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Science of The Total Environment，December 2024
Guanglei Li, Han Wang，Shouguo Zhang，Chang Ge，Wu Jiansheng
Abstract: Climate and landscape structure are widely recognized as the primary drivers of soil erosion; however, the spatiotemporal variability of their effects remains insufficiently understood, limiting our comprehension of the dynamic processes of soil erosion. To address this gap, this study analyzed soil erosion trends on the Loess Plateau from 2000 to 2018. extreme Gradient Boosting was used to identify key climatic and landscape structural factors, while a geographically and temporally weighted regression model was applied to assess the spatiotemporal variability of these influences. The results indicate a decreasing trend in soil erosion from 2000 to 2008, followed by a sharp increase from 2008 to 2018. Grassland edge density emerged as the most important factor, followed closely by grassland percentage and annual precipitation. Temporally, the positive effect of annual precipitation has been intensifying since 2010, contributing to increased erosion, while landscape structural factors progressively enhanced their hydrological regulatory roles, reflecting dynamic interactions with climate. Spatially, the direction of climatic influences remained generally stable, consistently promoting erosion, although by 2018, the effects of average annual temperature and annual sunshine duration reversed to suppress erosion in specific areas. In contrast, landscape structural influences exhibited greater spatial variability, often fluctuating or reversing depending on topography, human activity, and land use. This variability applied specifically and differentially to each metric of fragmentation and diversity, highlighting the critical importance of trade-offs in landscape management. The findings emphasize the complexity and dynamics of soil erosion in response to climate and landscape structure, suggesting implications for the development of spatially targeted soil erosion control strategies that accommodate the phases of temporal variation.
111.Effects of ecological control line on habitat connectivity: A case study of Shenzhen, China
Ecological Indicators，October 2024
Shengyong Zhang, Zheng Zhang , Jingqi Wang, Yiheng Zhang, Wu Jiansheng，Xiwen Zhang
Abstract: Ecological control line (ECL) has become an important policy for enhancing ecological conservation and achieving sustainable urban development. Landscape connectivity of ecological network provides a method for exploring the effect of ECL policy on biodiversity conservation. This study used Shenzhen as an example to analyze the distribution of important habitats based on species occurrence points, environmental factors and artificial neural network methods. Four-phase ecological networks of focal species (Ardea cinerea, Callosciurus erythraeus, Copsychus saularis, Egretta garzetta, Pycnonotus sinensis) in 2000, 2010, 2015, and 2020 were constructed, and the effects and changes of ECL on habitat connectivity of species, geographical zone, and species zone scales were sequently analyzed using the difference-in-difference method. The results showed that: (1) Forty-one important habitats were identified, with a total area of 743 km2, and the average area of each habitat was 18.1 km2. The number of ecological corridors and the area of ecological pinch points in Shenzhen decreased in the first ten years but remained stable over the final ten years. (2) ECL delineation can promote habitat connectivity of regional species and with the passage of time, this promoting effect increases. The protective effect in the high habitat quality zone was greater than that in the low habitat quality zone. (3) City managers can develop habitat connectivity conservation schemes for different species according to the five habitat quality zones: high, mid-high, middle, mid-low, and low. This study proposes a method to assess the effectiveness of the existing ecological control line, and provide a scientific basis for formulating, adusting and optimizing ecological management.
Sustainable Cities and Society，October 2024
Yuan Wang, Han Wang, Fei Yao, Rudi Stouffs, Wu Jiansheng
Abstract:An urban heat island (UHI) refers to a metropolitan area significantly warmer than its rural surroundings. Accurately quantifying UHI intensity (UHII) relies on selecting appropriate rural areas, which lack a universal definition. A crucial aspect in UHII quantification is considering the spatial extent of the UHI effect, known as its footprints (UHIFP). Here, we propose a framework to jointly estimate UHII and UHIFP, integrating the latter into the former. Our approach involves creating 12 equal-area buffer zones around each urban boundary and initially selecting the three farthest zones as rural areas. Using a seamless 1-km daily land surface temperature dataset on Google Earth Engine, we construct exponential decay models to characterize the temperature variations along the urban-area gradient of each city and to extract UHIFP from these models. The results reveal that the average UHIFP during daytime and nighttime are 2.6 and 2.7 times of the urban size, respectively, predominantly located before the three farthest buffer zones, thereby verifying the effectiveness of the selected rural areas for accurate UHII calculations. This framework is critical for evaluating the risks associated with extreme heatwaves and heat stress. It also provides suggestions for UHI mitigation measures from an urban–rural gradient perspective.
