Search Results (36)

Life-history plasticity allows fishes to exploit heterogeneous freshwater networks, and proactive habitat selection enhances their capacity to cope with climatic and human-induced stressors. Coilia brachygnathus, long regarded as a freshwater resident, nevertheless has a poorly understood habitat use and selection. We reconstructed habitat use of C. brachygnathus across the middle-lower Yangtze by coupling water ⁸⁷Sr/⁸⁶Sr baselines with otolith ⁸⁷Sr/⁸⁶Sr transects. We used 60 water samples, compiled published datasets, and measured additional water samples from the mainstem, major tributaries, and connected lakes. In situ ⁸⁷Sr/⁸⁶Sr profiles were smoothed with generalized additive models, revealing significant within-profile variation for all fish. Two modes emerged: (i) residents, whose otolith values remained within local water ranges, consistent with limited movement; and (ii) migrants, whose profiles departed from local baselines, indicating exchanges among lakes, tributaries, and the mainstem. Several fish captured at Anqing and Zhenjiang possess Poyang-like core signatures that declined to mainstem values, while bidirectional shifts were common in the Dongting-Xiang system. These results overturn the residency paradigm, demonstrate flexible partial migration, and indicate proactive habitat selection in the face of environmental change, thereby supporting management that maintains river–lake connectivity and quantifies lake contributions to mainstem stocks. Full article

Background: Phylogeographic surveys of obligate freshwater fishes could serve as a pivotal lens through which the biological footprints of historic drainage rearrangements can be deciphered. Methods: Focusing on the headwater-restricted cyprinid Acrossocheilus kreyenbergii in the Pearl, Yangtze, and Huai river basins, we examined variations in mitochondrial cytochrome b gene (Cyt b) to elucidate the phylogeographic architecture and evolutionary history of this stream fish in South–Central China through integrative analyses of phylogeny, ancestral area reconstruction, genetic structure, and population demography. Results: A time-calibrated phylogeny recovered two primary lineages, K-I and K-II, which diverged ca. 2.15 Ma: K-I split into K-Ia (Huai River) and K-Ib (Yangtze–Poyang Lake catchment) at 1.53 Ma, whereas K-II gave rise to K-IIa, K-IIb, and K-IIc through sequential divergences at 1.29 Ma and 0.83 Ma, with K-IIa restricted to the Poyang Lake catchment. K-IIb was shared between the Poyang Lake catchment and the Qiupu River (Yangtze basin), and K-IIc was distributed in the Xijiang River (Pearl basin) as well as the Yangtze–Dongting Lake catchment. Conclusions: Our findings reveal that the phylogeographic architecture of A. kreyenbergii was sculpted by a succession of geologic and anthropocentric events: the Late-Cenozoic collapse of the Zhe–Min Uplift first fractured its range; the intervening Mufu–Lianyun–Luoxiao Mountains then acted as a persistent barrier; the large waters of Poyang and Dongting Lakes served as biological filters; and the 2200-year-old Lingqu Canal—constructed during the Qin dynasty—briefly re-established a corridor for gene flow. Together, these forces disrupted and reorganized the species’ genetic connections, leaving a visible imprint today. Full article

