Search Results (122)

Long-term shoreline change on tropical islands is spatially heterogeneous, but alongshore contrasts remain insufficiently resolved. We quantified shoreline change along the 151.1 km eastern sandy coast of Hainan Island, China, from 1987 to 2025 using Landsat-derived visually interpreted shoreline proxies and the Digital Shoreline Analysis System across 1413 transects. The coast was broadly stable to accretional, with a mean linear regression rate (LRR) of 0.49 m/yr and a mean net shoreline movement (NSM) of 17.72 m. Under the uncertainty-aware classification, 28.0% of transects were stable, 42.1% accretional, 8.2% erosional, and 21.7% indeterminate. For descriptive comparison, the eight sectors were grouped into three broad alongshore zones: a stable northern zone (Beaches A–B), an accretion-dominated central zone (Beaches C–E), and a heterogeneous southern zone (Beaches F–H). The strongest accretion occurred at Beach D (LRR = 7.63 m/yr), whereas the strongest erosion occurred south of the offshore artificial island at Beach F (LRR = −3.97 m/yr). These contrasts show that coast-wide stability or accretion can mask localized erosion. The observed patterns were spatially associated with differences in headland-bay morphology, nearshore seagrass beds, engineering structures, estuarine processes, and lagoon-inlet settings. The findings support beach-sector monitoring and differentiated coastal management. Full article

Surface deformation in rapidly urbanizing coastal cities is often shaped by the interplay between hydrogeological setting and development disturbance, yet these controls remain insufficiently constrained in tropical coastal environments. Using 119 ascending Sentinel-1A scenes acquired between September 2020 and August 2025, we derived a high-density line-of-sight (LOS) deformation field over Haikou, China, through the combined use of PS-InSAR and DS-InSAR time-series analysis. The results show pronounced spatial heterogeneity, with negative LOS anomalies concentrated in reclaimed coastal sectors, port-adjacent zones, and Jiangdong New District, where cumulative LOS displacement locally approaches 90 mm. DS-InSAR increased the number of valid observations to 764,573, approximately 2.8 times that of PS-InSAR, and showed good internal consistency with collocated PS estimates (R² = 0.8048). Positive LOS zones are present but are generally weaker and more spatially diffuse than the major negative anomalies, indicating that the near-zero city-wide mean partly reflects compensation between localized negative and positive signals. Spatial attribution analysis suggests that groundwater type, aquifer water-yield property, and geological zoning provide the main hydrogeological background associated with deformation, whereas human activity intensity, road density, and land-use intensity are associated with stronger negative deformation where hydrogeological conditions are susceptible. Because the dataset is limited to a single ascending viewing geometry, the reported deformation is interpreted as LOS motion rather than a fully resolved vertical subsidence field. These results support a cautiously framed interpretation in which coastal urban deformation in Haikou is hydrogeologically conditioned and development-amplified, providing a basis for targeted monitoring and risk-informed planning in newly developed coastal districts. Full article

Tropical–subtropical monsoon Asia faces pronounced hydroclimatic change under future warming, yet the regional patterns and emission scenario dependence of drought risk remain unclear. Using a 14-member CMIP6 multi-model ensemble from the NEX-GDDP-CMIP6 dataset, we assessed drought evolution under SSP1-2.6 and SSP5-8.5 (2015–2100). Combining the 3-month Standardized Precipitation Evapotranspiration Index (SPEI-3) with event-based run theory and Mann–Kendall trend analysis, we evaluated four complementary drought dimensions: annual mean SPEI, frequency, intensity, and duration. Regional drought area was used as a spatial diagnostic of extent. A persistent west-to-east moisture gradient characterizes present-day conditions: chronic deficits prevail in southwestern China, southern Myanmar, and Thailand, whereas southeastern China and the equatorial belt maintain relative surpluses. This contrast intensifies through the century, with negative SPEI anomalies deepening by 0.2–0.4 units and chronic drought zones expanding into previously marginal areas. Under SSP1-2.6, no metric shows statistically significant trends. By contrast, SSP5-8.5 produces robust drying, with 8.0% of the area showing significant SPEI declines and up to 30.9% exhibiting significant intensification. Scenario-driven increments affect 89–99.7% of the area across all indicators, confirming that higher emissions systematically elevate drought frequency, persistence, and severity. Scenario uncertainty surpasses model structural uncertainty first for intensity (2067), then area (2078), duration (2079), and frequency (2090), reflecting earlier model convergence on the forced thermodynamic shift than on threshold-dependent frequency counts. Stringent mitigation consistent with the Paris Agreement can largely stabilize regional moisture regimes, whereas continued high emissions will drive pervasive drought intensification across one of the world’s most populous and biodiverse forest regions. Full article

