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Animal husbandry is an important source of carbon emissions. As a large country, China must measure the carbon emissions from animal husbandry to reveal the spatial and temporal characteristics and determine the influencing factors to realize low-carbon animal husbandry and carbon emission reduction. In this paper, the carbon emissions of the livestock industry in each province of China were calculated with the emission coefficient method, considering the temperature change factor. The spatial and temporal characteristics and influencing factors of livestock industry carbon emissions were analyzed using the kernel density model, the spatial autocorrelation model, and the Tobit model. The results indicated that: (1) From 2000 to 2020, carbon emissions from the livestock industry in China experienced four stages: rapid rise, rapid decline, slow rise, and fluctuating decline, with an overall downward trend. Carbon emissions in the eastern and central regions showed a downward trend, while carbon emissions in the western regions showed an upward trend. (2) In terms of time, the relative gap in carbon emissions among the provinces narrowed first and then widened; the spatial agglomeration of carbon emissions from livestock farming in China increased, gradually forming the characteristics of “high agglomeration, low agglomeration”, and showing a gradually decreasing pattern from northwest to southeast. (3) Nationwide, industrial structure, population, and farmers’ income levels have had significantly promoting effects on animal husbandry carbon emissions, and the urbanization and agricultural mechanization levels have had significant inhibitory effects on carbon emissions. Finally, based on the above factors, it can be concluded that recognizing the location conditions, promoting the upgrading of industrial structures, and adopting differentiated strategies will help to promote the reduction in carbon emissions in animal husbandry and achieve its high-quality development.

One of the purposes of agri-environment schemes (AESs) is to persuade farmers to make good environmental contributions. Understanding the determinants of farmer behavior and the decisions they make regarding AESs is crucial because it helps policymakers create schemes with a broader reach and a higher likelihood of achieving environmental goals. This paper aims to explore the impacts of land transfer, farmers' subjective well-being, and participation in AESs in environmentally fragile areas of China by using data of 6840 sampled farmers obtained from China Family Panel Studies (CFPS). A relatively novel approach of ordinary least square (OLS), the ordered probit model approach, and the mediation effect model is used to assess the association between the land transfer mechanism, subjective well-being, and participation in AESs. The model outcomes indicate that land transfer has a considerable influence on AES involvement and that it can boost farmers' subjective well-being. The findings of our study also indicate that the marginal effect of land transfer on the subjective well-being of nonpoor households is greater than that of poor households, and the impact degree of land transfer on the subjective well-being of farmers reveals a weakening trend from east to west regions. Local conditions should be taken as guidance to effectively coordinate the regional resource allocation.

Aeolian sediments are widely distributed in the Lake Qinghai basin of the northeastern Tibetan Plateau (TP), but the history of aeolian activities in the basin is indistinct, and the underlying impacting factors are still poorly understood. In this study, depositional history of a mega-dune from the eastern Lake Qinghai basin was determined by optically stimulated luminescence (OSL) dating. The results show that nearly 30 m thick of sands accumulated during the interval of 7-6 ka, followed by soil formation during the last ∼5 ka. Together with previously published OSL ages of aeolian sediments, the Holocene aeolian activity in the Lake Qinghai basin was reconstructed as following: (1) The temporary aeolian activity appears to be characterized with a pattern of strengthened intensity during the first half of Holocene but relatively lowered intensity with a gradual decreasing trend afterward; (2) The interval of 7-6 ka in the middle Holocene witnessed a transition from dune activation towards stabilization; (3) A very low sand accumulation rate during the period of 5-3 ka and the contemporaneous extensive palaeosol development imply the least aeolian activity at that period. We inferred that the Holocene aeolian activity in the Lake Qinghai basin was mainly controlled by sediment supply, which was in turn modulated by the lake-level change of Lake Qinghai. Large amounts of sand were available, when the lake level dropped and then beach sands could exposure for deflation.

