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.

Urbanization reduces diversity, simplifies community and filter bird species based on their functional traits in a tropical city

Understanding how organisms are coping with major changes imposed by urban intensification is a complex task. In fact, our understanding of the impacts of urbanization on biodiversity is scarce in the global south compared to the north. In this study, we evaluated how bird communities are affected by impact of urban intensification in a tropical city. Thus, we assessed whether increased urban intensification 1) jeopardizes bird diversity (taking into account taxonomic-TD, phylogenetic-PD, and functional-FD dimensions), 2) drives changes in bird community composition and enables the detection of indicator species of such impact, and 3) leads to changes in bird functional traits linked to reproduction, resource acquisition, and survival. We found that urban intensification has a direct impact on the bird community, reducing all three types of diversity. Communities in areas of greater urban intensity are represented by fewer species, and these species are PD and FD less distinct. In addition, we detected at least ten species of areas of lower urban intensity that proved to be more sensitive to urban intensification. With regard to bird traits, we found no significant responses from reproductive, habitat use and feeding variables. Body weight and tail length were the only variables with significant results, with higher urbanization intensity areas selecting for species with lower weights and longer tails. Given the global biodiversity loss we are observing, this information can guide urban managers and planners in designing urban landscapes to maintain biodiversity in cities.

Characteristics and effects of global sloping land urbanization from 2000 to 2020

Cities usually expand on flat land. However, in recent decades, the increasing scarcity of available flat land has compelled many cities to expand to sloping land (sloping land urbanization, SLU), and the understanding for global SLU is still unclear. This study, based on the currently available high-precision global Digital Elevation Model (FABDEM) and global land cover dataset (GlobeLand30), investigated the characteristics and impacts of SLU in 26,402 urban residential areas worldwide from 2000 to 2020. Results show that the total area of SLU globally is 16,383 km2, accounting for 9.54 % of the overall urban expansion. This phenomenon is widespread globally and relatively concentrated in a few countries, with 42.78 %, 24.35 %, and 21.83 % of the area coming from cultivated land, forest, and grassland respectively. Global SLU has accommodated 34.78 million urban population, and indirectly protected 8922 km2 of flat cultivated land, while causing a net loss of 4372 km2 of green ecological land. Deliberately balancing the dual effects of SLU is crucial for advancing sustainable global urbanization.

Spatial patterns of urban expansion and cropland loss during 2017-2022 in Guangdong, China

Urban expansion often occurs at the expense of cropland loss, posing challenges to sustainable urban growth and food security. However, detailed investigations into urban expansion and cropland loss remain limited, particularly in regions with varying levels of urbanization. Here, we take Guangdong Province, China, as a case study to exemplify how urban expansion affects cropland using remotely sensed land use products. We adopted geospatial analysis, correlation indicators, and landscape metrics to uncover their spatial relationships at 10-m spatial resolutions. Results showed that urban areas increased by 6335 km2 while cropland decreased by 3780 km2 from 2017 to 2022. Notably, 41 % of newly expanded urban areas were from croplands, and 45 % of lost croplands were converted to urban areas. Western Guangdong experienced the largest extent of urban expansion and cropland loss, emerging as a hotspot region in recent years. Additionally, our analysis observed the increasing compactness of urban areas and the growing fragmentation of cropland landscapes over time. These findings shed light on the intricate dynamics between urban expansion and cropland loss in rapidly urbanizing regions, which provide valuable insights for sustainable urban development, agricultural practice, and land management in the future.

Dynamics of urban expansion and form changes impacting carbon emissions in the Guangdong-Hong Kong-Macao Greater Bay Area counties

Cities are the main carriers of social and economic development, and they are also important sources of carbon emissions. Therefore, it is essential to explore the impact of urban expansion and form changes on carbon emissions. Here, we attempted to analyzes the relationship between urban expansion and carbon emissions at the county level in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) from 1997 to 2017. It further decomposes the driving effects of carbon emissions from multiple factors, and considers the spatial heterogeneity between different urban form changes and driving effects. The results show that: The relationship between urban expansion and carbon emissions in the GBA has gone through three stages from 1997 to 2017, with 2012 as a turning point. Optimization of economic development models and strict protection of the ecological environment can effectively control carbon emissions. After 2012, the economic development effect (GE) and population scale effect (PE) are the driving factors of carbon emissions, while the carbon emission intensity effect (CE) and urban land intensity effect (UE) are the inhibitory factors of carbon emissions. The contribution rate of UE to carbon emission reduction can reach 86 %. The impact of urban form changes on carbon emissions has spatial heterogeneity. The changes in urban form have a significant impact on the carbon emissions of counties in Dongguan and Shenzhen. The increase in fragmentation indirectly promotes carbon emissions. In 2007-2012, the increase in centrality significantly weakened the economic development effect, which is conducive to emission reduction. After 2007, the increase in compactness in counties in the eastern part of the GBA, including Zhongshan and Zhuhai, is not conducive to emission reduction.

Employing post classification comparison to detect land use cover change patterns and quantify conversions in Abakaliki LGA Nigeria from 2000 to 2022

Rapid urbanization is restructuring landscapes across sub-Saharan Africa. This study employed post-classification comparison of multi-temporal Landsat imagery to characterize land cover changes in Abakaliki Local Government Area, Ebonyi State, Nigeria between 2000 and 2022, addressing the need for empirical baselines to guide sustainable planning. Four classes were considered and images classified with overall accuracy of 95% for the year 2000 and 97% for the year 2022. Notably, 21,000 hectares of vegetation were lost, while built-up and bare land increased by 7500 and 13,700 hectares respectively. Spatial patterns revealed built-up encroachment from vegetation and bare land; this establishes the first standardized quantification of Abakaliki LGA's shifting landscape, with results supporting compact development models while conserving ecological services under ongoing transformations. The study makes a significant contribution by establishing an empirical baseline characterizing Nigeria's urbanization trajectory essential for evidence-based stewardship of regional resources and livelihoods in a period of accelerating change.

Telecoupling between urban expansion and forest ecosystem service loss through cultivated land displacement: A case study of Zhejiang Province, China

Urbanization can either directly occupy forests or indirectly lead to forest loss elsewhere through cultivated land displacement, resulting in further forest fragmentation and ecosystem service (ES) loss. However, the effects of urban expansion on forest area and ESs are unknown, and this is especially true for indirect effects. Taking Zhejiang Province, China, a typical deforested province, as an example, this study quantified the direct and indirect effects of urban expansion on forest area and five ESs (timber yield, water yield, carbon sequestration, soil conservation, and biodiversity) from 2000 to 2020, explored the relationship between forest structure (forest proportion, mean patch area, edge density, and mean euclidean nearest neighbor distance) change and ESs, and revealed the telecoupling of urban expansion and forest loss and cascade effects among urbanization, deforestation, forest structure, and ESs. The results indicated that the indirect forest loss (4.30%-6.15%) caused by cultivated land displacement due to urban expansion was larger than the direct forest loss (2.42%). Urban expansion has a greater negative impact on carbon sequestration (6.40%-8.20%), water yield (6.08%-7.78%), and biodiversity (5.79%-7.44%) than on timber yield (4.77%-6.17%) and soil conservation (4.43%-5.77%). The indirect forest ES loss was approximately 2.83-4.34 times greater than the direct forest ES loss. Most forest ESs showed a nonlinear significant positive correlation with changes in forest proportion and mean patch area and a significant nonlinear negative correlation with changes in edge density and mean Euclidean nearest neighbor distance (p < 0.05). There is telecoupling between urban expansion in one region and forest ES loss in other distant regions. This study contributes to guiding sustainable forest conservation and management globally.

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.

