As competition among cities increases, shrinkage is increasingly observed in contemporary urban development. However, the systematic, fine-scale ecological impact of shrinkage, particularly on vegetation dynamics, remain poorly characterized. This study identified shrinking and non-shrinking counties in China using nighttime-light data during 2001-2020, examined vegetation growth dynamics using net primary productivity (NPP) validated by normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and leaf area index (LAI), and analyzed influencing mechanisms via XGBoost modelling and SHAP interpretation. We reported three findings: (1) 39.8% of 2891 counties shrank, most severely in Northeast China. (2) Most shrinking counties showed an amplified vegetation greening trend, with median NPP trend (3.43 g C m-2 yr-1) 11.7% higher than non-shrinking counties (3.07 g C m-2 yr-1). Shrinkage intensity exerted a hump-shaped relationship with NPP trend, peaking at moderate levels, indicating an optimal shrinkage intensity for greening. (3) Differentiated strategies are needed: moderately shrinking counties can amplify gains with passive rewilding; severely shrinking ones need enhanced fiscal transfers for erosion controls and afforestation; non-shrinking collided with an NPP ceiling at ∼20% land conversion, necessitating densification-resistant designs and strict urban-growth boundaries. These findings advance our understanding of social-ecological coupling mechanisms between shrinkage and vegetation dynamics, offer critical insights for developing context-differentiated ecological strategies and enhancing county-level development quality.

BackgroundThe installation of outdoor gyms (OGs), also known as the National Fitness Route (NFR) program in China, is increasing in popularity as a government-funded solution to declining population physical activity (PA) levels. However, evidence regarding how these facilities are used and whether they effectively support PA remains limited.MethodsSystematic in situ observations were conducted across four representative NFRs in Yangling District, Shaanxi Province, China, during three seasons. Demographic characteristics, behavioral patterns, and OGs use were recorded using the System for Observing Play and Recreation in Communities (SOPARC). Behavior mapping and kernel density estimation were used to examine the spatial distribution of activities, and binary logistic regression was performed to identify factors associated with moderate-to-vigorous physical activity (MVPA).ResultsA total of 9,704 person-observation records were collected, OGs accounted for 15.2% of all observation records, with seniors representing the largest user group. The air walker, leg and waist/back massager were the most frequently used types of OGs. Sitting, standing, and walking were the predominant activities, and behavioral activities exhibited clear spatial clustering around seating areas, dedicated pathways, and open activity spaces. After adjustment for potential confounders, age, time period, week period, temperature, air quality, and site characteristics were independently associated with MVPA, whereas gender and season were not.ConclusionOGs use represented only a small proportion of activities observed within NFRs, indicating that these spaces function not only as settings for PA but also as important places for recreation and social interaction. Integrating age-appropriate OGs with walking paths, seating areas, tree shade, and flexible open spaces may better support diverse recreational behaviors and promote PA. These findings provide evidence-based guidance for optimizing the planning and spatial design of NFRs to support healthier and more inclusive public fitness environments.

Vegetation resilience in urban ecosystems is increasingly being challenged by the intensification of compound drought and heatwave (CDHW) events, which pose substantial risks to vegetation growth and the provision of ecological services. However, research on the resilience of urban vegetation remains limited, and little is known about how vegetation responds to CDHWs in different urbanization contexts. In this study, we identified CDHWs in 232 cities in China during 2003-2020 and quantified vegetation resistance and recovery in different urbanization areas based on satellite-based Enhanced Vegetation Index (EVI). We found that, for most regions, areas with higher urbanization were with increased vegetation resistance, but decreased recovery. However, in the warmer regions of southern China, both resistance and recovery were lower in highly urbanized areas, where vegetation faced greater risks from CDHWs. Greater CDHW frequency, duration, or severity erodes vegetation resistance in both high- and low-urbanization areas, while simultaneously accelerating early-stage recovery. Yet once drought exceeded a more severe threshold, the recovery boost weakened. And the resistance declined more substantially in high-urbanization areas when exposed to more severe CDHWs. Sustained investment in urban greening management can partially enhance vegetation recovery. Our results underscore that escalating CDHWs pose a growing threat to urban ecological stability. Strengthening dynamic monitoring and real-time risk mapping, along with the differentiated adaptive vegetation management strategies, are therefore critical to safeguard urban ecosystems resilience.

