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1.
Lake Qinghai, the largest saline lake in China, covers 4234 km2 (2007) with a catchment area of 29 660 km2 on the northeastern margin of the Qinghai‐Tibet Plateau. The ecosystem of the lake is extremely vulnerable and sensitive to global climate change and human interference. However, little information is available on land use/cover change (LUCC) in Lake Qinghai watershed. Using a geographical information system (GIS) and remote sensing (RS), this study analysed land use and land cover change pattern in Lake Qinghai watershed between 1977 and 2004 and discussed major environmental issues in this area. LUCC analysis indicated that grassland (63 per cent) and water body (18 per cent) dominated in the watershed and the magnitude of the land use and land cover change was generally low; the percentage of the change of various land types relative to the total area was less than 1 per cent. From 1977 to 2004, cropland, sandy land, bare rock, salinized land, swampland and built‐up areas increased by 0·43, 0·35, 0·24, 0·06, 0·03 and 0·03 per cent of the total area, respectively; in contrast, water body, grassland and woodland decreased by 0·99, 0·22 and 0·05 per cent, respectively. Moreover, the area of LUCC tended to expand from places around the lake to the upper reaches of the watershed during the last three decades. The LUCC transition pattern was: woodland converted to grassland, grassland converted to cropland and water body converted to sandy land. Lake level decline and grassland degradation are major ecological and environmental problems in Lake Qinghai watershed. The level and area of the lake decreased at the rate of 6·7 cm a−1 and 6·4 km2 a−1, respectively, between 1959 and 2007, resulting in sandy land expansion and water quality deterioration. Lake level decline and area shrinkage was mainly attributed to climate change, but grassland degradation was mainly resulted from anthropogenic activities (increasing population, overgrazing and policy). Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

2.
The combined effects of erosive rains, steep slopes and human land use have caused severe land degradation in the Ethiopian Highlands for several thousand years, but since the 1970s, however, land rehabilitation programmes have been established to try to reverse deterioration. In order to characterize and quantify the transformations in the north Ethiopian Highlands, a study was carried out over 8884 km2 of the Tigray Highlands of northern Ethiopia. Using Landsat Multispectral Scanner and later Thematic Mapper imagery (1972, 1984/1986 and 2000), historical terrestrial photographs (1974–1975) and fieldwork (2008), we prepared land use and cover maps. For assessing the use of the historical terrestrial photographs, Landsat images from 1972 were classified using two different methods, namely conventional change detection (image differencing) and ground truthing (using the historical photographs of 1974–1975). Results show that the use of terrestrial photographs is promising, as the classification accuracy based on this method (Kappa coefficient 0·54) is better than the classification accuracy of the method based on image differencing (Kappa coefficient 0·46). Major land use and cover changes indicate the following: (1) a gradual but significant decline in bare ground (32 per cent in 1972 to 8 per cent in 2000); (2) a significant increase of bushland (25 to 43 per cent) and total forest area (including eucalypt plantations, 2·6 to 6·3 per cent); and (3) creation of numerous lakes and ponds. The dominant change trajectory (27 per cent of the study area) indicates a gradual or recent vegetation increase. These changes can be linked to the population growth and the introduction of land rehabilitation initiatives, complemented by growing awareness of land holders. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

3.
在对"两湖一库"(红枫湖、百花湖和阿哈水库)地区1973,1993,2001和2010年的4期卫星遥感影像进行解译的基础上,利用RS和GIS技术,建立区域土地利用/覆被类型空间数据库,定量分析了研究区域近40a来土地利用/覆被时空变化特征及其生态环境效应。结果表明:(1)该地区土地利用/覆被类型以旱地、水田和林地为主。(2)与1973年相比,2010年荒草地急剧减少,只占区域面积的1.02%;建设用面积急剧增加,比1973年增加了207.93%;林地面积增加了13.51%;耕地面积(旱地、水田)减少了18.41%;水域面积增加42.06%。(3)耕地主要向林地和建设用地转移,荒草地主要向林地和水域转移,林地则主要向建设用地转移。  相似文献   