The spatiotemporal assessments for tidal flat erosion associated with urban expansion in the conterminous coastal United States from 1985 to 2015

Tidal flats are of great importance to coastal residents and environments, which are recently facing unprecedented challenges due to massive urban expansions. While some case studies have been conducted in small areas, it is yet to come a picture to examine the issue at the nationwide level. To fill this void, it is necessary to reconsider whether the analytical and statistical methods used in the previous studies are still appropriate to the larger scales, which accordingly needs to be refined and updated. Aiming at this issue, this study implemented a justification for the conterminous United States, in which nearly 70 % of the counties by the seashore with intensified tidal flats in 1985 were selected to conduct a comprehensive assessment. Based on the 156 selected counties, this paper firstly analyzed the spatiotemporal change patterns of tidal flats and urban extents from 1985 to 2015, and then combined these results and implemented a series of correlation assessments between tidal flat loss and urban expansion. As a result, we found that urban expansions in the conterminous coastal United States have not only substantially squeezed the space of tidal flats, but also significantly affected the surrounding tidal flat environments during the three decades.

Relocating built-up land for biodiversity conservation in an uncertain future

Land use changes associated with habitat loss, fragmentation, and degradation exert profoundly detrimental impacts on biodiversity conservation. Urban development is one of the prevailing anthropogenic disturbances to wildlife habitat, because these developments are often considered permanent and irreversible. As a result, the potential benefits of built-up land relocation for biodiversity conservation have remained largely unexplored in environmental management practices. Here, we analyze recent built-up land relocation in Shanghai and explore how such restoration programs can affect future land change trajectories with regards to biodiversity conservation. Results show that 187.78 km2 built-up land in Shanghai was restored to natural habitat between 2017 and 2020. Further simulation analysis highlights that relocating built-up land can substantially promote conserve biodiversity. In particular, there would be less habitat loss, better natural habitat quality and more species habitat-suitable range under the scenarios with built-up land relocation. Species extinction assessment suggest that amphibians, mammals, and reptiles will all have an increasingly high extinction risk without built-up land relocation. However, there will even be a marginal decrease in extinction risk over time for mammals and reptiles if the relocation of built-up land is permitted, but still a moderate increase in extinction risk for amphibians. This study highlights the importance of incorporating rigorous conservation planning prior to development activities, thereby underpinning a sustainable approach to environmental management.

Spatio-temporal dynamics and human-land synergistic relationship of urban expansion in Chinese megacities

Megacities play important roles in countries' politics, economy, culture, etc. Exploring the law of urban expansion of megacities has important reference for sustainable urbanization. Here, the spatiotemporal dynamics of urban expansion were quantified analyzed in 21 Chinese megacities from 2000 to 2020 with quantitative measurement indicators and explored the human-land synergistic relationship used the decoupling model. Results are as follows: (1) China's megacities experienced significant expansion, and urban expansion characterized as rapid initially but slowed down thereafter. (2) Urban expansion in megacities was characterized as having significant spatial differences, and rapidly expanding megacity centers moved from eastern to midwestern China. (3) Urban spatial expansion of megacities was mainly an enclave type in 2000-2010 and marginal type in 2010-2020. (4) The main type of human-land synergistic relationship in megacities were weak decoupling, there is a significant increase in expansive coupling and expansive negative decoupling in 2010-2020; (5) Lastly, human-land synergy relationship in most megacities was uncoordinated based on the per capita urban land area and decoupling type. The findings of this study can deepen the understanding of the characteristics and quality of urbanization evolution, and provides reference for high-quality development planning and decision-making in megacities.

Urban expansion patterns and their driving forces analysis: a comparison between Chengdu-Chongqing and Middle Reaches of Yangtze River urban agglomerations

Urban agglomerations have emerged as the primary drivers of high-quality economic growth in China. While recent studies have examined the urban expansion patterns of individual cities, a comparative study of the urban expansion patterns of urban agglomerations at two different scales is required for a more comprehensive understanding. Thus, in this study, we conduct a two-scale comparative analysis of urban expansion patterns and their driving factors of the two largest urban agglomerations in western and central China, i.e., Chengdu-Chongqing urban agglomeration (CCUA) and the Middle Reaches of Yangtze River urban agglomerations (MRYRUA) at both the urban agglomeration and city levels. We investigate the urban expansion patterns of CCUA and MRYRUA between 2000 and 2020 using various models, including the urban expansion rate, fractal dimension, modified compactness, and gravity-center method. Then we use multiple linear regression analysis and geographically weighted regression (GWR) to explore the magnitude and geographical differentiation of influences for economic, demographic, industrial structure, environmental conditions, and neighborhood factors on urban expansion patterns. Our findings indicate that CCUA experienced significantly faster urban growth compared to MRYRUA. There is an excessive concentration of resources to megacities within the CCUA, whereas there is a lack of sufficient collaboration among the three provinces within the MRYRUA. Additionally, we identify significant differences in the impacts of driving forces of CCUA and MRYRUA, as well as spatial heterogeneity and regional aggregation in the variation of their strength. Our two-scale comparative study of urban expansion patterns will not only provide essential reference points for CCUA and MRYRUA but also serve as valuable insights for other urban agglomerations in China, enabling them to promote sustainable urban management and foster integrated regional development.

Impact of global urban expansion on the terrestrial vegetation carbon sequestration capacity

Continuous urban expansion has a negative impact on the potential of terrestrial vegetation. Till now, the mechanism of such impact remains unclear, and there have been no systematic investigations. In this study, we design a theoretical framework by laterally bridging urban boundaries to explain the distress of regional disparities and longitudinally quantify the impacts of urban expansion on net ecosystem productivity (NEP). The findings demonstrate that global urban expanded by 37.60 × 10⁴ km² during 1990-2017, which is one of the causes of vegetation carbon loss. Meanwhile, certain climatic changes (e.g., rising temperature, rising CO₂, and nitrogen deposition) caused by urban expansion indirectly boosted vegetation carbon sequestration potential through photosynthetic enhancement. The direct decrease in NEP due to the urban expansion (occupying 0.25 % of the Earth's land area) offsets the 1.79 % increase due to the indirect impact. Our findings contribute to a better understanding of the uncertainty associated with urban expansion towards carbon neutrality and provide a scientific reference for sustainable urban development worldwide.

Governance matters: Urban expansion, environmental regulation, and PM2.5 pollution

Increasing PM2.5 pollution in urban expansion threatens citizens' health. Environmental regulation has proven to be an effective tool to directly combat PM2.5 pollution. However, whether it can moderate the impacts of urban expansion on PM2.5 pollution, in the context of rapid urbanization, is an interesting and unexplored topic. Therefore, this paper constructs a Drivers-Governance-Impacts framework and explores in depth the interactions among urban expansion, environmental regulation, and PM2.5 pollution. Based on 2005-2018 sample data from the Yangtze River Delta region, the estimation results of the Spatial Durbin model imply that (1) urban expansion has an inverse U-shaped association with PM2.5 pollution. The positive correlation may reverse when the ratio of urban built-up land area hits 0.21. (2) Of the three environmental regulations, investment in pollution control has little impact on PM2.5 pollution. Pollution charges and public attention exhibit a U-shaped and inverted U-shaped relationship with PM2.5 pollution, respectively. (3) In terms of moderating effects, pollution charges can exacerbate PM2.5 pollution from urban expansion, while public attention can inhibit it through its monitoring role. Therefore, we suggest that cities adopt differentiated strategies of urban expansion and environmental protection according to their urbanization levels. Meanwhile, appropriate formal regulation and strong informal regulation will help improve air quality.

The effects of urban growth on natural areas: the three metropolitan areas in Türkiye

Today, more than half of the world's population of 7.6 billion lives in cities, and by 2030, it is estimated that the population of urban residents will exceed 5 billion worldwide. Since growth in cities destroys agriculture, forests, and wetlands, an increasing carbon footprint brings many environmental problems, such as global climate change. Among the developing countries, Türkiye's largest cities have been experiencing a rapid urbanization process. The study aims to analyze the adverse effects of urban growth in Türkiye's largest metropolises on natural areas such as agriculture, forests, and wetlands. In this context, the Istanbul, Ankara, and Izmir metropolitan areas have been determined as case areas. The correlation between the changes in the land cover and the urban expansion processes of the three big cities from 1990 to 2018 has been systematically analyzed in the GIS environment using Corine land cover program data. The study indicates the devastating effect of urban growth on agricultural areas in all three case areas. In addition, the urbanization pressure in Istanbul continues to destroy northern forests.