Under ongoing climate change and rapid urbanization, urban hydrothermal regimes are being reshaped, intensifying drought hazards and increasing stress on urban forests. Yet, systematic assessments of drought-induced stability dynamics of urban vegetation remain limited. We identified drought events across 330 Chinese cities during 2000-2022 and quantified vegetation resistance and resilience using multi-source remote sensing data. Pronounced latitudinal divergence emerged: high-latitude cities showed lower resistance but higher resilience, whereas low-latitude cities exhibited stronger resistance but weaker recovery. Across climatic zones, resistance was greater in humid and arid cities, whereas resilience was stronger in sub-humid and semi-arid cities, indicating a climate-dependent trade-off between disturbance buffering and recovery capacity. From 2000-2011 to 2012-2022, resistance increased significantly, whereas resilience declined. Seasonally, resistance was lowest and resilience highest in summer. Drought severity and climatic background-especially drought intensity and duration-primarily governed stability patterns: stronger droughts reduced resistance but enhanced recovery. Anthropogenic factors, including population density, economic development, and CO2 emissions, also played a significant role in shaping vegetation stability. These findings highlight the need for long-term drought monitoring and climate-specific urban forest management to strengthen ecosystem stability in rapidly urbanizing regions.

Buddhist and Taoist temples are long-lived cultural infrastructures whose present-day distributions may reflect aspects of long-term human-environment interaction and persistence. Using national records of 29,415 Buddhist and 8181 Taoist temples in China, this study examines associations between contemporary temple density and stable topographic and geologic settings. Within a unified 1-km framework, this study combines KDE, Ripley’s L(d)–d, Moran’s I, LightGBM, and SHAP analyses. Both temple systems are strongly east-oriented and clustered, with major concentrations in eastern and southeastern China. Among the selected environmental variables, elevation and slope are the most important predictors. Buddhist temples are more spatially extensive, whereas Taoist temples are more regionally concentrated and more strongly associated with geologic background. SHAP analysis identifies approximate terrain-related transition zones and context-dependent river-distance responses. These findings suggest a long-term mountain-river template associated with the contemporary spatial expression of temple landscapes, rather than direct evidence of site-specific historical continuity or causality.

The Ziwuling region, a critical ecological barrier on the Loess Plateau, was analyzed using land use and land cover (LULC) data from 1990, 2005, and 2020 to assess three decades of carbon storage dynamics via five methods: land use classification and transfer matrix, SHapley Additive exPlanations (SHAP) model, the Patch-generating Land Use Simulation (PLUS) model, and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. Results showed a net decline of approximately 4.31 million tons in carbon storage over the past fifteen years, with Yintai, Xifeng, and Dingbian experiencing the steepest losses, while a Y-shaped growth corridor has emerged centered on Huachi County. Four 2035 scenario simulations-Natural development priority (ND), Arable land protection priority (AP), Ecological protection priority (EP), and Urban development priority (UD), suggest further declines relative to 2020, decreasing by approximately 3.75 million tons, 3.48 million tons, 1.29 million tons, and 5.04 million tons respectively. These trends highlight the region’s severe challenges in meeting China’s carbon peaking and neutrality targets. The study explored the causes of this decline from three perspectives: driving factors, ecosystem structure, and ecological protection measures, and proposes four strategies to enhance carbon storage by integrating urban development with ecological protection via scientific land-use-planning and eco-compensation-policies. These strategies provide guidance for other ecologically sensitive regions globally.

