Advance and Future Prospects of Urban Land Use/Cover Change and Ecological Regulation of Thermal Environment
Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
Major Projects of the National Natural Science Foundation of China (41590842), Key Projects of Beijing Natural Science Foundation (8171004);
Urban land use/cover change (LUCC) and ecological regulation on thermal environment are hot topics of urban ecology and climate adaptation. This study proposed the significances in linking urban LUCC/spatial structure with the thermal regulation of ecological services. In this paper, the research progress of urban LUCC, the role of urban green infrastructure in heat island mitigation and climate adaptability, the integration of observational experiments, quantitative remote sensing, quantitative modeling of process models, and ecological regulation of thermal environment are reviewed. On this basis, a remotely sensed detection methods on urban structure components with high-precision at local or regional scales was proposed. We advanced synchronically implement field observation with satellite transits (e.g., Landsat 8, MODIS) and remotely sensed retrieval of micro-climate, eddy covariance, land surface temperature and other parameters along an urban-rural gradient in metropolitan area. The integration of these parameters into EcoCity V1.0 will be used to examine the mechanisms of the impacts of impervious surface area and green space components, their radiation and surface heat fluxes, and anthropenic heat sources on urban thermal environment, and to analyze the spatio-temporal heterogeneity of urban heat island effect induced by urban expansion of different city sizes and configuration. The impacts of urban high-precision underlying surface with multi-scale (functional zones/land-cover components/configuration and material, etc.) on local air temperature, and radiation and energy budget, the regulating threshold of urban surface structure components for alleviating urban heat island, and the quantitative knowledge of influence of urban LUCC on biogeophysical mechanisms at regional and global scales will be the important prospective contents in the future. So, the effective linking between spatial planning with urban ecology and urban climate will be of significance in this field. The overarching objectives of this study are to identify the ecological threshold on regulating urban underlyding impervious surface area and green space component for alleviating extreme weather heat and improving human comfortability aiming to UN Sustainable Development Goals 2030. This research will promote our understanding of the urban biophysical mechanisms of the urban thermal environment and provide the scientific fundamentals in building livable urban environment and urban ecology security.
urban land use/cover change;heat island;regulation of thermal environment;climate adaptability;impervious surface;quantitative remote sensing;
城市热岛效应（Urban Heat Island, UHI）是人类活动对城市气候环境系统产生的最显著影响之一。1833年Howard通过对伦敦城区和郊区的气象进行对比观测,首次对城市中心温度高于郊区的现象进行了文字记载。Manley于1958年提出城市热岛(UHI)的概念。城市不同土地利用类型会改变城市局地大气和地表与其周围的郊区温差,因而过度和无序的城市扩张使土壤和植被表面转变为城市不透水地表(如混凝土、沥青等)是引起城市热岛效应的主要原因,从而产生全球性的负效应。城市热环境生态调控是减缓城市热岛效应的有效手段之一,该方法通过地表热环境要素的差异来识别城市不同土地利用/覆盖类型的热贡献,提出有利于热岛强度减缓的城市内部空间结构和组分,进而优化城市空间格局。
当前地表热量平衡模拟模型有SEBS（ Surface Energy Balance System）、SEBAL（Surface Energy Balance Algorithm for Land）,PCACA（Pixel Component Arranging Comparing Algorithm）和能量切割法等。耦合陆表模型或城市冠层模型,在中尺度区域上形成的MM5（Fifth-Generation Penn State/NCAR Mesoscale Model）、RAMS（ Regional Atmospheric Modeling System）、WRF（Weather Research and Forecasting Model）等。Grimmond等[38,39]在全球范围内开展了城市能量平衡的模型比较计划,涉及到的模型有LUMPS（Local-Scale Urban Meteorological Parameterization Scheme）、BEP02（Building effect Parameterization）、CLMU（Community Land Model-urban)、MUCM （Multi-layer Urban Canopy Model)、NJU-UCM-S/M （Nanjing University Urban Canopy Model-single/multi Layer)、SM2-U（Soil Model for Sub-Mesoscale Urban)、TEB （Town Energy Balance)等数十个模型。它们既包括了单层模型,也包括了多层模型;既有中尺度下的模块,也有单独的城市气候模型,既有半经验模型,也有基于数值模拟的模型。针对城市生态评价模型有美国林业组织开发的Citygreen模型等。
城市生态学理论研究一再强调理解和分析城市生态系统的复杂性：包括空间格局和结构组成的异质性对生态过程和服务功能的影响机制。Pickett等和Grimm等呼吁发展新一代的空间显式的多尺度生态系统模型,以将人类控制下的格局动态和环境干扰同生物地球化学循环过程有机整合。基于Wu等提出的HPDM-PHX（Hierarchical Patch Dynamics Model of the Phoenix urban landscape）城市模型框架,Zhang等发展了多尺度耦合的HPM-UEM(Hierarchical Patch Mosaic-Urban Ecosystem Model)模型,这些模型主要针对城市生物地球化学过程。但是长期以来缺乏将城市空间等级尺度结构与生物地球物理机制相互有效联系起来的研究方法和案例。城市作为一个高度空间异质性和多因素耦合的复杂有机体,在城市土地利用/覆盖变化和热环境调控方面仍有待通过观测实验、过程模型模拟和定量遥感集成方法深入解决如下问题（图2）：对城市内部空间异质性和破碎化程度,特别是不透水地表和绿地结构的有效镶嵌,以及建筑三维空间峡谷效应、立体受光表面积增加和建筑阴影对生态系统热调节影响机制认识;它们对城市热辐射的扩散、阻挡、挤压、传导、波动等效应;以及与之交互的大气污染、人为热源排放对城市生态系统热调节影响的拮抗、胁迫、消长和适应作用机制综合效应。
Integrated methods of quantitative remote sensing, observational experiments and process models
