The uncertainties in soil erosion (SE) are further intensified by various factors, such as global warming, regional warming and humidification, and vegetation cover changes. Moreover, quantitative evaluations of SE in major basins of Central Asia (CA) under changing environments have rarely been conducted. This study conducted quantitative evaluation of SE in four major basins (Syr Darya Basin (SDB), Amu Darya Basin (ADB), Ili River Basin (IRB) and Tarim River Basin (TRB) using the Revised Universal Soil Loss Equation (RUSLE) and analyzed the main driving factors. SE quantities in the basins presented relatively consistent upward fluctuating trends from 1982 to 2017. Vegetation cover variation fluctuated significantly from 1982 to 2017. Specifically, vegetation cover decreased continuously in SDB, ADB, and IRB, but increased gradually in TRB. Pixels with positive spatial variation of vegetation mainly occurred around lakes and oases near rivers. The Normalized Difference Vegetation Index (NDVI) showed higher correlation with precipitation (80.5%) than with temperature (48.3%). During the study period, the area of arable land (AL) exhibited the largest change among all land use types in CA. Under long-term human activities, the proportion of NDVI of other land types converting to AL was the highest. In the structural equation model (SEM), precipitation, temperature, Shannon Diversity Index (SHDI), and NDVI strongly influenced SE. Overall, the major basins in CA were jointly affected by climate, human activities, and vegetation. Specifically, climatic factors exerted the strongest influence, followed by SHDI (human activities). SE was found to be relatively serious in ADB, SDB, and IRB, with SE in SDB even approaching that in the Loess Plateau. Under the background of global changes, appropriate water and land resource management and optimization configurations should be implemented in CA with reference to TRB in order to relieve local SE problems.

Ecosystem services (ESs) are important for supporting human development. However, a changing climate and anthropogenic impacts are resulting in the degradation of dryland ecosystems to varying degrees. While there has been the global implementation of Ecological Restoration Programs (ERPs) to restore degraded ecosystems, there remains limited comprehensive assessment of their impacts on ESs of drylands. In this study, the sandy areas of northern China were used as the study area. The RUSLE, RWEQ, CASA, and InVEST models were used to simulate four major ESs: soil conservation (SC), sand fixation (SF), carbon sequestration (CS), and water yield (WY). The study aimed to evaluate the influences of various ERPs on major ESs. The dominant factors affecting the overall benefits provided by ESs were also identified. Since ERPs were implemented, forest areas have increased by 2.8 × 10⁴ km², whereas the areas of cropland, shrubland, and grassland have decreased. There were generally increasing trends in SF, SC, and CS, whereas there was a decreasing trend in WY. We then used a scenario-based simulation approach to eliminate the influence of climate variability on ESs. The results showed increasing trends in SF, SC, and CS, whereas there were minimal changes in WY. The results suggested that although ERPs can significantly increase regional ESs, unregulated expansion in vegetation can result in a water crisis and affect regional water security.

For this study, we collected a total of 77 topsoil samples from urban, suburban, and rural gradients in the Urumqi city area in northwest China and analyzed their concentrations of seven trace elements: Arsenic (As), cadmium (Cd), nickel (Ni), lead (Pb), mercury (Hg), copper (Cu), and Zinc (Zn). To assess and compare the contamination levels and the potential health risk of trace elements in topsoil along an urbanization gradient, we employed the pollution index and the health risk assessment model introduced by the US Environmental Protection Agency; we also used geostatistical analysis to analyze the spatial distribution patterns. The results we obtained indicate that the contamination levels of trace elements in soil decreased in the order of urban > rural > suburban gradients. We found a similar spatial distribution pattern of contamination levels of Ni, Zn, Cd, and Pb elements, with a zonal distribution pattern, while the spatial distribution patterns of As, Cu, and Hg elements show high concentration patches in many of the areas investigated in this study. Furthermore, based on the identified concentrations, the topsoil is heavily contaminated by Hg and slightly contaminated by Pb, As, and Zn in the urban gradient, whereas it is heavily contaminated by Hg in suburban and rural gradients and slightly contaminated by As in the suburban gradient. The total non-carcinogenic risk index of the analyzed trace elements for adults and children decrease in the order of urban > suburban > rural gradients, whereas the total carcinogenic risk index of the analyzed elements for adults and children decreased in the order of suburban > urban > rural gradients. However, the contamination of topsoil in all gradients is more harmful to children’s health than to that of adults. Overall, urbanization has had obvious effects on the accumulation of trace elements in soil, and As is the main carcinogenic and non-carcinogenic risk factor among the investigated elements in topsoil in all urbanization gradients.