Landscape connectivity changes analysis for monitoring desertification of Minqin county, China

Landscape connectivity, as an important indicator of regional landscape functional pattern measured by cost–distances model, could both reveal evidence of, and act as an indicator, for desertification. Using Minqin county as a case study, this study was further to test cost–distance connectivity for indicating desertification, and to analyze temporal changes of connectivity in the county from 1977 to 1997. The results further indicate the connectivity interpreted as lower cost–distance and higher risk of desertification. The temporal change analysis of connectivity provides more detail supplement of desertification processes. Landscape connectivity changes in the county had three distinctive phases, the strongest decline of log cost–distance with overwhelming decrease area and decrease amount in the period 1977–1984, and its slight decline with the relative balance between the high decrease amount and high increase amount in the period 1984–1992, then its the slight decline with the relative balance between the low decrease amount and low increase amount in the period 1992–1997. The frequent temporal and spatial transition in source class, grassland, alkali–saline land and irrigated cultivated land caused negative effects on the oasis environment.     

Regional landscape-ecological planning and desertification control in arid regions of the Commonwealth of Independent States

Scale-dependent present-day landscape mapping and assessment were used to study the relationship among physical environment, land use, and degree of landscape modification in the Aral Sea region and the Karakum Desert, areas prone to desertification in the Commonwealth of Independent States (CIS). Applying geographic information system (GIS) techniques at global (1:15,000,000), regional (1:1,000,000), and local (1:300,000) scales, researchers found that large-scale landscape assessment and mapping allow them to recognize landscape changes under desertification processes and assess the type and intensity of these processes. Remote sensing has been widely used to evaluate data reliability, to fill information gaps, and to reveal the dynamics of land use types resulting from landscape changes.     

Dynamics of aeolian desertification and its driving forces in the Horqin Sandy Land,Northern China

Aeolian desertification is one of the most serious environmental and socioeconomic problems in arid, semi-arid, and dry subhumid zones. Understanding desertification processes and causes is important to provide reasonable and effective control measures for preventing desertification. With satellite remote sensing images as data source to assess the temporal and spatial dynamics of desertification from 1975 to 2010 in the Horqin Sandy Land, dynamic changes of aeolian desertification were detected using the human–machine interactive interpretation method. The driving factors of local desertification were analyzed based on natural and socioeconomic data. The results show that aeolian desertified land in the study area covered 30,199 km² in 2010, accounting for 24.1 % of the study area. The total area of aeolian desertified land obviously expanded from 30,884 km² in 1975 to 32,071 km² in 1990, and gradually decreased to 30,199 km² in 2010; aeolian desertified land represented an increasing trend firstly and then decreased. During the past 35 years, the gravity centers of desertified lands that are classified as extremely severe and severe generally migrated to the northeast, whereas those that are moderate and slight migrated to the northwest. The migration distance of severely desertified land was the largest, which indicated the southern desertified lands were improved during the last few decades. In addition, the climatic variation in the past 35 years has been favorable to desertification in the Horqin Sandy Land. Aeolian desertified land rapidly expanded from 1975 to 1990 under the combined effects of climate changes and unreasonable human activities. After the 1990s, the main driving factors responsible for the decrease in desertification were positive human activities, such as the series of antidesertification and ecological restoration projects.     

A hierarchical approach for desertification assessment

Environmental systems are complex and multi-scaled open systems. To understand land degradation, one has to consider the interactions between landscape patterns and environmental processes at different scales. Patterns and processes in the landscape are perceived to be organized in nested hierarchical structures. To study land degradation in this context, a coupled top-bottom/bottom-up approach was developed. The top-bottom landscape analysis is aimed at identifying landscape systems at different scales. The bottom-up analysis focuses on system dynamics at finer scales. Applied in a study in central Spain, the approach is aimed at understanding the functional differences between three types of degraded seminatural slopes at different scales. Six levels of organization were distinguished: ped-level, terracette-level, hummock-level, slope part-level, slope level, and watershed level. Properties that characterize these levels were selected for different disciplines. The bottom-up analysis focused on water movement at different spatial scales. Successfully applying this approach revealed the importance for land degradation of the close linkage between spatial patterns and hydrological processes at different spatial scales. Identifying constraining and dynamic indicators related to water conservation at different scales can be useful for assessing desertification.     

