Urban expansion dynamics and natural habitat loss in China: a multiscale landscape perspective

Impacts of urban expansion on air temperature and humidity during 2022 mega-heatwave over the Yangtze River Delta, China

The Yangtze River Delta (YRD) experienced record-breaking heat in the summer of 2022. However, the urban heat pattern and the role of urban expansion over the last two decades in this hot summer have not been explored. Using the advanced mesoscale Weather Research and Forecasting (WRF) model, we reproduced the fine spatial features and investigated the urban heat island (UHI) and dry island (UDI) effects during the two identified heatwaves in 2022. We further replace the current (2020) land use with the historical (2001) land use in WRF to evaluate the impacts of urban expansion from 2001 to 2020 on air temperature and moisture. Our finding revealed that the conversion of land use resulted in near-surface warming and drying, with pronounced diurnal variations, especially during the July heatwave. The analysis of surface energy balance demonstrated that the substantial decrease in evapotranspiration (ET) was the primary driver of daytime warming, elevating temperatures by 7 °C (July heatwave) and 2 °C (August heatwave). This ET reduction also led to the strong daytime coupling of warming and drying effects over new urban areas. At night, the release of stored heat resulted in the temperature increase of 2 °C (1 °C) during July (August) heatwave, highlighting the nighttime as a critical period for heightened thermal risk. Additionally, urban expansion at the periphery contributed modestly to the warming of urban cores, exacerbating conditions in an already hot environment. This study enhances understanding of the impacts of urban expansion on air temperature and humidity during extreme heatwaves, thereby supporting targeted adaptation and mitigation for extreme events within large cities.

Unexpected response of terrestrial carbon sink to rural depopulation in China

China is experiencing large-scale rural-urban migration and rapid urbanization, which have had significant impact on terrestrial carbon sink. However, the impact of rural-urban migration and its accompanying urban expansion on the carbon sink is unclear. Based on multisource remote sensing product data for 2000-2020, the soil microbial respiration equation, relative contribution rate, and threshold analysis, we explored the impact of rural depopulation on the carbon sink and its threshold. The results revealed that the proportion of the rural population in China decreased from 63.91 % in 2000 to 36.11 % in 2020. Human pressure decreased by 1.82% in rural depopulation areas, which promoted vegetation restoration in rural areas (+8.45 %) and increased the carbon sink capacity. The net primary productivity (NPP) and net ecosystem productivity (NEP) of the vegetation in the rural areas increased at rates of 2.95 g C m-2 yr-1 and 2.44 g C m-2 yr-1. Strong rural depopulation enhanced the carbon sequestration potential, and the NEP was 1.5 times higher in areas with sharp rural depopulation than in areas with mild rural depopulation. In addition, the rural depopulation was accompanied by urban expansion, and there was a positive correlation between the comprehensive urbanization level (CUL) and NEP in 75.29 % of urban areas. In the urban areas, the vegetation index increased by 88.42 %, and the urban green space partially compensated for the loss of carbon sink caused by urban expansion, with a growth rate of 4.96 g C m-2 yr-1. Changes in rural population have a nonlinear impact on the NEP. When the rural population exceeds 545.686 people/km2, an increase in the rural population will have a positive impact on the NEP. Our research shows that rural depopulation offers a potential opportunity to restore natural ecosystems and thus increase the carbon sequestration capacity.

Dual effects on vegetation from urban expansion in the drylands of northern China: A multiscale investigation using the vegetation disturbance index

Drylands contribute roughly 40 % of the global net primary productivity and are essential for achieving sustainable development. Investigating the effects on vegetation from urban expansion in drylands within the context of rapid urbanization could help enhance the sustainability of dryland cities. With the use of the drylands of northern China (DNC) as an example, we applied the vegetation disturbance index to investigate the negative and positive effects on vegetation from urban expansion in drylands. The results revealed that the DNC experienced massive and rapid urban expansion from 2000 to 2020. Urban land in the entire DNC increased by 19,646 km2 from 8141 to 27,787 km2, with an annual growth rate of 6.3 %. Urban expansion in the DNC imposed both negative and positive effects on regional vegetation. The area with negative effects reached 7736 km2 and was mainly concentrated in the dry subhumid zones. The area with positive effects amounted to 5011 km2 and was comparable among the dry subhumid, semiarid, and arid zones. Land use/cover change induced by population growth significantly contributed to these negative effects, while the positive effects were largely caused by economic growth. Therefore, it is recommended to strike a balance between urban growth and vegetation conservation to mitigate the adverse effects on vegetation from urban expansion in drylands. Simultaneously, it is imperative to expand urban green spaces and build sustainable and livable ecological cities to facilitate sustainable urban development.

Milder, wilder, drier: Understanding preferences for urban nature-based solutions in China

Nature-based solutions have gained recognition for their potential to address urban environmental challenges, particularly in rapidly urbanising countries such as China. However, financial and spatial constraints hinder their widespread adoption. Here we explore urban residents' preferences for nature-based solutions targeting stormwater management, urban heat island reduction, and biodiversity support through monetary, time, and space contributions. We carried out three choice experiment surveys with 1536 Chinese respondents, employing three payment vehicles: willingness to pay (WTP), willingness to contribute time (WTCT), and a novel metric, willingness to contribute space (WTCS). The WTCS metric assesses individuals' willingness to voluntarily convert sealed surfaces on private land into greenspace. We found strong preferences for temperature and flooding reduction across all payment vehicles, reflecting substantial challenges of urban heat islands and flooding in China. Additionally, we reveal a preference for moderate greenspace management intensity, highlighting the potential for biodiversity benefits through reduced management intensities. The introduction of the WTCS payment vehicle expands the methodological toolkit for choice experiments and offers a novel approach to assess citizen support for nature-based solutions. These findings have practical implications for designing effective nature-based solutions programs to address urban environmental challenges and meet the preferences of urban residents in China and beyond.

Land-use intensification dominates China's land provisioning services: From the perspective of land system science

A pressing challenge to global sustainability is meeting the escalating needs of a growing population while safeguarding land resources from degradation. In recent decades, China's rapid growth, expanding population, urban sprawl, and diminishing high-quality farmland have presented a compelling case suitable for exploring solutions and challenges related to this critical issue. Therefore, there is an urgent need for comprehensive and detailed information regarding land systems. Here, we developed the first fine-scale dataset of the China Land System at a spatial resolution of 1 km, covering the period from 2000 to 2015. By leveraging this comprehensive land information, we identified five primary types of land systems and their respective subsystems, thereby delineating distinct patterns of human-environmental interaction. Land system dynamics followed diverse developmental trajectories characterized by incremental shifts toward more functionally centralized systems. Land use intensification played a significant role in increasing the population capacity and food production in China, contributing nearly 93.94% and 84.99%, respectively. In contrast, land cover changes accounted for only 4.69% and 11.43%, respectively. These findings underscore the tendency of previous studies to overestimate the impact of land cover change and underestimate the influence of land use intensification in meeting the growing demands of land-based production. This study emphasizes the importance of transcending traditional land cover-based approaches and integrating land systems into land representation and global land change scenario simulations to promote sustainability.

Biodiversity loss through cropland displacement for urban expansion in China

As a result of rapid economic development, urban expansion reduced the cropland in China. To secure the food supply, cropland displacement to maintain the quantity and quality of cropland has been implemented. Here, we quantified the biodiversity losses due to cropland displacement resulting from urban expansion from a telecoupling perspective in China from 1980 to 2020. A comprehensive multimodel assessment demonstrated that the indirect biodiversity losses due to cropland displacement resulting from urban expansion were approximately 2 to 3 times higher than its direct biodiversity losses, at a total loss of approximately 0.6 % to 1.0 %, as indicated by three biodiversity indicators. Displaced cropland with a higher biodiversity cost but lower cropland productivity is the main reason for the excessive indirect losses and suggests that socioecological processes may be detrimental to the synergistic benefits of the UN Sustainable Development Goal (SDG) for food security and terrestrial biodiversity. This study also identified source-sink hotspots for indirect biodiversity losses, which can contribute to improving biodiversity conservation, optimizing the spatial distribution of cropland and thus enhancing socioecological system sustainability.