Under a background of a significantly warming climate, current aeolian desertification in China's northeastern Tibetan Plateau (NETP) has been widely studied, but disagreements related to its causes continue to persist. In order to understand the present through the past, this study determined the various phases of aeolian desertification in the NETP based on the statistical analysis of 40 optically stimulated luminescence (OSL) aeolian sand dates from 23 aeolian sections. Because the redistribution of aeolian sand by wind processes can reduce the number of older sand dates, this research only affects exactly the past millennium. Following this, we analyzed the relationships between aeolian desertification phases in conjunction with reconstructed climatic data. Results revealed three distinct aeolian desertification phases that approximately correspond to 1480 CE, 1680 CE, and 1800 CE, respectively. By comparing these dates to well-established paleoclimate records, we determined that these three aeolian desertification phases all occurred under a cold and dry climate background. Accordingly, aeolian desertification in the NETP today under its current warm and wet climate background can therefore be attributable to irrational human activities rather than rising temperatures. Accordingly, we can infer that under the current warmer and wetter climate background, aeolian desertification in the NETP today can be reversed as long as human activities remain moderate, even without the implementation of artificial revegetation initiatives.

Chronostratigraphic records in the drylands of north China provide essential archives to reveal the dynamic connections between climate changes and behaviours of aeolian systems. This study presents a detailed investigation of aeolian sediment accumulation around the Tengger Desert during the late Quaternary, comprising of grain-size characteristics and sources, sediment types and burial ages, and potential responses to external and localised forces. A combination of previously published chronostratigraphic records and 91 newly dated optically stimulated luminescence (OSL) samples collected from multiple sites covering a wide region of the south margin of the desert are used to constrain the accumulation of aeolian sediments during the late Quaternary. The prevailing strong near-surface winds at 22–19 ka, 18–14 ka, 13–10 ka, and 3–0 ka are found to be in anti-phase relation with the strength of the East Asia summer monsoon (EASM). The widespread attenuation of aeolian activity occurred between 7 and 3 ka. The accumulation of aeolian sediments during the past 250 ka has been controlled by multiple factors, including wind, aridity, sediment availability, and preservation capacity. We demonstrate that the interpretation of chronostratigraphic records is significantly affected by the number of available records, which emphasises the importance of sampling at multiple sites. The synchronous accumulation of aeolian sand and sandy loess at certain periods and the significant overlapping of volume percentage distributions at certain grain-size intervals between the two types of sediments indicate that their responses to external forces may not be independent and that the palaeoclimatic significance of sandy loess accumulated in the desert-loess transition zone requires a reassessment.

Pakistan is the world’s most susceptible country to extreme climatic events, such as floods. As such, for many years, the country has faced the risk of losses from natural calamities without crop insurance. However, in recent years, the national government has undertaken crop insurance initiatives in Pakistan. Consequently, there is limited knowledge available on the adoption of crop insurance in Pakistan. To fill this gap, this study aims to examine the factors influencing the adoption of crop insurance as a risk management strategy by Pakistani farmers. Primary data were collected from 400 farm households through a structured questionnaire in four flood-prone districts of the northwestern regions (Khyber Pakhtunkhwa). A probit model was used to analyze the relationships among dependent and independent variables. Risk attitude and risk perception of floods for each farm household were calculated and used as independent variables. Age, farming experience, education level, risk perception of floods, land ownership status, landholding size, access to credit, access to information sources, agricultural extension services, and distance from river were significantly associated with farm households’ decisions to purchase crop insurance. The findings of this study are expected to guide government, insurance companies, and policymakers in implementing crop insurance. Further the government should subsidize and frame a crop insurance policy and awareness about crop insurance should be improved for betterment of small farmers.

The variations in farming risk are classified into three key categories: market liberalization, natural disasters such as floods or drought, and climate change. This study aims at filling the exist...

The Zoige Basin is located in the northeastern Tibetan Plateau, at an altitude of around 3500 m. To fully understand and assess the current status and future trend of aeolian activity in the Zoige Basin, it is necessary to reveal the history of aeolian activity of this region. In this study, 11 Optically stimulated luminescence (OSL) ages from three typical sections were used to reconstruct the history of aeolian activities in the region during the Holocene. The results of the chronologies show that the oldest OSL age (10.27 ± 0.81 ka) occurred in the early Holocene, but aeolian sediment deposition primarily occurred in the late Holocene, after around 3.20 ± 0.33 ka. In the whole Holocene, the aeolian activities of the Zoige Basin occurred contemporaneously with nearby sites in the northeastern Tibetan Plateau. Episodic weak aeolian activities were recorded in nearby sites in the northeastern Tibetan Plateau. However, we postulate here that the combination of a flat, low-lying landscape along with higher precipitation during the mid-Holocene resulted in this area being relatively insensitive to short term arid climatic changes and aeolian activity.