Urban-rural disparities of carbon storage dynamics in China's human settlements driven by population and economic growth

China has experienced a rapid expansion of human settlement in both urban and rural areas over the past three decades. Regarding the impacts on carbon storage, previous studies that only focus on certain ecosystems cannot reflect urban-rural disparities, resulting in the carbon storage changes in human settlement remaining unknown. In this study, we aimed to explore China's urban-rural disparities in human settlement expansion and direct impacts on carbon storage by using the big Earth data technology. The results showed that from 1990 to 2018, the total amount of China's human settlement expansion reached 175,703.80 km², and the inner-city, peri-urban, and rural components accounted for 21.00 %, 20.18 %, and 58.82 %, respectively. Along with the general tendency of impervious surface area (ISA) growth, there was more soil organic carbon (SOC) (1254.33 TgC) being sealed beneath ISA (0-100 cm depth), compared to a huge reduction in vegetation biomass carbon (VBC) (91.44 TgC) during the study period. The results further indicated that the change density of either VBC or SOC presented a slightly rising trend along the urban-rural gradient, due to the increasingly common encroachment on vegetation and soil types with higher carbon content. We also found that socioeconomic drivers had a greater influence in urban areas than rural areas, and the related correlation exhibited a descending trajectory in both urban and rural areas. There is thus an urgent need to preserve lands with abundant carbon storage and contain the waste of land resources in rural areas. All stakeholders should pay more attention to concerted and targeted regulation policies for well-planned and eco-friendly human settlement expansion such as enhancing rural land use efficiency and promoting large-scale afforestation and continuous urban greening, which will be critical not only for guiding sustainable urbanization all over China but also for mitigating climate change for the entire world.

Mapping and evaluating sustainable and unsustainable urban areas for ecological management towards achieving low-carbon city: an empirical study of Asir Region, Saudi Arabia

Urbanisation can cause a variety of environmental and health issues, which has prompted experts to evaluate degraded areas and develop management strategies aimed at promoting urban sustainability and reducing carbon emissions. In low-carbon cities, sustainable urban areas have low carbon emission and prioritised carbon reduction by implementing sustainable transportation, green infrastructure, and energy-efficient buildings. On the other hand, unsustainable urban areas tend to lack these priorities and rely heavily on non-renewable energy sources and have high carbon emission. Therefore, this study aims to identify the most sustainable and unsustainable regions in the Abha-Khamis Mushayet Twin City region of Saudi Arabia in respect to urbanisation and carbon emission during the period between 1990 and 2020. To do so, we used Landsat datasets to create land use land cover (LULC) maps and then calculated carbon storage, emission, and absorption using InVest software. Additionally, the study examined micro-climatic conditions by calculating the urban heat island (UHI) effect, which allowed determining sustainable and unsustainable regions by comparing the UHI model and carbon similarity and mismatch model using coupling coordination degree model (CCDM). The study found that during the last three decades, the LULC pattern of the region underwent significant alterations, resulting in a substantial decline in carbon storage from 710,425 Mg C/hm² in 1990 to approximately 527,012.9 Mg C/hm² in 2020. Conversely, carbon emissions were observed to be very high in areas with high built-up density, with emission levels exceeding 20 tons per annum. Whilst the areas of excess carbon have decreased significantly, the areas of excess carbon emission have increased over time, resulting in the UHI effect due to high greenhouse gases. By comparing the UHI and carbon similarity and mismatch model, the researchers found that over 280 km² of the study area is unsustainable and has increased since 1990. In contrast, only about 410 km² of the study area is currently sustainable. To promote sustainability, the study recommends several strategies such as carbon capture, utilisation, and storage; green infrastructure; and the use of renewable energy to manage carbon emissions.

Landslide susceptibility prediction considering land use change and human activity: A case study under rapid urban expansion and afforestation in China

China has been subject to rapid urban expansion and afforestation since the economic reform in 1978. However, the influence of land use and cover changes (LUCCs) and human activities on landslide occurrence is often ignored in landslide susceptibility mapping and zonation (LSMZ). In this study, Enshi City, China, was selected as the study area because of dramatic LUCCs during the last two decades. This study divided landslide affecting factors (AFs) into base affecting factors (BAFs) and land-related affecting factors (LAFs), and 15 landslide susceptibility maps were created by three different types of models. The results showed that the combination 6 of heuristic multi-layer perceptron model with LAFs (HMLP-LAFC₆) model obtained the highest model performance. In addition, any factor combinations of HMLP-LAF model outperformed other two types of models, and the use of land use and cover (LULC) in different periods as well as LUCCs may significantly impact the model performance. Given that land policy adjustments are normally core drivers of LUCC in China, a land planning based LSMZ framework was proposed, which is suitable for LSMZ in rapid LUCC regions with radical land policies. Finally, this paper strongly suggests developing more hybrid models that coupling dynamic AFs, clarifying the quantitative boundaries of time-irrelevant and dynamic AFs, increasing the accuracy of LULC prediction, and improving the abilities of bilateral understanding for effective, integrated, and systematic management of land planning and landslide hazards.

Ecological consequences of urban blue space transformation

This study presents the ecological consequences of the blue space conversion and its qualitative degradation in the English Bazar Municipality (EBM) and its surrounding area. The primary blue spaces of the area, the marshy wetland called Chatra and Mohananda river, are the most affected due to urban activities like built-up expansion and sewage and wastewater discharge. Built-up development encroached more than 300 m within wetland territory and caused a 0.57 km² conversion of wetland area. It is also evident within the bed of the Mohananda river. Agriculture also caused the conversion of the blue space. As a result, the wetland's ecosystem service value (ESV) was reduced by 12.7%, along with a reduction of cultural services by 27.86%. The massive pouring of sewage and wastewater caused hyper-eutrophication in almost the entire wetland area. The trophic state index (TSI) value increased significantly in the last 10 years, causing high growth and areal expansion of water hyacinth. The expanding settlements and agricultural land that captured the river channel face inundation vulnerability during peak discharge. Extreme danger level discharge causes floods in the extensive municipality area. The areal encroachment, water extraction, sewage and wastewater discharge, and water quality deterioration caused severe hydro-ecological degradation of the river. Since blue space is critically essential for urban environmental health, these ecological consequences can cause a crisis for urban wellbeing. Therefore, the anthropogenic adversities towards the urban blue space must be restricted, and the blue space's ecological sustenance must be paid enough attention.

Impacts of urban expansion on the livelihoods of local farming communities: The case of Burayu town, Ethiopia

In most African countries, including Ethiopia, there is growing interest in the need to comprehend the connection between urban expansion and farmers' livelihoods. The aim of the study is to assess the impact of urban expansion on the livelihoods of expropriated farmers in Burayu, Ethiopia. In addition to the paired Sample T-Test model, we used the mixed research approach and the sustainable livelihood framework as analytical tools to understand the links and coping strategies. The analysis of the different urban expansion parameters revealed that the expansion was driven mainly due to increase in investment (56.3%) and as a result of the designation of the town as an industrial development corridor at country level by the government. On average, 42.19% of respondents were entirely expropriated and evicted while the majority of respondents (57.81%) only lost part of their agricultural land. According to a logistic regression analysis, women's economic position was 13.71 times more likely to improve than men's following urbanization (AOR = 13.71, 95%: 1.61-116.79). In comparison to their counterparts, those without employment opportunities had a 98% lower likelihood of improving after urbanization (AOR = 0.02, 95%: 0.00-0.56). The findings of this research indicated that urban biased policy and policy actions drive informal developments. To make urban expansion orderly and sustainable, development policies need to be comprehensive; the expropriation process should be transparent and participatory and livelihood restoration plan should be part of the urban expansion scheme. The adoption of the framework for sustainable livelihood as an analytical tool in urban settings is one of the novel contributions of the study.