Traditional species distribution models can identify climatically suitable areas but offer limited guidance for spatially explicit agricultural planning. In this study, we constructed a three-dimensional coupled framework of “suitability prediction–habitat quality filtering–ecological security screening” by integrating BIOMOD2 ensemble modeling, InVEST habitat quality assessment, and ecological security evaluation to identify candidate cultivation zones for Piper nigrum L. in China under climate change. Based on occurrence records and environmental variables, we simulated potential suitable habitats under current and future climate scenarios, identified key climatic drivers, and delineated candidate zones by overlaying habitat quality and ecological security levels. The results show that the current total suitable area for P. nigrum is 87.76 × 10⁴ km², with low-, moderate-, and high-suitability areas accounting for 37.28 × 10⁴ km², 25.12 × 10⁴ km², and 25.36 × 10⁴ km², respectively. Temperature seasonality and winter cold stress were identified as the dominant factors shaping the suitability pattern. Under future climate scenarios, the total suitable area shows an increasing trend, with highly suitable areas expanding toward the coastal regions of South China and the low-latitude hilly zones. After overlaying with habitat quality and ecological security, climatically suitable but ecologically fragile or intensively disturbed areas were effectively excluded, and the current candidate cultivation zones were identified as mainly concentrated in the southern Yunnan–southern Guangxi–Guangdong–Hainan coastal region. This framework enables a transition from identifying climatic suitability to collaborative climate–habitat–ecology screening, providing a scientific basis for sustainable cultivation and germplasm management of P. nigrum, and is transferable to priority cultivation area identification for other tropical cash crops. Full article

Under the background of global warming, high-tide floods pose growing threats to China’s coastal ecosystems, infrastructure and freshwater supplies. Although the occurrence of high-tide flooding events is widely recognized as being related to relative sea-level rise, tides, and residuals, the analysis and attribution of individual events remain relatively scarce. Based on tide-gauge data and numerical simulations, this study conducted a quantitative analysis of the high-tide flooding events along China’s southern coast around 19 November 2024 and provides mitigation recommendations. Results indicate that coastal sea levels south of the Yangtze River Estuary in November 2024 hit the third-highest November value on record. Sea levels south of the Taiwan Strait were 26 cm above those of normal years, with the highest monthly level since that recorded in 1980. Around 19 November, the coastal area levels coincided with the astronomical spring tide period, with the astronomical high water levels in Shanwei (Guangdong), Dongfang (Hainan), and Beihai (Guangxi) reaching 116 cm, 186 cm, and 292 cm above local mean sea level, respectively. Additionally, influenced by the outer circulation of the tropical cyclone Man-Yi and a cold-air process, an extensive coastal surge occurred, with 30~80 cm surges persisting for nearly 30 h. The combined effects of high sea levels, spring tides, and abnormal surges triggered extreme sea levels that broke historical records, with multiple stations reaching once-in-20-year levels. The contributions of astronomical tides to the extreme sea levels in Shanwei, Dongfang and Beihai were 49.5%, 69.3%, and 77.8%, respectively, while the contributions of surges were 23.6%, 6.4%, and 4.6%. This high-tide flooding event affected multiple coastal areas in Guangdong, Guangxi, and Hainan. Developing a comprehensive adaptation strategy encompassing emergency observation and early warning, risk assessment and zoning, coastal protection, coastal adaptive planning, and freshwater resources management is crucial for effectively addressing the risks of high-tide flooding events. Full article