Freeform and precise irradiance tailoring in arbitrarily oriented planes is an ultimate goal of nonimaging optics and has not been well addressed. In this paper, we develop a general formulation for arbitrary and precise irradiance tailoring in three-dimensional (3D) space using freeform lenses. This method breaks any symmetric constraints imposed on the geometrical arrangement of conventional beam shaping systems, yielding high-performance beam shaping systems with new functions and flexible geometrical arrangements in 3D space. This method paves a way for the broad application of freeform optics. The robustness and effectiveness of the method is demonstrated by two interesting but challenging designs.

Aeolian processes and their role in desertification have been studied extensively at low elevations, but have been rarely studied at high elevations in areas such as the Tibetan Plateau, where aeolian processes were active in the geologic past and remain active today. In this review, we summarize research that improves our understanding of aeolian processes on the Tibetan Plateau, including the distribution, characteristics, and provenance of aeolian sediments; the history of aeolian activity; aeolian geomorphology; and wind-driven land degradation. Contemporary aeolian processes primarily occur in dry basins, in wide river valleys, on lakeshores, on mountain slopes, and on gravel pavements. Sediment characteristics suggest a local origin, and provide interesting contrasts with those of China's Loess Plateau. The history of aeolian activity and its paleoclimatic implications, reconstructed based on aeolian archives, is short (mostly since the Late Glacial) and shows wide regional differences. Aeolian geomorphology is simple and suggests short formation time. Wind-driven land degradation is less severe than previously thought, driven by different factors in different areas, and exhibited complex interactions with freeze–thaw processes. Aeolian research has been conducted within the general framework of aeolian science, but addresses issues specific to the Tibetan Plateau that arise due to the low air temperature, low air density, and the presence of a cryosphere. We propose six priorities for future research: aeolian physics, the effect of freeze-thaw cycles, comparisons with other areas, regional differences, effects of wind-driven land degradation, and integrated observation and monitoring.

The Headwater Region of the Yellow River (HRYR) is the catchment upstream of Duoshi Gorge, covering an area of 29,588 km2. The HRYR is located in the northeastern Tibet Plateau with an altitude higher than 4000 m above sea level, and is especially sensitive to climate change. Since the late 19th century, the mean annual temperature in Tibet Plateau has increased sharply. As a result of increasing air temperature, a significant number of environmental problems have occurred during the past decades, including aeolian desertification. In recent decades, aeolian desertification has become a severe environmental problem in the Tibet Plateau due to permafrost degradation, because permafrost plays an important role in maintaining the grassland vegetation. With the increase in ground temperature, the aeolian activity in the HRYR is likely to become more serious. However, the history of aeolian activity in the HRYR remains unknown due to a lack of chronological studies. In this study, 15 Optical Stimulated Luminescence (OSL) ages from three typical sections were used to reveal the history of aeolian activities in the HRYR during the Holocene. All of the OSL ages were late Holocene, and the oldest age is 2.13 ± 0.16 ka BP. The relative young OSL ages and deep aeolian sediment indicated very high sedimentation rates in the late Holocene, especially after around 1 ka BP. The intensive aeolian activity and low TOC content indicate a drier climate in the late Holocene. The well-sorted sediments and similar grain size distributions of the three sections imply their similar wind regimes. Based on the evolution history of the Yellow River's headward erosion, it is inferred that little aeolian activity occurred in this region during the early and mid-Holocene.

Wind regime is typically highly variable in space and in time, and the studies of aeolian geomorphology often use a single meteorological station as representative of a specific dune field due to the scarcity of meteorological stations in remote areas. However, the wind regime may vary greatly even between sites located just a few kilometers apart. In this study, to fully understand the relationship between wind regime and aeolian landforms of the dune field on the eastern shore of the Qinghai Lake, 1-year hourly recorded wind data from an average wind year 2012 from four stations, namely Gangcha Station, Eri Station, Wendu Station and Daotanghe Station was used to analyze the wind regime and resultant potential sand transport. The wind data analysis revealed that the drift potential (DP) at Gangcha, Eri, Wendu and Daotanghe stations is 144, 537, 829 and 431 VU, respectively. The resultant drift potential (RDP) at Gangcha, Eri, Wendu and Daotanghe stations is 112, 143, 544 and 125 VU, respectively. The high-energy wind environment, in addition to multidirectional and locally highly variable wind regime are the principal factors likely responsible for the coexistence of several types of aeolian landforms (e.g., Reversing transverse, barchanoid and stardunes).