Determinant factors hinder urban structure plan implementation: The case of Nekemte Town, Ethiopia

Urban structure plan is widely used plan in the process of urbanization and rapid urban spatial expansion. However, rapidly growing urban centers of Ethiopia are facing challenges to implement their structure plan within the time horizon. Thus, this study aims to investigate the determinant factors that hinder structure plan implementation in Nekemte town. Questionnaire survey, interview, observation and land use survey were used to collect data. Descriptive data analysis and regression model were used to analyze the data. The main findings of the study show that all identified factors: lack of active participation, lack commitment, political instability and lack of sufficient budget significantly contribute for the failure of structure plan implementation at P-value of 0.05. The regression analysis further indicated that, lack of community participation; - 0.0499 coefficients is the most determining factors and followed by customary land tenure and lack of awareness -0.0489 and -0.0468 coefficients respectively. Hence, future structure plan implementation endeavors of Nekemte city must be underpinned by inculcating community participation and awareness of structure plan that is required to implement the plan to the expected level. Furthermore, use of modern technology like GIS and appropriate man power are also equally recommended to enhance structure plan implementation of Nekemte city.

Simulating future land use by coupling ecological security patterns and multiple scenarios

A land use simulation model with coupling constraints of ecological security patterns (ESPs) and multiple scenarios (MSs) was developed using the PLUS model. The research scale was zoned with environmental functional regions, where land management policies were formulated. A case study in Anji County successfully demonstrated the application of the ESP-MS-PLUS model. First, we constructed three different levels of ESPs as ecological constraints by utilizing ecosystem services evaluation and circuit theory. Second, four scenarios of land use and land cover changes (LUCCs) in 2034 were assumed, namely business as usual (BAU), priority given to urban development (PUD), priority given to ecological protection (PEP), and balanced urban development and ecological protection (BUE). Then, the basic ecological constraints (ecological red line areas and waters) and three types of ESPs were coupled with the four scenarios. The results of the simulation and analysis of landscape metrics under each scenario showed that the PEP and BUE scenarios would effectively reduce the degree and speed of ecological destruction. In addition, there were three environmental functional areas that could be used as priority areas for urban construction to ensure economic development. This study provides a new mechanism for land use optimization in the context of ecological protection at scales conducive to practice.

Scenario modeling to predict changes in land use/cover using Land Change Modeler and InVEST model: a case study of Karaj Metropolis, Iran

Models for land cover/land use simulation are appropriate and important tools for decision-makers, helping them build future plausible landscape scenarios. Due to the fact that the simulation results of different models may be different, it is sometimes difficult for users to choose a suitable model. Therefore, in this study, an integrated approach is used, combining the data obtained from remote sensing and GIS with Land Change Modeler (LCM) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) models to simulate and predict land cover/land use changes for 2028 in Karaj metropolis (Northern Iran as a poor region-in terms of data-which is under intense and rapid urbanization. In this sense, three land cover/land use maps related to the study area were primarily generated using satellite image data for the period 2006, 2011, and 2017. They were used as a basis to define two scenarios: business-as-usual (BAU) scenario and participatory plausible scenario (PPS) for 2028. Afterwards, the necessary input data used in running of both models were prepared and, then, the outputs of the models were interpreted and compared. According to the results, while human-made coverage and low-density grasslands increased by about 74% and 12%, respectively, it was from 2006 to 2017 that agricultural lands, gardens, and high-density grasslands decreased by 42%, 34%, and 7%, respectively. According to the business-as-usual scenario, which was projected using the LCM model, the increase in human-made cover will continue by about 29% by 2028, and the reduction rate of agricultural lands, gardens, and low-dense and dense grasslands will experience decrease by about 20%, 3%, 11%, and 9%, respectively. The participatory plausible scenario for 2028, which was defined using the InVEST model, confirmed the same results, but having different quantities. Accordingly, while human-made cover will increase by about 73%, the reduction rate of agricultural lands, gardens, and low-dense and dense grasslands will decrease by about 41%, 10%, 16%, and 1%, respectively. The output quantities of InVEST scenario model seem to be closer to reality with less uncertainty, because this model estimates the quantity of demand for land and its suitability for different uses, based on the views of different stakeholders, and considers landscape development future policies and plans. In contrast, the LCM model is based solely on trend extrapolation from the past to current time and changes in the landscape structure.

Urban expansion dynamic and its potential effects on dry-wet circumstances in China's national-level agricultural districts

Although urbanization has been widely examined in individual city and urban agglomeration scales, urban expansion patterns and dynamics in large-scale agricultural districts remain absent. In this study, multifaceted characteristics in urban expansion were quantified in China's nine national-level agricultural districts, and responses of dry-wet circumstances to urban sprawl were evaluated. From 1980 to 2018, China has undergone an extensive urban sprawl. Huang-Huai-Hai Plain (HHHP) has the maximum urban coverage extent, followed by Middle-lower Yangtze Plain (MLYP) and Southern China (SC). The largest annual increase was recorded in MLYP, reaching 816.12 km²; followed by HHHP, with an annual increase of 725.22 km². There are prominent heterogeneities in expansion rate and direction among various districts. The dominating growth patterns were edge- and leapfrogging-expansion, accompanying by a less percentage of infilling-expansion. Accompanying by urbanization, connectedness in urban landscapes gradually improved, while separation degree decreased. Upon many occasions, holistic average dry-wet circumstances in non-urbanized areas are superior to those in urban areas, although this is not absolute for all the districts or periods. In urbanization progress, the development of leapfrogging-expansion has a potential to ameliorate dry-wet circumstances in both urban and non-urban zones, while infilling- and edge-expansion would constitute an inverse effect. In comparison to urban zones, leapfrogging-expansion would cause a more prominent effect on dry-wet environment in non-urbanized zones. Increased connectivity in urbanized landscapes would improve dry-wet environments, especially for urbanized zones. Inversely, increased spatial separated extent among urban landscapes would perform an opposite effect. This study provides a potential for understanding the dynamic features of urban expansion in large-scale agricultural districts. Moreover, the results can also provide a potential opportunity for optimizing dry-wet environments by regulating urbanization pattern and landscape configuration.

Slope climbing of urban expansion worldwide: Spatiotemporal characteristics, driving factors and implications for food security

The tendency of global urban expansion to be slope climbing has partly become possible with scarce cropland resources in plains. However, the scientific understanding of the quantity, intensity, pattern, and effect of the slope climbing of urban expansion (SCE) is minimal globally. In this study, we have attempted to quantify and evaluate global SCE from Suomi National Polar-orbiting Partnership (SNPP)-Visible Infrared Imaging Radiometer Suite (VIIRS)-like data and other auxiliary data. Results revealed that global SCE areas unevenly increased from 22,760 km² to 90,720 km² from 2000 to 2020, with an annual growth rate of 21.72%, in which low-environment cost type areas increased from 21,550 km² to 84,010 km² while high-environment cost type (HEC) areas increased from 1210 km² to 6710 km². One remarkable phenomenon is that China's SCE areas in 2020 were more than 11 times those in 2000. In addition, global SCE intensity increased by about 3.4-fold from 2000 to 2020 and the rapid growth of HEC intensity is concentrated in Asia and North America. SCE is mostly affected by urban population growth and terrain. Economic development also promotes its development to a certain extent. We also noted that global SCE potentially made a considerable contribution to saved cropland, saving about 46,747 km² with a theoretical increased grain yield of 25,020 × 10³ t. Our study provides timely and transparent monitoring of global SCE and offers new insights into sustainable urban development.

Habitat quality assessment provides indicators for socio-ecological management: a case study of the Chinese Loess Plateau

The impact of changing land use and land cover (LULC) on regional habitat quality have attracted extensive attention. The Loess Plateau is an ecologically fragile area; LULC changes in this region have complex impacts on habitat quality at multiple spatiotemporal scales. This study developed an integrated assessment method based on multi-source data to assess habitat quality changes in the Loess Plateau during recent years (2000-2015) and in the future (2015-2050) under four typical scenarios. A significant increase in urban land use was observed on the Loess Plateau from 2000 to 2050, which resulted in a continuous decrease in the cropland area. The area of forest and grassland landscapes was also reduced by both urban and cropland expansion, with the most significant loss in the grasslands. A future overall decreasing trend in overall habitat quality is predicted, but the SSP1-2.6 scenario is significantly better than the SSP5-8.5 scenario. Urban expansion contributes a rapidly increasing proportion of habitat quality decline on the Loess Plateau; urban land will become the most significant threat to regional habitat quality by 2030. Policies for socio-ecological protection with clear, high-level objectives can effectively promote habitat quality. It is recommended that national nature reserves be delineated and ecological functions in the study area be continuously monitored. This research provides a potential socio-ecological baseline and implementation strategy for the habitat conservation-oriented management of large and fragile ecological regions.