Land-use change poses a growing threat to ecological security, yet existing regional assessments often rely on a single ecological indicator and lack direct linkage to territorial spatial planning. This study develops an integrated ESV–ERI framework coupled with quadrant zoning to provide spatially explicit, planning-compatible guidance for ecological protection in tropical island regions. Taking Hainan, China, as a case study, this research draws on land-use data from 1994 to 2024, applying ESV and ERI assessments coupled with Z-score standardization to examine their spatiotemporal evolution characteristics. The results indicate the following: (1) forest land persistently dominated land use (>63%), while construction land expanded by 197.68% and forest land and grassland decreased by 9.36% and 93.78%, respectively. (2) ESV showed a downward trend, decreasing by 14.683 billion yuan, with forest land accounting for over 83% of total ESV. Spatially, ESV exhibited a “high inland, low coast” pattern, with high-value zones across inland water bodies and central nature reserves and low-value zones in coastal urban agglomerations. (3) ERI increased from 0.0371 to 0.0539, with low-risk zones in the middle mountains and high-risk zones around the island. (4) Based on the dual dimensions of ESV and ERI, the entire island was delineated into four ecological zones. These findings provide scientific decision support for territorial spatial planning and differentiated ecological protection in tropical island regions. Full article

Bacterial communities play vital roles in coastal biogeochemical cycling and ecological stability. Despite their importance, a significant knowledge gap exists regarding their spatiotemporal dynamics and assembly mechanisms in the tropical coastal waters of the Leizhou Peninsula, China. To investigate the bacterial community structure, co-occurrence networks, and assembly processes, we conducted 16S rRNA gene amplicon sequencing on water samples collected seasonally from August 2022 to June 2023. The bacterial communities were dominated by Proteobacteria and Cyanobacteria, and were characterized by a distinct warm-season peak in the relative of Cyanobium. Alpha diversity indices exhibited significant seasonal fluctuations, reaching a minimum in August (autumn) and a maximum in December (winter). These variations were strongly regulated by water temperature and phosphate availability. Redundancy analysis (RDA) identified salinity as the primary deterministic factor shaping community composition. Seasonal environmental heterogeneity, rather than spatial variation, primarily governed bacterial community dynamics. We also observed a seasonal succession in community assembly mechanisms with deterministic filtering dominated in autumn, whereas stochastic processes prevailed in other seasons. Predicted functional profiles indicated a stable core metabolism, although local anthropogenic inputs stimulated specific metabolic adaptations in industrial and aquaculture zones. Our findings reveal that seasonal environmental filtering (especially temperature and salinity) and a shifting balance between stochastic and deterministic assembly processes govern bacterial dynamics in this tropical coastal ecosystem, with anthropogenic inputs modulating local metabolic functions. This study provides fundamental insights into the mechanisms maintaining microbial diversity and stability in tropical coastal waters facing seasonal and human pressures. Full article

Offshore pipeline landfall sections in tropical coastal zones are often exposed to dynamic hydrodynamic forcing, which may induce seabed erosion and wave-driven liquefaction and thereby affect burial stability. This study presents an integrated assessment of seabed stability for an offshore gas pipeline along the Sarawak coast of the South China Sea, aiming to support burial-depth design in the nearshore surf zone. A multi-model framework was applied to simulate regional hydrodynamics, sediment transport, storm-induced seabed morphodynamics, and wave-induced liquefaction. Model performance was evaluated using field observations, bathymetric survey data, and laboratory experimental results. The results indicate that the seabed remains generally stable under normal environmental conditions, whereas extreme storm-wave forcing may induce localized surf-zone erosion and shallow seabed weakening. Under the 100-year storm-wave scenarios, the maximum simulated erosion depth reaches approximately 0.82 m, and the potential liquefaction response is mainly confined to the upper approximately 1.0 m of the seabed. These results suggest that storm-induced morphodynamic cover loss and wave-induced degradation of near-surface soil support should be evaluated jointly. Based on this integrated process envelope, a minimum burial depth of 2 m is recommended as a conservative engineering requirement for the examined landfall conditions. This process-integrated assessment workflow offers an applicable reference for the design and risk mitigation of analogous offshore pipeline projects in tropical coastal zones. Full article