4.
Land degradation is a natural and socioeconomic cause–effect phenomenon that is widespread all over the world. This study investigated the socioeconomic factors and causes of land degradation (e.g. population growth and urbanization, poverty, overgrazing, pollution, biodiversity, erosion) in the eastern part of the Mediterranean region. The study revealed a significant land use change from agricultural and natural vegetation to urbanized areas due to the high population increase during the last ca. 80 years (51‐times the magnitude of the total built‐up area). The high poverty rate that exists in the area (57 per cent of the population can be classed as ‘poor’) has resulted in damaging environmental practices (overgrazing and intensive usage of natural plants); we found 83 per cent of the farmers admitted to the adoption of these practices. Poverty has also resulted in an inverse and significant correlation (at the 95 per cent confidence level) between holding size and the sale of land for urban uses. We also noted that 75 per cent of the smallholder farmers surveyed had sold their lands for immediate benefits to cope with poverty. This relation was affected by the education level of the farmers; we found a direct and significant (95 per cent confidence level) correlation existed between these factors. Overgrazing was practised by 70 per cent of the farmers and was found to be one of the most important environmental consequences of land use change (1600 ha have been transformed from natural grazing to built‐up (urban) in the study area). Socio‐economic induced land degradation demands efforts to improve farmer environmental awareness as well as environmental standards, laws and bylaws and the reduction of mismanagement of land. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

5.
China has long been experiencing intense land use/cover changes (LUCC). Undesirable land use/cover changes have resulted in widespread land degradation. This study examines the temporal and spatial dynamics of land use change and land degradation as evident from land use survey datasets (1991–2001). Six prominent land degradation processes were identified, namely: desertification, secondary salinisation, loss of agricultural use, deforestation, grassland degradation and loss of wetland. Rates of conversion were calculated and distribution patterns were mapped with the aid of GIS. The results showed that these land use changes have affected the wider environment and accelerated land degradation. It provided a more complete and up‐to‐date picture of China's land degradation which helps to develop improved conservation policies that combat land degradation and promote sustainable land management. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

6.
Understanding spatial and temporal patterns in land susceptibility to wind erosion is essential to design effective management strategies to control land degradation. The knowledge about the land surface susceptible to wind erosion in European contexts shows significant gaps. The lack of researches, particularly at the landscape to regional scales, prevents national and European institutions from taking actions aimed at an effective mitigating of land degradation. This study provides a preliminary pan‐European assessment that delineates the spatial patterns of land susceptibility to wind erosion and lays the groundwork for future modelling activities. An Index of Land Susceptibility to Wind Erosion (ILSWE) was created by combining spatiotemporal variations of the most influential wind erosion factors (i.e. climatic erosivity, soil erodibility, vegetation cover and landscape roughness). The sensitivity of each input factor was ranked according to fuzzy logic techniques. State‐of‐the‐art findings within the literature on soil erodibility and land susceptibility were used to evaluate the outcomes of the proposed modelling activity. Results show that the approach is suitable for integrating wind erosion information and environmental factors. Within the 34 European countries under investigation, moderate and high levels of land susceptibility to wind erosion were predicted, ranging from 25·8 to 13·0 M ha, respectively (corresponding to 5·3 and 2·9% of total area). New insights into the geography of wind erosion susceptibility in Europe were obtained and provide a solid basis for further investigations into the spatial variability and susceptibility of land to wind erosion across Europe. © 2014 The Authors. Land Degradation and Development published by John Wiley & Sons, Ltd.  相似文献   