Urban parks effectively mitigated the urban heat island (UHI) effects. The field extent and boundary of cold island effects, influenced by internal landscape characteristics of parks, external urban morphology and regional climatic factors, determined cooling service magnitude. The study used buffer analysis to calculate the park's cold island effect, introduced fundamental concepts and delineation methodologies of the cold island rose and cold island effect field. Ultimately, the study explored the coupling relationship between the park's cold island effect and its internal landscape, external urban morphology, across various wind speeds and heat island gradients. It was found that the parks located in the warmer zone of the urban heat island gradient showed greater maximal cooling distances (LMAX) and intensities (CPCI). LMAX and CPCI were more influenced by internal landscape metrics than external urban morphological metrics. The 3-4 m/s of wind speed was a threshold discriminating the effects of wind speed on cold island effects. Below this threshold, greater LMAX and CPCI were shown for the upwind area; exceed, downwind area did. UHI could be alleviated by utilizing the internal landscape features of the park, arranging the external urban form, and increasing urban ventilation corridors based on urban wind and thermal conditions.

Urbanization environments provide a harbinger for vegetation productivity response to future global change. However, the urban-rural ecosystem is complex, featuring a variety of vegetation types, particularly crops and their accompanying intensive human management activities, which may introduce bias in the quantitative assessment of the vegetation net primary productivity (NPP) responses to urbanization. Using a 30-m resolution NPP dataset for Xi'an, China, this study indicated that NPP indirect enhancement in urbanization environments would decrease after removing crop-dominated pixels. Also, the sensitivity of vegetation productivity to temperature along the urban-rural gradient increased markedly after cropland removal, with the response nearly doubling in magnitude. A threshold phenomenon was observed that, as the temperature increased to 14.66 ± 0.04 °C (corresponding to urban intensity >94 %), the indirect enhancement would reach its limit. We advocate that future urban planning should control construction intensity and maintain a certain proportion of green spaces to mitigate potential heat-related stress.

In the natural river network, the confluences play an important role as control nodes. It is of great scientific value to study the transport and mixing process of water quality at the confluence of the mainstream and tributaries to improve the health of the river environment. In this study, dissolved oxygen (DO, the essential survival conditions for aquatic organisms) was used as a water quality index, and a 3D transport model of DO considering atmospheric reoxygenation and biodegradation oxygen consumption was constructed. The hydrodynamic mechanism of DO transport, mixing and reoxygenation at confluence under different flow ratios, junction angles and water temperature conditions was studied. The results show that the secondary flow is the main driving force of the transversal mixing at confluence, and there is a high coupling relationship between the evolution of the secondary flow and the mixing process of water quality at confluence. With the increase of flow ratio and junction angle, the intensity of secondary flow at confluence shows an exponential increase, which in turn promotes the transversal mixing efficiency of DO at confluence. The water quality of the polluted confluence under different water temperature conditions showed a trend of gradual recovery, but the higher the water temperature, the weaker the recovery rate. This study can provide theoretical support to deal with the threat to aquatic organisms caused by pollution accumulation at confluence, and provide scientific basis for the improvement of the water environment and water ecology protection in the river confluence and downstream.

Green infrastructure has been confirmed to be nature-based solution for mitigating urban warming. However, knowledge about whether urban parks would cool down surroundings in the hotter weather as usual days is still limited. In this study, we integrated light detection and ranging (LiDAR) data and remote sensing satellite to obtain vertical vegetation structures and cooling performance of urban parks under different background climate, within dense area of Beijing, China's capital city. The results found that the parks reduced temperature by 2.71 +/- 1.52 C-degrees on average, and the average cooling distance could reach 182.34 +/- 117.51 m. The cooling effect of parks largely depends on factors related to canopy cover and canopy volume. Tree quantity correlated with three-dimensional accumulative cooling amount, indicating the importance of constructing cooling indicator from three-dimension perspective. As local background temperature increased, the cooling amplitude response was a hump-shaped curve, implying that the cooling amplitude would gradually tended to flatten or decrease after certain threshold warming temperature. These findings will provide a better perspective for urban planners to improve park design to mitigate the urban heat island (UHI) effect.