Land use/land cover change and their effects on landscape patterns in the Yanqi Basin, Xinjiang (China)

Human modification of land use and land cover change (LUCC) drives the change of landscape patterns and limits the availability of products and services for human and livestock. LUCC can undermine environmental health. Thus, this study aimed to develop an understanding of LUCC in the Yanqi Basin, Xinjiang, China, an arid area experiencing dramatic water and land resource use. A time series of satellite images (1964, 1973, 1989, 1999, and 2009) were used to calculate the index of landscape patterns to study the processes involved in changes to land uses and landscape patterns and the influence of this changes on landscape patterns. The results show that land uses in the Yanqi Basin have changed dramatically since 1964 with grassland being mainly converted to cropland. Landscape fragmentation and diversity have decreased in the study area, although landscape fragmentation increased from 1964 to 1999 and then decreased by 2009. The index of landscape diversity decreased from 1.64 in 1964 to 0.71 in 2009. The heterogeneity and complexity of the landscape increased during this period. In contrast, the index of dominance decreased from 0.85 in 1964 to 0.83 in 2009. Land use change drives landscape patterns of the development of the watershed toward diversity and a fragmented structure. Population growth, economic development, and industrial policies were the dominant driving forces behind LUCC in the Yanqi Basin. Sustainable use of land resources is a significant factor in maintaining economic development and environmental protection in this arid inland river basin.     

The relative role of climate change and human activities in the desertification process in Yulin region of northwest China

To overcome the shortcoming of existing studies, this paper put forward a statistical vegetation–climate relationship model with integrated temporal and spatial characteristics. Based on this model, we quantitatively discriminated on the grid scale the relative role of climate change and human activities in the desertification dynamics from 1986 to 2000 in Yulin region. Yulin region’s desertification development occurred mainly in the southern hilly and gully area and its reverse in the northwest sand and marsh area. This spatial pattern was especially evident and has never changed thoroughly. From the first time section (1986–1990) to the second (1991–1995), the desertification was developing as a whole, and either in the desertification development district or in the reverse district human activities’ role was always occupying an overwhelmingly dominant position (they were 98.7% and 101.4%, respectively), the role of climate change was extremely slight. From the second time section (1991–1995) to the third (1996–2000), the desertification process was reaching a state of stability, in the desertification development district the role of climate change was nearly equivalent to that of human activities (they were 46.2% and 53.8% separately), and yet in the desertification reverse district, the role of human activities came up to 119.0%, the role of climate change amounted to ?19.0%. In addition, the relative role of climate change and human activities possessed great spatial heterogeneity. The above conclusion rather coincides with the qualitative analysis in many literatures, which indicates that this method has certain rationality and can be utilized as a reference for the monitoring and studying of desertification in other areas.     

Dynamic Changes of Sandy Land in Northwest of Beijing, China

The area northwest of Beijing is one of the most important regions where many organizations invest and pay most attention. The environmental problems in this region affect not only Beijing but also the surrounding area. Based on observation of the characteristics of the change in sandy land, this study classified four types of dynamic change of sandy land, including extended sandy land, the reversely changed sandy land, the potential sandy land and no change in sandy land. Then the process and the trend of changes in sandy land and their environmental impact on the area northwest of Beijing were analyzed. The results show that the area of sandy land has increased in this region in the period of 1991 to 2002. Change between sandy land and grassland was the dominant change. It is found that the monitoring zones of Hunshandake sandy land and north of Yin Shan are regions with high ratio of extended sandy land, and are connected with widespread potential change of sandy land. This implies that these two regions have a high probability of increase in sandy land in the future. On the other hand, in the monitoring zone of Horqin sandy land and Ba Shang Plateau and its surrounding area, desertification had been controlled and the area of sandy land is expected to decrease. This indicates that the direction of the sandstorm to Beijing is expected to gradually move to the northwest. Furthermore, the decreases in sandy land and the reversing change from arable land to grassland and forests in the study region will affect the land quality and atmosphere. And the logistic multiple regression (LMR) model was employed to better understand the complexity and processes of increases in sandy land. This model predicts that there is a high probability of increases in sandy land in north of Siziwang Banner, Zhengxiangbai Banner and Zhenglan Banner. Finally, suggestions to the ecological construction of the study area have been proposed.     