城市绿地(Urban Green Space, UGS)作为城市生态系统的重要组成部分,在改善城市环境,特别是空气和水质净化,建筑节能,适宜空气温度,紫外线减少方面具有重要作用[43,44]。城市中适宜比例的绿地面积有调节城市内部气候环境,影响城市内部辐射能量平衡,降低城市地表温度等作用,对生态服务热调节功能具有决定性作用[45,46,47]。通过仪器测量方法分析公园绿地对周边区域的温度影响,发现绿地温度明显低于周边区域,且面积越大,植被覆盖越高的绿地冷岛效应越明显。研究表明,增加10%的绿地,城市热辐射将减少2℃,当绿地斑块面积大于5 km2,地表辐射温度急剧下降。绿地和周边城市温度差异夏季大,冬季小,冷岛效应可以在夜晚的城市区域延伸200~300 m,而夏季8~10月间,范围可以超过500 m,有效地降低了城市温度。中国城市不透水地表比例过高,绿地面积不够集中,较大程度上影响了城市热调节功能。
为进一步保护城市内部绿地覆盖,美国已实施了不同的城市绿地发展计划,如种植大量绿地植被[50,51]、保护现有植被和发展城市冠层目标等。针对城市内部不透水与森林覆盖结构组分研究,国际林业研究组织联盟(International Union of Forestry Research Organizations,IUFRO)曾建立专门的项目组来探讨人类居住区的绿地和城市森林覆盖方面的问题。2000年以来,欧洲、中国等多个国家政府以绿地结构和城市规划为研究内容,展开专项科研计划[55,56]。国内外绿地植被对缓解城市热岛效应的作用研究证实了公园绿地的“冷效应”和不透水层的“热效应”[57,58,59]。不仅如此,已有研究表明部分位于热带荒漠环境中的城市,由于城市内部大面积的灌溉植被增加了地表蒸散发,进而呈现城市“冷岛效应”[60,61]。多项研究证明绿地和水体具有缓减热岛效应的作用,但是针对一定面积的绿地或水体具体的影响范围的量化研究不多,而绿地和水体的结构、配置等对热效应的调节作用,需要深入研究。
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Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quantitative relationship with thermal environment are still poorly understood, resulting in ineffective application in urban ecological planning and management. Through the integration of 渟patial structure theoryin urban geography and 渟urface energy balancein urban climatology, we proposed a new concept of urban surface structure and thermal environment regulation to reveal the mechanism between urban spatial structure and surface thermal environment. We developed the EcoCity model for regulating urban land cover structure and thermal environment, and established the eco-regulation thresholds of urban surface thermal environments. Based on the comprehensive analysis of experimental observation, remotely sensed and meteorological data, we examined the spatial patterns of urban habitation, industrial, infrastructure service, and ecological spaces. We examined the impacts of internal land-cover components (e.g., urban impervious surfaces, greenness, and water) on surface radiation and heat flux. This research indicated that difference of thermal environments among urban functional areas is closely related to the proportions of the land-cover components. The highly dense impervious surface areas in commercial and residential zones significantly increased land surface temperature through increasing sensible heat flux, while greenness and water decrease land surface temperature through increasing latent heat flux. We also found that different functional zones due to various proportions of green spaces have various heat dissipation roles and ecological thresholds. Urban greening projects in highly dense impervious surfaces areas such as commercial, transportation, and residential zones are especially effective in promoting latent heat dissipation efficiency of vegetation, leading to strongly cooling effect of unit vegetation coverage. This research indicates that the EcoCity model provides the fundamentals to understand the coupled mechanism between urban land use structure and surface flux and the analysis of their spatiotemporal characteristics. This model provides a general computational model system for defining urban heat island mitigation, the greening ratio indexes, and their regulating thresholds for different functional zones.
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Abstract China is the largest and most rapidly urbanizing nation in the world, and is projected to add an additional 200 million city dwellers by the end of 2030. While this rapid urbanization will lead to vast expansion of built-up areas, the possible climate effect and associated human health impact remain poorly understood. Using a coupled urban-atmospheric model, we first examine potential effects of three urban expansion scenarios to 2030 on summer climate in eastern China. Our simulations indicate extensive warming up to 500°C, 300°C, and 200°C in regard to low- (>0%), high- (>75%), and 100% probability urban growth scenarios, respectively. The partitioning of available energy largely explains the changes in 2-m air temperatures, and increased sensible heat flux with higher roughness length of the underlying urban surface is responsible for the increase of nighttime planetary boundary layer height. In the extreme case (the low-probability expansion pathway), the agglomeration of impervious surfaces substantially reduces low-level atmospheric moisture, consequently resulting in large-scale precipitation reduction. However, the effect of near-surface warming far exceeds that of moisture reduction and imposes non-negligible thermal loads on urban residents. Our study, using a scenario-based approach that accounts for the full range of urban growth uncertainty by 2030, helps better evaluate possible regional climate effects and associated human health outcomes in the most rapidly urbanizing areas of China, and has practical implications for the development of sustainable urban regions that are resilient to changes in both mean and extreme conditions.