7.
1998-2005年石羊河流域土地利用/覆盖变化及其分析   总被引：3，自引：1，他引：2  
根据1998年和2005年两期影像数据,利用RS和GIS技术,分析了近7 a来石羊河流域土地利用/土地覆盖的数量、结构、类型和空间分布上的变化情况,并对土地利用/土地覆盖变化的驱动力作了探讨.研究结果表明,7 a间石羊河流域草地、戈壁、沙地、林地、旱地和盐碱地面积呈减少趋势;高山、居民点、水浇地呈增加趋势;水浇地增加幅度最大,增幅为89 485.22 hm2,主要是由林地、盐碱地、居民点、沙地和戈壁转变而来;人工林地、重轻度盐碱地和水浇地的土地利用动态度明显,依次为4.14%,3.48%,2.23%和2.56%;人口压力、经济因素、生态政策是影响该流域土地利用/土地覆盖变化的主要驱动力.  相似文献   

8.
土地利用/覆盖及其变化的土水资源效应研究   总被引：1，自引：1，他引：0  
土地利用/覆盖及其变化的土水资源效应是LUCC环境效应研究的重点。在分析土水资源以及土地利用与土水资源之间相互关系的基础上,对国内外土地利用/覆盖变化及其对土壤质量和水资源影响的研究现状进行回顾,指出LUCC土壤效应的研究主要集中在土壤养分和土壤侵蚀两个方面,LUCC水效应侧重水质、水量方面。在此基础上,提出了土地利用/覆盖变化土水效应研究中存在的侧重单项因素影响研究、反馈机制研究较少、综合动态模拟不够、研究尺度单一等问题,阐明了研究内容的综合性、研究尺度的多样性、研究方法的定量性等未来研究的趋势方向。  相似文献   

9.
Land‐use and cover changes around Budongo Forest Reserve (BFR) were analysed from multi‐temporal LandSat images (1988 and 2002) and associated field‐based studies in 2003–2004. Three major land‐use and cover classes: forest/woodland, sugarcane plantations and grassland/shifting‐cultivation/settlements were clearly discriminated. The area under sugarcane cultivation increased over 17‐fold, from 690 ha in 1988 to 12729 ha in 2002, with a concomitant loss of about 4680 ha (8·2 per cent) of forest/woodland, mainly on the southern boundary of BFR. Land‐use and cover changes were a result of (a) agricultural expansion, (b) increasing human population, exacerbated by large influxes of refugees, (c) conflicts of interest and political interference in the management of BFR and (d) unclear land tenure. Agriculture is the main land‐use practice and source of income to local people, with commercial sugarcane and tobacco as the primary cash crops. Individual smallholder sugarcane plantations covered distances ranging from 30 to 1440 m along the BFR edge, with no buffer zone, resulting in direct conflicts between farmers and forest wild animals. There is an ever‐increasing need for more land for agricultural expansion, resulting in continued loss of forest/woodland on private/communal lands and encroachment into BFR. This unsustainable agricultural expansion and the local people's perception of BFR as an obstacle to agriculture, threatens the conservation of its threatened wild plants (e.g. Raphia farinifera) and the endangered chimpanzees. Therefore, their sustainable management for both development and conservation will require strong and incorruptible institutions that will seek a balance between resource exploitation and conservation. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

