The southwestern Iran is one of the regions that are most prone to dust events. The objective of this study is the analysis of the spatial and temporal distributions of dust deposition rate as a key factor for finding the relative impact of the dust. First, the monthly mean aerosol optical thickness (AOT) from Moderate Resolution Imaging Spectroradiometer (MODIS) was analyzed and compared with the dust amount variations from ground deposition rate (GDR), and the results were further used to investigate the spatial and temporal distributions of dust events in southwestern Iran for the period between 2014 and 2015. Moving air mass trajectories, using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, were proven to be a discriminator of their local and regional origin. The results from GDR analysis produced a correlation coefficient between dust event history and deposition rates at dust magnitudes of >0.93 that is meaningful at the 95% confidence level. Furthermore, the deposition rates varied from 3 g/m² per month in summer to 10 g/m² per month in spring and gave insight into the transport direction of the dust. Within the same time series, AOT correspondences with MODIS on Terra in four aerosol thickness layers (clean, thin, thick, and strong thick) were shown in relation to each other. The deepest mixed layers were observed in spring and summer with a thickness of approximately 3500 m above ground level in the study area. Investigations of ground-based observations were correlated with the same variations for each aerosol thickness layer from MODIS images and they can be applied to discriminate layers of aeolian dust from layers of other aerosols. Together, dust distribution plots from AOT participated to enhance mass calculations and estimation deposition rates from the thick and strong thick aerosol thickness layers using the results from GDR. Despite all the advances of AOT, under certain circumstances, ground-based observations are better able to represent aerosol conditions over the study area, which were tested in southwestern Iran, even though the low number of observations is a commonly acknowledged drawback of GDR.

High water consumption and inefficient irrigation management in the agriculture sector of the middle and lower reaches of the Amu Darya River Basin (ADRB) have significantly influenced the gradual shrinking of the Aral Sea and its ecosystem. In this study, we investigated the crop water consumption in the growing seasons and the irrigation water requirement for different crop types in the lower ADRB during 2004-2017. We applied the FAO Penman-Monteith method to estimate reference evapotranspiration (ET₀) based on daily climatic data collected from four meteorological stations. Crop evapotranspiration (ET_c) of specific crop types was calculated by the crop coefficient. Then, we analyzed the net irrigation requirement (NIR) based on the effective precipitation with crop water requirements. The results indicated that the lowest monthly ET₀ values in the lower ADRB were found in December (18.2 mm) and January (16.0 mm), and the highest monthly ET₀ values were found in June and July, with similar values of 211.6 mm. The annual ET_c reached to 887.2, 1002.1, and 492.0 mm for cotton, rice, and wheat, respectively. The average regional NIR ranged from 514.9 to 715.0 mm in the 10 Irrigation System Management Organizations (UISs) in the study area, while the total required irrigation volume for the whole region ranged from 4.2×10⁹ to 11.6×10⁹ m³ during 2004-2017. The percentages of NIR in SIW (surface irrigation water) ranged from 46.4% to 65.2% during the study period, with the exceptions of the drought years of 2008 and 2011, in which there was a significantly less runoff in the Amu Darya River. This study provides an overview for local water authorities to achieve optimal regional water allocation in the study area.

The Aral Sea Basin in Central Asia is an important geographical environment unit in the center of Eurasia. It is of great significance to the ecological protection and sustainable development of Central Asia to carry out dynamic monitoring and effective evaluation of the eco-environmental quality of the Aral Sea Basin. In this study, the arid remote sensing ecological index (ARSEI) for large-scale arid areas was developed, which coupled the information of the greenness index, the salinity index, the humidity index, the heat index, and the land degradation index of arid areas. The ARSEI was used to monitor and evaluate the eco-environmental quality of the Aral Sea Basin from 2000 to 2019. The results show that the greenness index, the humidity index and the land degradation index had a positive impact on the quality of the ecological environment in the Aral Sea Basin, while the salinity index and the heat index exerted a negative impact on the quality of the ecological environment. The eco-environmental quality of the Aral Sea Basin demonstrated a trend of initial improvement, followed by deterioration, and finally further improvement. The spatial variation of these changes was significant. From 2000 to 2019, grassland and wasteland (saline alkali land and sandy land) in the central and western parts of the basin had the worst ecological environment quality. The areas with poor ecological environment quality are mainly distributed in rivers, wetlands, and cultivated land around lakes. During the period from 2000 to 2019, except for the surrounding areas of the Aral Sea, the ecological environment quality in other areas of the Aral Sea Basin has been improved in general. The correlation coefficients between the change in the eco-environmental quality and the heat index and between the change in the eco-environmental quality and the humidity index were -0.593 and 0.524, respectively. Climate conditions and human activities have led to different combinations of heat and humidity changes in the eco-environmental quality of the Aral Sea Basin. However, human activities had a greater impact. The ARSEI can quantitatively and intuitively reflect the scale and causes of large-scale and long-time period changes of the eco-environmental quality in arid areas; it is very suitable for the study of the eco-environmental quality in arid areas.