River–lake systems are essential for sustaining ecosystems and human livelihoods. However, the complexity and variability of large river–lake systems, coupled with characteristic differences in water bodies across regions, have made quantifying their extent and changes inherently challenging. This study implements a robust water extraction method based on the multidimensional X-means clustering algorithm. This method leverages the advantages of Sentinel-2 imagery for water detection. Utilizing the X-means algorithm, it generates a new seasonal surface water area (SWA) product for the mid-lower reaches of the Yangtze River (MLRYR). The implemented method achieved an overall accuracy of 97.98%, a producer’s accuracy of 98.02%, a user’s accuracy of 96.01%, a Matthews correlation coefficient of 0.954, and a Kappa coefficient of 0.954. Analysis of water body dynamics reveals that over the past six years, the overall trend of SWA in the MLRYR has remained stable. However, within a broad range including multiple sub-basins, a decline in SWA has been observed on an inter-annual scale. Among the large lakes and reservoirs in the MLRYR, the water areas of Poyang Lake, Dongting Lake and Shijiu Lake all showed a marked decline. Among all water bodies with a significant increase in area, the Danjiangkou Reservoir is the largest. Further correlation analysis indicates that SWA exhibited the strongest correlations with precipitation and drought index in most sub-basins. In sub-basins where large lakes and reservoirs exist, the presence of river networks played a buffering role by regulating and storing water, thereby reducing the direct influence of climatic factors on lake and reservoir water extent. These findings highlight the complex interplay of climatic and hydrological factors. By integrating satellite imagery and Earth observation, this study advances understanding of MLRYR surface water dynamics, providing a robust framework for monitoring in other regions. It offers critical insights into drought impacts and informs effective water resource management and conservation strategies. Full article

Synthetic Aperture Radar (SAR) technology offers unparalleled advantages by delivering high-quality images under all-weather conditions, enabling effective flood monitoring. This capability provides massive remote sensing data for flood mapping, while recent rapid advances in deep learning (DL) offer methodologies for large-scale flood mapping. However, the full potential of deep learning in large-scale flood monitoring utilizing remote sensing data remains largely untapped, necessitating further exploration of both data and methodologies. This paper presents an innovative approach that harnesses convolutional neural networks (CNNs) with Sentinel-1 SAR images for large-scale inundation detection and dynamic flood monitoring in the Yangtze River Basin (YRB). An efficient CNN model entitled FloodsNet was constructed based on multi-scale feature extraction and reuse. The study compiled 16 flood events comprising 32 Sentinel-1 images for CNN training, validation, inundation detection, and flood mapping. A semi-automatic inundation detection approach was developed to generate representative flood samples with labels, resulting in a total of 5296 labeled flood samples. The proposed model FloodsNet achieves 1–2% higher F1-score than the other five DL models on this dataset. Experimental inundation detection in the YRB from 2016 to 2021 and dynamic flood monitoring in the Dongting and Poyang Lakes corroborated the scheme’s outstanding performance through various validation procedures. This study marks the first application of deep learning with SAR images for large-scale flood monitoring in the YRB, providing a valuable reference for future research in flood disaster studies. This study explores the potential of SAR imagery and deep learning in large-scale flood monitoring across the Yangtze River Basin, providing a valuable reference for future research in flood disaster studies. Full article

Compound dry and hot events or extremes (CDHEs) have emerged as major climatic threats to agricultural production and food security in the middle reaches of the Yangtze River Basin (MRYRB), a critical grain-producing region in China. However, agricultural risks associated with CDHEs, incorporating both natural and socio-economic factors, remain poorly understood in this area. Using a Hazard-Exposure-Vulnerability (HEV) framework integrated with a weighting quantification method and supported by remote sensing technology and integrated geographic data, we systematically assessed the spatiotemporal dynamics of agricultural CDHE risks and corresponding crop responses in the MRYRB from 2000 to 2019. Results indicated an increasing trend in agricultural risks across the region, particularly in the Poyang Lake Plain (by 21.9%) and Jianghan Plain (by 9.9%), whereas a decreasing trend was observed in the Dongting Lake Plain (by 15.2%). Spatial autocorrelation analysis further demonstrated a significant negative relationship between gross primary production (GPP) and high agricultural risks of CDHEs, with a spatial concordance rate of 52.6%. These findings underscore the importance of incorporating CDHE risk assessments into agricultural management. To mitigate future risks, we suggest targeted adaptation strategies, including strengthening water resource management and developing multi-source irrigation systems in the Poyang Lake Plain, Dongting Lake, and the Jianghan Plain, improving hydraulic infrastructure and water source conservation capacity in northern and southwestern Hunan Province, and prioritizing regional risk-based adaptive planning to reduce agricultural losses. Our findings rectify the longstanding assumption that hydrological abundance inherently confers robust resistance to compound drought and heatwave stresses in lacustrine plains. Full article