Land-cover changes in an urban lake watershed in a mega-city, Central China

Urbanization can exert a profound influence on land covers and landscape characteristics. In this study, we characterize the impact of urbanization on land cover and lacustrine landscape and their consequences in a large urban lake watershed, Donghu Lake watershed (the largest urban lake in China), Central China, by using Landsat TM satellite images of three periods of 1987, 1993 and 1999 and ground-based information. We grouped the land covers into six categories: water body, vegetable land, forested land, shrub-grass land, open area and urban land, and calculated patch-related landscape indices to analyze the effects of urbanization on landscape features. We overlaid the land cover maps of the three periods to track the land cover change processes. The results indicated that urban land continuously expanded from 9.1% of the total watershed area in 1987, to 19.4% in 1993, and to 29.6% in 1999. The vegetable land increased from 7.0% in 1987, 11.9% in 1993, to 13.9% in 1999 to sustain the demands of vegetable for increased urban population. Concurrently, continuous reduction of other land cover types occurred between 1987 and 1999: water body decreased from 30.4% to 23.8%, and forested land from 33.6% to 24.3%. We found that the expansion of urban land has at least in part caused a decrease in relatively wild habitats, such as urban forest and lake water area. These alterations had resulted in significant negative environmental consequences, including decline of lakes, deterioration of water and air quality, and loss of biodiversity.     

A holistic approach towards assessment of severity of land degradation along the Great Wall in northern Shaanxi Province,China

The farming and grazing interlocked transitional zone along theGreat Wall in northern Shaanxi Province is particularly vulnerable to desertification due to its fragile ecosystem and intensive human activity. Studies reveal that desertification isboth a natural and anthropogenic process. Four desertificationindicators (vegetative cover, proportion of drifting sand area, desertification rate, and population pressure) were used to assess the severity of desertification in a GIS. The first threefactors were derived from multitemporal remote sensing and landinventory data. The last factor was calculated from census data.It was found that the overall severity of land degradation in thestudy area has worsened during the last two decades with severely, highly and moderately degraded land accounting for 84.2% of the total area in 1998. While the area affected by desertification has increased, the rate of desertification has also accelerated from 0.74 to 0.87%. Risk of land degradation in the study area has increased, on an average, by 155% since 1985. Incorporation of both natural and anthropogenic factors inthe analysis provides realistic assessment of risk of desertification.     

Assessing the impact of multiple drivers of land sensitivity to desertification in a Mediterranean country

Experiencing climate changes and increased human pressure, Mediterranean regions are considered representative hotspots of desertification. However, relatively few studies have been devoted to quantify the individual impact of different factors shaping land sensitivity to desertification in these contexts. Our study contributes to this deserving (positive and normative) issue with a diachronic analysis of the impact of multiple drivers of desertification risk on six indicators of land sensitivity based on the Environmentally Sensitive Area (ESA) approach. Indicators (average and maximum ESA score, coefficient of variation and normalized range in the ESA scores, share of ‘fragile’ and ‘critical’ areas in total landscape) were calculated in 777 rural districts of Italy at three time points (early-1960s, early-1990s, and early-2010s). Multivariate models were used to determine the impact of 12 predictors (climate, soil, vegetation, and land management quality) on each indicator of land sensitivity. Results of the analysis identified two non-redundant dimensions respectively associated with the average level of land sensitivity and its intrinsic variability across space. Impacts of climate and vegetation qualities on the level of land sensitivity were high, decreasing over time, and more intense respectively in Northern and Southern Italy. Impacts of soil and land management qualities were moderate, increasing over time, and involving almost all the country's area. Our study emphasizes the role of context-based measures promoting sustainable land management. The ‘local’ dimension proved to be crucial in any strategy of risk mitigation undertaken at disaggregated spatial scales.     