10.
In the tropics, conversion of woodland and forest into cropland and pasture has risen drastically during the last decade. Rapid population growth and poverty are believed to be the main factors of change in land use in these zones. Southern Burkina Faso experienced rapid population growth due to massive peasants' migration from the north and central regions of the Country, exacerbated by decreasing rainfall and arable land in the area of origin. This paper assessed the impact of such increased population on land use change in the attracting zones from 1986 to 2006. Satellite images were used to measure changes in land cover types over time and national population census data were used to examine the population dynamics over the same time. Results showed that the forest land was progressively converted to croplands at an annualized rate of 0·96 per cent, while the population density shifted from 17 inhabitants per km2 in 1986 to 30 inhabitants per km2 in 2006. Pearson correlation analysis revealed the positive role of population size and distribution in explaining land cover change. Policy initiatives that will lead to better environmental management are recommended. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
Soil erosion in the upper reaches of the Yangtze River in China is a major concern and the Central Government has initiated the Grain‐for‐Green Programme to convert farmland to forests and grassland to improve the environment. This paper analyses the relationship between land use and soil erosion in Zhongjiang, a typical agricultural county of Sichuan Province located in areas with severe soil erosion in the upper reaches of the Yangtze River. In our analysis, we use the ArcGIS spatial analysis module with detailed land‐use data as well as data on slope conditions and soil erosion. Our research shows that the most serious soil erosion is occurring on agricultural land with a slope of 10∼25 degrees. Both farmland and permanent crops are affected by soil erosion, with almost the same percentage of soil erosion for corresponding slope conditions. Farmland with soil erosion accounts for 86·2 per cent of the total eroded agricultural land. In the farmland with soil erosion, 22·5 per cent have a slope of < 5 degrees, 20·3 per cent have a slope of 5∼10 degrees, and 57·1 per cent have a slope of > 10 degrees. On gentle slopes with less than 5 degrees inclination, some 6 per cent of the farmland had strong (5000∼8000 t km−2 y−1) or very strong (8000∼15000 t km−2 y−1) erosion. However, on steep slopes of more than 25 degrees, strong or very strong erosion was reported for more than 42 per cent of the farmland. These numbers explain why the task of soil and water conservation should be focused on the prevention of soil erosion on farmland with steep or very steep slopes. A Feasibility Index is developed and integrated socio‐economic assessment on the feasibility of improving sloping farmland in 56 townships and towns is carried out. Finally, to ensure the success of the Grain‐for‐Green Programme, countermeasures to improve sloping farmland and control soil erosion are proposed according to the values of the Feasibility Index in the townships and towns. These include: (1) to terrace sloping farmland on a large scale and to convert farmland with a slope of over 25 degrees to forests or grassland; (2) to develop ecological agriculture combined with improving the sloping farmland and constructing prime farmland and to pay more attention to improving the technology for irrigation and cultivation techniques; and (3) to carry out soil conservation on steep‐sloping farmland using suggested techniques. In addition, improving ecosystems and the inhabited environment through yard and garden construction for households is also an effective way to prevent soil erosion. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

12.
土地利用变化的驱动要素研究是当前土地利用／土地覆盖变化(LUCC)研究的热点和关键问题之一。黄土丘陵沟壑区因其严重的水土流失问题，成为全国实施退耕还林还草措施的重点区域之一。运用典型相关分析，通过对典型区安塞县耕地数量、耕地质量变化驱动要素的定量分析，探讨了县域耕地变化的驱动要素，并运用典型相关系数和冗余度分析，对诊断结果进行了检验。为进一步研究整个黄土高原地区实施退耕还林还草政策提供借鉴，为该区土地利用的合理调整和水土保持的有效实施服务。  相似文献   

13.
A simple methodology is presented for assessing the risk of water erosion at the global level. It uses a ½° latitude by ½° longitude soil database, developed at ISRIC, and auxiliary databases on climate and land cover with a similar spatial resolution. Area estimates are presented for (1) susceptible areas, as determined by rainfall erosivity, topography and soil erodibility, and (2) vulnerable areas as further determined by the pressure of current land use. Model output for vulnerability is evaluated against observed data on severity of soil degradation by water as presented on the map of human-induced soil degradation (GLASOD). Cross-tabulation of the vulnerability and GLASOD subsets gave a significant Cramer's correlation coefficient of 0·72 (P ≪ 0·005). Thus a fair geographic agreement was observed between the grid cells considered vulnerable to water erosion, under current conditions of land cover, and regions in which water erosion occurs currently. The qualitative model can serve to raise awareness on issues of soil degradation by water at the global level by identifying regions at risk, where more detailed studies are needed. However, it does not provide any information on the actual rate of erosion at the field scale, nor on the associated decrease in crop productivity and biodiversity. The study of productivity changes associated with water erosion, at different scales, is currently an important topic on ISRIC's research agenda.  相似文献   