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The number of hot days is increasing in many parts of the world because of the heat island phenomenon and global climate change. High air temperature greatly affects human thermal comfort and public health, particularly in urban areas. Therefore, the challenging task of, urban designers and urban planners in accommodating the increasing population is to make cities with the least level of vulnerability to future climate change. Interest in transferring urban climatic knowledge into urban planning practices, and developing mitigation strategies to adapt to climate change, has been increased in recent years. The use of vegetation and appropriate urban geometry are shown very promising in mitigating the adverse effects of heat island and providing a better pedestrian thermal comfort. This article reviews studies on pedestrian level urban greening and geometry in improving thermal comfort in cities. Such strategies can be applied at the preliminary stages of urban planning and thus directly affect the microclimate. The analyzed data include simulation and field measurement studies. The discussion of this research clearly reflects how urban design guidelines can be applied to enhance outdoor thermal comfort and minimize the heat island effect. This study is helpful in controlling the consequences of city design from the early design stage.
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China has experienced an unprecedented urbanization and industrialization in the past decades. In this research, we examined the dynamics of construction lands and impervious surface areas (ISA) based on land use/cover change and ISA datasets between 2000 and 2008, which were provided by the national resources and environmental remote sensing information platform. The results indicated that the construction areas and ISA increased by 3468.30 and 2212.24 km(2)/a in this period primarily due to the implementation of national macro-development strategies and fast-growing economy. In 2008, ISA accounted for 0.86% of the total land area in China. Urban land areas increased by 43.46% between 2000 and 2008. The annual growth rate of 1788.22 km(2)/a in this period was 2.18 times that in the 1990s. In particular, urban ISA increased by 53.30% between 2000 and 2008 with an annual growth rate of 1348.85 km(2)/a. During the 8 years, the ISA in China increased rapidly, especially in the Beijing-Tianjin-Tangshan Metropolitan Region, Pearl River Delta, Yangtze River Delta, and the western China region. The increasing ISA may influence potentially water environmental quality in the major basins. In particular, the number of subbasins having ISA of greater than 10% increased considerably, which were primarily distributed in the Haihe River, Yangtze River and Pearl River basins. In 2008, 14.42% of the basin areas were affected by the increased ISA.
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China's extensive urbanization has resulted in a massive loss of natural habitat, which is threatening the nation's biodiversity and socioeconomic sustainability. A timely and accurate understanding of natural habitat loss caused by urban expansion will allow more informed and effective measures to be taken for the conservation of biodiversity. However, the impact of urban expansion on natural habitats is not well-understood, primarily due to the lack of accurate spatial information regarding urban expansion across China. In this study, we proposed an approach that can be used to accurately summarize the dynamics of urban expansion in China over two recent decades (1992-2012), by integrating data on nighttime light levels, a vegetation index, and land surface temperature. The natural habitat loss during the time period was evaluated at the national, ecoregional, and local scales. The results revealed that China had experienced extremely rapid urban growth from 1992 to 2012 with an average annual growth rate of 8.74%, in contrast with the global average of 3.20%. The massive urban expansion has resulted in significant natural habitat loss in some areas in China. Special attention needs to be paid to the Pearl River Delta, where 25.79% or 1518 km(2) of the natural habitat and 41.99% or 760 km(2) of the local wetlands were lost during 1992-2012. This raises serious concerns about species viability and biodiversity. Effective policies and regulations must be implemented and enforced to sustain regional and national development in the context of rapid urbanization.
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Records of hemispheric average temperatures from land regions for the past 100 years provide crucial input to the debate over global warming. Despite careful use of the basic station data in some of these compilations of hemispheric temperature, there have been suggestions that a proportion of the 0.5 C warming seen on a century timescale may be related to urbanization influences - local warming caused by the effects of urban development. We examine here an extensive set of rural-station temperature data for three regions of the world: European parts of the Soviet Union, eastern Australia and eastern China. When combined with similar analyses for the contiguous United States the results are representative of 20% of the land area of the Northern Hemisphere and 10% of the Southern Hemisphere. The results show that the urbanization influence in two of the most widely used hemispheric data sets is, at most, an order of magnitude less than the warming seen on a century timescale.
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Efforts to develop a global understanding of the functioning of the Earth as a system began in the mid-1980s. This effort necessitated linking knowledge from both the physical and biological realms. A motivation for this development was the growing impact of humans on the Earth system and need to provide solutions, but the study of the social drivers and their consequences for the changes that were occurring was not incorporated into the Earth System Science movement, despite early attempts to do so. The impediments to integration were many, but they are gradually being overcome, which can be seen in many trends for assessments, such as the Intergovernmental Platform on Biodiversity and Ecosystem Services, as well as both basic and applied science programs. In this development, particular people and events have shaped the trajectories that have occurred. The lessons learned should be considered in such emerging research programs as Future Earth, the new global program for sustainability research. The transitioning process to this new program will take time as scientists adjust to new colleagues with different ideologies, methods, and tools and a new way of doing science.