Journal of Environmental Management，May 2024
Wang Han, Danni Zhang, Xiwen Zhang, Chang Gao, Zhenyu Wang, Wu Jiansheng
Abstract:With the extensive industrialization and urbanization taking place in China during the recent decades, land use throughout the country has experienced profound changes influenced not only by the demand for population growth and living standard improvement but also by the constraints of series of land use policies. However, whether the conflict between the expansion of settlement land (SL) and the loss of cultivated land (CL) have been resolved at the national scale or transferred between the local regions remains unclear. Based on yearly ESA CCI land use and land cover products from 1992 to 2020, the long-term trends of quantity and spatial pattern of SL expansion and CL change in China from national and local views were investigated using trend statistic methods, and finally a comprehensive zoning framework was proposed to recognize the trade-off and synergies relationships between SL expansion and CL change. There are a continuous expansion of SL with global linear trends showing three breakpoints in 2000, 2005, and 2012, and a fluctuation decline of CL presented with four breakpoints in 1997, 2002, 2006, and 2013. Aggregation and dispersion tendencies with linear characteristics of SL expansion and CL change were found with breakpoints in 2001, 2008, 2012, and 2016 and breakpoints in 2001 and 2010, respectively. A spotty spatial pattern of SL was shown spatially coincident with urban agglomerations in China while the planar continuous characteristic was found for CL. Local counties were classified into five tradeoff and synergies zones (TSZs), where general synergies (G-S) and decoupling (D) of SL expansion and CL change were rare cases and the different change in quantity and trend of SL expansion and CL change in local counties was concealed by the national trend. A few scattered counties were belonging to G-S and D TSZs, while most of the counties in the central-east and western China were in General-Tradeoff (G-T) and Superior-Tradeoff (S-T) TSZs. Counties in south and north China with higher percentages of CL were more prevalent in Superior-Synergy (S–S) TSZ. Our findings explicated the complex relationships between SL expansion and CL change of China at the national scale and in local counties, which pointed out the differences of unified land use management activities across scales and could provide insights for future policy-making and management measures of land use to both ensure the national food security and promote regional sustainable development more synchronously.
108.How Does Fire Suppression Alter the Wildfire Regime? A Systematic Review
Fire，November 2023
Hai Jiaying, Zhang Ling, Gao Cong, Wang Han, Wu Jiansheng
Abstract:Fire suppression has become a fundamental approach for shaping contemporary wildfire regimes. However, a growing body of research suggests that aggressive fire suppression can increase high-intensity wildfires, creating the wildfire paradox. Whether the strategy always triggers the paradox remains a topic of ongoing debate. The role of fire suppression in altering wildfire regimes in diverse socio-ecological systems and associated research designs demands a deeper understanding. To reconcile these controversies and synthesize the existing knowledge, a systematic review has been conducted to screen 974 studies on the relationship between fire suppression and wildfire regimes. The rigorous screening process led to the selection of 37 studies that met our stringent criteria for inclusion. The selected literature was quantitatively analyzed in terms of study areas, study design and methods, and the impact of fire suppression on wildfire regimes. Several critical findings were revealed: 1. Numerous studies have focused on northern mid- and high-latitude biomes, neglecting tropical savannas where wildfires are frequent and intense. Further exploration in these regions is imperative. 2. Existing studies have predominantly employed methods such as difference analysis, regression analysis, and scenario simulations. Appropriate methods could be selected based on the study area, data availability, and understanding of fire regimes. 3. Despite the consensus that fire suppression reduces the total burned area, the emergence of the wildfire paradox remains controversial, with approximately equal amounts of the literature supporting and contradicting the wildfire paradox. A noteworthy pattern was observed: the wildfire paradox is more likely to occur in fuel-limited systems, specific vegetation types, and smaller scale and longer term studies. This systematic review highlights that the occurrence of the wildfire paradox is intricately tied to ecosystem feedback mechanisms for suppression and the research scale adopted. It is necessary to incorporate a comprehensive and multi-scale assessment of how local wildlands respond to suppression into wildfire management policy-making processes. This assessment will ensure a more informed and effective wildfire management strategy adapted to local conditions.