For a long time, drought disasters have brought about a wide range of negative impacts on human socio-economics. Especially in large basins with many tributaries, once hydrological drought occurs synchronously in several tributaries, the hydrological drought condition in the mainstream will be aggravated, which will lead to more serious losses. However, there is still a lack of research on the probabilistic risk of simultaneous hydrologic droughts in various areas of large watersheds. In this study, the Standardized Runoff Index was used to characterize hydrological drought, and the Standardized Runoff Index (SRI) sequence characteristics of each region were analyzed. Subsequently, a multiregional hazard encounter probability distribution model with an R-vine structure was constructed with the help of the vine copula function to study the risk pattern of simultaneous hydrological drought in multiple tributaries under environmental changes. The model results showed that the probability of the four basins gradually decreased from 7.5% to 0.16% when the SRI changed from ≤−0.5 to ≤−2.0, indicating that the likelihood of the joint distribution of the compound disaster decreases with increase in the drought extremes. Meanwhile, the probability of hydrological drought in the three major basins showed significant spatial differences, and the risk ranking was Dongting Lake Basin > Poyang Lake Basin > Han River Basin. The model constructed in this study reveals the disaster risk law, provides theoretical support for the measurement of hydrological drought risk in multiple regions at the same time, and is of great significance for the prediction of compound drought disaster risk. Full article

Anthropogenic and climatic stresses threaten water security across the Yangtze River Basin (YZRB), which safeguards the population and economic development that is responsible for nearly half China’s GDP. Understanding trends and drivers of open surface water in the YZRB is crucial yet remains poorly investigated. This study proposes a new method to eliminate shadow impacts on water extraction, achieving 96% accuracy, and develops a long-term dataset from 1986 to 2022 using Landsat imagery on the Google Earth Engine platform. Trends in water area changes were analyzed for source region, typical river and lake dominated regions of YZRB, and partial least squares regression was used to attribute the major climatic and anthropogenic drivers of water change. The results show that water area generally increased by 39.88%, with divergent trends across regions. Source and river dominated regions both exhibited notable growths by 49.43% and 37.01%, respectively. Increases in the water area in the source region comes from both lakes and rivers, driven by increasing temperature and precipitation in permafrost regions, while increases in river dominated regions come from permanent water induced by construction of mega dams. Changes of the water body in lake dominated regions are mainly influenced by seasonal water and show varied trends. Poyang and Dongting lakes have decreasing water area, from 3354.24 to 2168.82 km² and 1504.79 to 850.47 km², respectively, which are both attributed to the impoundment of the Three Gorges Reservoir and alterations in precipitation patterns. While Tai Lake Basin experienced an increase from 1986 to 2003 due to expanded anthropogenic water bodies, it was followed by a decline after 2003 which was driven by urbanization. We therefore suggest systematically optimizing reservoir dispatching and land–water configurations to balance economic, societal, and environmental benefits. Full article

X-ray electron probe microanalyzer technology was used to study the microchemistry and habitat history of Coilia nasus collected from the Dawanzhou section of the Yangtze River between May and June 2023. The Sr/Ca ratio from the otolith core to the otolith diameter was low (640–1100 µm), representing the first stage of development. In the second stage, C. nasus exhibited two distinct types. The first type, which included individuals 5HK05 and 6HK03, exclusively inhabited brackish estuarine waters. The second type, comprising 13 individuals, resided in higher-salinity seawater environments (Sr/Ca > 7). Furthermore, individuals 5HK01, 5HK03, 5HK07, and 6HK05 displayed a phase with a high Sr/Ca ratio compared to other fish. Freshwater coefficient analysis indicated that C. nasus in the Dawanzhou water area was unlikely to continue upstream to Dongting Lake in the middle reaches of the Yangtze River but may have entered Poyang Lake through its mouth or reproduced in its upper reaches. Analysis of sexual maturity and migration history suggested that the Dawanzhou section primarily serves as a migration channel for C. nasus, with a potential spawning ground for this high-value fish located nearby. Full article