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The regional-scale climatic impact of urbanization is examined using two land cover parameters, fractional vegetation cover (Fr) and surface moisture availability (M0). The parameters are hypothesized to decrease as surface radiant temperature (T0) increases, forced by vegetation removal and the introduction of non-transpiring, reduced evaporating urban surfaces. Fr and M0 were derived from vegetation index and T0 data computed from the Advanced Very High Resolution Radiometer (AVHRR), and then correlated to a percentage of urban land cover obtained from a supervised classification of Landsat TM imagery. Data from 1985 through 1994 for an area near State College, PA, USA, was utilized. Urban land cover change (at the rate of 3 per cent perkm2 per year) was statistically significant when related to a decrease in normalized values of Fr and increase in normalized values of T0. The relationship between urbanization and M0, however, was ill-defined due to variations in the composition of urban vegetation. From a nomogram of values of Fr and T0, a Land Cover Index (LCI) is proposed, which incorporates the influence of local land cover surrounding urbanized pixels. Such an index could allow changes in land use at neighbourhoodscale to be input in the initialization of atmospheric and hydrological models, as well as provide a new approach for urban heat island analyses. Furthermore, the nomogram can be used to qualify urbanization effects on evapotranspiration rates.
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We present the first global inventory of the spatial distribution and density ofconstructed impervious surface area (ISA). Examples of ISA include roads, parking lots,buildings, driveways, sidewalks and other manmade surfaces. While high spatialresolution is required to observe these features, the new product reports the estimateddensity of ISA on a one-km2 grid based on two coarse resolution indicators of ISA 01040000“ thebrightness of satellite observed nighttime lights and population count. The model wascalibrated using 30-meter resolution ISA of the USA from the U.S. Geological Survey.Nominally the product is for the years 2000-01 since both the nighttime lights andreference data are from those two years. We found that 1.05% of the United States landarea is impervious surface (83,337 km2) and 0.43 % of the world0104000064s land surface (579,703km2) is constructed impervious surface. China has more ISA than any other country(87,182 km2), but has only 67 m2 of ISA per person, compared to 297 m2 per person in theUSA. The distribution of ISA in the world0104000064s primary drainage basins indicates that watersheds damaged by ISA are primarily concentrated in the USA, Europe, Japan, China and India. The authors believe the next step for improving the product is to include reference ISA data from many more areas around the world.
Lu DS, MoranE, HetrickS.Detection of impervious surface change with multitemporal Landsat images in an urban-rural frontier[J]. , 2011, 66(3): 298-306.
Mapping and monitoring impervious surface dynamic change in a complex urban–rural frontier with medium or coarse spatial resolution images is a challenge due to the mixed pixel problem and the spectral confusion between impervious surfaces and other non-vegetation land covers. This research selected Lucas do Rio Verde County in Mato Grosso State, Brazil as a case study to improve impervious surface estimation performance by the integrated use of Landsat and QuickBird images and to monitor impervious surface change by analyzing the normalized multitemporal Landsat-derived fractional impervious surfaces. This research demonstrates the importance of two-step calibrations. The first step is to calibrate the Landsat-derived fraction impervious surface values through the established regression model based on the QuickBird-derived impervious surface image in 2008. The second step is to conduct the normalization between the calibrated 2008 impervious surface image with other dates of impervious surface images. This research indicates that the per-pixel based method overestimates the impervious surface area in the urban–rural frontier by 50%–60%. In order to accurately estimate impervious surface area, it is necessary to map the fractional impervious surface image and further calibrate the estimates with high spatial resolution images. Also normalization of the multitemporal fractional impervious surface images is needed to reduce the impacts from different environmental conditions, in order to effectively detect the impervious surface dynamic change in a complex urban–rural frontier. The procedure developed in this paper for mapping and monitoring impervious surface area is especially valuable in urban–rural frontiers where multitemporal Landsat images are difficult to be used for accurately extracting impervious surface features based on traditional per-pixel based classification methods as they cannot effectively handle the mixed pixel problem.