Science of The Total Environment,December 2023
Wang Han, Zhang Danni, Liu Songyue, Ye Sheng, Jin Xueru, Wu Jiansheng
Abstract:Unravelling the evolution of landscape patterns is essential to understand regional socioecological processes and to solve conflicts between environment protection and human development. However, the role of landscape transition in regional landscape pattern evolution remains unclear. Taking 325 county-level areas in the middle reaches of the Yangtze River (MRYR) as an example, this study explored the spatiotemporal associations between landscape quantity and pattern from the 1970s to 2020. Employing the methods of landscape metrics and trend and correlation analysis, associations between landscape transition and landscape pattern were found. The main results were as follows: (1) From the 1970s to 2020, urban land nearly doubled from 0.93 to 1.89 million km2. Arable land and forest showed the largest quantity reductions of 0.88 million km2 and 0.28 million km2, respectively. Other landscapes showed both decreasing and increasing trends with a spatial overlap among counties. (2) Transition in landscape quantity drives the change in landscape patches, thus affecting the land-scape pattern in counties. The percentage of landscape area at the class level (CPLAND) showed relative changes in the quantities of landscape categories in each observation year, but their extreme outliers presented larger changes. (3) Diverse correlation coefficients in terms of magnitude and direction suggested that the transition from natural landscape to human-influenced landscape and the reverse processes occurred. Aggregation and diversity metrics showed spatial interaction with similar distances and the perimeter-area fractal dimension (PAFRAC) showed spatial autocorrelation at local scale. Optimal bandwidths among arable land, forest, and urban land (129.2 km) revealed direct spatial interactions and causal relationships, as did waters and unused land (66.7 km). The findings explained the evolution of landscape patterns and highlighted key areas where various landscape changes occurred, and can provide scientific support for policy-making in regional landscape transition governance.
106.Key attributes of greenspace pattern for heat mitigation vary with urban functional zones
Landscape Ecology, November 2023
Wang Qi, Peng Jian, Yu Shuying, Dan, Yuzhuo, Dong Jianquan, Zhao Xiang, Wu Jiansheng
Abstract：ContextUrban green space (UGS) has been widely acknowledged to effectively reduce ambient temperature, and thus improving its cooling effect has become a hot topic in urban planning. Although the impact of UGS spatial pattern on land surface temperature (LST) has been investigated in previous studies, the differences caused by the heterogeneity of human activities within urban areas have not been fully understood.ObjectivesThis study attempted to explore different relationships between UGS spatial pattern and LST among various human activity dominated zones to effectively support urban heat mitigation.MethodsTaking the urban area within the third ring road of Changsha City as the study area, the random forest model was applied to evaluate the contribution of UGS spatial pattern on LST and partial dependence curves were generated to identify their nonlinear relationships among different urban functional zones (UFZs).ResultsIn terms of varied dominant influencing factors affecting LST, the area proportion of UGS was the most important factor in residential, industrial, campus, and public zones, which showed a negative impact on the variation of LST. The cohesion between UGS patches was also an important factor in residential zones, and the more aggregated the more conducive to cooling. UGS patch density interpreted the highest importance in commercial zones, which played a significantly negative role when less than a specific threshold. However, the influence of landscape shape complexity on LST was limited in five built-up functional zones.ConclusionsThe impact of UGS spatial pattern on heat mitigation was quite different in various UFZs. The findings can provide targeted guidance for green space planning in regard to effectively mitigating the urban heat island effect.
105.Understanding the determinants of where and what kind of home accommodation to build
Ecological Indicators,October，2023
Qian Yun, Zhu Huizhen, Wu Jiansheng
Abstract：As homestays have developed rapidly, it is necessary to understand the factors affecting their density and type distribution at the micro scale. Based on the Internet data of home accommodation, the spatial distribution characteristics of homestays in Shenzhen are studied by the nearest neighbour analysis, and type distribution characteristics are analysed by NVivo. The impacts of factors are discussed through geographical detectors. We conclude that Shenzhen's homestays are multi-centre agglomeration and development in space with the flat floor as the main house structure and the modern style as the main decoration style. The spatial distribution is mainly affected by social and economic factors such as the density of bus stations and subways. The density and diversity of the homestays is high with the nearest and farthest distance to the railway station and the popular tourist destination beach while low with the mediate distance, featured with dumbbell shape.