The inflow of heavy polluted tributaries is one of the main factors that destroy the water quality at the river confluence area and downstream, especially in the wide-shallow river confluence area. In this study, a generalized model of a two-dimensional confluence was established and validated, and dissolved oxygen concentration was used as the water quality indicator. The influence laws and mechanisms of different spur dike layout patterns on the water quality distribution characteristics and the transport and mixing processes at the confluence were explored through numerical simulation. The results show that there is a large area of water pollution at the confluence with the polluted tributary, which is distributed near the outlet of the tributary, and the water quality in this area recovers slowly. The flow ratio is the main factor affecting the distribution of water quality transport at the confluence. Arranging dikes on the opposite bank of the tributary can significantly reduce the area of pollution by adjusting the flow field. Arranging dikes on the tributary side of the confluence can effectively promote water quality mixing through vortex suction between dikes and improve water quality near the tributary side of the river bank. The dissolved oxygen concentration between dikes at the river bank on the tributary side showed an increasing trend along the river direction, and vortex flow velocity showed a decreasing trend, and the increment of dissolved oxygen concentration had a good linear correlation with the interval between dikes and the change in vortex flow velocity between dikes.

Urban densification has heightened residents’ demand for equitable access to urban park services, particularly those that support physical activity (PA). This access is crucial for public health and sustainable urban development. We developed the Park-Based Physical Activity Composite Attractiveness Score (PCAS) to assess the supply and service equity of parks at the sub-district scale in the central city of Xianyang, western China. The average PCAS for all parks in the study area was 46, with 69% scoring below the benchmark of 60, indicating that the parks fail to meet residents’ PA needs. We found a significant imbalance in park distribution. The 14 sub-districts we measured had an average supply score of 42 and a demand score of 49, demonstrating a clustering of park services in areas with natural resources and higher socioeconomic status. While the overall park service level was found to be reasonably equitable (Gini coefficient of 0.38), a large gap in the sub-dimensional indicators point to inequities in park services. The following scenario optimization suggested that adding new parks could more effectively enhance equity and residents’ PA levels than simply increasing park facilities. Our results provide valuable insights for urban park planning and policy-making, and contribute to the development of more equitable and accessible park services to achieve public health objectives.

This study aimed to explore the evolution of Jingdang and Famen towns near the Zhouyuan site, the capital city site of the Western Zhou Dynasty in China, to elucidate the relationship between township development and the essential ancient relics conservation areas. Based on the remote sensing satellite images from 1982 to 2022, combining with historical demographic data, this study used four methods, including land use classification, land use transfer matrix, landscape pattern center of gravity changes, and population count statistics, to study the spatial–temporal evolution of land, population, and ecology in the region over the past 40 years. The results showed that under the strict relic conservation regimen, these two towns are in a declining stage. To improve their decaying status, some potential strategies valuable for township development are proposed to balance the relationship between relic conservation and township development for their mutual benefit and coexistence.

As the control cell of river networks, the complex hydrodynamic conditions at river junctions pose significant challenges to pollution control and water ecology protection. The purpose of this study is to construct a 3D hydrodynamic model for dissolved oxygen (DO) transport at the confluence, studying its unsteady mechanism under different flow ratios and junction angles. The results of the study show that: i) The atmospheric reoxygenation distribution at the confluence exhibits a typical layered 3D feature, and the strong flow turbulence therein exerts a significant promoting effect on such reoxygenation. ii) The DO transport pattern at the confluence is characterized by the formation of an arc-shaped concentration distribution zone, followed by a contraction towards the opposite bank of the tributary and downstream transportation. A delay in DO concentration increase occurs within the separation area, while lateral oscillations are observed during downstream transport. iii) The flow ratio primarily governs the lateral migration extent of DO, while the junction angle serves as the main driver for downstream transport rate of DO. Increasing both flow ratio and junction angle can expedite mixing efficiency of DO at the confluence. The findings of this study can further enhance the hydrodynamic mechanism for water quality control at the confluent flume, and serve as a valuable reference for improving water environments and protecting water ecology in natural river confluence.