Impervious surface can be defined as any materials that prevent the infiltration of water into the soil. Principally, roads and rooftops in the urban are the most prevalent and easily identified types of impervious surfaces. Other types include sidewalks, patios, bedrock outcrops, and compacted soils in the urban areas. Impervious surface not only indicates urbanization, but also is a major contrihutor to the environmental impacts of urbanization. Impervious surface area (ISA) is the index of impervious surface landscape components, which uses the percentage in a pixel for representation. It is an index to monitor the urban ecological system and environmental change, and is an important indicator of the ecological and environmental model, which can affect urban hydrological cycle, surface runoff, water quality, local climate, and biological diversity. This paper reviews the development of remote sensing technology of impervious surface, and summarizes how it impacts urban ecosystem and urban environmental system. From the aspect of remote sensing technology, sub-pixel decomposition including spectral mixture analysis and regression analysis, and other new methods for interpreting image, will be the trend of the application of remote sensing research to urban natural resources and environmental studies in the future. From the aspect of remote sensing data source, the data of medium-resolution (10-100 m) image and high-resolution (0.3-5 m) image, which are used to estimate the index of impervious surface in multi-temporal and large-spatial area, can provide a reliable basis to monitor urban land use/cover change and environmental response. As an environmental indicator, impervious surface area (ISA) can be used to monitor urban land cover change and simulate future urban development, providing a basis for the decision making of urban planning and management. Referring to the fact that impervious surface has an important relation to the hydrological cycle, non-point source pollution, land surface temperature, vegetation variation and biological diversity, if we can understand the relationship between impervious surface area and the environmental or ecological indicators, we(an better understand urban landscape pattern and ecological processes. Impervious surface area plays an important role in studying the eco-environmental effects of urbanization.
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ABSTRACT Growing interest in urban systems as ecological entities calls for some standards in parameterizing biophysical composition of urban environments. A vegetation-impervious surface-soil ( V-I-S) model is presented as a possible basis for standardization. The V-I-S model may serve as a foundation for characterizing urban/near-urban environments universally, and for comparison of urban morphology within and between cities. Inasmuch as the model may be driven by satellite digital data, it may serve as a global model of urban ecosystem analysis and comparison world-wide. The V-I-S model may prove useful for urban change detection and growth modelling, for environmental impact analysis from urbanization, for energy- and water-related investigations, and for certain dimensions of human ecosystem analysis of the city as well.
Kuang WH, Chi WF, Lu D S et al. A comparative analysis of megacity expansions in China and the U.S.: patterns, rates and driving forces[J]. , 2014, 132: 121-135.
Research on physical characteristics and land-cover dynamic changes of megacities over time provides valuable insights for effectively regulating urban planning and management. This study conducts a comparative analysis of 30-year urban expansion patterns and rates among three metropolises in China (Beijing, Shanghai, and Guangzhou) and another three in the USA (New York, Los Angeles, and Chicago) based on time-series impervious surface area (ISA) data extracted from multitemporal Landsat images using the linear spectral mixture analysis approach. This research indicates significantly different urbanization patterns and rates between the Chinese and American megacities. The ISA expansion area in Chinese megacities was five times higher than that in American megacities during the past three decades. The Chinese megacities expand outward from the urban core to the periphery in a concentric ring structure, whereas the American megacities increase ISA mainly within the inner cities with patch-filling patterns. The Chinese megacities are in the development stage where population and economic conditions significantly influence urban expansion patterns and rates, but the American megacities are in the developed stage where population and economic conditions are not important forces driving the ISA expansion. The ISA intensity in the American megacities decreases constantly and smoothly, but ISA intensity in Chinese megacities decays abruptly within certain distances, depending on different cities and years. The most obvious urban expansions were between 8 and 20km in Beijing in the 1980s, between 14 and 50km in Shanghai in the 2000s, and between 8 and 18km in Guangzhou in the 1990s.
[YueWenze, WuCifang.Urban impervious surface distribution estimation by spectral mixture analysis. , 2007, 11(6): 914-922.]
ZhangL, Weng QH, Shao ZF.An evaluation of monthly impervious surface dynamics by fusing Landsat and MODIS time series in the Pearl River Delta, China, from 2000 to 2015[J]. , 2017, 201: 99-114.
react-text: 444 Accurate, up-to-date, and consistent information of urban extents is vital for numerous applications central to urban planning, ecosystem management, and environmental assessment and monitoring. However, current large-scale urban extent products are not uniform with respect to definition, spatial resolution, temporal frequency, and thematic representation. This study aimed to enhance,... /react-text react-text: 445 /react-text [Show full abstract]
ChristenA, VogtR.Energy and radiation balance of a central European city[J]. , 2004, 24(11): 1395-1421.
Results from an experimental network of seven energy balance stations in and around a European city are presented. The network of micrometeorological stations was part of the Basel Urban Boundary Layer Experiment (BUBBLE) carried out in the city of Basel, Switzerland. Three urban sites provided turbulent flux densities and radiation data over dense urban surfaces. Together with a suburban site and three rural reference sites, this network allowed the simultaneous comparison of urban, suburban, and rural energy balance partitioning during one month of summertime measurements. The partitioning is analysed together with long-term data to evaluate the magnitude of the urban flux density modification, and to document characteristic values in their diurnal and yearly course. Simple empirical relations between flux densities and surface characteristics are presented. The energy balance partitioning is addressed separately for daytime and nocturnal situations. All four components of the surface radiation budget are analysed. Moreover, the vertical flux density divergences within the urban canopy layer are discussed.
[LiuGang, SunJianning, Jiang Weinei et al. Comprehensive observation research on urban atmospheric boundary layer-Description of field experiment and analysis of micrometeorological properties in the surface layer. , 2009, 39(1): 23-32.]
Miao SG, Dou JX, Chen F et al. Analysis of observations on the urban surface energy balance in Beijing[J]. , 2012, 55: 1881-1890.