Vegetation serves as a critical ecological barrier on tropical islands, but conventional assessments often emphasize greening magnitude while overlooking persistence, structural quality, and scale-dependent attribution. In this study, we reconstructed a high-precision fractional vegetation cover (FVC) dataset for Hainan Island, China, covering the period from 2000 to 2024 using Google Earth Engine (GEE). We then combined trend analysis, emerging hot spot analysis (EHSA), the coupling coordination degree model (CCDM), RESTREND, and Geodetector to examine vegetation change from complementary perspectives. The results show that FVC increased overall and gradually shifted toward a more stable state over time. EHSA further revealed a distinct core-periphery pattern, with persistent hot spots concentrated in the central mountainous region, persistent cold spots distributed along the coastal urban belt, and oscillating hot spots occurring within agricultural transition zones. Regarding quantity-structure coupling, FVC and the aggregation index (AI) generally improved together across the island; however, some agricultural ecotones exhibited weaker structural improvement despite increasing vegetation cover, suggesting potential risks of homogenization and structural simplification. In the broad attribution analysis, vegetation recovery was primarily associated with the combined influence of climatic and human-related improvement. In the factor-specific analysis, land cover and slope showed the strongest explanatory power, and their interactions with other variables further enhanced spatial differentiation. These results demonstrate that greening magnitude alone is insufficient for evaluating vegetation change on tropical islands. Structural coordination and scale-dependent attribution should also be considered when interpreting ecological improvement and related management implications. Full article

The rapid expansion of sustainable construction practices has significantly increased research on recycled aggregate concrete (RAC) over the past four decades. However, despite the growing volume of studies, a comprehensive longitudinal assessment of the thematic and structural evolution of RAC research remains limited. This study presents a bibliometric and thematic evolution analysis of global research on recycled aggregate concrete from 1983 to 2025, based on 1624 documents indexed in Scopus and analyzed using PRISMA guidelines and VOSviewer mapping techniques. Results reveal four indicative stages of development: (i) an exploratory feasibility phase focused on compressive strength and replacement ratios (1983–2000); (ii) a mechanical validation phase emphasizing durability and interfacial transition zone performance (2000–2010); (iii) a performance enhancement phase integrating supplementary cementitious materials and service-life assessment (2010–2018); and (iv) a recent sustainability-driven phase characterized by life-cycle assessment, circular economy frameworks, and emerging AI-assisted optimization approaches (post-2018). China, India, and the United States dominate scientific production, while co-citation networks highlight the consolidation of specialized yet interconnected research communities. Keyword evolution analysis indicates a progressive shift from mechanical feasibility toward environmental impact mitigation and predictive modeling. Despite substantial advances, research gaps persist in tropical climate performance assessment, full-scale structural applications, and standardized mix-design methodologies for high-replacement RAC. The findings provide a structured understanding of the intellectual structure and evolution of the field, offering guidance for future research directions and performance-based sustainable concrete design strategies. Full article

The forest within the Ben En National Park has a diverse flora, which, although protected, remains subject to degradation. The analysis and management strategies for forest degradation within this park were conducted using a phytogeographical approach supplemented by satellite imagery and a SWOT analysis. As a result, the area is characterized by nine distinct vegetation types comprising 1417 vascular plant species (from 902 genera and 196 families). These species belong to endemics from Northern, Central, and all of Vietnam, as well as 16 other phytogeographical elements. Tropical Asian and South China elements dominate the community structure in evergreen broad-leaved closed forests on both limestone and non-limestone mountains. Forest degradation is evident in changes to both floristic composition and vegetation structure. Floristic composition shows a trend of decreasing native elements while simultaneously increasing non-native or introduced elements. This “anthropogenic tropicalization” leads to a declining chain of ecological function from palaeotropical to introduced elements, resulting in biological invasion. For instance, the invasive species, Mimosa pigra, currently occupies about 442 ha in the semi-submerged zone of the Song Muc reservoir, indicating a loss of ecological function and a likely hydrological pathway for further spread. As a consequence of “anthropogenic tropicalization”, the vegetation is fragmented and gradually altered from a natural system to an anthropogenic one through a regressive succession from primary forest to bare land/invaded area. Based on the SWOT analysis, four management actions were proposed: 1—Establish a “sustainable native forest” program and “invasive species control” in the Song Muc reservoir; 2—Launch a “green livelihoods for the buffer zone” initiative; 3—Implement a “Smart forest monitoring” system; and 4—Forge an “ecotourism-conservation-community” alliance. Full article