Climate change is an environmental threat to all the sectors, especially the agricultural sector around the globe. Pakistan is one of the most vulnerable regions to extreme climatic events in developing world especially in Southeast Asia. Pakistan has detrimentally affected by the climatic variations due to its high exposure to extreme climatic events. Several studies have reported the farm households’ perception, adaptation and mitigation about climate change but there is inadequate knowledge available on the awareness of farm households about climate change in Pakistan. To fill this research gap, the purpose of research aims to examine the Pakistani farm household’s awareness level of climate change and its associated factors. By using structured questionnaire in data of 400 study participants were collected from four districts of Khyber Pakhtunkhwa (KP) province of Pakistan through a household’s survey. A stratified random sampling technique was utilized for collection of primary data. A probit model approach was employed to analyze the farm households’ awareness of climate change and its associated socioeconomic and demographic variables. Results of our study exposed that 73 % farm households were aware of climate change. Socio economics and demographic variables such as age of farm households, education level, farming experience, land ownership status, extension and information sources access were pointedly related to farm households’ awareness of climate change. Further, results of our study showed that the evaluation of farm households’ adaptation behavior suggests that farm households are active in using several adaptation strategies such as crop diversification and use of irrigation etc. It is expected that the findings of the present research will be helpful to guide governmental agencies and policymakers and contribute to the construction of sustainable adaptation measures in Pakistan and other regions in the framework of climate change.

Understanding past human-environment interactions over a long time-scale offers an analogue to predict, adapt and mitigate the environmental issues caused by global change and human activities in the future. The transient existence of historical cities from arid northern China can provide a valuable reference for this issue. In this study, we investigated a set of sand dunes which accumulated alongside the city wall of South Heishuiguo ancient city (SHC) from the middle Hexi Corridor in arid northern China. Dating these dune sands can provide the timing of both desertification and city abandonment. A series of sand samples (a total of 20) were collected, and their ages were determined by luminescence dating of K-feldspar fraction. The results suggest an abrupt sand dune accumulation between 0.40 ± 0.03 ka and 0.25 ± 0.02 ka, corresponding to 1590–1790 CE. This study confirms a phase of desertification between the late 16th century and the late 18th century in the Hexi Corridor, and the abandonment of the SHC at the ~17th century. In order to assess the anthropogenic influences on desertification, we also reconstructed the population history of the Hexi Corridor over the last 2000 years based on historical literature as a quantitative index of human activity intensity. By comparison of the timing of onset of desertification around the SHC with robust paleoclimate and historical population reconstructions, we conclude that (1) the desertification of 1590–1790 CE was likely the result of considerably enhanced human activities between the late Ming and the early Qing Dynasties, as this period was dominated by a relatively moist climate and could restrain the sand deflation; and (2) the desertification in turn caused abandonment of SHC as the impact of environmental changes on people.

Understanding the relationship between the changes in lake water volume and climate change can provide valuable information to the recharge sources of lake water. This is particularly true in arid areas such as the Badain Jaran Sand Sea, an ecologically sensitive area, where the recharge sources of lakes are heatedly debated. In this study, we determined the areas of 50 lakes (representing 70% of the total permanent lakes in this sand sea) in 1967, 1975, 1990, 2000 and 2010 by analyzing remote-sensing images using image processing and ArGIS software. In general, the total lake area decreased from 1967 to 1990, remained almost unchanged from 1990 to 2000, and increased from 2000 to 2010. Analysis of the relationship between these changes and the contemporaneous changes in annual mean temperature and annual precipitation in the surrounding areas suggests that temperature has significantly affected the lake area, but that the influence of precipitation was minor. These results tend to support the palaeo-water recharge hypothesis for lakes of the Badain Jaran Sand Sea, considering the fact that the distribution and area of lakes are closely related to precipitation and the size of mega-dunes, but the contemporaneous precipitation can hardly balance the lake water.

