Healthy soil is the key foundation of the world’s agriculture and an essential resource to ensure the world’s food security. Soil erosion is one of the serious forms of soil degradation and a major threat to sustainable terrestrial ecosystems. In this study, we utilized a continuous Landsat satellite image dataset to map soil erosion changes (1990–2020) based on the RUSLE model across the Pearl River Basin. The study results indicated that: (1) The multi-year area-specific soil erosion average in the Pearl River Basin is approximately 538.95 t/(km²·a) with an annual soil loss of approximately 353 million tons; (2) The overall soil erosion displayed a decreasing trend over the past 30 years with an annual decreasing rate of −13.44(±1.53) t/(km²·a); (3) Soil erosion, dominated by low- and moderate-level erosion, primarily occurred in the tributary basin of Xijiang River, especially in the areas with slopes > 15°, low vegetation coverage, or poorly managed forests; (4) the NDVI and land cover were the dominant factors regulating soil erosion dynamics versus the insignificant role of precipitation played in the erosion procedure. The study results are valuable for soil erosion management and water conservation in the Pearl River Basin.

In recent decades, global climate change has made natural hazards increasingly prevalent. Droughts, as a common natural hazard, have been a hot study topic for years. Most studies conducted drought monitoring in arid and semi-arid regions. In humid and sub-humid regions, due to climate change, seasonal droughts and seasonal water shortages were often observed too, but have not been well studied. This study, using a MODIS satellite-based aridity index (SbAI), investigated spatiotemporal changes in drought conditions in the subtropical Pearl River Basin. The study results indicated that the inter-annual SbAI exhibited a significant decreasing trend, illustrating a wetter trend observed in the basin in the past two decades. The decreasing trend in the SbAI was statistically significant in the dry season, but not in the monsoon season. The drought conditions displayed an insignificant expansion in the monsoon season, but exhibited statistically significant shrinking in the dry season. The Pearl River Basin has become wetter over past two decades, probably due to the results of natural impacts and human activities. The areas with increased drought conditions are more likely impacted by human activities such as water withdrawal for irrigation and industrial uses, and fast urbanization and increased impervious surfaces and resultant reduction in water storage capacity. This study provided a valuable reference for drought assessment across the Pearl River Basin.

Precipitation is a key component of the hydrological cycle and one of the important indicators of climate change. Due to climate change, extreme precipitation events have globally and regionally increased in frequency and intensity, leading to a higher probability of natural disasters. This study, using the long-term APHRODITE dataset, employed six precipitation indices to analyze the spatiotemporal changes in extreme precipitation in the Pearl River Basin during 1951–2015. The Mann–Kendall (M–K) test was used to verify the significance of the observed trends. The results indicate that: (1) the interannual PRCPTOT showed a trend with an average positive increase of 0.019 mm/yr, which was followed by an increase in SDII, R95P, and RX1day, and a decrease in R95D and CWD; seasonal PRCPTOT also displayed an increase in summer and winter and a decrease in spring and autumn, corresponding to increases in R95P and SDII in all seasons. (2) The annual precipitation increases from the west to east of the basin, similar to the gradient distribution of SDII, R95P and RX1day, with the high R95D happening in the middle and lower reaches of the Xijiang River, but the CWD increased from the north to south of the basin. The seasonal spatial distributions of PRCPTOT, SDII, and R95P are relatively similar except in autumn, showing an increase from the west to east of the basin in spring and winter and a gradual increase from the north to south of the basin in summer, indicating that the Beijiang and Dongjiang tributary basins are more vulnerable to floods. (3) The MK test results exhibited that the Yunnan–Guizhou Plateau region in the upper reaches of the Xijiang River Basin became drier, and there was an increase in extreme precipitation in the Beijiang and Dongjiang river basins. The study results facilitate valuable flood mitigation, natural hazard control and water resources management in the Pearl River Basin.