Assessing urban wetlands dynamics in Wuhan and Nanchang, China

Urban wetlands play a crucial role in sustainable social development. However, current research mainly focuses on specific wetland types, and fine extraction of urban wetlands remains a challenge. This study proposes a fine extraction framework based on hierarchical decision trees and shape features for urban wetlands, using Sentinel-2 remote sensing data to obtain detailed wetland data of Wuhan and Nanchang from 2016 to 2022. Our framework applies random forests to classify land cover, extracts urban fine wetlands by hierarchical decision trees and shape features, and assesses the dynamics of wetlands in the two cities. We also analyzed and discussed the characteristics of urban wetlands in the two cities. The results show that wetland accuracies of Wuhan and Nanchang are greater than 84.5 % and 82.9 %, respectively. The wetland areas of Wuhan in 2016, 2019, and 2022 are 1969.4 km2, 1713.8 km2, and 1681.1 km2, while those in Nanchang are 1405.9 km2, 1361.6 km2, and 766.9 km2. Inland wetlands are the main wetland types in both regions, with lake wetlands accounting for the highest proportion (over 40 %). The urban wetlands in the two cities exhibit different spatial and temporal evolution patterns, with varying change trends of wetland area and the structural proportions of fine wetlands. Besides, Wuhan's urban wetlands are primarily located in the south, while Nanchang's urban wetlands are concentrated in the east, exhibiting higher spatial and temporal dynamics. Analysis suggests that the reduced urban wetlands from 2016 to 2022 are related to fluctuating decreasing precipitation, growing population, and gross domestic product (GDP). Our study provides support for the conservation of urban wetland resources in Wuhan and Nanchang and highlights the need for targeted management strategies.

Does a scaling exist in urban ecological infrastructure? A case for sustainability trade-off in China

So far, urban scaling theory has proven that urban area, infrastructure, and economic output have a scaling relation with population. But if we consider ecological space as a part of urban infrastructure, would the same scaling characteristics exist? What is the scaling relationship between ecological spaces and economic social development in different stages of urbanization? This paper is based on this question and explores the trade-off between social economic system and ecosystem in 370 cities of China. The results show that the relationship between population and urban ecological space generally follows the scaling theory in terms of different types of ecological spaces and ecosystem services. For every 10-fold increase in population size, the total area of ecological space and ecosystem services increase by approximately 4 times. The manifestation of ecological space following the scaling laws is the aggregation behavior of better network connectivity. There is a trade-off between urban ecological space and socioeconomic development, with flow equilibrium reached at a population of 2 million and efficiency equilibrium reached at a population of 1 million. Starting from type I and type II megapolis, urban development gradually tends to stabilize, and there may even be a trend of slow decline in urban development potential. In the absence of ecological space, virtual network space can serve as a substitute for ecological space. The driving factors affect scaling behavior of ecological space, including connectivity of ecological space, spatial heterogeneity of natural conditions, and disturbance of economic and social activities. This research can help city to expand ecological space, promoting the added value of urban ecological assets and keeping the urban development potential within the optimal threshold range continuously.

Examining human disturbances and inundation dynamics in China's marsh wetlands by using time series remote sensing data

The hydrological regime is one of the most significant characteristics of wetlands, which maintains the structural and functional integrity of wetland ecosystems. China experienced rapid economic development since the 1990s, which caused severe degradation of all types of wetlands, especially marsh wetlands that are easily converted through filling or draining. Therefore, it is crucial to examine the inundation alterations in marshes as well as the forces behind the changes. In this study, the inundation dynamics in marsh wetlands of China were documented using time-series Landsat observations from 1992 to 2018. Then, nighttime light data was utilized to indicate the intensity of urbanization and infrastructure construction, which was incorporated with historical statistics to conduct attribution analyses of wetland inundation changes. Great spatial heterogeneity in the water distribution and change trajectory was observed in different areas. Severe wetland desiccation took place in Inner Mongolia and East China, in which the inundation area decreased by 51.3 % and 20.9 %, respectively. By contrast, the water area in North China and Tibetan Plateau increased by 58.2 % and 21.0 %, respectively. Behind the tremendous changes, anthropogenic factors played dominant roles. The marsh wetlands in East China, North China, and Southwest China took up only 1.9 % of the total marsh area but accounted for 26.0 % of the entire nighttime light volume. In East China and Southwest China, urbanization and infrastructure construction had significantly negative effects on wetland inundation. Overgrazing or unregulated irrigation altered the original inundation dynamics of marsh wetlands in Inner Mongolia, Southwest China, the Tibetan plateau, and Northeast China. This study illustrated the possible driving forces behind wetland inundation changes, which could help to locate degrading marsh wetlands triggered by anthropogenic activities. Then, targeted management and conservation actions could be implemented.

Estimating potential illegal land development in conservation areas based on a presence-only model

Conservation areas are facing increasing threats from anthropogenic land use activities. It is important to reasonably recognize and predict suspected illegal land development in advance. However, traditional methods easily suffer from selection bias due to the lack of accurate and reliable absence data. To tackle this problem, we have presented a novel method for estimating potential illegal land development based on the presence-only maximum entropy (MAXENT) model. The principle of MAXENT can guarantee that no additional unknown information (e.g., inaccurate pseudo-absence samples) will be introduced into the estimation procedure. This method was applied to the conservation areas in a fast-growing city, and the robustness of the MAXENT models was confirmed by the high AUC scores (over 0.80). The results indicated that the proposed method performs more effectively than the presence-absence random forest model. In addition, topographic conditions and proximity to transportation networks played dominant roles in the emergence of suspected illegal land development. Moreover, the probability map generated by MAXENT suggests that a considerable amount of forest, farmland, grassland, and water bodies will face a high degree of danger. Therefore, both superior and local governments should pay much more attention to regions with a higher potential for illegal land development. In summary, our findings are expected to support decision-making in the management and assessment of conservation areas in fast-growing regions. More importantly, the proposed method can be further applied to illegal land development estimation in many other regions.

Integrating ecosystem services and landscape connectivity into the optimization of ecological security pattern: a case study of the Pearl River Delta, China

The ecological security pattern (ESP) focuses on key ecological elements in ecosystems by identifying, combining, and evaluating these elements. This study attempts to identify the ESP of the Pearl River Delta (PRD) and provide suggestions for optimization. Ecosystem services were calculated and applied to construct the ecological resistance surface; morphological spatial pattern analysis (MSPA) and landscape connectivity analysis were used to identify ecological sources; and minimum cumulative resistance (MCR) model was applied to extract ecological corridors and ecological nodes. The results show that during 1995 to 2015, the main landscape transformation occurred between forest, cropland, and urban land, and the location of the transformation was mainly in the central part of the study area. Regarding the ESP, the average resistance value increased from 0.30 to 0.33; the area of ecological sources decreased by 5.12%; the ratio of total cumulative resistance to the length of the corridors increased by 14.82%; and the number of ecological nodes increased from 71 to 99. For the ESP optimization, based on the correction of the resistance surface, 1348 km blue corridors and 61 blue nodes were extracted. Based on hot spot analysis, nine stepping stones were identified. This optimization compensates for the lack of ecological elements in the center of the study area, enhances weaker corridors, and improves the connectivity of the ESP, thus making the ESP more stable and complete. The ESP constructed and optimized in this paper holds great significance and serves as a valuable reference for ecological protection and environmental management.

Habitat change and biodiversity loss in South and Southeast Asian countries

South and Southeast Asia is by far the most populous region in Asia, with the greatest number of threatened species. Changes in habitat are a major contributor to biodiversity loss and are more common as a result of land-use changes. As a result, the goal of this study is to use negative binomial regression models to investigate habitat change as one of the important drivers of biodiversity loss in South and Southeast Asian countries from 2013 to 2018. According to the negative binomial estimates, the findings for the habitat change measures are quantitatively similar for the impacts of agricultural land and arable land on biodiversity threats. Agricultural and arable land both have a positive impact on biodiversity loss. We found that, contrary to our expectations, the forest area appears to have an unexpected direct influence on the number of threatened species. A higher number of threatened species is associated with rising per capita income, human population and a low level of corruption control. Finally, the empirical findings are consistent across taxonomic groups, habitat change measures and Poisson-based specifications. Some policy implications that could mitigate biodiversity loss include educating and promoting good governance among the population and increase the conservation effort to sustain green area and national forest parks in each country.