China's Badain Jaran Sand Sea features the tallest dunes on Earth and a unique mega-dune–lake landscape. It had been explored little until the 1990s, though early scientific explorations surrounding the sand sea had begun by the early 20th century. Heated debates now focus on the desert environment, and particularly how the mega-dunes and desert lakes develop and evolve. This paper reviews the status of these debates and summarizes the supporting evidences. The environmental research mainly concerns formation and evolution of the sand sea, and its relationship with climate change. The proposed formation time ranges from the Early Pleistocene to the Holocene. Opinions vary about climate change on different time scales. The reconstructed climate change history is shorter than the sand sea's history, with the longest record extending to the Late Pleistocene. The mega-dune research focuses on sediments, dune morphology, and formation processes. It remains unclear whether the mega-dunes result primarily from wind action, control by the underlying topography, or groundwater maintenance. The sources of lake water are also debated, but there are four main hypotheses: atmospheric precipitation, groundwater from nearby areas, precipitation and snowmelt in remote areas such as the Qilian Mountains and the Qinghai–Tibetan Plateau, or paleowater that formed during past periods of wet climate. We believe that the sand sea deserves further study in terms of its dune geomorphology, evolution, and hydrology, and their responses to climate change. Meteorological and hydrological observations and monitoring in the sand sea are particularly necessary.

Environmental degradation resulting from desertification often accelerates biodiversity loss and alters carbon (C) and nitrogen (N) stocks within grassland ecosystem. In order to evaluate the effect of desertification on plant diversity and carbon (C) and nitrogen (N) stocks, species compositions and C and N contents in plants and soil were investigated along five regions with different degrees of desertification in the northeastern margin of the Qinghai-Tibetan Plateau (control, light, moderate, severe and very severe stages). The study showed: (1) species composition and richness changed significantly with the development of grassland desertification; (2) the aboveground biomass C and N contents in the control were 101.60 and 4.03 g m−2, respectively. Compared to the control, the aboveground tissue C and N contents significantly decreased from light, moderate, severe to very severe stages. (3) The root C and N contents in the control in 0–40 cm depth are 1,372.83 and 31.49 g m−2, respectively, while the root C and N contents in 0–40 cm were also declining from the control, light, moderate, severe to very severe stages. (4) Compared to the plant, the soil made a greater contribution for C and N distribution, in which the soil organic C and total N contents in 0–40 cm depth in the control are 20,386.70 and 3,587.89 g m−2, respectively. At the same time, soil organic C and N contents also decreased significantly from the control to very severe stages. These results suggest that grassland desertification not only alters species compositions and leads to the loss of plant diversity, but also results in greater loss of organic C and N in alpine meadow, in which there is a negative effect on reducing greenhouse gas emission.

The source region of the Yellow River, located in the northeastern portion of the Qinghai–Tibet Plateau, plays a critical role in water conservation, biodiversity protection, and wetland conservation. Aeolian desertification of this area is an important concern. Remote sensing and GIS technology were employed to assess the trends in aeolian desertification from 1975 to 2005. The monitoring results showed that, aeolian desert land increased from 15,112 to 17,214 km2 during 1975–2005. In addition, it was found that the area of aeolian desertification increased rapidly from 1975 to 1990, was stable from 1990 to 2000, and slightly decreased from 2000 to 2005. Increasing temperature, overgrazing, and drainage of wetlands have been key driving factors of aeolian desertification. Thus, to control the expansion of aeolian desert lands in the source region of the Yellow River and to rehabilitate existing desert areas, the priority should be given to altering human behavior in these areas.