Satellite monitoring of desert plant community response to moisture availability

Our study demonstrates the utility of coarse spatial-resolution satellite spectra for analysis of vegetation phenophases and response to moisture availability in an arid ecosystem. We show the feasibility of deriving information on vegetation parameters such as stress and growth patterns in arid regions through the use of satellite-derived vegetation indices, despite the usual problems associated with a high ratio of soil to vegetation cover. Vegetation in our study area consists of Chihuahuan Desert grassland and scrub, including extensive zones of mixed desert scrub and grassland. Historic vegetation change has been well documented and is exemplified by decreasing grass cover and increasing shrub cover, a general trend of desertification. Our analysis suggests that satellite-based inputs can be used to improve our understanding of the spatial dynamics of climatic impacts on natural vegetation and to help us distinguish these processes from human-caused desertification.     

Assessment of land cover changes & water quality changes in the Zayandehroud River Basin between 1997–2008

Water quality of rivers is strongly influenced by landscape characteristics of their watershed, including land use /cover types, and their spatial configuration. This research evaluates the effects of land cover changes on the water quality of the Zayandehroud River, which is the most important river in the center of Iran. The main goal of this study was to quantify the change in rangelands, forests, and bare lands in the Zayandehroud river basin, which suffered intense human interference, in a period of 11 years (1997–2008), and to evaluate how landscape patterns (including the number of patches, edge density, percentage of rangelands, forests, and bare lands) influence on the 14 water quality indices (including BOD5, EC, NO3, P, and TDS) measured in 10 stations along the river. Results showed that from 1997 to 2008, bare lands increased from 5.8 to 20 %, while rangelands decreased from 70 to 55 % in the whole basin. The results indicated that water quality was significantly correlated with both the proportions and configuration of rangeland and bare land areas. The total edge (TE) of rangeland area had positive effects on water quality, especially on BOD5 and EC. Percentage of landscape (PLAND) and largest patch index (LPI) metrics of rangeland had positive effect on decreasing nutrient (NO₃, PO₄). The results showed that water quality was more likely degraded when there was high edge density (ED) of bare lands. Results of this study also revealed that degradation of rangeland lead to the degradation of water quality. Finding of this study highlights the importance of rangeland conservation in water quality management at landscape scale.     

Land desertification monitoring and assessment in Yulin of Northwest China using remote sensing and geographic information systems (GIS)

The objective of this study is to develop techniques for assessing and analysing land desertification in Yulin of Northwest China, as a typical monitoring region through the use of remotely sensed data and geographic information systems (GIS). The methodology included the use of Landsat TM data from 1987, 1996 and 2006, supplemented by aerial photos in 1960, topographic maps, field work and use of other existing data. From this, land cover, the Normalised Difference Vegetation Index (NDVI), farmland, woodland and grassland maps at 1:100,000 were prepared for land desertification monitoring in the area. In the study, all data was entered into a GIS using ILWIS software to perform land desertification monitoring. The results indicate that land desertification in the area has been developing rapidly during the past 40 years. Although land desertification has to some extent been controlled in the area by planting grasses and trees, the issue of land desertification is still serious. The study also demonstrates an example of why the integration of remote sensing with GIS is critical for the monitoring of environmental changes in arid and semi-arid regions, e.g. in land desertification monitoring in the Yulin pilot area. However, land desertification monitoring using remote sensing and GIS still needs to be continued and also refined for the purpose of long-term monitoring and the management of fragile ecosystems in the area.     

Quantitative assessment of desertification in south of Iran using MEDALUS method

The main aim of this study was the quantitative assessment of desertification process in the case study area of the Fidoye-Garmosht plain (Southern Iran). Based on the MEDALUS approach and the characteristics of study area a regional model developed using GIS. Six main factors or indicators of desertification including: soil, climate, erosion, plant cover, groundwater and management were considered for evaluation. Then several sub-indicators affecting the quality of each main indicator were identified. Based on the MEDALUS approach, each sub-indicator was quantified according to its quality and given a weighting of between 1.0 and 2.0. ArcGIS 9 was used to analyze and prepare the layers of quality maps using the geometric mean to integrate the individual sub-indicator maps. In turn the geometric mean of all six quality maps was used to generate a single desertification status map. Results showed that 12% of the area is classified as very severe, 81% as severe and 7% as moderately affected by desertification. In addition the plant cover and groundwater indicators were the most important factors affecting desertification process in the study area. The model developed may be used to assess desertification process and distinguish the areas sensitive to desertification in the study region and in regions with the similar characteristics.     

