. It can be observed that input redundancy and undesired output redundancy have a significant negative effect on cultivated land use efficiency. (3) The TFP of cultivated land use under the constraints of carbon emissions and nonpoint source pollution in China’s main grain-producing areas is estimated by the GML index. The results show that the TFP of cultivated land use in the main provinces in the main grain-producing regions is greater than 1, indicating that the productivity levels of all the provinces in China’s main grain-producing areas are increasing. From the perspective of the power sources in each province, global pure technological change (GPTC) and global scale technological change (GSTC) are the main driving forces for the TFP of cultivated land use, while global pure efficiency change (GPEC) and global scale efficiency change (GSEC) are the bottlenecks for increasing the TFP of cultivated land use.

Impacts of Urbanization on the Net Primary Productivity and Cultivated Land Change in Shandong Province, China

With rapid social and economic development, pressure on the land ecosystem in Shandong Province, China, is becoming more and more obvious. This study aimed to gain insight into the impacts of urbanization on several ecosystem and land characteristics. Carnegie-Ames-Stanford Approach was used to estimate the terrestrial vegetation net primary productivity (NPP) from 2001 to 2010 in Shandong. The spatio-temporal pattern of NPP was analyzed. Subsequently, the pressure index of cultivated land in Shandong was calculated and used to analyze the spatiotemporal characteristics and the problem of supply and demand for cultivated land by using geographical information system technology. The relationship between NPP and the pressure index of cultivated land was further analyzed, and the influence of both natural and manmade factors was discussed. Based on the above, some suggestions have been proposed for the sustainable development of land use/cover change in Shandong Province. A weak increasing trend in the overall NPP has been observed over the study period, and the NPP in the southwest was higher than in other regions. Impacts of the land use types on NPP were different. About 34.6 × 1012 g of carbon was absorbed every year, of which nearly 75% was absorbed by farmland. Cultivated land initially decreased and then increased during the period. With the help of technology, science, macroeconomic policy, and other developments, the total grain yield increased with some fluctuation. Moreover, the actual area of cultivated land has increased. These changes improved the theoretical minimum cultivated land area per capita, while the pressure index decreased. The pressure on cultivated land also showed obvious regional differences during this period, which is mainly concentrated in the coastal regions and the cities of Jinan and Laiwu. In the western and northern regions, on the other hand, the pressure was relatively lower due to slower economic growth. These results reflect that the urbanization has huge impact on the cultivated land resources.

Research on Cultivated Land Change Based on GIS and High Resolution Remote Sensing Images

This paper study an automatic monitoring method for land change based on high resolution remote sensing images and GIS data, and we use three classification methods to classify and fuse the research area. Secondly, the paper calculates the corresponding map class components and compares them with their historical attributes; it can automatically monitor land use change. The experimental results show that the fuzzy decision fusion classification can significantly improve the classification effect, and it can accurately determine the change area accurately and automatically. However, there are some partial errors in the region.

Dynamic evolution of landscape spatial pattern in Taihu Lake basin, China

Based on the land-use satellite image datasets of 2000, 2010 and 2015, the landscape index, dynamic change model, landscape transfer matrix and CLUE-S model were integrated to analyze the dynamic evolution of the landscape spatial pattern of Taihu Lake basin. The results showed that the landscape type of the basin was dominated by cultivated land and construction land, and the degree of landscape fragmentation was strengthened from 2000 to 2015, and the distribution showed a uniform trend. From the point of transfer dynamic change, the cultivated land and construction land changed significantly, which was reduced by 6761 km2 (2.1%) and increased by 6615.33 km2 (8.4%), respectively. From the landscape transfer, it could be seen that the main change direction of the cultivated land reduction was the construction land, and the cultivated land with 7866.30 km2 was converted into construction land, accounting for 91.6% of the cultivated land change, and the contribution to the construction land was 96.5%. The trend of dynamic changes of cultivated and construction land in the counties and cities was the same as that of the whole Taihu Lake basin. For Shanghai Central Urban, as well as Pudong District, Lin'an City, Baoshan District, Minhang District, Jiading District and Changzhou City, the area of the cultivated land and construction land changed more prominently. However, compared with the CLUE-S model for the landscape pattern change in 2030, the change of cultivated and construction lands would be the largest in the natural development scenario. Under the ecological protection scenario, the area of grassland would increase and the dynamic degree would reach 54.5%. Under the situation of cultivated land protection, the conversion of cultivated land to construction land would be decreased.

Does Expressway Consume More Land of the Agricultural Production Base of Shandong Province?

The effect of expressways on cultivated land is ambiguous. Many studies conclude that building and upgrading expressways increases pressure on cultivated land while others find expressways reduce the rate of cultivated land loss. In this paper, we use satellite remote sensing images of cultivated land in Shandong province of China to test whether the existence of expressway in 2005 affected the level of cultivated land in 2010 and the rate of change from 2005 to 2010. To account for expressway access for each of our 1 $$\hbox {km}^2$$ (‘pixel’) units of cultivated land we measure whether or not and what type of roads penetrate the ‘watershed’ in which the pixel lies. These watersheds allow more plausible measures of accessibility than those traditional ‘crowfly’ distance measures that ignore topography. To account for possible confounding we also use 24 additional covariates. Although simple univariate OLS regressions analysis show that cultivated land is always lower while cultivated land increasing rates are higher either when there is an expressway, these results are not robust. Controlling for all of the covariates and also using recently developed covariate matching techniques to estimate treatment effects, we find that expressway can most safely be described as putting a positive impact on cultivated land changes.