The 1-year (2009–2010) measurements are analyzed of the urban surface energy balance (SEB) obtained from the sensors located at three vertical layers of a 325-m tower in downtown Beijing. Results show that: (1) The measurements from the 325-m tower represent the SEB characteristics of the cities located in semi-humid warm-temperate continental monsoon climate zone. In a typical hot and rainy summer, cold and dry winter, the measured Bowen ratio is minimum in summer and maximum in winter. The Bowen ratio measured at 140 m for spring, summer, autumn, and winter are 2.86, 0.82, 1.17, and 4.16 respectively. (2) At the height of 140-m (in the constant flux layer), the noontime albedo is 650.10 for summer, 650.12 for spring and autumn, and 650.14 for winter. The ratios of daytime sensible heat flux, latent heat flux, and storage heat flux to net radiation are 0.25, 0.16, and 0.59 for clear-sky days, and 0.33, 0.19, and 0.48 for cloudy days respectively. (3) Under clear-sky days, the nighttime sensible heat flux is almost zero, but the latent heat flux is greater than zero. For cloudy days, the nighttime sensible heat flux is slightly greater than the latent heat flux in winter. The nighttime upward heat flux is presumably due to the anthropogenic release (mainly latent heat for summer, while latent and sensible heat for winter).
[ZhangRenhua, SunXiaomin, Wang Weimin et al. An operational two-layer remote sensing model to estimate surface flux in regional scale: Physical background. , 2004, 34: 200-216.]
GrimmondC, BlackettM, Best M et al. The international urban energy balance models comparison project: First results from phase1[J]. , 2010, 49(6): 1268-1292.
GrimmondC, BlackettM, Best M et al. Initial results from phase 2 of the international urban energy balance model comparison[J]. , 2011, 31(2): 244-272.
Urban land surface schemes have been developed to model the distinct features of the urban surface and the associated energy exchange processes. These models have been developed for a range of purposes and make different assumptions related to the inclusion and representation of the relevant processes. Here, the first results of Phase 2 from an international comparison project to evaluate 32 urban land surface schemes are presented. This is the first large-scale systematic evaluation of these models. In four stages, participants were given increasingly detailed information about an urban site for which urban fluxes were directly observed. At each stage, each group returned their models' calculated surface energy balance fluxes. Wide variations are evident in the performance of the models for individual fluxes. No individual model performs best for all fluxes. Providing additional information about the surface generally results in better performance. However, there is clear evidence that poor choice of parameter values can cause a large drop in performance for models that otherwise perform well. As many models do not perform well across all fluxes, there is need for caution in their application, and users should be aware of the implications for applications and decision making. Copyright 2010 Royal Meteorological Society
Pickett S TA, Cadenasso ML, Grove JM. Biocomplexity in coupled natural human systems: a multidimensional framework[J]. , 2005, 8: 225-232.
As defined by Ascher, biocomplexity results from a "multiplicity of interconnected relationships and levels." However, no integrative framework yet exists to facilitate the application of this concept to coupled human-natural systems. Indeed, the term "biocomplexity" is still used primarily as a creative and provocative metaphor. To help advance its utility, we present a framework that focuses on linkages among different disciplines that are often used in studies of coupled human-natural systems, including the ecological, physical, and socioeconomic sciences. The framework consists of three dimensions of complexity: spatial, organizational, and temporal. Spatial complexity increases as the focus changes from the type and number of the elements of spatial heterogeneity to an explicit configuration of the elements. Similarly, organizational complexity increases as the focus shifts from unconnected units to connectivity among functional units. Finally, temporal complexity increases as the current state of a system comes to rely more and more on past states, and therefore to reflect echoes, legacies, and evolving indirect effects of those states. This three-dimensional, conceptual volume of biocomplexity enables connections between models that derive from different disciplines to be drawn at an appropriate level of complexity for integration.
Grimm NB, FosterD, Groffman P et al. The changing landscape: ecosystem responses to urbanization and pollution across climatic and societal gradients[J]. , 2008, 6(5):264-272.
ZhangC, WuJ, Grimm B N et al. A hierarchical patch mosaic ecosystem model for urban landscapes: Model development and evaluation[J]. , 2013, 250: 81-100.
Urbanization effects on ecosystem functions are both important and complex, characterized by scale multiplicity, spatial heterogeneity, and intensive human disturbances. Integrating the hierarchical structure of urban landscape pattern with ecosystem processes through simulation modeling can facilitate our understanding of human揺nvironment interactions in urban environment. Current ecosystem models often focus on plant physiological and biogeochemical processes in homogeneous land covers, incapable of addressing the structural complexity in urban landscapes with multiple anthropogenic drivers across a range of spatial scales. Here we present the Hierarchical Patch Mosaic-Urban Ecosystem Model (HPM-UEM), a multi-scaled model that explicitly treats spatial pattern and hierarchical structure of urban landscape by incorporating both top-down controls and bottom-up mechanisms in urban environment. By addressing six hierarchical levels from individual plant to the urbanized region, HPM-UEM provides a ierarchical ladderto scale up local ecosystem functions across the nested urban land hierarchies (i.e., land cover, land use, landscape, and the urbanized region), and facilitate linking ecosystem processes and socioeconomic drivers. By organizing human influences in a spatially nested hierarchical patch mosaic structure, HPM-UEM models the complex spatiotemporal pattern of multiple environmental constraints on urban ecosystem functions. The model was evaluated based on extensive datasets developed by the Long-Term Ecological Research (LTER) network, especially the Central Arizona-Phoenix (CAP) LTER. Model testing results showed that HPM-UEM predicted both C fluxes and spatial pattern of C stocks with reasonable accuracy. HPM-UEM enabled us to assess spatial patterns and multiple-scaled dynamics of C cycle of the urban landscape, revealing the distinct productivities and C densities of different urban land types across different spatial scales. Sensitivity analyses indicated that future environmental changes and landscape modifications could have strong and complex effects on urban ecosystem functions. By matching ecological processes, anthropogenic environmental controls, and land and socioeconomic dynamics based on hierarchical levels, HPM-UEM could be coupled to multiple-scaled urban land-use models, climate models, and socioeconomic models to gain a comprehensive understanding of urban biogeochemical cycles.