Precipitation is a fundamental element in terrestrial water circulation and ecosystem hydrological balance. The occurrence of concentrated precipitation is closely linked to vegetation growth and soil fertility rather than accumulated or averaged precipitation. Despite its importance, the characteristics of continuous precipitation and its specific effects on vegetation cover remain uncertain. In this study, we formulated a new continuous precipitation index system, including $C{P}_d$ (continuous precipitation days); $AC{P}_t$ (annual continuous precipitation times); $C{P}_a$ (continuous precipitation amount); and $FCP$ (frequency in different ranges of $AC{P}_a$). We utilized daily precipitation data from 467 meteorological stations across China, which were divided into eight vegetation type regions. We observed that the spatial distribution of continuous precipitation differed to varying degrees from accumulated precipitation. The national average of $MAC{P}_a$ for a single event was 16.7 mm, ranging from 3.8 mm in the temperate desert region to 37.1 mm in the tropical monsoon forest and rainforest region. Similarly, the national average of $MC{P}_d$ ($MMC{P}_d$) for a single event was approximately 2.3 or 9 days. At the regional level, the tropical monsoon forest and rainforest region experienced the longest $MMC{P}_d$. Furthermore, the national average of $MAC{P}_t$ occurrences for 1 year was 57.7 times, varying from 29.8 times in the temperate desert region to 77.9 times in the tropical monsoon forest and rainforest region. Vegetation responses to precipitation regimes exhibit significant regional heterogeneity across China. Our analysis reveals that $MAC{P}_t$ and $M{P}_a$ show markedly positive correlations with vegetation growth. In subtropical monsoon climate zones, particularly the Yunnan–Guizhou Plateau and Qinling Mountains, $MAC{P}_t$ demonstrates strong positive correlations (r = 0.6–1.0) with NDVI, where sustained rainfall provides stable moisture availability for vegetation. While a positive correlation between vegetation (NDVI) and mean annual consecutive precipitation is observed in some arid northern regions, in ecosystems such as the Loess Plateau (TG/TM), vegetation growth shows greater dependence on $M{P}_a$, highlighting the crucial role of total precipitation amount in water-limited ecosystems. Notably, extreme precipitation events display dual effects on vegetation dynamics. Prolonged heavy rainfall ($MMC{P}_d$/$MMC{P}_a$) exhibits significant negative impacts on NDVI (r = −1.0 to −0.6) in topographically complex regions, including the Hengduan Mountains and Yangtze River Basin (SE), likely due to induced soil erosion and waterlogging stress. Our findings underscore the importance of incorporating continuous precipitation indices to evaluate and forecast the influence of precipitation on ecosystem stability. This understanding is vital for developing informed conservation and management strategies to address current and future climate challenges. Full article