In the past few decades, human activities have caused the emission of large amounts of carbon dioxide, which has severely impacted the Earth's ecosystem and human health. Therefore, carbon reduction has become the focus of global attention. In this study, the Zhouyuan region of China, which is rich in ancient remains, is taken as an example. Based on the land use characteristics in 1990, 2000, 2010, and 2020, the spatial-temporal evolution of land use and carbon storage in the Zhouyuan region is simulated using four methods, including land use classification, land use transfer maps, patch-level land-use simulation (PLUS), and the integrated valuation of ecosystem services and trade-offs (InVEST) models under three scenarios, including the natural development scenario, urban development priority, and heritage conservation priority in 2030. According to the results, the carbon storage in the area in 2030 under all three scenario simulations has decreased compared with 2020, indicating that the region faces great challenges in achieving its targets of carbon peak and carbon neutrality. The paper points out four causes for the decrease in carbon storage, and five suggestions for increasing carbon storage are proposed, such as developing a carbon storage master plan, applying energy-saving technologies, establishing an ecological substitution mechanism, and so on. Through the study of carbon storage in the Zhouyuan region, this paper hopes to establish a mechanism to balance urban development, heritage conservation, and carbon sinks on the one hand, and encourage more scholars to participate in the study of carbon sinks in areas rich in ancient remains, so as to to jointly promote their healthy development on the other.

The Yellow River flows through multiple provinces in China, shaping the North China Plain, the largest alluvial plain in China. As the control node of basin ecological environment, the confluence of Weihe River and Yellow River is deemed as the gateway to North China Plain. In this study, a numerical simulation of the Weihe River–Yellow River confluence is conducted using a 2D hydrodynamic model and a coupled transport model for dissolved oxygen–biochemical oxygen demand. The results show that: (i) The typical flow field with multiple backflow areas is formed at the stagnant area where main stream and tributary converge and abrupt channel change area in different hydrological periods. The spur dike here mainly affects the velocity of the Weihe River outlet. (ii) There is an obvious concentration transition mixing zone downstream of the confluence, and the width of the mixing zone gradually linear increases with the direction of water flow. (iii) The self‐purification ability of the confluence is strongest in dry period, weaker in level period, and weakest in wet period. Water bodies have stronger self‐purification capacity on riverbanks than in the middle, and it is stronger in the upper reaches of Weihe River compared to Yellow River. Lower reaches also have a stronger self‐purification capacity than upper reaches. The study results can serve as a scientific reference for protecting the ecological environment of the Yellow River.

Urban parks are considered as an effective, sustainable, and affordable heat mitigation strategy. At present, there is a lack of understanding of the carbon saving potential of urban parks in the context of urban warming. Here we provide a simple approach to estimate the potential carbon savings due to heat mitigation based on analysis of 1510 parks in 26 major urban areas of the years 2017-2021 within the Yangtze River Economic Belt (YREB), China's largest sustainability experiment. On average, an urban park with 26.9 +/- 1.5 ha in the YREB could avoid 23.7 +/- 1.6 t CO2 (1.08 +/- 0.03 t CO2/ha) in emissions due to heat mitigation per summer day. Considered altogether, the 1510 urban parks can offset 5.37% of the daily fossil fuel emissions in the YREB. To boost carbon saving efficiency, lush vegetation should be first considered and the coupled green and blue infrastructures are always advocated. The total parks carbon saving of cities gradually improved along the Yangtze River from west to east, among which Shanghai city (in the east of the YREB) is with the largest amount (4341 t CO2). The strategies using exquisite landscape design for improving carbon saving may differ across different climate zones. These findings can inform decision-making for urban sustainable development and climate change mitigation, which may benefit China's movement toward carbon neutrality.