Land use/land cover change and statistical modelling of cultivated land change drivers in Nigeria

In recent decades, human activities have significantly influenced land use/land cover. Identifying pattern changes in regional land use/land cover and their drivers is crucial for land use planning and management decision making. This study aims to (1) describe land use/land cover changes that have taken place in Nigeria in the study period of 10 years (2000–2010), (2) determine the factors that drive those changes with emphasis on transition to cultivated land use and (3) examine the spatiotemporal intensity of land use. The study utilized the GlobeLand30 land cover datasets produced by the National Geomatics Center of China. We used the spatial calculating analysis model to analyse land use/land cover change, logistic regression to model drivers of cultivated land expansion and land use intensity comprehensive index model to examine the intensity of land use. Our results revealed that (1) conversions to cultivated land dominate the land use/land cover change processes and expansion was largely at the detriment of the grassland, shrubland and forests; (2) biophysical, socio-economic and proximity factors are significant determinants of transition to cultivated land use. Population density is negatively related to cultivated land expansion, which suggests labour scarcity in the agricultural sector that can consequently result into low productivity and (3) significant discrepancies exist in the intensity of land use between the southern and northern regions of the country. Policy measures aimed at improving agricultural productivity remain one of the best ways to reduce pressure on increasingly scarce land resource and conserve natural ecosystems in Nigeria.

Urbanization-induced site condition changes of peri-urban cultivated land in the black soil region of northeast China

The site condition of cultivated land greatly influences the utilization and management of cultivated land resources and is an element that is disturbed tremendously by urbanization. Since the rejuvenation of the northeast old industrial base strategy in 2003, urbanization in northeast China has progressed rapidly. The excessive urban sprawl has profoundly changed land use structure in the peri-urban area of the black soil region, and the subsequent site condition changes will impede the full utilization of cultivated land resources. This study used the suburb of Changchun Kuancheng District as an empirical case, and employed a patch-scale site assessment system to analyze dynamic changes in cultivated land site conditions at a typical rural-urban interface of the black soil region from 2004 to 2014. Cultivated land loss and land use changes were prominent in the study area and the land conversion rate was shown to be accelerating. Most of the occupied cultivated land was converted to urban areas such as industrial land or urban settlements. However, a part of the occupied cultivated land was left unutilized, which indicates how the urban sprawl is jeopardizing benefits of both urban development and cultivated land protection. Besides direct occupation of cultivated land resources, urbanization has led to a loss of cultivated land with good site conditions and a deterioration of the site conditions of unconverted cultivated land in the peri-urban area. Urbanization has fragmented peri-urban cultivated land, increased farming distance and brought more frequent anthropogenic disturbances. On the other hand, it has also improved transportation conditions and the local ecological environment. As site condition is believed to be closely related to both cultivated land loss and cultivation abandonment, the deterioration will aggravate the loss of cultivated land resources in a disguised form.

The influences of spatiotemporal change of cultivated land on food crop production potential in China

The impact of changes in cultivated land on the production potential of food crops in China during the period of 1990–2010 was studied using land use data and the Global Agro-ecological Zones (GAEZ) model. The contribution of crop production potential per unit cultivated land area (PPCLA) to the total food-energy based production potential (TPP) of food crops was further investigated. From 1990 to 2010, China has experienced a net increase of cultivated land, resulting from a net increase in northern China and a smaller net decrease in the south. However, the TPP reduced by 9.64 × 1012 kcal despite an overall cultivated land increase for crops. This was attributed to the spatial heterogeneity of PPCLA in the cultivated land, whereby the average PPCLA of the newly cultivated land was much lower than that of the lost land. The PPCLA gap between the newly developed land and the lost cultivated land expanded from 3.16 × 106 kcal/ha in the first decade (1990–2000) to 6.49 × 106 kcal/ha in 2000–2010. Contributions of PPCLA to TPP varied among regions, and the regions with the largest contributions were consistent with those with the largest PPCLA gaps. Such regions included the Sichuan Basin and surrounding region in 1990–2000, and the Huang-Huai-Hai Plain during 2000–2010. Based on these research findings, key implications for land use policies in relation to major food crops in China are discussed.

The basic characteristics and spatial patterns of global cultivated land change since the 1980s

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.

Impacts of land use/cover change on terrestrial carbon stocks in Uganda

Land use/cover change, especially conversion and degradation of forest land, is the key factor causing terrestrial carbon stocks declines in Uganda. How local ecological assemblages are responding is less clear—a concern given their importance for many ecosystem functions and services. The main objectives are to assess status and variation in carbon stocks across land covers and quantify spatial distribution and dynamic variation of terrestrial carbon stocks in response to land use/cover change. This paper presents a methodology for quantifying and assessing changes in carbon stocks as a result of land use change using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. The model was used to map and quantify carbon stocks for Uganda for 2006 and 2010 land use conditions. Our result showed that the total carbon stocks have a sharp decline from 2.42 billion Tg C in 2006 to 1.72 billion Tg C in 2010 in aboveground, belowground and soil. During 2006 to 2010, losses in carbon stocks from land use and land cover were 705.59 million Tg C. To be more specific, estimated carbon stocks in Uganda decreased 849.94 million Tg C because forest land changed to other land use and covers. Cultivated land change, which is from other types of land, resulting in carbon stocks decreased 71.11 million Tg C, and estimated carbon stocks increased 177.34 million Tg C with grassland changed to other land use and covers. Finally, we suggested potential policy measures to mitigate negative effects of land use and cover change on carbon stocks in Uganda.