Integrating circuit theory and landscape pattern index to identify and optimize ecological networks: a case study of the Sichuan Basin, China

The notion of ecological networks (EN) and their identification can support approaches to nature conservation strategies aiming at biodiversity, landscape connectivity, and people's well-being. Integrating ecosystem services (ESs), morphological spatial pattern analysis (MSPA), circuit theory, and landscape pattern index analysis, we proposed a new framework for mapping EN that was expected to promote economic development and ecological protection. Specifically, source areas were extracted through a combination of ESs and MSPA that integrated functional and morphological spatial attributes. Resistance surfaces were determined based on habitat quality. A network linking ecological source areas was then identified using circuit theory, and landscape pattern index analysis was used to identify ecological strategy nodes in view of the heterogeneity within ecological corridors. The results showed that the Sichuan Basin involved 553 ecological sources, 641 ecological corridors, and 33 ecological nodes that altogether included 20 ecological strategy nodes. Constructing regional EN can promote the transformation of multiple, chaotic, and scattered ecological elements to systematic and networked ecological elements and ultimately promote harmonious coexistence between humans and nature. This study provided a methodology for the extraction of ecological source areas and strategy nodes and can provide a significant reference for the management and optimization of EN.

Construction and Optimization of an Ecological Security Pattern Based on the MCR Model: A Case Study of the Minjiang River Basin in Eastern China

The Minjiang River Basin is one of the first pilot areas for ecological conservation and the restoration of mountain–river–forest–farmland–lake–grass in China. Taking the Minjiang River Basin as an example, this paper selected the importance of ecosystem service functions and ecological sensitivity to evaluate the ecological environment and identify ecological sources. Furthermore, we constructed an ecological resistance surface using artificial and natural interference factors. Through a minimum cumulative resistance model (MCR), the ecological security pattern (ESP) of “two barriers, one belt, many corridors, and many spots” was constructed. Research shows that: (1) In total, 43 ecological sources were identified, with a total area of 523 km², accounting for 0.6% of the total land area. These were mainly distributed in the southwest and northwest of the Minjiang River Basin, such as in Zhangping, covered forest land, and cultivated land. (2) The connectivity of the network was low, and the spatial distribution of the ecological pinch points was uneven. A total of 118 ecological corridors and 22 important ecological pinch points were identified. The total length of the ecological corridor is 3,732,051.88 km, which is dense on the left side and sparse on the right side. (3) The ecological restoration area was composed of a low ecological safety area and a lower ecological safety area; the ecological control area was composed of a medium ecological safety area and a higher ecological safety area; and the ecological conservation area was composed of a high ecological safety area, at 6.5%, 27.7%, and 65.8%, respectively. Constructing the ESP of the Minjiang River Basin is important for promoting harmonious socioeconomic development and ecological protection. In addition, it can provide a reference basis for other experimental areas of mountain–river–forest–farmland–lake–grass.

China's Mismatch of Public Awareness and Biodiversity Threats under Economic Trade

China is one of the countries with high biodiversity on the globe, but suffers extreme biodiversity loss due to the increasingly interconnected economy. Understanding the nation-level public awareness of biodiversity under economic trades is crucial for implementing sustainable production and consumption of Sustainable Development Goals (SDGs). This study is the first to assess the public awareness of biodiversity loss associated with China's interprovincial trades by utilizing social media data and the multiregion input-output (MRIO) table. Results show that China's interprovincial trades cause heavy threats not only to local species but to distant species. Approximately 60% of provinces displace over half of their consumption-based biodiversity threats to other provinces. Nevertheless, individuals do not clearly realize their responsibility for the distant biodiversity they consumed, with a large mismatch both in popularity (Gini index = 0.51, Robin index = 39.57) and donation (Gini index = 0.69, Robin index = 54.58). To alleviate this phenomenon, our analysis suggests that the expansion of national-level nature reserves may be effectively beneficial to public biodiversity awareness, showing significantly positive partial correlation coefficients with individuals' popularity and donations. These insights provided by this study offer targeted information for conservation and call for synergistic collaboration between the civil society, especially consumers, and governments to turn the tide of biodiversity loss.

Annual Wetland Mapping in Metropolis by Temporal Sample Migration and Random Forest Classification with Time Series Landsat Data and Google Earth Engine

Wetlands provide various ecosystem services to urban areas, which are crucial for sustainable urban management. With intensified urbanization, there has been marked loss of urban natural wetland, degradation, and related urban disasters in the past several decades. Rapid and accurate mapping of urban wetland extent and change is thus critical for improving urban planning toward sustainability. Here, we have developed a rapid method for continuous mapping of urban wetlands (MUW) by combining automatic sample migration and the random forest algorithm (SM&RF), the so-called MUW_SM&RF. Using time series Landsat images, annual training samples were generated through spectral angular distance (SAD) and time series analysis. Combined with the RF algorithm, annual wetland maps in urban areas were derived. Employing the Google Earth Engine platform (GEE), the MUW_SM&RF was evaluated in four metropolitan areas in different geographical and climatic regions of China from 1990 to 2020, including Tianjin, Hangzhou, Guangzhou, and Wuhan. In all four study areas, the generated annual wetland maps had an overall accuracy of over 87% and a Kappa coefficient above 0.815. Compared with previously published datasets, the urban wetland areas derived using the MUW_SM&RF approach achieved improved accuracy and thus demonstrated its robustness for rapid mapping of urban wetlands. Urban wetlands in all four cities had variable distribution patterns and showed significantly decreased trends in the past three decades. The annual urban wetland data product generated by the MUW_SM&RF can provide invaluable information for sustainable urban planning and management, so as for assessment related to the United Nation’s sustainable development goals.

Phylogeography of Tridentiger bifasciatus (Gobiidae) in the Northwestern Pacific

The shimofuri goby (Tridentiger bifasciatus) is native to marine, brackish, and fresh waters along the coasts of the northwest Pacific. Our study examined the population genetic structure, diversity, and demography of T. bifasciatus in the China Seas, including the Yellow Sea, East China Sea, and South China Sea, using the sequences of mitochondrial DNA [mtDNA cytochrome b (cyt b) gene and d-loop region] and nuclear DNA [nuDNA ryanodine receptor 3 (Ryr3) gene]. The mtDNA dataset revealed a significant population differentiation, but the nuDNA dataset displayed the absence of genetic differentiation. The discordance between these two datasets was accounted for by population admixture, selection, and incomplete lineage sorting. Although the mtDNA and nuDNA displayed a discordant population structure, these genetic markers revealed the same population history: (1) the populations retreated into two refugia during glaciations and (2) the populations declined recently. Our study revealed that after glaciations, the re-flooding in Taiwan Strait did not shape the migrations of the southern lineage from the South China Sea to the East China Sea, and displayed that two mtDNA lineages have diverged before they migrated southward during glaciations. These results offer important resources for the further study of conservation genetics.

Land Use and Climate Change Altered the Ecological Quality in the Luanhe River Basin

Monitoring and assessing ecological quality (EQ) can help to understand the status and dynamics of the local ecosystem. Moreover, land use and climate change increase uncertainty in the ecosystem. The Luanhe River Basin (LHRB) is critical to the ecological security of the Beijing–Tianjin–Hebei region. To support ecosystem protection in the LHRB, we evaluated the EQ from 2001 to 2020 based on the Remote Sensing Ecological Index (RSEI) with the Google Earth Engine (GEE). Then, we introduced the coefficient of variation, Theil–Sen analysis, and Mann–Kendall test to quantify the variation and trend of the EQ. The results showed that the EQ in LHRB was relatively good, with 61.08% of the basin rated as ‘good’ or ‘excellent’. The spatial distribution of EQ was low in the north and high in the middle, with strong improvement in the north and serious degradation in the south. The average EQ ranged from 0.58 to 0.64, showing a significant increasing trend. Furthermore, we found that the expansion of construction land has caused degradation of the EQ, whereas climate change likely improved the EQ in the upper and middle reaches of the LHRB. The results could help in understanding the state and trend of the eco-environment in the LHRB and support decision-making in land-use management and climate change.

Remote Sensing of Surface Water Dynamics in the Context of Global Change—A Review

Inland surface water is often the most accessible freshwater source. As opposed to groundwater, surface water is replenished in a comparatively quick cycle, which makes this vital resource—if not overexploited—sustainable. From a global perspective, freshwater is plentiful. Still, depending on the region, surface water availability is severely limited. Additionally, climate change and human interventions act as large-scale drivers and cause dramatic changes in established surface water dynamics. Actions have to be taken to secure sustainable water availability and usage. This requires informed decision making based on reliable environmental data. Monitoring inland surface water dynamics is therefore more important than ever. Remote sensing is able to delineate surface water in a number of ways by using optical as well as active and passive microwave sensors. In this review, we look at the proceedings within this discipline by reviewing 233 scientific works. We provide an extensive overview of used sensors, the spatial and temporal resolution of studies, their thematic foci, and their spatial distribution. We observe that a wide array of available sensors and datasets, along with increasing computing capacities, have shaped the field over the last years. Multiple global analysis-ready products are available for investigating surface water area dynamics, but so far none offer high spatial and temporal resolution.