Accurate and near-real-time flood monitoring is crucial for effective post-disaster relief efforts. Although extensive research has been conducted on flood classification, efficiently and automatically processing multi-source imagery to generate reliable flood inundation maps remains challenging. In this study, a new automatic flood monitoring method, utilizing optical and Synthetic Aperture Radar (SAR) imagery, was developed based on the Google Earth Engine (GEE) cloud platform. The Normalized Difference Flood Vegetation Index (NDFVI) was innovatively combined with the Edge Otsu segmentation method, utilizing SAR imagery, to enhance the initial accuracy of flood area mapping. To more effectively distinguish flood areas from non-seasonal water bodies, such as lakes, rivers, and reservoirs, pre-flood Landsat-8 imagery was analyzed. Non-seasonal water bodies were classified using multi-index methods and water body probability distributions, thereby further enhancing the accuracy of flood mapping. The method was applied to the catastrophic floods in Poyang Lake, Jiangxi Province, in 2020, and East Dongting Lake, Hunan Province, China, in 2024. The results demonstrated classification accuracies of 92.6% and 97.2% for flood inundation mapping during the Poyang Lake and East Dongting Lake events, respectively. This method offers efficient and precise information support to decision-makers and emergency responders, thereby fully demonstrating its substantial potential for practical applications. Full article

In the context of global warming and intensified human activities, the loss and fragmentation of species habitats have been exacerbated. In order to clarify the trends in the current and future suitable wintering areas for hooded cranes (Grus monacha), the MaxEnt model was applied to predict the distribution patterns and trends of hooded cranes based on 94 occurrence records and 23 environmental variables during the wintering periods from 2015 to 2024. The results indicated the following. (1) The elevation (Elev, 43.7%), distance to major water (DW, 39.5%), minimum temperature of the coldest month (Bio6, 9.7%), and precipitation of the wettest month (Bio13, 2.6%) were dominant factors influencing the wintering distribution of hooded cranes. (2) Under current climate and land use scenarios, highly suitable areas for hooded cranes in China cover approximately 1.274 × 10⁵ km², primarily located in inland lakes such as Dongting Lake, Liangzi Lake, Poyang Lake, Shengjin Lake, and Caizi Lake in the middle and lower reaches of the Yangtze River, as well as in coastal wetlands such as Chongming East Beach, Shandong Peninsula, Bohai Bay, and Liaodong Peninsula. (3) Under future climate and land use scenarios, the suitable habitat areas (high and moderate suitability) for hooded cranes are projected to contract substantially in the middle and lower reaches of the Yangtze River and expand slightly in the areas of Shandong Peninsula, Bohai Bay, and Liaodong Peninsula. Under the SSP126 (low emissions), SSP245 (medium emissions), and SSP585 (high emissions) scenarios, the average area reduction percentages were 29.1%, 28.8%, and 31.6%, respectively. (4) The increases in Bio6 and water areas in northern China were the main reasons for the shift of the wintering distribution centroid for hooded cranes toward northeastern China. The minor expansion of suitable habitat in the north covers mainly cultivated land, and this singular foraging habitat could intensify both intraspecific and interspecific competition among waterbirds, thus exacerbating the survival risks for hooded cranes. To more effectively protect the wintering population of hooded cranes in China, the restoration of natural habitats and population monitoring in the middle and lower reaches of the Yangtze River should be strengthened. Additionally, nature reserves or protected areas should be established in the northern expansion regions. Full article