Wolf KM.Public response to the urban forest in inner-city business districts[J]. , 2003, 29(3): 117-126.
ByomkeshT, NakagoshiN, Dewan AM.Urbanization and green space dynamics in greater Dhaka, Bangladesh[J]. , 2011, 8(1): 45-58.
AbstractGreen space is particularly indispensable for proper functioning of the ecosystem in an urban environment. This study was an attempt to dynamically map and monitor green spaces in Greater Dhaka of Bangladesh. Both primary and secondary data were acquired to document the spatial–temporal dynamics of green spaces in the study area. Using a supervised classification algorithm, multi-temporal land use/cover data were extracted from a set of satellite images. A number of spatial metrics were employed to understand the landscape condition in a multi-temporal manner. In addition, 50 key informants along with focus group discussion and observation techniques were used to document existing management aspects of green spaces and their conservation policies. The analysis revealed that green spaces in Greater Dhaka are rapidly disappearing over the course of time even though they provide a number of natural, economic and social benefits. The disappearance of green spaces was primarily attributed to a rapid increase in the urban population, mainly driven by rural–urban migration. As a result, the landscape became highly fragmented and less connected. A substantial reduction of green patches is also leading to deterioration of the ecological condition of the landscape. The drastic reduction of green spaces in Greater Dhaka has been attributed to a lack of policy, low political motivation, and poor management. In order to ensure sustainability of green spaces and proper functioning of the city’s ecosystem, there is an urgent need for strategic green space planning.
PengJ, XieP, Liu Y X et al. Urban thermal environment dynamics and associated landscape pattern factors: A case study in the Beijing metropolitan region[J]. , 2016, 173: 145-155.
61LST dynamic was examined in Beijing during 2001–2009.61LST increased averagely in the whole metropolitan area but decreased in city center.61Built-up areas and barren land contribute most to UHI.61Cooling effects of ecological land is obvious with the proportion above 70%.61LST is determined more by landscape composition than spatial configuration.
Ca VT, AsaedaT, Abu EM.Reductions in air conditioning energy caused by a nearby park[J]. , 1998, 29(1): 83-92.
Field observations were carried out to determine the influence of a park on the urban summer climate in the nearby areas. The possibilities of reduction in air conditioning energy were investigated. Air temperature, relative humidity and other meteorological factors were measured at many locations inside a park and in the surrounding areas in the Tama New Town, a city in the west of the Tokyo Metropolitan Area, Japan. The observations indicated that vegetation could significantly alter the climate in the town. At noon, the highest temperature of the ground surface of the grass field in the park was 40.3 °C, which was 19 °C lower than that of the asphalt surface or 15 °C lower than that of the concrete surface in the parking or commercial areas. At the same time, air temperature measured at 1.2 m above the ground at the grass field inside the park was more than 2 °C lower than that measured at the same height in the surrounding commercial and parking areas. Soon after sunset, the temperature of the ground surface at the grass field in the park became lower than that of the air, and the park became a cool island whereas paved asphalt or concrete surfaces in the town remained hotter than the overlying air even late at night. With a size of about 0.6 km 2 , at noon, the park can reduce by up to 1.5 °C the air temperature in a busy commercial area 1 km downwind. This can lead to a significant decrease of in air conditioning energy in the commercial area.
Kuang WH, Dou YY, Zhang C et al. Quantifying the heat flux regulation of metropolitan land use/land cover components by coupling remote sensing modeling with in situ measurement[J]. , 2015, 120(1):113-130.
Abstract <p>Quantifying the effects of urban land use/land cover with regard to surface radiation and heat flux regulation is important to ecological planning and heat stress mitigation. To retrieve the spatial pattern of heat fluxes in the Beijing metropolitan area, China, a remote sensing-based energy balance model was calibrated with synchronously measured energy fluxes including net radiation, latent heat flux (LE), and sensible heat flux ( H ). Our model calibration approach avoided the uncertainties due to subjective judgments in previous empirical parameterization methods. The land surface temperature (LST), H , and Bowen ratio ( 尾 ) of Beijing were found to increase along the outskirt-suburban-urban gradient, with strong spatial variation. LST and H were negatively correlated with vegetation fraction cover (VFC). For example, the modern high-rise residential areas with relatively higher VFC had lower H and 尾 than the traditional low-rise residential areas. Our findings that indicate thermal dissipation through vegetation transpiration might play an important role in urban heat regulation. Notably, the thermal dissipating strength of vegetation (calculated as LE/VFC) declined exponentially with increased VFC. For the purpose of heat stress regulation, we recommend upgrading the traditional low-rise residential areas to modern high-rise residential areas and focusing urban greenery projects in areas whose VFC
[YingTianyu, LiMingze, Fan Wenyi et al. Analysis of urban forest and heat island effect based on GIS technology. 2010, 38(8): 63-67.]