A cross-scale study on the relationship between urban expansion and ecosystem services in China

Clarifying the relationship between urban expansion and ecosystem services (ESs) is critical for sustainable management of land resources and ecosystems. However, little is known about the relationship between the two at the cross-scale (particularly at the national-provincial scale). Therefore, we conducted a systematic assessment of the spatiotemporal dynamics and the relationship between urban expansion and ESs including food production (FP), soil conservation (SC), carbon sequestration (CS), and water yield (WY) in China from 1992 to 2020 on the national-provincial scale. The results show that China's urban expansion took up a large amount of cropland, accounting for 79.35% of the newly-added built-up land. Shandong had the largest expansion scale and the highest speed, Shanghai had the most pronounced expansion intensity, and more than 50% of the provinces were dominated by outlying expansion pattern. In terms of total change, the three ESs of FP, SC, and WY increased by 286.5 × 10⁶ t, 1893.61 × 10⁶ t, and 8337.20 × 10⁶ mm, respectively, and CS decreased by 683.90 × 10⁶ Mg C. However, in the urban expansion area, FP and CS net decreased by 1757.6 × 10⁴ t and 19,640.19 × 10⁴ Mg C, respectively, while SC and WY net increased by 347.52 × 10⁴ t and 20,264.11 × 10⁴ mm, respectively. Shandong contributed the most to changes in ESs in urban expansion areas. Urban expansion was significantly negatively correlated with FP and CS with the correlation coefficients > -0.8; it was significantly positively correlated with SC and WY, with coefficients of 0.714 and 0.413, respectively, and urban expansion had a lagged effect on ESs. The impact of urban expansion on ESs had a spatial spillover effect and showed prominent spatial clustering in Anhui, Henan, and Shandong. Based on these results, we proposed urban planning countermeasures grounded in the perspective of ES improvement, which would provide policy references for the sustainable management of the ecological environment and land resources.

Key Social Determinants to Narrow the Gap between Health-adjusted Life Expectancy and Life Expectancy in Megacities

OBJECTIVE

Improvement in the quality of life is reflected in the narrowing of the gap between health-adjusted life expectancy (HALE) and life expectancy (LE). The effect of megacity expansion on narrowing the gap is rarely reported. This study aimed to disclose this potential relationship.

METHODS

Annual life tables were constructed from identified death records and population counts from multiple administrative sources in Guangzhou, China, from 2010 to 2020. Joinpoint regression was used to evaluate the temporal trend. Generalized principal component analysis and multilevel models were applied to examine the county-level association between the gap and social determinants.

RESULTS

Although LE and HALE in megacities are increasing steadily, their gap is widening. Socio-economic and health services are guaranteed to narrow this gap. Increasing personal wealth, a growing number of newborns and healthy immigrants, high urbanization, and healthy aging have helped in narrowing this gap.

CONCLUSION

In megacities, parallel LE and HALE growth should be highly considered to narrow their gap. Multiple social determinants need to be integrated as a whole to formulate public health plans.

Future land-use competition constrains natural climate solutions

Natural climate solutions (NCS) are an essential complement to climate mitigation and have been increasingly incorporated into international mitigation strategies. Yet, with the ongoing population growth, allocating natural areas for NCS may compete with other socioeconomic priorities, especially urban development and food security. Here, we projected the impacts of land-use competition incurred by cropland and urban expansion on the climate mitigation potential of NCS. We mapped the areas available for implementing 9 key NCS strategies and estimated their climate change mitigation potential. Then, we overlaid these areas with future cropland and urban expansion maps projected under three Shared Socioeconomic Pathway (SSP) scenarios (2020-2100) and calculated the resulting mitigation potential loss of each selected NCS strategy. Our results estimate a substantial reduction, 0.3-2.8 GtCO₂ yr^-1 or 4-39 %, in NCS mitigation potential, of which cropland expansion for fulfilling future food demand is the primary cause. This impact is particularly severe in the tropics where NCS hold the most abundant mitigation potential. Our findings highlight immediate actions prioritized to tropical areas are important to best realize NCS and are key to developing realistic and sustainable climate policies.

Carbon and nutrient burial within Peruvian coastal marsh driven by anthropogenic activities

This research assessed carbon and nutrient burial during the past ~60 years within a Peruvian coastal marsh ecosystem affected by anthropogenic activities, by examining total organic carbon (TOC), total nitrogen (TN) and isotopes (δ¹³C and δ¹⁵N) tracers in two dated sediment cores. Significantly higher TOC and TN burial, up to 416.4 ± 65.0 and 0.7 ± 0.1 g m^-2 year^-1 respectively, were observed after an uncontrolled urban expansion starting in the early 1970's to the 1990's. The TOC and TN burial rates were up to twofold higher than those observed for preserved coastal marshes. Furthermore, the decreased δ¹³C values (-16.1 ± 0.6 ‰) and increasing δ¹⁵N values (+10.6 ± 2.6 ‰) indicate higher deposition of algal material and urban sewage during the same period. The higher burial rates during 1970's-1990's and reduced rates thereafter evidenced the role of coastal marsh ecosystems plays in sequestering carbon and nutrients.

Impact of urban expansion on carbon storage under multi-scenario simulations in Wuhan, China

Carbon storage in terrestrial ecosystems, which is the basis of the global carbon cycle, reflects the changes in the environment due to anthropogenic impacts. Rapid and effective assessment of the impact of urban expansion on carbon reserves is vital for the sustainable development of urban ecosystems. Previous studies on future scenario simulations lacked research regarding the driving factors of changes in carbon storages within urban expansion, and the economic value accounting for changes in carbon storages. Therefore, this study examined Wuhan, China, and explored the latent effects of urban expansion on terrestrial carbon storage by combining the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) and Patch-generating Land Use Simulation (PLUS) model. Based on different socioeconomic strategies, we developed three future scenarios, including Baseline Scenario (BS), Cropland Protection Scenario (CP) and Ecological protection Scenario (EP), to predict the urban built-up land use change from 2015 to 2035 in Wuhan and discussed the carbon storage impacts of urban expansion. The result shows that (1) Wuhan's urban built-up land area expanded 2.67 times between 1980 and 2015, which is approximately 685.17 km² and is expected to continuously expand to 1349-1945.01 km² by 2035. (2) Urban expansion in Wuhan has caused carbon storage loss by 5.12 × 10⁶ t during 1980-2015 and will lead to carbon storage loss by 6.15 × 10⁶ t, 4.7 × 10⁶ t and 4.05 × 10⁶ t under BS, CP, and EP scenarios from 2015 to 2035, accounting for 85.42%, 81.74%, and 78.79% of the total carbon loss, respectively. (3) The occupation of cropland by urban expansion is closely related to the road system expansion, which is the main driver of carbon storage reduction from 2015 to 2035. (4) We expect that by 2035, the districts facing carbon loss caused by the growth of urban built-up land will expand outward around secondary roads, and the scale of outward expansion under various scenarios will be ranked as BS > CP > EP. In combination, the InVEST and the PLUS model can assess the impact of urban expansion on carbon storage more efficiently and is conducive to carrying out urban planning and promoting a dynamic balance between urban economic development and human well-being.

Increasing global urban exposure to flooding: An analysis of long-term annual dynamics

An improved understanding of global Urban Exposure to Flooding (UEF) is essential for developing risk-reduction strategies for sustainable urban development. This study is the first to assess the long-term historical global UEF at a fine spatial resolution (i.e., 30 m) and annual temporal frequency, with consideration of smaller urban areas in the exposure assessment compared to those using coarse resolution data. We assessed the UEF by investigating the spatially explicit urban expansion in the 100-year floodplain extents. The global UEF increased more than four-fold from 16,443 km² in 1985 to 92,233 km² in 2018 with accelerated temporal trends. The most notable growth in UEF occurred in Asia (74.1%), followed by Europe (11.6%), Northern America (8.7%), Africa (2.9%), Southern America (2.2%), and Australia (0.5%). Notably, China and US were the two countries with the largest UEF, accounting for about 61.5% of global growth in UEF. In addition, only 1.2% of global floodplains were occupied by urban expansion by 2018, whereas this percentage reached 20% in the basins of Western Europe, Eastern Asia, and Northeastern US. Moreover, although the floodplains only accounted for 5.5% of the global land areas, 12.6% of the urban expansion occurred in the floodplains from 1985 to 2018, with the most rapid increases in the basins in Southeastern and Eastern China. Our findings highlight that the trends of accelerated increasing urban exposure to flooding have been occurring for at least the past three decades.