The Yangtze River is the China’s longest river and the third-longest river in the world. The river’s source region in the Qinghai-Tibet Plateau is especially sensitive to global environmental change because of its high elevation and cold environment. Under the influence of global warming, aeolian desertified land has expanded rapidly in this area. To assess the trends in aeolian desertification from 1975 to 2005, remote-sensing and GIS technology were used to monitor the extent of aeolian desertification in 1975, 1990, 2000, and 2005. The data sources included Landsat multi-spectral scanner images acquired in 1975, Enhanced Thematic Mapper (ETM+) images acquired in 2000, and Thematic Mapper (TM) images acquired in 1990 and 2005. Images recorded between June and October were selected, when vegetation grew well, because aeolian desertified land was more easily recognized during this period. Thematic maps, including land use and geomorphologic maps, were used as supplementary data. Aeolian desertification maps (1:100000) were produced for each year from the Landsat images through visual interpretation. The area of aeolian desertified land increased by 2,678.43 km2 from 1975 to 2005, accounting for 8.8% of the total area of aeolian desertified land in 1975, an increase of 89.28 km2 a−1. Increasing mean annual temperature and the combination of a dry, cold, and windy climate in winter and spring were mainly responsible for the expansion of desertified land.

Climate change and human activities in high-altitude, cold pasture areas with fragile environments can cause land use changes that significantly affect ecosystem services and functions. Our study investigated changes in ecosystem services in response to land use changes caused mainly by climate change and human activities on the Zoige Plateau, a region in the eastern fringe of the Tibetan Plateau with large areas of grassland and wetland. The aim was to provide guidance for sustainable management of high, cold pasture areas. We used remote sensing to evaluate land use changes, and then applied a fast method for evaluating ecological service values in 1975, 1990, and 2005. The value of ecosystem services dropped from 61.46 × 109 yuan in 1975 to 58.61 × 109 yuan in 2005, exhibiting an accelerating rate of decrease, mainly due to the degradation of wetlands and, to a lesser extent, high-cover grassland. Waste treatment and water supply were the two largest service functions, contributing about 42% of the total service value. The results suggest that future land use planning should emphasize the protection of wetlands, high-cover grassland, and woodland, which have the highest ecosystem service values and showed the greatest degradation during the study period.

Linear dunes are extensive in sand seas and dune fields around the world, but they take a range of forms due to the complex factors that control their development. “Raked” linear dunes, composed of primary ridges and subsidiary ridges that lie almost perpendicular to the primary ridges, were recently identified in the northern part of China's Kumtagh Desert. The primary ridges are typical linear dunes, but the subsidiary ridges display vestiges of barchan dunes. The subsidiary ridges are sufficiently short that they do not greatly affect the general appearance of the linear dunes. However, the raked linear dunes in the Kumtagh Desert have several unique characteristics that distinguish them from typical linear dunes. These dunes develop in an environment that is deficient in available sediment, and under a wind regime typical of linear dunes: an environment with a high wind energy and a directional variability index (RDP/DP) around 0.5. The raked linear dunes appear to have evolved from barchans following a modified form of Tsoar's (1984) model. Barchans formed under a northern wind regime were modified by an eastern wind regime oriented at an oblique angle to the barchans. The strengths of the two wind regimes are similar. Under these conditions, the barchans became reoriented, with the limbs farthest from the eastern winds extending to form subsidiary ridges and the limbs closest to the eastern winds forming the primary ridges, which appear to form mainly from dune collisions.

Crescent-shaped barchan dunes often display an asymmetric shape, with one limb longer than the other. As shown in previous studies, asymmetric bimodal winds constitute one major cause of barchan asymmetry, but the heterogeneous conditions of sand availability or flux, as well as topographic influences, may be also important. Understanding the morphology and dynamics of asymmetric barchans may have an impact in a broad range of areas, particularly as these dunes may serve as a proxy for planetary wind regimes and soil conditions in extraterrestrial environments. However, in addition to the existing theories and numerical models that explain barchan asymmetry, direct measurements of migration rates and morphologic changes of real asymmetric barchans over a time span of several years would be beneficial. Therefore, here we report such measurements, which we have acquired by investigating asymmetric barchans in the Hexi Corridor, northwest of China. We have found that dune interactions and asymmetric influx conditions are the most important causes of barchan asymmetry in this field. Particle size distributions in the Hexi Corridor display strong variations over different parts of the asymmetric barchans, as well as over different dunes, with gravel particles being incorporated from the substrate as the dunes migrate. Our observations have shown that upwind sediment sources are important for dune formation in the Hexi Corridor, and that interdune interactions affect dune shape in different ways, depending on their offset. The asymmetric barchans in the Hexi Corridor are active, with an average migration rate (MR) between 8 and 53 m year&minus, 1, in spite of the different asymmetric shapes. Our data for dune migration rates can be described well by a scaling of MR = A/(W + W0), where W is the barchan cross-wind width, A &asymp, 2835 m2 s&minus, 1, and W0 &asymp, 44 m. A similar scaling fits very well the migration rate as a function of dune along-wind width L, (i.e., MR = B/(L + L0), with B &asymp, 1722 m2 s&minus, 1 and L0 &asymp, 13 m). Linear relations are also found between both dune widths and the average limb and windward side lengths, thus indicating that the morphometric relations that are predicted from models for steady-state, symmetric crescent-shaped dunes can be applied to different transitional morphologies of interacting, asymmetric barchans.