玛纳斯河流域荒漠草地沙化遥感监测研究

以1989—2016年玛纳斯河流域TM/OLI遥感影像为数据源,利用混合像元分解技术,计算玛纳斯河流域草地总覆盖度和裸沙面积。在此基础上通过监测年与基期年的比较,计算草地覆盖度相对基期年的减少率和裸沙面积相对基期年的增加率两个监测指标,依据《天然草地退化、沙化、盐渍化的分级指标》(GB 19377—2003),对计算出的两个指标分别进行沙化等级评定和赋值,将两种评定结果相综合来监测草地沙化。结果表明,玛纳斯河流域近30年来荒漠草地沙漠化总体呈现先增加后降低的趋势。分析表明,玛纳斯河流域草地沙化是人为和自然因素双重作用的结果。     

Land-Cover Changes and Its Impacts on Ecological Variables in the Headwaters Area of the Yangtze River, China

Land cover changes affect ecological landscape spatial pattern, and evolving landscape patterns inevitably cause an evolution in ecosystem functionality. Various ecological landscape variables, such as biological productivity (plant biomass and stock capacity), soil nutrients (organic matter and N content) and water source conservation capacity are identified as landscape function characteristics. A quantitative method and digital model for analyzing evolving landscape functionality in the headwaters areas of the Yangtze River, China were devised. In the period 1986–2000, patch transitions of the region's evolving landscapes have been predominantly characterized by alpine cold swamp meadow, with the highest coverage tending to be steppified meadow or steppe, and desertification landscape such as sand and bare rock land expansion. As the result of such changes, alpine swamp areas decreased by 3.08 × 10³ km² and the alpine cold sparse steppe and bare rock and soil land increased by 6.48 × 10³ km² and 5.82 × 10³ km², respectively. Consequently, the grass biomass production decreased by 2627.15 Gg, of which alpine cold swamp meadows accounted for 55.9% of this loss. The overall stock capacity of the headwaters area of the Yangtze River decreased by 920.64 thousand sheep units, of which 502.02 thousand sheep units decreased in ACS (Alpine cold swamp) meadow transition. Soil organic matter and N contents decreased significantly in most alpine cold meadow and swamp meadow landscape patches. From 1986 to 2000 the total losses of soil organic matter and total N in the entire headwaters region amounted to 150.2 Gkg and 7.67 Gkg. Meanwhile, the landscape soil water capacity declined by 935.9 Mm³, of which 83.9% occurred in the ACS meadow transition. In the headwater area of the Yangtze River, the complex transition of landscape resulted in sharp eco-environmental deterioration. The main indication for these changes involved the intensity of the climate in this region is becoming drier and warmer, resulting in a gradual degradation of the permafrost.     

Vegetation dynamics, and land use and land cover change in the Bale Mountains, Ethiopia

Shifts in biological communities are occurring at rapid rates as human activities induced global climate change increases. Understanding the effects of the change on biodiversity is important to reduce loss of biodiversity and mass extinction, and to insure the long-term persistence of natural resources and natures’ services. Especially in remote landscapes of developing countries, precise knowledge about on-going processes is scarce. Here we apply satellite imagery to assess spatio-temporal land use and land cover change (LULCC) in the Bale Mountains for a period of four decades. This study aims to identify the main drivers of change in vegetation patterns and to discuss the implications of LULCC on spatial arrangements and trajectories of floral communities. Remote sensing data acquired from Landsat MSS, Landsat ETM + and SPOT for four time steps (1973, 1987, 2000, and 2008) were analyzed using 11 LULC units defined based on the dominant plant taxa and cover types of the habitat. Change detection matrices revealed that over the last 40?years, the area has changed from a quite natural to a more cultural landscape. Within a representative subset of the study area (7,957.5?km^?2), agricultural fields have increased from 1.71% to 9.34% of the total study area since 1973. Natural habitats such as upper montane forest, afroalpine grasslands, afromontane dwarf shrubs and herbaceous formations, and water bodies also increased. Conversely, afromontane grasslands have decreased in size by more than half (going from 19.3% to 8.77%). Closed Erica forest also shrank from 15.0% to 12.37%, and isolated Erica shrubs have decreased from 6.86% to 5.55%, and afroalpine dwarf shrubs and herbaceous formations reduced from 5.2% to 1.56%. Despite fluctuations the afromontane rainforest (Harenna forest), located south of the Bale Mountains, has remained relatively stable. In conclusion this study documents a rapid and ecosystem-specific change of this biodiversity hotspot due to intensified human activities (e.g., deforestation, agriculture, infrastructure expansion). Specifically, the ecotone between the afromontane and the afroalpine area represent a “hotspot of biodiversity loss” today. Taking into consideration the projections of regional climate warming and modified precipitation regimes, LULCC can be expected to become even more intensive in the near future. This is likely to impose unprecedented pressures on the largely endemic biota of the area.     