District-based urban expansion monitoring using multitemporal satellite data: application in two mega cities

Urban expansion is a process of urban development as a result of population growth. Urban sprawl, known as unplanned and unrestricted urban expansion, is among the most important topics in urban studies. In recent decades, many cities around the world in both developing and developed countries have experienced urban expansion. Istanbul and Sydney are two of those cities encountering the urban expansion. Thus, in this study, the spatial and temporal pattern of urban expansion of the most urbanized districts of Istanbul (Arnavutköy) and Sydney (Hills Shire) was analyzed using multi-temporal remote sensing data. Initially, the Landsat images were classified to evaluate the land use/land cover (LULC) changes. The change detection analysis revealed that urban area of Arnavutköy district has increased about 669% from 1997 to 2017 and urban area of Hills Shire Local Government Area (LGA) increased by 78% between 1996 and 2018. The relationship of land surface temperature (LST) and urban areas extracted by recoding the LULC maps was also evaluated in different buffer zones. The results showed that with the increase in urban area extent, the LST has also increased. Then, Shannon's entropy and spatial landscape metrics were used to analyze the district-based urban expansion. The results showed that both study areas expanded over the time but the main differences observed are that Arnavutköy has more fragmented and Hills Shire has a more compact urban growth process.

Urban growth and land subsidence: Multi-decadal investigation using human settlement data and satellite InSAR in Morelia, Mexico

Limited attention is typically paid to the cause-effect relationship between land subsidence due to aquifers overexploitation in expanding metropolises and urban growth models and patterns. This paper implements an integrated urban and satellite Interferometric Synthetic Aperture Radar (InSAR) approach to investigate subsidence, multi-decadal urban growth and peopling trends in the Metropolitan Area of Morelia (ZMM) in the Mexican state of Michoacán. Stacking of JRC's Global Human Settlement Layer, DLR's World Settlement Footprint and INEGI's National Geostatistical Framework datasets reveals a predominant edge-expansion growth model, with urban densification in 1975-2020 and some sprawling in 1990-2000. Population of the ZMM doubled in the last 30 years, reaching over 1 million inhabitants. The ENVISAT and Sentinel-1 InSAR analysis confirms that subsidence is structurally-controlled by the main normal faults within the Cuitzeo half-graben. Differential sinking and ground discontinuities are aligned with buried tectonic faults and contrasting compressible sediment thickness. Non-linearly deforming subsidence bowls develop at extraction wells in both old and newly urbanized sectors of the ZMM. Maximum vertical displacement velocities increased from -2.5 cm/year in 2003-2010 to -9.0 cm/year in 2014-2021, with subsidence migrating towards recently urbanized zones. More than 250 new groundwater wells were added to the public registry since 2000, many of which within new urban sectors. Time-lapse InSAR reveals a 4 km² rapidly subsiding bowl that formed at the largest social housing neighbourhood of Villas del Pedregal, as building lots were progressively completed and sold, and new wells registered. With angular distortions due to the differential subsidence reaching 0.12% in 2014-2021, new buildings and roads are exposed to fracturing and surface faulting risk of comparable level as the city historic building blocks located along the main faults. By providing useful insights into the relationship between urban growth and land subsidence in the ZMM, the approach proves valuable for application to other metropolises worldwide.

Molecular detection of Mansonella mariae incriminates Simulium oyapockense as a potentially important bridge vector for Amazon-region zoonoses

OBJECTIVE

To assess the emergent zoonotic disease risk posed by the voracious human-biting blackfly species Simulium oyapockense in the peripheral regions of an expanding urban centre situated deep in the Brazilian Amazon rainforest.

METHODS

We performed nine human landing catches at three periurban sites surrounding the Brazilian Amazon town of São Gabriel da Cachoeira. Using the detection of non-human primate filarial parasites as an indicator of the zoonotic disease threat posed by a biting insect, we screened 3328 S. oyapockense blackflies for the presence of zoonotic filarial DNA with an ITS-1 PCR assay and Sanger sequencing.

RESULTS

Between 98 and 100% of the biting insects captured during our nine collections were identified as S. oyapockense; at our three collection sites and during our three seasonally-distinct collections this species was captured at rates between 28 and 294 blackflies per hour. PCR screening of the march-collected S. oyapockense detected infectious-stage (L3) Mansonella mariae parasites (which are only known to infect non-human primates) in >0.15% of the tested head samples.

CONCLUSIONS

Our results show that residents of the periurban regions of São Gabriel da Cachoeira are routinely exposed to the bites of S. oyapockense blackflies which have previously fed on non-human primates.

Prediction of urban expansion by using land cover change detection approach

Bangladesh has been experiencing rapid urban expansion over the last few decades, contributing much to the region's land cover transition into the urban area. The study aims to employ geospatial modeling techniques to investigate land cover scenarios in the Pabna municipality of Bangladesh. Therefore, the research examined Cellular Automata Markov and Multi-Layer Perceptron Markov models to detect land cover for 2023 and 2028. The study selected the Multi-Layer Perceptron Markov as the best fit model over Cellular Automata Markov based on the highest kappa value. The result reveals that urban area has increased from 3.39 to 8.79 km² over 1998–2018. Urban expansion and its surrounding area are primarily occurring towards the northeast directions. However, the extent of urban build-up land will grow from 3.39 km² in 1998 to 11.01 km² in 2023 and 12.44 km² in 2028. Moreover, the future land cover map delineated that the urban growth will expand in the northeast part of the study area. The scenario shown in this paper would assist urban planners in quantifying the urban growth under different land cover features and thus preparing proper strategic measures.

Elucidating the impacts of rapid urban expansion on air quality in the Yangtze River Delta, China

Urban expansion not only results in land use transformation, but also introduces extra anthropogenic emissions over the expanded urban areas, which is usually neglected in existing studies. In this study, we consider both the changes in land use categories and added anthropogenic emissions from 2001 to 2018 in the Yangtze River Delta (YRD) which we define as the city of Shanghai and the nearby provinces of Zhejiang, Jiangsu, and Anhui, China and explore the individual and combined impacts of these factors on air pollution using the WRF-Chem model. Calibrated by available observations, the model performs well (IOA (index of agreement) > 0.8) in reproducing the meteorological fields and ambient PM_2.5 and O₃ concentrations in September 2018. We show that the land use transformation from non-urban to urban and the introduced anthropogenic emissions over new urban areas exert opposite influences on ambient PM_2.5 concentrations over YRD, particularly in the expanded urban areas, and the PM_2.5 decrease due to land use changes is significantly offset by the increase due to added emissions. The response of ambient O₃ concentration to these two factors is highly variable in space, which is dependent on the chemical regime of tropospheric O₃ formation and influenced by the chemistry-meteorology feedback. As the total effect, strong increases in O₃ concentration occur over the central areas of YRD. These results highlight that it is essential to take into account the additional anthropogenic emissions over expanded urban areas in the assessment of environmental impacts of urban expansion.