Bibliometric Analysis of Global Research on Ecological Networks in Nature Conservation from 1990 to 2020

As a nature-based solution to land-use sustainability, ecological networks (ENs) have received substantial attention from researchers, planners, and decision-makers worldwide. To portray the global research on ENs in nature conservation during the period of 1990–2020, 1371 papers in 53 subject categories were reviewed with bibliometric methods and CiteSpace. The results showed a successive growth of publications at an annually averaged rate of 18.9% during the past three decades. Co-citation analysis indicated that the most popular topic was connectivity, on which the studies concentrated on quantifying connectivity, identifying priority areas, and integrating conservation planning. A recent hotspot is to study the landscape fragmentation effects on natural habitats or biodiversity under land-use changes in urbanized areas. Multidisciplinary approaches have been increasingly used to tackle more complex interplays among economic, social, ecological, and cultural factors, with the aim of alleviating ecological service losses attributed to human activities. Spatiotemporal dynamics and participatory design of ENs at different scales have become an emerging trend. In order to address increasing pressures on biodiversity or landscape connectivity brought about by land use and climate change, it is suggested to develop more research on the evaluation and management of the resilience of ENs.

Association between residential greenspace structures and frailty in a cohort of older Chinese adults

Background

Frailty is a late-life clinical syndrome resulting from the accumulation of aging-induced decline. Greenspaces measured with normalized difference vegetation index (NDVI) are protective of frailty. However, NDVI is not as informative as structure indices in describing greenspaces' constitution, shape, and connectivity measured by the largest patch index (LPI), shape index, and cohesion index representing larger, more complex, and more dense greenspaces through higher values. We aim to study the association between greenness structures and frailty in a cohort of Chinese older adults.

Methods

We included older adults from 2008-2014 China Longitudinal Healthy Longevity Survey (CLHLS). We used greenspace indices from satellite to quantify structures (area-edge, shape, proximity) at county-level, and calculated frailty index (FI) as an outcome. We did cross-sectional analyses using linear and logistical regression, and longitudinal analyses using the generalized estimating equations (GEE).

Results

Among 8776 baseline participants, mean LPI, shape, cohesion, and FI are 7.93, 8.11, 97.6, and 0.17. In cross-sectional analyses, we find negative dose-response relationships for greenspace structures and frailty, especially in females, centenarians, illiterate people, city residents, unmarried people, and individuals with increased frailty. Participants living in the highest quartile of LPI, shape, and cohesion have 32% (95%CI: 21-42%), 35% (95%CI: 24-44%), and 37% (95%CI: 26%-46%) lower odds of frailty than the lowest quartile. However, we do not find a significant association in longitudinal analyses.

Conclusions

Higher levels of greenness structures (area-edge, shape, and proximity) might be related to lower frailty, while a clear longitudinal benefit cannot be identified in this analysis.

Impact of Power on Uneven Development: Evaluating Built-Up Area Changes in Chengdu Based on NPP-VIIRS Images (2015–2019)

In the context of uneven development studies of China, urban built-up area changes are the index of the impact of power, as the local government is the only party that is able to acquire agricultural land and convert it to construction urban land. Existing studies generally use statistical data to describe the built-up area changes and struggle to meet the requirement of an updated and inexpensive monitoring of uneven development, especially for western cities with tight budgets. Open access NPP-VIIRS (Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite), NDVI (Normalized Difference Vegetation Index), and nighttime LST (Land Surface Temperature) data ranging from 2015 to 2019 were analyzed with a stratified SVM (Support Vector Machine) method in this study to track urban built-up area changes in Chengdu, one of the biggest cities in Western China. The SDE (Standard Deviation Ellipse) and Moran’s I were then applied to evaluate the spatial variations of the built-up area changes. It was revealed that the spatial evolution of built-up area change in Chengdu over the period 2015–2019 demonstrated a “northwest-southeast” spatial expansion pattern, and the change distance in the center of gravity in 2018 and 2019 was greater than that from 2015 to 2017, which reflected the faster uneven development in 2018 and 2019 in Chengdu. The results were verified with finer resolution Landsat-8 OLI images; the high OA (all larger than 92%) and KAPPA (all larger than 0.6) values showed the accuracy of the method. The methodology proposed in this study offers a practical way for cities with tight budgets to monitor uneven development, and this study suggests a further adaption using higher-resolution remote sensing images and field experiments.

Global impacts of future urban expansion on terrestrial vertebrate diversity

Rapid urban expansion has profound impacts on global biodiversity through habitat conversion, degradation, fragmentation, and species extinction. However, how future urban expansion will affect global biodiversity needs to be better understood. We contribute to filling this knowledge gap by combining spatially explicit projections of urban expansion under shared socioeconomic pathways (SSPs) with datasets on habitat and terrestrial biodiversity (amphibians, mammals, and birds). Overall, future urban expansion will lead to 11–33 million hectares of natural habitat loss by 2100 under the SSP scenarios and will disproportionately cause large natural habitat fragmentation. The urban expansion within the current key biodiversity priority areas is projected to be higher (e.g., 37–44% higher in the WWF’s Global 200) than the global average. Moreover, the urban land conversion will reduce local within-site species richness by 34% and species abundance by 52% per 1 km grid cell, and 7–9 species may be lost per 10 km cell. Our study suggests an urgent need to develop a sustainable urban development pathway to balance urban expansion and biodiversity conservation.

Population growth in the coming decades will lead to increasing land conversion to urban areas. Here, the authors use spatially explicit projections of global urban expansion to analyze its effects on habitat changes, and terrestrial mammals, birds and amphibians under the main shared socioeconomic pathways.

Comparing the population structure of the specialist Butler’s Gartersnake (Thamnophis butleri) and the generalist Eastern Gartersnake (Thamnophis sirtalis sirtalis) in Ontario (Canada) and Michigan (USA)

Species differing in life-history attributes vary in their responses to features within a shared landscape. We evaluated genetic structure of sympatric gartersnake species in southwestern Ontario (Canada) and southeastern Michigan (USA), where habitat fragmentation is high due to agriculture and urbanization. We surveyed genetic structure of a habitat specialist, Butler’s Gartersnake (Thamnophis butleri (Cope, 1889)), and a habitat generalist, Eastern Gartersnake (Thamnophis sirtalis sirtalis (Linnaeus, 1758)), using DNA microsatellites. Bayesian clustering, discriminant analysis of principal components, and pairwise population comparisons revealed genetic differentiation among three major regional clusters of Butler’s Gartersnake with evidence of further division within one. Genetic clustering of Butler’s Gartersnake suggest that inhospitable habitat limits dispersal. Eastern Gartersnakes showed less structure, with assignment tests implying a single genetic cluster. We found positive significant Mantel’s r for both species in the smallest distance class (<15 km), but significant isolation by distance for Butler’s Gartersnake only. These findings together imply that connectivity for Eastern Gartersnakes is less impacted by habitat loss and fragmentation or that we were less able to detect their effects. Our study shows the value of multispecies comparisons in studies seeking to understand the underlying causes of genetic structure in natural populations.

The role of urban waterbodies in maintaining bird species diversity within built area of Beijing

This study aims to provide a comprehensive understanding of the role of urban waterbodies in avian ecology, which is instructive for both biodiversity conservation and urban planning. Based on bird surveys conducted in 41 urban parks in Beijing during the breeding and wintering seasons of 2018-2019, and using standardized regression analyses, we identified the specific effects of waterbody attributes on the full avian community and forest bird guilds. We assessed this at multiple spatial scales, first within the focal parks, and then within buffer zones with radius of 200 m and 1000 m. We found that waterbodies can serve as avian diversity "hotspots" in the urban landscape. More specifically, they support avian diversity in the following ways: (1) Parks with waterbodies maintain a higher number of bird species than parks without waterbodies during the breeding season and attract resident forest birds during the wintering season. (2) When not frozen, waterbodies inside and outside parks contribute equally to resident forest bird species richness, while more individuals were attracted by waterbodies within neighborhoods. (3) In parks without waterbodies, the number of forest bird species significantly increases with the number of waterbody patches within neighborhoods, while the corresponding relationship for parks with waterbodies is insignificant. These findings suggest a preference for habitats nearby waterbodies among forest birds residing highly urbanized areas. This study provides new insights into avian ecology in urban landscapes and scientific support for the idea that creating and maintaining urban waterbodies can conserve biodiversity.