Studies and efforts to control aeolian desertification in China have focused on the arid and semiarid lands in the north. However, the aeolian desertification that is occurring on the high-altitude Qinghai–Tibetan Plateau, which has a cold and humid climate, has received attention only in recent years. In this paper, we report the results of monitoring this aeolian desertification between 1975 and 2005 and of our analysis of its causes on the Zoige Plateau, which is located in the northeastern part of China’s Qinghai–Tibetan Plateau. Aeolian desertified lands expanded at a compound annual rate of 4.07% between 1975 and 2005. They expanded most rapidly between 1975 and 1990, at an annual rate of 7.73%. Factors responsible for this expansion include increasing temperature, decreasing precipitation, over-grazing, drainage of water systems, and land reclamation for agriculture. Increasing temperature, over-grazing, and the drainage of water systems were the key factors. The climatic variations between 1975 and 2005 were not sufficient by themselves to lead to aeolian desertification. Human disturbances such as over-grazing and drainage of water systems must thus have been primarily responsible for the observed changes, and human behavior must be adjusted to control the expansion of aeolian desertification and rehabilitate the desertified lands.

The Source Region of the Yangtze River locates in the Qinghai-Tibet Plateau with an area of 142299 km2, which is especially sensitive to global warming because of its high elevation and cold environment. To assess the land use and land cover changes from 1975 to 2005, we employed remote sensing and GIS technology to monitor the area of land use and land cover at four times (1975, 1990, 2000, and 2005). The data sources included Landsat multi-spectral scanner (MSS) images acquired in 1975 with an 80-m spatial resolution, Enhanced Thematic Mapper (ETM+) images acquired in 2000 with a 30-m resolution, and Thematic Mapper (TM) images acquired in 1990 and 2005 with a 30-m spatial resolution. The monitoring result shows that, the study area experienced an overall environmental degradation between 1975 and 2005. The environmental degradation includes deforestation, grassland degradation and sandy land expansion.

The Source Region of Yellow River locates in the hinterland of Qinghai-Tibet Plateau, which is especially sensitive to global environment change because of its high elevation and cold environment. Under the influence of global warming, aeolian desertified land expanded rapidly in this area during the last decades. To assess the trends of aeolian desertification from 1975 to 2005, we employed remote sensing and GIS technology to monitor the extent of aeolian desertification at four times (1975, 1990, 2000, and 2005). The data sources included Landsat multi-spectral scanner (MSS) images acquired in 1975 with an 80-m spatial resolution, Enhanced Thematic Mapper (ETM+) images acquired in 2000 with a 30-m resolution, and Thematic Mapper (TM) images acquired in 1990 and 2005 with a 30-m spatial resolution. The remote sensing monitoring result shows that the area of aeolian desertification land increased rapidly between 1975 and 1990, kept stable between 1990 and 2000, and turned to decrease slightly between 2000 and 2005.

The Zoige Wetland lies in the northeastern Qinghai-Tibet plateau, a region that is highly sensitive to global environment change because of its high elevation and cold environment; thus, it's a hotspot for land use and cover change (LUCC) research. In this study, we used Landsat images to monitor LUCC in this region using GIS techniques, as well as topographic, vegetation, and soil maps combined with field investigations. LUCC processes from 1975 to 2005 in the Zoige Wetland were gained through visual interpretation of multi-temporal remote-sensing images at a scale of 1:100,000. The monitoring result shows that the region's eco-environment degraded steadily in the 30 years.