Precipitation and urban expansion caused jointly the spatiotemporal dislocation between supply and demand of water provision service

A clear quantification and spatial mapping between supply and demand of water provision service in relation to climate change and urban expansion can provide some guidance to water resources management. Nevertheless, so far, most researches ignored the dynamic changes and influences of supply-demand coupling correlations. In this study, water yield and water demand were quantified and mapped in the Xiangjiang River Basin (XRB) from 2000 to 2018 by using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) and water-demand models, then the spatial distribution characteristics and their matching relationship were identified by using the univariate local autocorrelation analysis and the common logarithm of water supply-demand ratio (WSDR). With that, the contributions of climate and socio-economic factors to the above-mentioned changes were explored by using geographic detector. Results showed that the annual water yield increased by 20.20% in 2000-2015 and decreased by 33.92% in 2015-2018 affected by precipitation and land use changes; Changsha-Zhuzhou- Xiangtan urban agglomeration (CZX) and Southwest of Yongzhou were the high value areas of water yield (>338 m³/hm²). Due to the urban expansion, the water demand increased by 40.50% from 2000 to 2005 and decreased by 36.39% after 2005; From 2000 to 2018, high value areas of water demand (>53566 m³/hm²) mainly appeared in midstream and downstream with high urbanization level, dense population and developed industry. Under the joint action of precipitation (prep) and urban expansion, the overall state of supply and demand in the upper reaches was surplus, and more than 90% of the regions in midstream and downstream were at the middle and high level of supply shortage, especially in Hengyang and Chenzhou. Consequently, the increasing needs of human beings should be emphasized from the overall perspective of the basin, the growth rate of construction land and the necessary green infrastructure should be controlled reasonably and configured for achieving win-win goals of coordinating environmental protection and urban development.

Change detection and urban expansion of Port Sudan, Red Sea, using remote sensing and GIS

During the last two decades, Port Sudan City has witnessed major environmental stresses resulting from urban expansion and port extensions. This research aims at analysing land water changes (LWCs), land use land cover (LULC) changes and urban expansion of Port Sudan using remote sensing and GIS. For that purpose, an integrated remote sensing and GIS approach was designed to analyse two Enhanced Thematic Mapper (ETM) and an Operational Land Imager (OLI) Landsat images covering the period from 1999 to 2018. LWCs were detected using mathematical remote sensing and GIS-based procedures, while LULC changes were analysed through a post-classification comparison (PCC) approach using a support vector machine (SVM) classifier for classification. Major detected LWCs include landfill activities in the port area and north lagoon of Kilo Tamanya, and dredging activities in Khor Mog. Areas gained by landfill may have improved the port and transport functions but buried coral reefs and caused environmental problems as well. Furthermore, the urban areas were twice doubled, which was mostly rapid and uncontrolled, adding more pressure to the already stressed services and administrative sectors. Threats to the agricultural and mangrove areas were also analysed. The agricultural and mangrove areas were decreased by 40% each, which has been shown to have negative impacts on society, food security and biodiversity. Sadly, the lost agricultural lands were changed into bare soil, slums and other industrial uses. In contrast, mesquite forests were naturally increased by 74%. Mesquites have a major role in combating desertification and providing energy for domestic use. The driving forces and constraints of the urban expansion were highlighted. The change information provided by the applied approach will support decision-makers in adopting integrated and compatible land and coast management planning in the studied coastal city.

Assessment of water quality in ponds across the rural, peri-urban, and urban gradient

The Prairie Pothole Region is one of the most wetland rich areas of the world and has experienced intense disturbance from increased agricultural demands and urban sprawl. This study assessed ponds across the urban gradient for the first time in the region to determine the impacts of urbanization on water quality. Thirty ponds (ten rural, ten peri-urban, and ten urban) were randomly selected and compared based on land use type and the impervious to pervious surface ratio within 1.6 km of each pond. Water quality samples were taken monthly in 2015 and 2016, across 3 and 6 months respectively. Assessment included chemical and physical parameters, which were compared spatially across the gradient and temporally between sampling periods. Results indicate disturbance from urbanization negatively impacts water quality. Spatially across the gradient, rural pond water quality was significantly different from both peri-urban and urban ponds, whereas peri-urban and urban pond water quality was not significantly different. Temporally, differences between water quality parameters and sampling periods indicate that surrounding land use, land cover, and precipitation influence parameter concentrations across the urbanization gradient. Information from this study is useful to water professionals dealing with urban development and sprawl that continue to impact water and natural habitat.

Assessing the quantitative relationships between the impervious surface area and surface heat island effect during urban expansion

As an important component of underlying urban surfaces, the distribution pattern and density of the impervious surface area (ISA) play an important role in the generation of surface urban heat island (SUHI) effects. However, the quantitative and localized exploration of the ISA’s influence on SUHIs in the process of urban expansion from the perspective of temporal and spatial changes is still not clear. Based on multisource remote sensing data, the SUHI effect of urban expansion is revealed by using geospatial analysis methods such as profile, difference and regression analysis. The results show the following: (1) urban expansion plays a significant role in aggravating SUHIs. Overall, the ISA and land surface temperature (LST) have obvious consistency in terms of spatial distribution patterns. However, local spatial differentiation is significant. The areas with the highest LST were not concentrated in the downtown area with the highest ISA but were scattered in the cultivated land and exposed surface areas under development in the northern part of the city. (2) In general, the ISA can explain the spatial distribution of LST well, there is an obvious positive correlation between them, and the quadratic polynomial function is the best fitting model between them. (3) The density and spatial allocation of ecological elements, such as green space and water bodies, play an important role in alleviating SUHIs. This study found that the urban center with the highest ISA coverage rate has no significant SUHI due to the reasonable allocation of green space and water bodies. The research results can provide a scientific basis for future urban planning and ecological environment construction.

Seeking sustainable development policies at the municipal level based on the triad of city, economy and environment: evidence from Hunan province, China

Keeping urbanization, economy and eco-environment in harmony is a core issue for attaining Sustainable Development Goals (SDGs) in any complex geographical regions. Previous studies mainly focused on seeking the balance between urban expansion levels, eco-environment quality and socioeconomic degree. But the challenges still exist in solving the negative influence of urban expansion that affects eco-environmental and economic development. Based on the Environmental Kuznets Curve theory, we involved inclusive indexes to analyze the interlinkages of eco-environment quality, economic level, and urban expansion degree, which closely relate to urban sustainable development goals and spatial complexity, as well as using available data corresponding to waterfront cities. Cities in Hunan were taken as a study-case, and the study period of 2006-2016 covers the last 10 years of the millennium development goals agenda and the first 2 years of SDGs agenda. The key indicators of city-economy-environment relationships were different at the provincial level, urban level and urbanization grade. According to the regression models and inverted N shape curve, urban expansion resulted in high positive effects on economic development level and negative effects on ecological environment quality, partically higher at high urbanization level than that of the low ones. But the overall trends were that the environmental quality of the cities was undergoing slowly improving processes both at low and high urban expansion levels. Promoting adaptations with the eco-environmental capacity when formulating policies and taking actions is necessary for realizing sustainable cities and communities (SDG11), life on land (SDG15), decent work and economic growth (SDG8) and responsible consumption and production (SDG12) at the same time. Regulating citizens' density, urban expansion speed in area, the quantity of enterprises with heavy pollution, and the structure of industry to the suitable urbanization stages is an important way for achieving SDGs at provincial and municipal levels.

Impact of urban expansion to peri-urban smallholder farmers' poverty in Tigray, North Ethiopia

Urban expansion in African and other developing countries occurred and happening by encroaching fertile agricultural land. As a result, close to fifteen million people are displaced every year. This paper examines the consequences of urban expansion on peri-urban farmers' poverty. Data was generated from 341 (101 treated, 240 control) smallholder Peri-urban farmers'. Inferential statistics, propensity score matching (PSM), econometric models, and poverty measurements were applied and analyzed using Stata version 14 software. The impact assessment estimation showed the prevalence of poverty was higher by 5% poverty than non-displaced households. The intensity and incidence of poverty were also found higher among displaced households. Displaced and non-displaced households were deprived 49.4% and 46.5% of weighted indicators respectively, while the incidence of poverty was found 69% and 59% respectively. In sum, 34.1% of displaced and 27.4% of non-displaced households were poor. Besides the overall percentage of contribution of education, health, and living standard dimensions were 15.4%, 28.8%, and 55.8% among displaced households respectively. While percentage contribution of education, health, and living standard among non-displaced households were 15.1%, 26%, and 58.9% respectively. Therefore, the prevalence of poverty was higher in displaced households than in non-displaced households. The binary logistic regression also revealed out of the 13 covariates only four variables were found statistically significant. Of the four variables, except treatment effect or being displaced the rest variables family size, farming experience, and market distance were negatively affect household poverty. In conclusion, in all aspects, the result indicated that the prevalence of poverty was higher among evicted farmers. Therefore, government bodies should design strong strategies to avert the impact of urban expansion on peri-urban farmers. A separate department should be established which follow and provide training on time, and horizontal urban expansion should be changed to vertical expansion.