Assessment of the Sustainable Utilization Level of Water Resources in the Wuhan Metropolitan Area Based on a Three-Dimensional Water Ecological Footprint Model

The shortage and overexploitation of water resources restrict the sustainable development of metropolitan areas. To evaluate the sustainable utilization level of water resources, we identified the occupancy of natural capital stock and the consumption of natural capital flow by water resources consumption and analyzed the factors influencing water resources consumption in metropolitan area development. We took the Wuhan Metropolitan Area in China from 2010 to 2019 as the research object and introduced footprint depth and size, the water ecological footprint (WEF) model was expanded into the three-dimensional WEF model. Based on this model, an evaluation system for the sustainable utilization level of water resources was constructed with five indices—water ecological deficit, water ecological surplus, water ecological pressure, WEF depth, and WEF size. Finally, the driving factors of WEF change were analyzed using the Logarithmic Mean Divisia Index. The evaluation of the sustainable utilization level of water resources showed that the Wuhan Metropolitan Area as a whole experienced water ecological surplus from 2010 to 2019, but there were different degrees of water ecological deficit in its inner urban areas, and the most serious cumulative deficit was 5.02 ha/cap in Ezhou. In 2011 and 2019, the sustainable utilization level of water resources in the metropolitan area reached a relatively unsustainable state. Xianning was the urban area with the most sustainable utilization level of water resources. During the study period, the metropolitan area did not occupy the natural capital stock of water resources, and the natural capital flow of water resources in the inner urban areas could meet the demand of the current consumption of the region in 2010 and 2016. The analysis of the driving factors of WEF change showed that economic development effect and population pressure effect had a positive driving effect on WEF change, while WEF intensity effect and water resources carrying capacity effect had the opposite effect. Finally, according to the research results, it can be seen that improving the efficiency of water resources utilization, protecting the natural capital stock of water resources, realizing differentiated regional development through the market economy and developing water policy can be helpful to improve the level of sustainable water resources utilization.

Functional Classification of Urban Parks Based on Urban Functional Zone and Crowd-Sourced Geographical Data

Urban parks have important impacts on urban ecosystems and in disaster prevention. They also have diverse social functions that are important to the living conditions and spatial structures of cities. Identifying and classifying the different types of urban parks are important for analyzing the sustainable development and the greening progress in cities. Existing studies have predominantly focused on the data extraction of urban green spaces as a whole, while there have been relatively few studies that have considered different categories of urban parks and their impact, which makes it difficult to characterize or predict the spatial distribution and structures of urban parks and limits further refinement of urban research. At present, the classification of urban parks relies on the physical features observed in remote sensing images, but these methods are limited when mapping the diverse functions and attributes of urban parks. Crowd-sourced geographic data may more accurately express the social functions of points of interest (POIs) in cities, and, therefore, employing open data sources may assist in data extraction and the classification of different types of urban parks. This paper proposed a multi-source data fusion approach for urban park classification including POI and urban functional zone (UFZ) data. First, the POI data were automatically reclassified using improved natural language processing (NLP) (i.e., text similarity measurements and topic modeling) to establish the links between urban park green-space types and POIs. The reclassified POI data as well as the UFZ data were then subjected to scene-based data fusion, and various types of urban parks were extracted using data attribute analysis and social attribute recognition for urban park mapping. Experimental analysis was conducted across Beijing and Hangzhou to verify the effectiveness of the proposed method, which had an overall classification accuracy of 82.8%. Finally, the urban park types of the two cities were compared and analyzed to obtain the characteristics of urban park types and structures in the two cities, which have different climates and urban structures.

Identifying and Mapping the Responses of Ecosystem Services to Land Use Change in Rapidly Urbanizing Regions: A Case Study in Foshan City, China

Rapid urbanization has degraded some important ecosystem services and threatens socioeconomic sustainability. Although many studies have focused on the effect of urbanization on ecosystem services, the effect and its threshold have not been well-identified spatially. In this study, we propose a research framework by integrating nighttime light data, the InVEST (Integrated Valuation of Environmental Service and Tradeoffs) model, and a spatial response index to characterize the response of ecosystem services to rapid urbanization. We considered Foshan City as a case study to explore the effect of rapid urbanization on ecosystem services during 2000–2018. Our results showed that rapid urbanization resulted in a 49.13% reduction in agricultural production and a 10.13% reduction in habitat quality. The spatial response index of agricultural production, habitat quality, soil retention, water yield, and carbon sequestration were 14.25%, 2.94%, 0.04%, 0.78%, and 0.07%, respectively. We found that developing urban areas had the highest spatial response index, indicating that this area was the crucial area for future land management. We consider that our research framework can help identify the key areas affected by rapid urbanization. Visualizing the spatial response index and extracting the threshold for different levels of urbanization will be conducive to sustainable urban management and planning.

Impact of the Kunming–Bangkok Highway on Land Use Changes along the Route between Laos and Thailand

Road construction fragments the landscape, reduces connectivity, and drives land use changes. To our knowledge, little is known about the scope and intensity of the effects of cross-border roads on changes in land use. Here, with the land use data products provided by the US Agency for International Development’s SERVIR Mekong project, using the GIS-based spatial analysis to quantitatively analyze and compare the effects of the cross-border road on land use changes within a 30 km buffer area along the Kunming–Bangkok Highway between Laos and Thailand. The results show the following: The greater the distance was from the highway, the smaller were the overall changes in land use within the buffer zone. A comparison of the situation before and after the road was opened in 2013 revealed significant differences in the most influential land use types of agricultural expansion, i.e., from 47.07% to 52.07% (the buffer zone was 1 km). In particular, 57.32% (1381.93 ha) and 40.08% (966.46 ha) of the land occupied by forests had been converted into land for plantation and agriculture, respectively, from 2013 to 2018. The scope of the impact of the operational route on the dynamics of land use was inconsistent. The largest impact before the road became operational was within 4 km of the buffer zone (0.26 to 0.24). Once the road had been opened, the range of its impact was beyond 10 km (0.63 to 0.57). The work here can provide a scientific basis for regional transportation planning and the sustainable use of land resources.

Long-term trends in the phylogenetic and functional diversity of Anatidae in South China coastal wetlands

Species loss has attracted much attention among scientists for more than half a century. However, we have little information on the trends in phylogenetic and functional changes behind the species loss although this information is always asynchronous and important for conservation and management. We measured community trends in Anatidae (ducks and geese) for the last 50 yr to quantify trends in phylogenetic and functional diversity patterns coinciding with taxonomic historical dynamics. We used one-way ANOVAs to test if there was a significant historical trend in communities of Anatidae. We characterized taxonomic, phylogenetic, and functional diversity of communities. For taxonomic diversity, we used species richness (SR). For phylogenetic diversity, we calculated the standardized effect size of mean pairwise distances (ses.MPD) and the standard effect size of mean nearest taxon distances (ses.MNTD) in communities. For functional diversity, we calculated functional richness (FRic), functional evenness (FEve), functional divergence (FDiv), and the community-level weighted means (CWM) of trait values for diet, foraging stratum, and body mass, separately. From the 1950s to 2010s, species richness declined without significant trends. The ses.MNTD of Anatidae communities showed no clear trends. However, ses.MPD of Anatidae communities declined dramatically during this period. For functional diversity, functional evenness of diet, foraging stratum, body mass, and functional dispersion of diet, foraging stratum did not increase or decline significantly. However, functional evenness of all traits, functional richness, and functional dispersion of body mass showed declined trends. The basic phylogenetic diversity and species body mass of Anatidae communities declined significantly because of a declining trend in the relative independent branch of geese. This makes it more challenging for implement community recovery in the future. More attention in conservation biology should consider taxonomic diversity and asynchrony in phylogenetic and functional diversity.

The patterns of vascular plant discoveries in China

AIM

(1) To understand geographic patterns of species discovery by examining the effect of growth form, range size, and geographic distribution on discovery probability of vascular plant species in China; (2) to find out which taxa harbor the largest number of undiscovered species and where those species locate; and (3) to find out the determinants of province-level mean discovery time and inventory completeness.

LOCATION

China.