The greenhouse gas emissions and climate change are closely linked, as are climate change effects on public health. Urban parks are regarded as sustainable and affordable cooling intervention to climate warming, though carbon saving potential of urban parks in thermal mitigation are hard to value especially from accumulative and accessibility perspectives. This study valued both outdoor and indoor carbon saving potential of 65 urban parks in thermal mitigation using an accumulative outdoor carbon saving model based on park's surface temperature cooling curve and network analysis for spatial accessibility to parks cooling area in Greater Xi'an. We found that the carbon saving potential of urban parks could offset 3.6% of the metropolis' fossil fuel carbon emissions. The outdoor carbon saving was related to background climate, which was 734.3 t CO2/day in hot extremes, higher than normal summer days in 2019. The indoor carbon saving was 814.9 t CO2/ day in hot extremes. To maximize the outdoor carbon saving potential, large ecological parks coupled with both blue and green infrastructures should be built in areas with sufficient land resources. And cooling networks are suggested with efficient small parks in densely populated areas. As all urban residents have higher requirements for thermal comfort in hot summers especially in hot extremes, the future park planning should be emphasized on both accumulative cooling effect and equitable accessibility. Though urban parks have substantial carbon saving potential, such potential is limited and only a decrease in CO2 emissions from fossil fuel burning would make the carbon neutrality goal achievable.

The Qinling Mountains north slope region constitutes a vital terrestrial ecosystem reserve within China. This study employs land use and land cover (LULC) data spanning from 1990 to 2020. Utilizing methodologies encompassing land use classification, transfer matrix analysis, and the application of the PLUS and InVEST models, this research endeavors to elucidate the spatial-temporal dynamics of land use patterns and associated carbon storage in the region. These analyses are conducted within the context of four prospective scenarios: Natural Development Priority, Arable Land Protection Priority, Ecological Protection Priority, and Urban Development Priority, all projected onto the landscape for 2030. Notably, our findings reveal a consistent decline in carbon storage across all four scenarios for 2030 compared to the baseline year 2020. This stark reality presents substantial challenges to achieving the region’s targets of carbon peaking and eventual carbon neutrality. Furthermore, this paper meticulously delineates six key drivers contributing to this decline in carbon storage. In conclusion, it proffers nine strategic recommendations aimed at augmenting carbon storage, with an overarching objective of establishing a harmonized mechanism capable of balancing urban development, safeguarding cultivated land, fortifying ecological preservation, and enhancing carbon sequestration within the area.

Urban parks are important places for residents to engage in physical activity (PA). Properly designed fitness facilities play a positive role in the PA level of park users. We conducted a quantitative evaluation of urban park systems based on the revised Chinese version of ParkScore (RCPS) from the perspective of national fitness. Baoji, one of the first National Ecological Garden Cities (NEGCs), was selected as a case study. We analyzed 19 parks and found that comprehensive parks and sports parks obtained high evaluation scores. The area of fitness facilities in Baoji urban parks was low, with an average of 1.85 hm2 per park. Professional sports venues and multifunctional sports venues each accounted for about one-third and children’s activity venues for about a quarter. There were many national fitness stations, but they covered a small area. Only 16% of parks had fitness trails, which was the least represented type of fitness facility. About 40% of the parks had children’s activity venues, with a 1:2 ratio of PA venue to amusement area. The area of free open venues accounted for only 0.1% of the total area of the parks. The number of parks per capita was about 52% of the overall NEGCs, accessibility of 500 m was 34%, and of 1000 m was about 54%. Overall, we found that the supply of Baoji urban parks was insufficient. These results directly reflect differences among fitness facilities in urban parks and can help form a quantitative basis for the optimization of urban park systems and advance the national fitness plan and promote public health.