Rapid urbanization and its driving mechanism in the Pan-Third Pole region

Rapid urbanization increasingly influences ecosystem stability and regional urban sustainability. Pan-Third Pole cities located in high-altitude regions around the Tibetan Plateau, Pamir, and Indo Kush have experienced rapid urbanization during the last few decades; however, an understanding of the urbanization rate and its driving mechanism remains lacking. Here, we investigate the urban land transformation dynamics of 14 major Pan-Third Pole cities and analyse their driving factors over two periods (2000-2010 and 2010-2017) based on the interpretation of historical Google Earth imagery using deep learning techniques. Our results show that the urbanized area has increased from 2809 km² to 4380 km², with an annual growth rate of nearly 3% during 2000-2017, which is probably the largest increase in the world. The analysis of potential driving factors reveals that population growth dominates urban expansion, elevation is a constrained topographical factor, and neighbourhoods to roads facilitate urbanization. Our findings would benefit policy making for urban sustainability in the most fragile region on Earth.

Which Should be Conserved According to Priority During Urban Expansion? Ecological Lands or Farmland?

Understanding the trade-off between the loss of ecological lands and farmland to urbanisation could alleviate negative consequences to the environment and food security. This study aims to analyse the impact of urbanisation on ecological lands and farmland by comparing respective losses of habitat quality and agricultural productivity potential. Different scenarios are established indicating the priority of conserving ecological lands or farmland based on their vulnerability as measured by weight. With a land-use simulation model LANDSCAPE, the demand for urban land is met by occupying inferior ecological lands or farmland. Land-use patterns in each scenario are projected to 2035 in Wuhan (a rapidly urbanising city in China). As the weight of habitat quality decreases, the loss of habitat quality increases from 2.56 to 5.80%, while the loss of agricultural productivity potential decreases from 4.16 to 2.94%. The higher vulnerability of habitat quality loss indicates that ecological lands need a priori conservation than farmland in exchange for urbanisation.

Urban form datasets of 194 cities delineated based on the contiguous urban fabric for 1990 and 2015

The present research datasets were processed for the article "The global homogenization of urban form. An assessment of 194 cities across time" [1]. They consist of land cover spatial layers, longitude and latitude point data and tabulated data with computed landscape metrics and the characterization of urban form of 194 cities for 1990 and 2015. Contiguous urban fabric at 30 m spatial resolution was derived from the Atlas of Urban Expansion database for 1990 and 2015 [2]. Landscape metrics were computed as quantitative measures of composition and spatial arrangement of each city and dimensions of the database were reduced employing correlation and principal components analysis. Hierarchical clustering was employed to group cities according to the similarity of their urban form and analysis of variance was applied to test for significant differences between them. The spatial layers contained in this article can be complemented with past and future land cover data to model urban form change at broader temporal scales. The landscape metrics are useful for cross-city comparisons at regional, national and global levels in combination with other complementary indicators. The datasets are valuable for urban planners, urban ecologists, NGO's, decision makers and other with interest on local and global landscape change in urban areas, particularly urban expansion and its impacts.

Can groundwater be protected from the pressure of china's urban growth?

Groundwater is expected to be more vulnerable to water-quality degradation in the future due to rapid urbanization. However, despite knowledge that protecting future groundwater resources is necessary for sustainable groundwater resource development, little is known about the role of groundwater policy in influencing the spatial distribution of urbanization. This study sheds light on how a policy that protects vulnerable groundwater could affect the distribution of urban expansion. Groundwater vulnerability to pollution under future climate change scenarios is used as a factor to generate urban expansion probability maps for China. The results indicate that there will be a significant and uneven urban growth by 2030, if current trends in urban expansion continue. The amount of urban land in 2030 will range from 2.9 to 4.2 times the urban area in 2010. Meanwhile, the urban expansion probability maps for projections with and without consideration of groundwater vulnerability in urban suitability are compared. The comparation shows that consideration of a groundwater policy would significantly alter the future spatial distribution of urban areas. Even with a weight of only 10% for groundwater vulnerability in the urban suitability consideration, the percentage of change area in the urban expansion probability distribution map can be as high as 60%. The probabilities of urban expansion are forecast to gradually transfer from the southeast coastal areas to inland areas as higher weight (from 10% to 50%) of groundwater vulnerability is given to urban suitability consideration. Our study demonstrates that groundwater protection from urbanization pressures can be achieved, provides support for policy and decision makers in evaluating options to modify existing urban expansion policies, and concludes that groundwater protection at the macro-scale is an appropriate policy goal.

Spatial gradient of urban green field influenced by soil sealing

Rapid urbanization and land expansion persistently shrink urban green field, which accelerates soil sealing and land degradation. Spatio-tempral pattern analysis of green field caused by soil sealing contributes to its protection but quantitative tools are rare. Taking Shanghai-Hangzhou Bay Urban Agglomeration (SHBUA) as an example, we interpreted Landsat imagery into three categories: green filed (such as farmland, grass, forest etc.), gray field (impervious surface) and water bodies in 1994, 2003, 2009, and 2015. We first analyzed swallowed green field by soil sealing and then calculated density (proportion) of green field in concentric rings using gradient analysis. Results show that green field density increases slowly around the city center followed by a sharp increase from urban core areas to urban fringe, and then slowly increases again until at a stable level, presenting an S-shape overall. We proposed an S-shaped function that can fit the spatial gradient of green field density well in nine represented cities. We further compare spatial gradients of densities of green field and gray field. This study provides a quantitative tool to characterize the spatial distribution of green field within cities, which supports to find hotspots of green field loss due to soil sealing and further identify prior areas for green field protection.

Scenario-based simulation of land use in Yingtan (Jiangxi Province, China) using an integrated genetic algorithm-cellular automata-Markov model

Yingtan is a rapidly urbanizing city in Jiangxi Province, South China. During rapid urbanization, construction land is expanded at the expense of cropland and forest. Although economic benefits are gained, ecological and environmental damage is irreversible. In this study, a methodological framework for land use simulation using an integrated genetic algorithm-cellular automata-Markov model is proposed to assess the relationship between economic development and cropland protection in Yingtan. This framework considers both the economic and ecological benefits of different land use types. Three land use scenarios are evaluated to seek recommendations for land use practice. The results show that the areas with high suitability for cropland and construction are mainly concentrated in urban fringes. Under the green development scenario, the area of new construction land can meet the land demand for population growth and economic development proposed for 2025 based on population forecasting and government interviews. The expansion for construction land is decreased by ~ 35 km² while the cropland area is increased by ~ 20 km² compared with those under natural and controlled development scenarios. Additionally, ecological losses are lowest under the green development scenario. In conclusion, the green development scenario is conducive to both cropland and ecological protection, which is of relevance for future spatial planning in Yingtan.

Combining habitat area and fragmentation change for ecological disturbance assessment in Jiangsu Province, China

Understanding where and how human land use causes ecological consequences is essential for habitat conservation. However, the assessment of the ecological disturbance caused by human land use is usually shaped by the area change in ecological land. The comprehensive evaluation of ecological disturbance based on the losses and gains of ecological patches is neglected. This paper analyzed the land use change between agricultural land, construction land, and ecological land from 1995 to 2015 in Jiangsu Province of eastern China. The ecological disturbance was quantificationally evaluated by a proposed index that considered both the changes of habitat area and fragmentation caused by the losses and gains of ecological landscape patches. The findings showed that there was a slight increase in area of ecological land in Jiangsu Province; however, ecological fragmentation was becoming severe with the growth of human land use, which, in turn, resulted in increased ecological disturbance. The losses and gains in the area and fragmentation of ecological land were comprehensively reflected using the proposed ecological disturbance index. Negative ecological disturbance was more likely to be observed at the edge of the city centers, ecologically sensitive areas, and counties with low area ratios of ecological land. Ecological governance policies should be formulated and implemented based on quantity, quality, and spatial relationships between human land use and ecological disturbance.