Benggang erosion is one of the most severe geomorphological hazards occurring on deeply weathered crusts in the hilly regions of southern China. Unraveling the susceptibility and pinpointing the risk areas of Benggang erosion are essential for developing effective prevention and management strategies. This study introduced the Maxent model to investigate Benggang erosion susceptibility (BES) and compared the evaluation results with the widely used Random Forest (RF) model. The findings are as follows: (1) the incidence of Benggang erosion is rising initially with an increase in elevation, slope, topographic wetness index, rainfall erosivity, and fractional vegetation cover, followed by a subsequent decline, highlighting its distinct characteristics compared to typical types of gully erosion; (2) the AUC values from the ROC curves for the Maxent and RF models are 0.885 and 0.927, respectively. Both models converge on elevation, fractional vegetation cover, rainfall erosivity, Lithology, and topographic wetness index as the most impactful variables; (3) both models adeptly identified regions prone to potential Benggang erosion. However, the Maxent model demonstrated superior spatial correlation in its susceptibility assessment, contrasting with the RF model, which tended to overestimate the BES in certain regions; (4) the Maxent model’s advantages include no need for absence samples, direct handling of categorical data, and more convincing results, suggesting its potential for widespread application in the BES assessment. This research contributes empirical evidence to study the Benggang erosion developing conditions in the hilly regions of southern China and provides an important consideration for the sustainability of the regional ecological environment and human society.

Precipitation is one of the most important factors in hydrological cycle and climate change. Due to global climate change, the global and regional hydrological cycle has been changed significantly, and the precipitation pattern has changed, which made natural disasters happened more frequent. In this study, we taken the Pearl River Basin as a case study area and used APHRODITE dataset to investigate the spatiotemporal trend of precipitation during the period of 1951-2015 based on six extreme rainfall indices recommended by the WMO. Then, the MK test was used to verify their trend and analyze the temporal and spatial variability. The results indicated that: (1) The annual PRCPTOT in the Pearl River Basin displayed an increasing trend with an increasing rate of 0.019mm/yr. Although the number of annual rainy days was decreasing, the annual SDII exhibited an increasing trend. The annual R95P and RX1day exhibited an increasing trend, but the R95D and CWD showed a decreasing trend. The seasonal PRCPTOT increased in summer and winter, but decreased in spring and autumn. R95P and SDII displayed an increasing trend in four seasons. (2) The annual variation of PRCPTOT increased from west to east, the trend of SDII, R95P and RX1day were similar with PRCPTOT, but the high value of R95D happened in the middle and lower reaches of Xijiang River, and CWD increased from north to south. Except autumn, the seasonal spatial distribution of PRCPTOT, SDII and R95P were similar. In spring and winter, the spatial distribution of PRCPTOT, SDII and R95P increased from west to east, and from north to south in summer, indicating that the Beijiang River basin and Dongjiang River basin had a higher flood risk. (3) MK test of indices shown that the Yunnan-Guizhou Plateau was becoming drier, and the risk of extreme rainfall was increasing in the Beijiang River basin and Dongjiang River basin. The study results are valuable for future water resources management and ecological environment protection in the Pearl River Basin.

Healthy soil is the key foundation of the world’s agriculture and an essential resource to ensure the world’s food security. Soil erosion is one of the important forms of soil degradation and a major threat to sustainable terrestrial ecosystem, leading to a series of inevitable consequences such as reduced soil productivity, deteriorated water quality, low food yield, lost reservoir capacity, and even flood hazards. Therefore, controlling soil erosion has been one of the most important tasks of ecosystem management. In our study, we utilized a continuous Landsat satellite image dataset to map soil erosion dynamics (1990-2020) based on RUSLE model across the Pearl River Basin. Based on the results, We also analyzed the spatiotemporal dynamics in soil erosion in the Pearl River Basin from 1990 to 2020, and derived the causes of the changes, to provide a reliable result for soil erosion management and water and soil conservation in the Pearl River Basin. The study results indicated that: (1) The multi-year area-specific soil erosion average in the Pearl River Basin is approximately 538.95 t/(km2·a) with an annual soil loss of approximately 353 million tons; (2) The overall soil erosion displayed a decreasing trend over the past 30 years with an annual decreasing rate of -13.44(±1.53) t/(km2·a). (3) soil erosion, dominated by low- and moderate-level erosion, primarily happened in the tributary basin of Xijiang River, especially in the areas with slopes > 15°, low vegetation coverage, or poorly managed forests; (4) NDVI and land cover were the dominant factors regulating soil erosion dynamics, versus the insignificant role of precipitation played in the erosion procedure. The study results are valuable for soil erosion management and water conservation in the Pearl River Basin.