In this study, we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930-2015 to investigate variations in river runoff and the impacts of climate change and human activities on river runoff. The Syr Darya River, which is supplied by snow and glacier meltwater upstream, is an important freshwater source for Central Asia, as nearly half of the population is concentrated in this area. River runoff in this arid region is sensitive to climate change and human activities. Therefore, estimation of the climatic and hydrological changes and the quantification of the impacts of climate change and human activities on river runoff are of great concern and important for regional water resources management. The long-term trends of hydrological time series from the selected 11 hydrological stations in the Syr Darya River Basin were examined by non-parametric methods, including the Pettitt change point test and Mann-Kendall trend tests. It was found that 8 out of 11 hydrological stations showed significant downward trends in river runoff. Change of river runoff variations occurred in the year around 1960. Moreover, during the study period (1930-2015), annual mean temperature, annual precipitation, and annual potential evapotranspiration in the river basin increased substantially. We employed hydrological sensitivity method to evaluate the impacts of climate change and human activities on river runoff based on precipitation and potential evapotranspiration. It was estimated that human activities accounted for over 82.6%-98.7% of the reduction in river runoff, mainly owing to water withdrawal for irrigation purpose. The observed variations in river runoff can subsequently lead to adverse ecological consequences from an ecological and regional water resources management perspective.

The gradual shrinkage of the Aral Sea has led to not only the degradation of the unique environments of the Aral Sea, but also numerous and fast developing succession processes in the neighborhood habitats surrounding the sea. In this study, we investigated the vegetative succession processes related to the Aral Sea shrinkage in the Eastern Cliff of the Ustyurt Plateau in Republic of Uzbekistan, Central Asia. We compared the results of our current investigation (2010-2017) on vegetative communities with the geobotany data collected during the 1970s (1970-1980). The results showed great changes in the mesophytic plant communities and habitat aridization as a result of the drop in the underground water level, which decreased atmospheric humidity and increased the salt content of the soil caused by the shrinkage of the Aral Sea. In the vegetative communities, we observed a decrease in the Margalef index (D_Mg), which had a positive correlation with the poly-dominance index (I-D). The main indications of the plant communities' transformation were the loss of the weak species, the appearance of new communities with low species diversity, the stabilization of the projective cover of former resistant communities, as well as the appearance of a new competitive species, which occupy new habitats.

Drought-prone grasslands provide a critical resource for the millions of people who are dependent on livestock for food security. However, this ecosystem is potentially vulnerable to climate change (e.g., precipitation) and human activity (e.g., grazing). Despite this, the influences of precipitation and grazing on ecological functions of drought-prone grasslands in the Tianshan Mountains remain relatively unexplored. Therefore, we conducted a systematic field investigation and a clipping experiment (simulating different intensities of grazing) in a drought-prone grassland on the northern slopes of the Tianshan Mountains in China to examine the influences of precipitation and grazing on aboveground biomass (AGB), soil volumetric water content (SVWC), and precipitation use efficiency (PUE) during the period of 2014-2017. We obtained the meteorological and SVWC data using an HL20 Bowen ratio system and a PR2 soil profile hydrometer, respectively. We found that AGB was clearly affected by both the amount and seasonal pattern of precipitation, and that PUE may be relatively low in years with either low or excessive precipitation. The PUE values were generally higher in the rapid growing season (April-July) than in the entire growing season (April-October). Overall, moderate grazing can promote plant growth under water stress conditions. The SVWC value was higher in the clipped plots than in the unclipped plots in the rapid growing season (April-July), but it was lower in the clipped plots than in the unclipped plots in the slow growing season (August-October). Our findings can enhance the understanding of the ecological effects of precipitation and grazing in drought-prone grasslands and provide data that will support the effective local grassland management.

Desertification is one of the most serious environmental problems in the world, especially in the arid desert regions. Combating desertification, therefore, is an urgent task on a regional or even global scale. The Taklimakan Desert in China is the second largest mobile desert in the world and has been called the ''Dead Sea'' due to few organisms can exist in such a harsh environment. The Taklimakan Desert Highway, the longest desert highway (a total length of 446 km) across the mobile desert in the world, was built in the 1990s within the Taklimakan Desert. It has an important strategic significance regarding oil and gas resources exploration and plays a vital role in the socio-economic development of southern Xinjiang, China. However, wind-blow sand seriously damages the smoothness of the desert highway and, in this case, mechanical sand control system (including sand barrier fences and straw checkerboards) was used early in the life of the desert highway to protect the road. Unfortunately, more than 70% of the sand barrier fences and straw checkerboards have lost their functions, and the desert highway has often been buried and frequently blocked since 1999. To solve this problem, a long artificial shelterbelt with the length of 437 km was built along the desert highway since 2000. However, some potential problems still exist for the sustainable development of the desert highway, such as water shortage, strong sandstorms, extreme environmental characteristics and large maintenance costs. The study aims to provide an overview of the damages caused by wind-blown sand and the effects of sand control measures along the Taklimakan Desert Highway. Ultimately, we provide some suggestions for the biological sand control system to ensure the sustainable development of the Taklimakan Desert Highway, such as screening drought-resistant species to reduce the irrigation requirement and ensure the sound development of groundwater, screening halophytes to restore vegetation in the case of soil salinization, and planting cash crops, such as Cistanche, Wolfberry, Apocynum and other cash crops to decrease the high cost of maintenance on highways and shelterbelts.