14.
新疆焉耆盆地地表温度时空分布对LUCC的响应   总被引：4，自引：3，他引：1  
为了辨析地表温度时空分布及其变化对土地利用/土地覆盖变化(land use/cover change,LUCC)的响应,以新疆焉耆盆地为研究区,将Landsat遥感影像数据、气象要素的观测数据和野外采样数据相结合,利用单窗算法和单通道算法反演研究区2000、2009、2011和2015年的地表温度,分析焉耆盆地地表温度时空分布特征,研究LUCC对地表温度的影响。结果表明:1)研究区温度时空分布图主要划分为低温区、中温区和高温区。从时空分布变化上来看,2000年高温区范围减少幅度最大、2009年次之、2015年最小;2009年低温区范围减少幅度最大、2000年次之、2015年最小;2)研究区地表温度的分布具有明显的空间差异性,高温区主要分布在沙漠区和山区与盆地之间的戈壁滩,具有明显的以博斯腾湖为中心的环状分布特点。低温区主要分布在水域、湿地和绿洲等区域;3)在2011年内不同时期不同LUCC的温度变化幅度不一,地表温度在不同下垫面上平均值大小不同,地表温度高低主要表现为沙漠盐碱地裸地小麦-玉米其他作物森林棉花芦苇湿地水域。由结果可知,焉耆盆地近十几年地表温度的时空变化与LUCC有着密切关系,农作物的结构、土地利用类型及其面积变化都会影响地表温度的时空分布。  相似文献   

15.
Changes in land use/land cover have important consequences on the management of natural resources including soil and water quality, global climatic systems and biodiversity. This study analysed the spatial and temporal pattern of land use/land cover change in the Camili forest planning unit that includes the Camili Biosphere Reserve Area within the Caucasian hotspot, in the northeast corner of Turkey. To assess the patterns during a 33‐year period, the necessary data were obtained from forest stand maps and evaluated with Geographic Information Systems and FRAGSTATS. Results showed that the total forested areas increased from 19 946·5 ha (78·6% of the study area) in 1972 to 20 797·3 ha (81·9 per cent) in 2005 with a slight net increase of 851 ha. Softwood cover types (411·8 ha) completely transitioned to other cover types over 33‐year period. In terms of spatial configuration, the total number of forest fragments increased from 172 to 608, and mean size of forest patch (MPS) decreased from 147·7 ha to 41·8 ha during the period. Nearly 84 per cent of the patches in 1972 and 93 per cent of them in 2005 generally seem to concentrate into 0–100 ha patch size class, indicating more fragmented landscape over time that might create a risk for the maintenance of biodiversity of the area. There were apparent trends in the temporal structure of forest landscape, some of which may issue from mismanagement of the area, social conflict, and illegal utilization of forest resources due to ineffective forest protection measurements. The study revealed that it is important to understand both spatial and temporal changes of land use/land cover and their effects on landscape pattern to disclose the implications for land use planning and management. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

16.
Whereas many studies point out the economic benefits of controlling land degradation through sustainable land management (SLM) approaches, there is often a lack of local adoption of SLM techniques. Analysis of the local impacts and costs of land degradation is critical for understanding farmers' responses to land degradation. The objective of this paper is to analyse the local costs of land degradation in the Puentes catchment in southeast Spain. This catchment has been identified as particularly vulnerable to erosion, yet farmers show a general lack of interest in applying erosion control techniques. The paper subsequently analyses land degradation processes in the Puentes catchment, the income derived from agriculture and several other ecosystem services, and the local costs of land degradation. Erosion is widespread in the catchment, comprising sheet and rill erosion as well as gulley erosion. Relatively high erosion rates are encountered in cropland. The most important source of local income is irrigated agriculture, with revenues of up to €1350/ha y−1. Dryland agriculture, hunting and herding provide additional income. The costs of erosion on cropland, calculated with a replacement method, vary from around €5/ha y−1 on slopes between five per cent and ten per cent, to around €50/ha y−1 on slopes between 30 per cent and 50 per cent. Except on the steepest slopes, these costs are relatively low for the farmers, which explains the limited application of erosion control techniques in the catchment. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