METHODS

We compiled the discovery time and province-level geographic distributions of ~31,000 vascular plant species described between 1753 and 2013 from Flora of China. We used a Cox proportional hazard model to determine the biological and geographic correlates of discovery probability. Accumulation curves of species discoveries were fitted by a logistic discovery model to estimate inventory completeness of different growth forms and of different provinces. We then used linear regression to identify the determinants of mean discovery time and beta regression to identify the determinants of inventory completeness.

RESULTS

We found that species with larger range size and distributed in northeastern part of China have a higher discovery probability. Coastal species were discovered earlier than inland species. Trees and shrubs of seed plants have the highest discovery probability while ferns have the lowest discovery probability. Herbs have the largest number of undiscovered species in China. Most undiscovered species will be found in southwest China, where three global biodiversity hot spots locate. Spatial patterns of mean discovery time and inventory completeness are mainly driven by the total number of species, human population density in an area, and latitude and longitude of a province.

MAIN CONCLUSIONS

Socioeconomic factors primarily determine the discovery patterns of vascular plants in China. Undiscovered species are most likely to be narrow-ranged, inconspicuous endemic species such as herbs and ferns, which are prone to extinctions and locate in biodiversity hot spots in southwestern China.

Changes in protist communities in drainages across the Pearl River Delta under anthropogenic influence

Drainages in the Pearl River Delta urban agglomeration (PRDUA) host vital aquatic ecosystems and face enormous pressures from human activities in one of the largest urban agglomerations in the world. Despite being crucial components of aquatic ecosystems, the interactions and assembly processes of the protistan community are rarely explored in areas with serious anthropogenic disturbance. To elucidate the mechanisms of these processes, we used environmental DNA sequencing of 18S rDNA to investigate the influence of environmental factors and species interactions on the protistan community and its assembly in drainages of the PRDUA during summer. The protistan community showed a high level of diversity and a marked spatial pattern in this region. Community assembly was driven primarily by stochastic processes based on the Sloan neutral community model, explaining 74.28%, 75.82%, 73.67%, 74.40% and 51.24% of community variations in the BJ (Beijiang), XJ (Xijiang), PRD (Pearl River Delta), PRE (Pearl River Estuary) areas and in total, respectively. Meanwhile, environmental variables including temperature, pH, dissolved oxygen, transparency, nutrients and land use were strongly correlated with the composition and assembly of the protistan community, explaining 40.40% of variation in the protistan community. Furthermore, the bacterial community was simultaneously analysed by the 16S rDNA sequencing. Co-occurrence network analysis revealed that species interactions within bacteria (81.41% positive) or protists (82.80% positive), and those between bacteria and protists (50% positive and 50% negative) impacted the protistan community assembly. In summary, stochastic processes dominated, whereas species interactions and environmental factors also played important roles in shaping the protistan communities in drainages across the PRDUA. This study provides insights into the ecological patterns, assembly processes and species interactions underlying protistan dynamics in urban aquatic ecosystems experiencing serious anthropogenic disturbance.

Improving an Urban Cellular Automata Model Based on Auto-Calibrated and Trend-Adjusted Neighborhood

Accurately simulating urban expansion is of great significance for promoting sustainable urban development. The calculation of neighborhood effects is an important factor that affects the accuracy of urban expansion models. The purpose of this study is to improve the calculation of neighborhood effects in an urban expansion model, i.e., the land-use scenario dynamics-urban (LUSD-urban) model, by integrating the trend-adjusted neighborhood algorithm and the automatic rule detection procedure. Taking eight sample cities in China as examples, we evaluated the accuracies of the original model and the improved model. We found that the improved model can increase the accuracy of simulated urban expansion in terms of both the degree of spatial matching and the similarity of urban form. The increase of accuracy can be attributed to such integration comprehensively considers the effects of historical urban expansion trends and the influences of neighborhoods at different scales. Therefore, the improved model in this study can be widely used to simulate the process of urban expansion in different regions.

Construction and Optimization of an Urban Ecological Security Pattern Based on Habitat Quality Assessment and the Minimum Cumulative Resistance Model in Shenzhen City, China

The rapid development of urbanization has caused many ecological issues and greatly threatened the sustainable development of human society. The construction of ecological security patterns (ESPs) offers an effective way to balance ecological conservation and urbanization. This study aimed to take the highly urbanized city of Shenzhen, China, as a study area to construct an urban ESP and put forward suggestions for the urban development of ecological security. Ecological sources were identified through the Habitat Quality module in the InVEST model, and ecological corridors, strategic ecological nodes, and stepping-stone patches were extracted based on the minimum cumulative resistance (MCR) model. These elements together constituted the ESP. In particular, with the results of the continuous decline in the overall habitat quality, this study identified ten ecological sources with superior habitat quality, mainly distributed in rural woodlands, in urban green land, and in forest park patches. An optimized pattern for Shenzhen City with one axis, three belts, and four zones is proposed, with the study area divided into an ecological preservation zone, a limited development zone, an optimized development zone, and a key development zone. Moreover, forty-five ecological corridors were extracted and graded into three levels, presenting a spatial pattern of one axis and three belts. The appropriate widths of these ecological corridors were suggested to be between 30 and 60 m in Shenzhen City. In addition, we identified twenty-five ecological nodes, sixteen ecological fracture points, and sixteen stepping stones to improve the maintenance and construction of the ecological corridor network. More generally, this study demonstrates a scientific approach to identifying ESPs based on habitat quality, and can serve as a reference for the planning of urban ecological function regionalization.

Altered Food Habits? Understanding the Feeding Preference of Free-Ranging Gray Langurs Within an Urban Settlement

Urbanization affects concurrent human-animal interactions as a result of altered resource availability and land use pattern, which leads to considerable ecological consequences. While some animals have lost their habitat due to urban encroachment, few of them managed to survive within the urban ecosystem by altering their natural behavioral patterns. The feeding repertoire of folivorous colobines, such as gray langur, largely consists of plant parts. However, these free-ranging langurs tend to be attuned to the processed high-calorie food sources to attain maximum benefits within the concrete jungle having insignificant greenery. Therefore, besides understanding their population dynamics, the effective management of these urbanized, free-ranging, non-human primate populations also depends on their altered feeding habits. Here, we have used a field-based experimental setup that allows gray langurs to choose between processed and unprocessed food options, being independent of any inter-specific conflicts over resources due to food scarcity. The multinomial logit model reveals the choice-based decision-making of these free-ranging gray langurs in an urban settlement of West Bengal, India, where they have not only learned to recognize the human-provisioned processed food items as an alternative food source but also shown a keen interest in it. However, such a mismatch between the generalized feeding behavior of folivorous colobines and their specialized gut physiology reminds us of Liem's paradox and demands considerable scientific attention. While urbanization imposes tremendous survival challenges to these animals, it also opens up for various alternative options for surviving in close proximity to humans which is reflected in this study, and could guide us for the establishment of a sustainable urban ecosystem in the future.

Impacts of Urban Expansion Forms on Ecosystem Services in Urban Agglomerations: A Case Study of Shanghai-Hangzhou Bay Urban Agglomeration

Exploring impacts of urban expansion on ecosystem services has become a hot topic for regional sustainable development, while analyzing the ecological effects of urban expansion forms under different expansion intensities and city sizes is relatively rare. Therefore, taking a typical urban agglomeration, Shanghai-Hangzhou Bay Urban Agglomeration, as a case study, this study first analyzed the dynamics of urban expansion forms (leapfrogging, edge-expansion, and infilling) and four critical ecosystem services (carbon sequestration, food supply, habitat quality, and soil retention) in three periods from 1990 to 2019. The multiple linear regression model and zonal statistics analysis model were used to quantitatively identify the impacts of urban expansion forms on ecosystem services, taking into account different expansion intensities and city sizes. The results showed that the urban expansion trend in the study area experienced a morphological change from integration to diffusion and then to integration in 1990–2019; edge-expansion was the dominant expansion form. Food supply decreased continuously while other ecosystem services had fluctuating changes, and they all had spatial heterogeneity. The leapfrogging, edge-expansion, and infilling all had negative impacts on ecosystem services, and among them, the edge-expansion intensity had the highest influence degree in the early expansion, and the leapfrogging intensity occupied the dominant position in all influences with the expansion of urban scales. For different city sizes, the impact of edge-expansion in large-scale cities was greater than in small-scale cities in the early expansion, and the impact of leapfrogging in large-scale cities exceeded the edge-expansion in the subsequent expansion. These findings will help further understand the influential mechanisms between urban expansion and ecosystem services and provide a scientific basis for formulating reasonable urban planning.