Carbon dioxide (CO₂) flux measurements were conducted throughout the year 2022 utilizing the eddy covariance technique in this study to investigate the characteristics of carbon fluxes and their influencing factors in the Chenhu wetland, a representative subtropical lake-marsh wetland located in the middle reaches of the Yangtze River in China. The results revealed that the mean daily variation of CO₂ flux during the growing season exhibited a U-shaped pattern, with measurements ranging from −12.42 to 4.28 μmolCO₂·m⁻²·s⁻¹. The Chenhu wetland ecosystem functions as a carbon sink throughout the growing season, subsequently transitioning to a carbon source during the non-growing season, as evidenced by observations made in 2022. The annual CO₂ absorption was quantified at 21.20 molCO₂·m⁻², a figure that is lower than those documented for specific subtropical lake wetlands, such as Dongting Lake and Poyang Lake. However, this measurement aligns closely with the average net ecosystem exchange (NEE) reported for wetlands across Asia. The correlation between daytime CO₂ flux and photosynthetically active radiation (PAR) can be accurately represented through rectangular hyperbola equations throughout the growing season. Vapor pressure deficit (VPD) acts as a constraining factor for daytime NEE, with an optimal range established between 0.5 and 1.5 kPa. Furthermore, air temperature (T_a), relative humidity (RH), and vapor pressure difference (VPD) are recognized as the principal determinants affecting NEE during the nocturnal period. The association between T_a and NEE during the non-growing season conforms to the van’t Hoff model, suggesting that NEE increases in response to elevated T_a during this timeframe. Full article

Flash droughts, characterized by their rapid onset and severe impacts, have critical implications for the ecological environment and water resource security. However, inconsistent definitions of flash droughts have hindered scientific assessments of drought severity, limiting efforts in disaster prevention and mitigation. In this study, we propose a new method for explicitly characterizing flash drought events, with particular emphasis on the process of soil moisture recovery. The temporal and spatial evolution of flash droughts over the Yangtze River Basin was analyzed, and the severity of the extreme flash drought in 2022 was assessed by comparing its characteristics and impacts with those of three typical dry years. Additionally, the driving factors of the 2022 flash drought were evaluated from multiple perspectives. Results indicate that the new identification method for flash droughts is reasonable and reliable. In recent years, the frequency and duration of flash droughts have significantly increased, with the Dongting Lake and Poyang Lake basins being particularly affected. Spring and summer were identified as peak seasons for flash droughts, with the middle reaches most affected in spring, while summer droughts tend to impact the entire basin. Compared to 2006, 2011, and 2013, the flash drought in 2022 affected the largest area, with the highest number of grids experiencing two flash drought events and a development rate exceeding 15%. Moreover, the summer heat in 2022 was more extreme than in the other three years, extending from spring to fall, especially during July–August. Its evolution was driven by the Western Pacific Subtropical High, which suppressed precipitation and elevated temperatures. The divergence of water vapor flux intensified water shortages, while anomalies in latent and sensible heat fluxes increased surface evaporation and heat transfer, further disturbing the regional water cycle. This study provides valuable insights for flash drought monitoring and early warning in the context of a changing climate. Full article

Agricultural cultural heritage is crucial in advancing comprehensive rural revitalization. The Yangtze River Basin is rich in biodiversity and abundant in fishery cultural resources. The cultural resources not only reflect the ecological wisdom of harmonious coexistence and the human–land relationship between humans and nature but also provide critical cultural support for rural revitalization and watershed sustainable development. This study investigates the spatial distribution, influencing factors, and historical evolution of fishery cultural resources in the Yangtze River Basin. The highest proportions of significant resources are found in fishery engineering and landscapes, culinary flavors, fishery customs, dances, fishery gear, and poetry. By analyzing 14 categories of fishery cultural resources and 157 national and provincial intangible cultural heritage items, this study reveals a significant geographical clustering of these resources in the mid-lower reaches, particularly around the middle reaches of the Yangtze River and Poyang Lake Basin, Wuhan and Dongting Lake, and the lower reaches of the Taihu Lake Basin. This study underscores the role of natural geographical conditions, aquatic biodiversity, socio-economic factors, and historical–cultural backgrounds in the distribution and evolution of fishery cultural resources, with these factors interacting dynamically. By advocating for a comprehensive approach to coordinating fishery culture preservation with rural revitalization, this study outlines a multidimensional strategy for the preservation and sustainable development of fishery cultural resources. Full article