17.
Land degradation due to soil erosion is the major problem facing Ethiopia today. In the Lake Alemaya catchment soil erosion is caused by the intense rainfall, steep topography, and poor vegetation cover coupled with cultivation of steep lands, and inadequate conservation practices. Sediment from the catchment has affected the storage capacity of Lake Alemaya. This study has integrated the Agricultural Non‐point Source Pollution Model (AGNPS) and the technique of the Gographic Information System (GIS) to quantify soil erosion in the Lake Alemaya catchment. After application of the AGNPS, it appears that 66 per cent of the catchment has a soil erosion rate of 10 to more than 80 t ha−1 y−1. The annual soil loss is estimated at 31 t ha−1, which is more than the permissible value of 1–16 t ha−1 for different agro‐ecological zones of Ethiopia. The sediment yield of the catchment is about 10 148 ton with a delivery ratio of 6·82 per cent. Therefore, an effective management plan is needed for the conservation and rehabilitation of the catchment and to maintain the storage capacity of Lake Alemaya. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

18.
Rapid land use/cover change and landscape fragmentation is occurring in many countries in central and southern Africa, as a result of colonial imbalances in land distribution, demographic pressure, agricultural expansion, government policies and environmental factors such as drought. This study analysed the dynamics of land use/cover and land degradation as revealed in landscape fragmentation in the Bindura District of Zimbabwe based on Landsat data for 1973 and 2000. A hybrid supervised/unsupervised classification approach coupled with GIS analyses was employed to generate land use/cover maps from which various class level landscape metrics were calculated using FRAGSTATS®, in order to analyse landscape fragmentation. The results show that agriculture, mixed rangeland, settlements, bareland and water increased, while woodland areas decreased. Consequently, the landscape became more highly fragmented as indicated by an increase in the patch number and a decrease in the mean patch size (MPS) of the woodland and mixed rangeland classes. This suggests that anthropogenic activities driven by agricultural expansion were the main causes of landscape fragmentation, leading to landscape degradation in the study area. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

19.
中国1999－2009年土地覆盖动态变化的时空特点   总被引：8，自引：4，他引：4  
基于SPOT NDVI时间序列研究中国近10 a来（1999－2009年）土地覆盖动态变化的时空特点。首先,对BISE模型进行改进并对数据进行预处理;其次,结合光谱角分类和最小距离分类算法各自的优势构建了一个新的分类算法（SAM-MDM）,并对多年NDVI数据分类和后处理,提高了分类精度,能满足土地覆盖变化趋势分析要求;再次,应用土地覆盖动态度模型和GIS叠加方法分析了全国土地覆盖的时空变化,建立了土地覆盖类型转移概率矩阵;最后,应用马尔科夫（Markov）过程建立了类型转移演化模型,对未来20 a土地覆盖动态变化过程进行了预测。通过该研究探讨了中国土地覆盖近10 a来在时间上的动态变化特点、空间上的变化差异、土地覆盖类型的转移概率分布和未来10～20 a的时空变化趋势。  相似文献   

20.
近10 a黄河三角洲LUCC及其驱动因素分析   总被引：5，自引：2，他引：3  
研究滨海脆弱生态区的土地利用/土地覆被时空变化过程,可以为区域土地资源的规划、开发和管理提供科学依据。该文应用遥感和GIS技术,分析黄河三角洲区域1995－2004年间土地利用/土地覆被的时空变化特征,并对区域土地利用/土地覆被变化的驱动因子进行了探讨。结果表明,近10 a来黄河三角洲的土地利用/土地覆被类型发生了复杂变化;黄河三角洲土地利用/土地覆被动态受到自然因素和人类活动的共同作用,而人类活动是近10 a区域土地利用/土地覆被变化的主要驱动因子。尽管近年来黄河三角洲的开发取得了快速发展,但部分人类经济活动给区域土地资源及其生态环境的可持续发展带来巨大压力,甚至导致区域土地质量的进一步退化。  相似文献   

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