Construction and Optimization of Ecological Security Pattern Based on Spatial Syntax Classification—Taking Ningbo, China, as an Example

Urbanization is the development trend of all countries in the world, but it has caused considerable ecological problems that need to be alleviated by building ecological security patterns. This study took Ningbo as an example to construct and optimize an ecological security pattern. We analyzed land use types, normalized difference vegetation index, and landscape connectivity for ecological sources selection. In constructing the resistance surface, we considered natural and socio-economic factors. On this basis, we identified ecological corridors based on a minimum cumulative resistance model. Finally, the ecological security pattern was optimized through space syntax. Results showed that Ningbo has 18 ecological sources, with an area of 3051.27 km2 and 29 ecological corridors, with a length of 1172.18 km. Among them, 11 are first-level, 10 are second-level, and 8 are third-level corridors. After optimization, the area and protection cost of the ecological security pattern were significantly reduced, which can effectively alleviate the trade-off between ecological protection and economic development. This research can provide a reference for the construction and optimization of ecological security patterns and has reference significance for ecological protection in rapidly urbanized areas.

The Effects of Urban Forms on the PM2.5 Concentration in China: A Hierarchical Multiscale Analysis

For a better environment and sustainable development of China, it is indispensable to unravel how urban forms (UF) affect the fine particulate matter (PM2.5) concentration. However, research in this area have not been updated consider multiscale and spatial heterogeneities, thus providing insufficient or incomplete results and analyses. In this study, UF at different scales were extracted and calculated from remote sensing land-use/cover data, and panel data models were then applied to analyze the connections between UF and PM2.5 concentration at the city and provincial scales. Our comparison and evaluation results showed that the PM2.5 concentration could be affected by the UF designations, with the largest patch index (LPI) and landscape shape index (LSI) the most influential at the provincial and city scales, respectively. The number of patches (NP) has a strong negative influence (-0.033) on the PM2.5 concentration at the provincial scale, but it was not statistically significant at the city scale. No significant impact of urban compactness on the PM2.5 concentration was found at the city scale. In terms of the eastern and central provinces, LPI imposed a weighty positive influence on PM2.5 concentration, but it did not exert a significant effect in the western provinces. In the western cities, if the urban layout were either irregular or scattered, exposure to high PM2.5 pollution levels would increase. This study reveals distinct ties of the different UF and PM2.5 concentration at the various scales and helps to determine the reasonable UF in different locations, aimed at reducing the PM2.5 concentration.

Multi-Scenario Analysis of Habitat Quality in the Yellow River Delta by Coupling FLUS with InVEST Model

The past decades were witnessing unprecedented habitat degradation across the globe. It thus is of great significance to investigate the impacts of land use change on habitat quality in the context of rapid urbanization, particularly in developing countries. However, rare studies were conducted to predict the spatiotemporal distribution of habitat quality under multiple future land use scenarios. In this paper, we established a framework by coupling the future land use simulation (FLUS) model with the Intergrated Valuation of Environmental Services and Tradeoffs (InVEST) model. We then analyzed the habitat quality change in Dongying City in 2030 under four scenarios: business as usual (BAU), fast cultivated land expansion scenario (FCLE), ecological security scenario (ES) and sustainable development scenario (SD). We found that the land use change in Dongying City, driven by urbanization and agricultural reclamation, was mainly characterized by the transfer of cultivated land, construction land and unused land; the area of unused land was significantly reduced. While the habitat quality in Dongying City showed a degradative trend from 2009 to 2017, it will be improved from 2017 to 2030 under four scenarios. The high-quality habitat will be mainly distributed in the Yellow River Estuary and coastal areas, and the areas with low-quality habitat will be concentrated in the central and southern regions. Multi-scenario analysis shows that the SD will have the highest habitat quality, while the BAU scenario will have the lowest. It is interesting that the ES scenario fails to have the highest capacity to protect habitat quality, which may be related to the excessive saline alkali land. Appropriate reclamation of the unused land is conducive to cultivated land protection and food security, but also improving the habitat quality and giving play to the versatility and multidimensional value of the agricultural landscape. This shows that the SD of comprehensive coordination of urban development, agricultural development and ecological protection is an effective way to maintain the habitat quality and biodiversity.

An Optimized Approach for Extracting Urban Land Based on Log-Transformed DMSP-OLS Nighttime Light, NDVI, and NDWI

Quantitative and accurate urban land information on regional and global scales is urgently required for studying socioeconomic and eco-environmental problems. The spatial distribution of urban land is a significant part of urban development planning, which is vital for optimizing land use patterns and promoting sustainable urban development. Composite nighttime light (NTL) data from the Defense Meteorological Program Operational Line-Scan System (DMSP-OLS) have been proven to be effective for extracting urban land. However, the saturation and blooming within the DMSP-OLS NTL hinder its capacity to provide accurate urban information. This paper proposes an optimized approach that combines NTL with multiple index data to overcome the limitations of extracting urban land based only on NTL data. We combined three sources of data, the DMSP-OLS, the normalized difference vegetation index (NDVI), and the normalized difference water index (NDWI), to establish a novel approach called the vegetation–water-adjusted NTL urban index (VWANUI), which is used to rapidly extract urban land areas on regional and global scales. The results show that the proposed approach reduces the saturation of DMSP-OLS and essentially eliminates blooming effects. Next, we developed regression models based on the normalized DMSP-OLS, the human settlement index (HSI), the vegetation-adjusted NTL urban index (VANUI), and the VWANUI to analyze and estimate urban land areas. The results show that the VWANUI regression model provides the highest performance of all the models tested. To summarize, the VWANUI reduces saturation and blooming, and improves the accuracy with which urban areas are extracted, thereby providing valuable support and decision-making references for designing sustainable urban development.

Quantifying Spatiotemporal Changes in Human Activities Induced by COVID-19 Pandemic Using Daily Nighttime Light Data

The COVID-19 pandemic caused drastic changes in human activities and nighttime light (NTL) at various scales, providing a unique opportunity for exploring the pattern of the extreme responses of human community. This study used daily NTL data to examine the spatial variations and temporal dynamics of human activities under the influence of COVID-19, taking Chinese mainland as the study area. The results suggest that the change in the intensity of NTL is not correlated to the number of confirmed cases, but reflects the changes in human activities and the intensity of epidemic prevention and control measures within a region. During the outbreak period, the major provincial capitals and urban agglomerations were affected by COVID-19 more than smaller cities. During the recovery, different regions showed different recovery processes. The cities in West and Northeast China recovered steadily while the recovery in coastal cities showed relatively greater fluctuations due to an increase in imported cases. Wuhan, the most seriously affected city in China, did not recover until the end of March. Nevertheless, as of 31 March, the overall NTL across China had recovered to an 89.5% level of the same period in the previous year. The high consistency between the big data of travel intensity and NTL further proved the validity of the results of this study. These findings imply that daily NTL data are effective for rapidly monitoring the dynamic changes in human activities, and can help evaluate the effects of control measures on human activities during major public health events.

Understanding Urban Expansion on the Tibetan Plateau over the Past Half Century Based on Remote Sensing: The Case of Xining City, China

The Tibetan Plateau (TP) is an important area that affects global sustainable development. Quantifying spatiotemporal patterns of urbanization is crucial for maintaining the sustainability on the TP. This study took Xining City, the largest city on the TP, as an example to understand the urban expansion in this region in the past 50 years. We combined the high-resolution spy satellite data and China’s long-term urban land dataset (CULD) to quantify the urban expansion of Xining City. The object-oriented random forest classification was performed to extract urban land from spy satellite data in 1969, and the inter-annual correction was used to combine urban land information from 1969 to 2017. We found that the proposed approach can accurately quantify the urban expansion of Xining City over the past half century with an overall accuracy of 91% and a kappa coefficient of 0.86. Such high accuracy benefits from the fine resolution of spy satellite data and the consistency of CULD. We also found that Xining City experienced accelerated and fragmented urban sprawl to higher altitude areas, as a result of socioeconomic development and topographical limitations. The acceleration of urban expansion was more obvious, and the urban landscape fragmentation was more serious at high altitude areas. Such urban expansion encroached on cropland and grassland, and caused increased risks of landslides and other geological disasters. Therefore, Xining City urgently needs to promote the development of compact cities to control urban sprawl at higher altitude areas and provide a reference for improving urban sustainability across the TP. In this study, we analyzed the urban expansion of Xining city from 1969 to 2017, and provided a reliable way to understand the long-term spatiotemporal urbanization based on remote sensing, which has the potential for wide applications. In addition, the extracted urban information can help to improve the urban sustainability of Xining City and the entire TP.