Ecological Indicators,September 2023
Wu Jiansheng;Fan Xuening; Li, Kaiyang; Wu, Yuwei
Abstract:Exploring the spatial flow pattern of ecosystem services and clarifying the transmission path between the supply area and the demand area will help to formulate more scientific and reasonable ecological protection policies. This paper takes the rapid urbanization area representing the Pearl River Delta urban agglomeration as an example. Using Invest model to quantitative the assessment of the supply and demand of carbon sequestration services and water ecosystem services from 2000 to 2020, a spatial flow model of ecosystem services is constructed to clarify the spatial flow of regional ecosystem services pattern. In addition, the Geo-detector model is used to explore the driving factors of the supply and demand relationship of ecosystem services, and the spatiotemporal geographic weighted regression model is further used to analyze the temporal and spatial differentiation of the impact degree. Finally, based on the Bayesian belief network, the optimal state factor configuration is selected to optimize the spatial pattern, and the corresponding optimization strategy is given. The main conclusions are as follows: (1) The supply of carbon sequestration services in the Pearl River Delta decreased gradually during 2000-2020, while the demand increased gradually. The supply of water ecosystem services increased first and then decreased, while the demand showed a downward trend. (2) In terms of spatial heterogeneity of supply and demand matching, the main driving factors of carbon sequestration services included night light brightness value, temperature and vegetation index; The main driving factors of water ecosystem services include night light brightness value, land use type and vegetation index. (3) In terms of optimal areas for supply and demand matching, carbon sequestration services were mainly distributed in Zhaoqing, Huizhou and Jiangmen; The optimal matching areas of water ecosystem service supply and demand were mainly distributed in Zhaoqing, Guangzhou, Huizhou and other cities.
Resources, Conservation and Recycling, February 2023
Zhang Danni, Zhao Yuhao, Wu Jiansheng
Abstract:Carbon sink in terrestrial ecosystems is critical for achieving carbon neutrality; however, its environmental sensitivity and potential remain uncertain. A comprehensive framework was established to assess the carbon balance attribution and carbon storage potential. The net ecosystem productivity was integrated with the maximum entropy model and the patch-generating land use simulation model for analysis. In 2017, ecosystems in China produce 0.44 Pg C and store 1.66 Pg C, with sources in the west and sinks in the east. The Sichuan Basin, North China Plain, Loess Plateau, Inner Mongolia Plateau and Northeast China Plain experience the historical carbon source-to-sink conversion. The potential for the sink-to-source conversion increases from central to eastern and western China and precipitation contributes 52.3%. A high possibility of potential sink-to-source conversion concentrates in Eastern Qinghai-Tibet Plateau, middle-lower Yangtze River plain and eastern coastal areas of China. The carbon sink in terrestrial ecosystems of China is expected to be 23.58 Pg C in 2030, with the central subtropical broad-leaved evergreen zone accounting for 21.33%. The risk of the decline in carbon stocks is 0.45-0.54 Pg C. The results serve as scientific references for achieving carbon neutrality and sustainable development goals.
Applied Geography, February 2023
Zhao Yanni, Wang Man, Lan Tianhan, Xu Zihan, Wu Jiansheng, Liu Qianyuan, Peng Jian
Abstract:Ecosystem services (ESs) trade-offs are directly influenced by land use change which resulted from urbanization and ecological restoration globally or locally. However, the impacts of land use policies on ESs and their trade-offs are always interacted, needing further distinguishment. In this study we simulated grain production and water purification of the Dongting Lake Basin under different land use scenarios in 2035, and explored the impact of land use policies on ESs and their trade-offs. The results showed that returning farmland to forest land was the main factor, which would lead to 3.19% decrease in grain production and 8.13% increase in water purification. Returning farmland to waterbody would also result in a reduction of grain production (-0.85%) slightly more than the improvement of water purification (0.37%). However, the impact of urbanization on ESs would be less but spatially heterogeneous. It is worth noting that returning farmland to forest land would increase the trade-off potential and intensity, while urbanization and returning farmland to waterbody could weaken both trade-off indices. This study provides a scenario approach to distinguishing land use policies' impact on ecosystem services trade-offs.
Urban Climate，January 2023
Zhang Xiwen, Mao Feng, Gong Zhaoya, Hannah David M., Cai Yunnan, Wu Jiansheng
Abstract:Resilience has been widely used as a concept to analyse, understand, and improve cities' coping capacities to disasters. However, it is still a challenge to operationalise and quantify resilience. This study proposes a framework for assessing resilience to disasters based on the relationship between disaster intensity and damage rate. We use intense (short-term heavy) rainfall-induced urban flooding in Shenzhen city, one of the largest cities in China, as an example to explore the main features and transferability of the proposed resilience assessment framework. In addition, we demonstrate the usability of the proposed framework by using it to assess and compare the effectiveness of two resilience-building strategies: (1) permeable pavement transformation and (2) land vulnerability reduction. This research makes an innovative contribution through its effective disaster-damage-based approach for quantitatively evaluating urban resilience to disasters, which can support building resilience and mitigating the impact of climate change.
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