The sustainable development of the water environment in the Yangtze River basin has become a critical issue in China. Turbidity is a comprehensive element for water quality monitoring. In this study, the baseline of water turbidity in the Yangtze River was constructed using 36 years of Landsat images from 1986 to 2021. The spatial and temporal dynamics of turbidity and its driving factors were explored. The results show that (i) the proposed Landsat-based turbidity model performs well, with a correlation coefficient (R²) of 0.68 and a Root Mean Square Error (RMSE) of 7.83 NTU for the whole basin. (ii) The turbidity level in the Yangtze River basin is spatially high in the upper reaches (41.7 NTU), low in the middle reaches (30.9 NTU), and higher in the lower reaches (37.6 NTU). The river turbidity level (60.1 NTU) is higher than the turbidity in lakes and reservoirs (29.6 NTU). The turbidity in the Yangtze River basin shows a decreasing trend from 1986 to 2021, with the most significant decrease in the mainstream of the Yangtze River. Seasonally, the mean turbidity in the Yangtze River basin shows a “low in summer and high in winter” trend, but opposite trends were revealed for the first time in rivers and lakes, such as Dongting Lake, Poyang Lake, and Taihu Lake, etc. (iii) Natural factors, including precipitation and natural vegetation cover (woodlands, grasslands, and shrubs) could explain 58% of the turbidity variations, while human activities including impervious surfaces, cropland, and barren land are lower impact. Annual precipitation was negatively correlated with water turbidity, while cropland and barren land showed a significant positive correlation. The study is of great practical value for the sustainable development of the water environment in the Yangtze River basin and provides a reference for remote sensing monitoring of the water environment in inland water bodies. Full article

Schistosomiasis is a helminth infection caused by the genus Schistosoma, which is still a threat in tropical and sub-tropical areas. In the China, schistosomiasis caused by Schistosoma japonicum is mainly endemic to the Yangtze River valley. The amphibious snail Oncomelania hupensis (O. hupensis) is the unique intermediate host of S. japonicum; hence, snail control is a crucial approach in the process of schistosomiasis transmission control and elimination. In 2016, a nationwide snail survey was conducted involving all snail habitats recorded since 1950 in all endemic counties of 12 provinces. A total of 53,254 existing snail habitats (ESHs) were identified, presenting three clusters in Sichuan Basin, Dongting Lake, and Poyang Lake. The overall habitat area was 5.24 billion m², of which 3.58 billion m² were inhabited by O. hupensis. The area inhabited by snails (AIS) in Dongting and Poyang Lakes accounted for 76.53% of the population in the country. Three typical landscape types (marshland and lakes, mountains and hills, and plain water networks) existed in endemic areas, and marshland and lakes had a predominant share (3.38 billion m²) of the AIS. Among the 12 endemic provinces, Hunan had a share of nearly 50% of AIS, whereas Guangdong had no ESH. Ditches, dryland, paddy fields, marshland, and ponds are common habitat types of the ESH. Although the AIS of the marshland type accounted for 87.22% of the population in the whole country, ditches were the most common type (35,025 or 65.77%) of habitat. Six categories of vegetation for ESHs were identified. A total of 39,139 habitats were covered with weeds, accounting for 55.26% of the coverage of the area. Multiple vegetation types of snail habitats appeared in the 11 provinces, but one or two of these were mainly dominant. Systematic sampling showed that the presence of living snails was 17.88% among the 13.5 million sampling frames. The occurrence varied significantly by landscape, environment, and vegetation type. The median density of living snails in habitats was 0.50 per frame (0.33 m × 0.33 m), and the highest density was 40.01 per frame. Furthermore, two main clusters with high snail densities and spatial correlations indicated by hotspot analysis were identified: one in Hunan and Hubei, the other in Sichuan. This national survey is the first full-scale census on the distribution of O. hupensis, which is significant, as transmission interruption and elimination are truly becoming the immediate goal of schistosomiasis control in China. The study discerns the detailed geographic distribution of O. hupensis with the hotspots of snail density in China. It is beneficial to understand the status of the snail population in order to finally formulate further national control planning. Full article