Cryphalus dilutus is an emerging invasive pest of tropical and subtropical regions, with Mangifera indica and Ficus carica being its primary host plants. Larval damage caused by this insect can lead to severe tree wilting, posing a direct threat to agricultural production and ecological security. Native to South Asia, C. dilutus has established introduced populations in the Near East, Mexico, and other areas. In recent years, it has invaded multiple regions, including southern China and southern Italy. Given the widespread global distribution of host plants and the intensification of climate change, their distribution ranges are expected to expand. However, research assessing the potential global geographical distribution of this pest under climate change is lacking. In this study, we used the Random Forest model to predict the potential distribution range of C. dilutus. Under historical climatic conditions between 1970 and 2000, suitable climatic regions for C. dilutus were primarily distributed across southern China, southeastern Brazil, southeastern Mexico, the Congo Basin periphery, and the Iberian Peninsula, with a total area of 12,192.42 × 10⁴ km². The Temperature Annual Range and Precipitation of Warmest Quarter were identified as key environmental determinants that shaped its distribution. Under the future RCP4.5 climate scenario projected for the 2050s, the total suitable area for C. dilutus is projected to contract. Specifically, high-, medium-, and low-suitability areas are projected to decline by 52.77%, 62.39%, and 24.02%, respectively. While the total area of the very low zones is expected to increase, the total area of the suitable region has been reduced to 11,891.17 ×10⁴ km². Future climate change is expected to drive the distribution northward to high-altitude areas and inland areas. Model projections indicate a poleward expansion of the fundamental climatic niche, with climatic suitability increasing in high-latitude and high-altitude regions, such as Northern Europe and western North America. Conversely, current core tropical habitats in the Indian subcontinent and the Amazon Basin are projected to face significant habitat degradation due to thermal stress. Agricultural regions previously considered relatively safe due to climatic constraints, such as northern China, the midwestern United States, and Eastern Europe, may face new challenges from pest infestation. These findings underscore the importance of proactive monitoring and implementation of preventive measures. This provides crucial decision support for countries and regions to formulate precise pest control strategies and offers a theoretical basis for early monitoring and prevention of cross-border invasions on a global scale. Full article

Quantifying the relative roles of climate change and human activities in vegetation change is essential for sustainable restoration planning, yet the impacts of extreme climate events and their time-lagged effects are often overlooked, biasing assessments of climatic controls. Here, we developed an integrated pattern–process–attribution framework to evaluate vegetation dynamics across China’s four major climatic zones using a long-term, high-resolution kernel normalized difference vegetation index (kNDVI) dataset for 2000–2024. Theil–Sen trend estimation and the coefficient of variation (CV) were used to characterize long-term changes and interannual stability. Partial correlation analysis was applied to isolate the independent associations between kNDVI and extreme climate indices while controlling for background mean temperature and precipitation, and lagged correlation analysis with 0–3-month lags was used to quantify delayed responses. A regression-based residual attribution was further used to decompose observed kNDVI changes into a climate-driven component and a human-activity-related component (approximated by the residual not explained by temperature and precipitation). Results show widespread greening with pronounced spatial heterogeneity, with the most extensive improvement in the Tropical and Subtropical Humid Region and the Temperate Humid and Semi-humid Region. Vegetation stability exhibits a southeast–northwest contrast, and the highest variability occurs in the Temperate Arid and Semi-arid Region and the western Qinghai–Tibet Plateau. Responses to climate extremes are region-dependent and generally short-lagged (mean 0.35–1.05 months), with drought constraints dominating in arid regions and thermal extremes (TXx) most relevant on the plateau. Nationally, human activities contribute 70.8% of vegetation change, exceeding the climate-driven contribution (29.2%). Full article

The Ecological Conservation Redline (ECR) is a key spatial policy tool in China’s efforts to protect the Ecosystem Services (ES) of Hainan Island. However, its effectiveness in promoting the coordinated restoration of Hainan Island’s ES remains unclear. This study employs the InVEST model to assess the spatiotemporal dynamics of carbon storage, habitat quality, water yield, and soil retention within the ECR zones of Hainan Island from 1990 to 2020. A Multiple Ecosystem Service Landscape Index (MESLI) was constructed, and Geographically Weighted Regression (GWR) was applied to examine the influence of ECR implementation on ES synergies and the spatial drivers underlying these patterns, aiming to elucidate the complex interactions between conservation policy and ecosystem functioning. The results show that (1) the delineation of the ECR has facilitated ecological restoration in the region. MESLI detrimentally declined before 2010 but positively increased by 12.7% during 2010–2020, indicating an improvement consistent with the period of ECR implementation. Moreover, (2) ESs within the ECR display marked spatial heterogeneity. GWR results reveal that MESLI is positively associated with vegetation cover and slope, and negatively associated with population density, with pronounced disparities in northern and central regions that call for differentiated governance strategies. Finally, (3) constructing a composite evaluation framework based on multiple ESs contributes to optimizing the delineation and management of ECRs, enhancing their scientific support for regional sustainable development. This study provides decision-making guidance for the zoned governance of conservation areas on tropical islands and offers insights for redline management in other ecologically sensitive regions. Full article