Change detection of sandy land areas in Minfeng oasis of Xinjiang, China

In recent years, much attention has been given to desertification in Xinjiang, China, particularly in the southern edge of the Taklimakan Desert. In this study, an oasis in Minfeng County, which is located in the southern edges of the Taklimakan Desert, was chosen as our case study area. Supervised classification for land types was conducted, and then the change detection and the trend of changes in sandy land areas were analyzed and compared. The results show that the area of sandy land has decreased in the region in the period of 1992-2001. The main change was between sandy land and sparse vegetation in the Desert-oasis ecotone. In addition, the change from woodland to grassland and/or arable land was quite obvious from 1992 to 2001. These changes would probably result in more fragile environment and higher potentiality in land desertification in the area.     

Landscape-based upstream-downstream prevalence of land-use/cover change drivers in southeastern rift escarpment of Ethiopia

Characterized by high population density on a rugged topography, the Gedeo-Abaya landscape dominantly contains a multi-strata traditional agroforests showing the insight of Gedeo farmers on natural resource management practices. Currently, this area has been losing its resilience and is becoming unable to sustain its inhabitants. Based on both RS-derived and GIS-computed land-use/cover changes (LUCC) as well as socioeconomic validations, this article explored the LUCC and agroecological-based driver patterns in Gedeo-Abaya landscape from 1986 to 2015. A combination of geo-spatial technology and cross-sectional survey design were employed to detect the drivers behind these changes. The article discussed that LUCC and the prevalence of drivers are highly diverse and vary throughout agroecological zones. Except for the population, most downstream top drivers are perceived as insignificant in the upstream region and vice versa. In the downstream, land-use/cover (LUC) classes are more dynamic, diverse, and challenged by nearly all anticipated drivers than are upstream ones. Agroforestry LUC has been increasing (by 25% of its initial cover) and is becoming the predominant cover type, although socioeconomic analysis and related findings show its rapid LUC modification. A rapid reduction of woodland/shrubland (63%) occurred in the downstream, while wetland/marshy land increased threefold (158%), from 1986 to 2015 with annual change rates of -?3.7 and +?6%, respectively. Land degradation induced by changes in land use is a serious problem in Africa, especially in the densely populated sub-Saharan regions such as Ethiopia (FAO 2015). Throughout the landscape, LUCC is prominently affecting land-use system of the study landscape due to population pressure in the upstream region and drought/rainfall variability, agribusiness investment, and charcoaling in the downstream that necessitate urgent action.     

The land ecological evolutional patterns in the source areas of the Yangtze and Yellow Rivers in the past 15 years, China

Based on land ecological classification of the source regions of the Yangtze and Yellow Rivers and field investigation, two phases of TM remote sensing data obtained in 1986 and 2000 were compared. From spatial variations and type transformation trends, the spatial changes and evolutional patterns of land ecosystem in the source regions of the two rivers were analyzed using the analytical method of landscape ecological spatial patterns. Results show that middle and high-cover high-cold steppe areas degraded considerably by 15.82%, high-cover high-cold meadow areas by 5.15%, while high-cold swamp meadow areas decreased by 24.36%. Lake water area was reduced by 7.5%, especially the lakes in the source region of the Yangtze River. Land desertification is developing rapidly and the average of desertified land area has increased by 17.11%. Desertified land in the source region of Yellow River is expanding at an annual rate of 1.83%. Analysis of the evolutional pattern of land ecotypes shows that the general tendencies of spatial evolution in the regions are coverage reduction and desertification of high-cold steppe, cover reduction and steppification of high-cold meadows, and desiccation of swamp meadows. As a result, land ecological spatial distribution pattern in the region is changing and the state of eco-environment declining.