An Improved Correction Method of Nighttime Light Data Based on EVI and WorldPop Data

Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) data has the shortcomings of discontinuous and pixel saturation effect. It was also incompatible with the Soumi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP/VIIRS) data. In view those shortcomings, this research put forward the WorldPop and the enhanced vegetation index (EVI) adjusted nighttime light (WEANTL) using EVI and WorldPop data to achieve intercalibration and saturation correction of DMSP/OLS data. A long time series of nighttime light images of china from 2001 to 2018 was constructed by fitting the DMSP/OLS data and NPP/VIIRS data. Corrected nighttime light images were examined to discuss the estimation ability of gross domestic product (GDP) and electric power consumption (EPC) on national and provincial scales, respectively. The results indicated that, (1) after correction, the nighttime light (NTL) data can guarantee the growth trend on national and regional scales, and the interannual volatility of the corrected NTL data is lower than that of the uncorrected NTL data; (2) on the national scale, compared with the established model of NTL data and GDP data (NTL-GDP), the determination coefficient (R2) and the mean absolute relative error (MARE) are 0.981 and 8.518%. The R2 and MARE of the established model of NTL data and EPC data (NTL-EPC) were 0.990 and 4.655%; (3) on the provincial scale, the R2 and MARE of NTL-GDP model under the provincial units are 0.7386 and 38.599%. The R2 value and MARE of NTL-EPC model are 0.8927 and 29.319%; (4) on the provincial scale, the R2 and MARE of NTL-GDP model on time series are 0.9667 and 10.877%. The R2 and MARE of NTL-GDP model on time series are 0.9720 and 6.435%; the established TNL-GDP and TNL-EPC models with 30 provinces data all passed the F-test at the 0.001 level; (5) the prediction accuracy of GDP and EPC on time series was nearly 100%. Therefore, the correction method provided in this research can be applied in estimating the GDP and EPC on multiple scales reliably and accurately.

Evaluating the Impacts of Future Urban Expansion on Surface Runoff in an Alpine Basin by Coupling the LUSD-Urban and SCS-CN Models

Effective evaluations of the future urban expansion impacts (UEI) on surface runoff in alpine basins are full of challenges due to the lack of reliable methods. Our objective was to provide a new approach by coupling the Land Use Scenario Dynamics-urban (LUSD-urban) and Soil Conservation Service-Curve Number (SCS-CN) models to estimate the future UEI on surface runoff. Taking the Qinghaihu-Huangshui basin (QHB) in the Tibetan Plateau, China, as an example, we first applied the SCS-CN model to quantify the surface runoff in 2000 and 2018 and analyzed the changes in surface runoff. Next, we applied the LUSD-urban model to simulate urban expansion under five localized shared socioeconomic pathways (SSPs) from 2018 to 2050. Finally, we assessed the UEI on surface runoff in the QHB from 2018 to 2050. We found that coupling the LUSD-urban and SCS-CN models could effectually evaluate the future UEI on surface runoff. Compared with the combination of the Future Land Use Simulation (FLUS) and SCS-CN models, our method reduced the absolute evaluation errors from 3.40% and 11.78% to 0.18% and 4.23%, respectively. In addition, the results showed that future urban expansion will have severe impacts on surface runoff in the valley region. For example, as a result of urban expansion, the surface runoff in the Huangzhong, Xining, and Datong catchments will increase by 4.90–9.01%, 4.25–7.36%, and 2.33–3.95%, respectively. Therefore, we believe that the coupled model can be utilized to evaluate the future UEI on surface runoff in alpine basins. In addition, the local government should pay attention to flood risk prevention, especially in the valley region, and adopt reasonable urban planning with soft and hard adaptation measures to promote the sustainable development of alpine basins under rapid urban expansion.

Analyzing Land-Use Change Scenarios for Ecosystem Services and their Trade-Offs in the Ecological Conservation Area in Beijing, China

It is generally believed that land-use changes can affect a variety of ecosystem services (ES), but the relationships involved remain unclear due to a lack of systematic knowledge and gaps in data. In order to make rational decisions for land-use planning that is grounded in a systematic understanding of trade-offs between different land-use strategies, it is very important to understand the response mechanisms of various ecosystem services to changes in land-use. Therefore, the objective of our study is to assess the effects of land-use change on six ecosystem services and their trade-offs among the ecosystem services in the ecological conservation area (ECA) in Beijing, China. To do this, we projected future land-use in 2030 under three different scenarios: Business as Usual (BAU), Ecological Protection (ELP), and Rapid Urban Development (RUD), using GeoSOS-FLUS model. Then, we quantified six ecosystem services (carbon storage, soil conservation, water purification, habitat quality, flood regulation, and food production) in response to land-use changes from 2015 to 2030, using a spatially explicit InVEST model. Finally, we illustrated the trade-offs and/or synergistic relationships between each ecosystem service quantified under each of the different scenarios in 2030. Results showed that built-up land is projected to increase by 281.18 km2 at the cost of water bodies and cultivated land from 2015 to 2030 under the RUD scenario, while forest land is projected to increase by 152.38 km2 under the ELP scenario. The carbon storage, soil conservation, habitat quality, and the sum of ecosystem services (SES) would enrich the highest level under the ELP scenario. Land-use strategies that follow the ELP scenario can better maintain the ecosystem services and sustainable development of natural and social economic systems.

Can the establishment of ecological security patterns improve ecological protection? An example of Nanchang, China

Establishing ecological security patterns provides new ideas for maintaining regional ecological security. Methods for establishing these patterns have been extensively investigated in several studies, but the ecological protection effects of these patterns need further examination. Nanchang is the capital city of Jiangxi province and a typical representative of rapidly developing cities. With the proposal of an ecological environment protection plan for Nanchang metropolitan area, the coordinated development of ecology, economy and society has become the local development goal. This study used Nanchang City as an example for the establishment of an ecological security pattern through the circuit theory. The ecological sources of a 1068.56 km² location and 20 ecological corridors with a total area of 957.39 km² were identified. Three development scenarios in 2015-2040 were set up, namely, unrestricted development (UD), core area protection (CP) and ecological security pattern restriction (ESPR) scenarios. The UD scenario followed the land expansion rate from 2010 to 2015. The CP scenario used a nature reserve as a forbidden conversion area. Under the ESPR scenario, ecological security pattern was regarded as a prohibited conversion area. The CLUMondo model was used in simulating land use and evaluating the ecological protection effects of the scenarios. Through comparison, we determined that the ecological security indices under UD, CP and ESPR were 0.230, 0.242 and 0.249, respectively, from the perspective of the overall ecological security of the region. In the evaluation of the landscape characteristics of EL, under ESPR, the landscape connectivity was the best. The detailed analysis results showed that the ecological security pattern not only could protect the regional ecological security on the regional scale but also had an outstanding protection effect on the local scale. In summary, compared with the UD and CP scenarios, ecological security patterns had a better effect on regional ecological protection.

Uncovering Ecosystem Services of Expropriated Land: The Case of Urban Expansion in Bahir Dar, Northwest Ethiopia

In Ethiopia, urban expansion happens at high rates and results in land expropriations often at the cost of agriculture and forests. The process of urban expansion does not include assessment of ecosystem services (ES). This has been causing unintended environmental problems. This study aims to uncover ES of three most important land use types (cropland, agroforestry, and grassland) that are threatened by land expropriation for urban expansion in Bahir Dar City. The study applied a participatory approach using community perception and expert judgments (N = 108). Respondents were asked to locate their perceptions on the use of 35 different ES, and then to evaluate the potential of the land use. Respondents were shown to have the ability to differentiate between ES and land use in terms of their potential to deliver ES. The results show that agroforestry is expected to have a high relevant potential to deliver 31% of all ES, but cropland 20% and grassland 14%. Food, fodder, timber, firewood, fresh water, energy, compost, climate regulation, erosion prevention, and water purification and treatment were identified as the ten most important services. It is not only the provisioning services that are being supplied by the land use types which are expropriated for urbanization, but also regulating, supporting and cultural services. To ensure sustainable urban land development, we suggest the consideration of the use of ES and the potential of the land use to supply ES when making land use decisions, including land expropriation for urban expansion.