HamadaS, OhtaT.Seasonal variations in the cooling effect of urban green areas on surrounding urban areas[J]. , 2010, 9(1):15-24.
We measured air temperature in an urban green area that includes forest and grassland and in the surrounding urban area for a full year in Nagoya, central Japan, to elucidate seasonal variations of the difference in air temperature between urban and green areas. We determined the range of the “cool-island” effect as well as the relationship between vegetation cover and air temperature throughout the year. The temperature difference between urban and green areas was large in summer and small in winter. The maximum air temperature difference was 1.9 °C in July 2007, and the minimum was 610.3 °C in March 2004. The difference was larger during the day than during the night in summer, whereas in winter the opposite relationship was true. However, winter diurnal variation was not particularly noticeable, a behaviour thought to be related to reduced shading by deciduous trees in the green area. During the night, the cooling effect of the green area reached 200–300 m into the urban area. During the day, the cooling effect between August and October 2006 exceeded 300 m and varied widely, although there was no correlation beyond 500 m. The correlation between air temperature and forest-cover ratio within a radius of 200 m from each measurement site was significant from 16:00 to 19:00. There was also a correlation during the night; this correlation was weakest in the early morning. The effect of the forest-cover ratio on air temperature was most pronounced in August 2006 and June 2007.
City of Pasadena. Pasadena Tree Protection Ordinance [EB/OL]. 2011. .[<date-in-citation content-type="access-date">2015-06-11</date-in-citation>].
City of Seattle. Seattle’s Canopy Cover [EB/OL]. 2011..[<date-in-citation content-type="access-date">2001-06-11</date-in-citation>].
Andresen JW.Selection of trees for endurance of high temperatures and artificial lights in urban areas. Publications-USDA[J]. , 1976, 22: 67-75.
Caroll RE.Changes affecting the employment cost index: An overview[J]. , 2006, 129(4): 3-5.
With the release of March 2006 data, BLS has updated the ECI to reflect the new industry and occupational classifications systems; rebased the index to 2005; and implemented new procedures to account for missing data and to compute seasonal adjustments
[JiaLiuqiang, ShuBo.Review and prospect of the relationship between urban green space and heat island effect. , 2012, 28(4): 37-40.]
CaoX, OnishiA, Chen J et al. Quantifying the cool island intensity of urban parks using ASTER and IKONOS data[J]. , 2010, 96(4): 224-231.
Urban parks can help mitigate urban heat island (UHI) effects and decrease cooling energy consumption in summer. However, it is unclear how park characteristics affect the formation of a park cool island (PCI). In this study, PCI intensity values for 92 parks in Nagoya, Japan were obtained from ASTER land surface temperature (LST) products and then correlated to detailed and use information derived from high-spatial-resolution IKONOS satellite data. The results indicate that (1) the cooling effect depends on the park size and seasonal radiation condition, and park size is non-linearly correlated to PCI intensity; (2) PCI intensity is mainly determined by the area of tree and shrub inside the park as well as the park shape, and grass has negative impact on PCI formation. The park vegetation and shape index (PVSI) proposed here well predicted PCI intensity of selected parks. These findings can help urban planners to understand PCI formation and design cool parks to counteract UHI effects.
ZhangY, OdehI, HanC.Bi-temporal characterization of land surface temperature in relation to impervious surface area, NDVI and NDBI, using a sub-pixel image analysis[J]. , 2009, 11: 256-264.
As more than 50% of the human population are situated in cities of the world, urbanization has become an important contributor to global warming due to remarkable urban heat island (UHI) effect. UHI effect has been linked to the regional climate, environment, and socio-economic development. In this study, Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) imagery, respectively acquired in 1989 and 2001, were utilized to assess urban area thermal characteristics in Fuzhou, the capital city of Fujian province in south-eastern China. As a key indicator for the assessment of urban environments, sub-pixel impervious surface area (ISA) was mapped to quantitatively determine urban land-use extents and urban surface thermal patterns. In order to accurately estimate urban surface types, high-resolution imagery was utilized to generate the proportion of impervious surface areas. Urban thermal characteristics was further analysed by investigating the relationships between the land surface temperature (LST), percent impervious surface area, and two indices, the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI). The results show that correlations between NDVI and LST are rather weak, but there is a strong positive correlation between percent ISA, NDBI and LST. This suggests that percent ISA, combined with LST, and NDBI, can quantitatively describe the spatial distribution and temporal variation of urban thermal patterns and associated land-use/land-cover (LULC) conditions.
Imhoff ML, ZhangP, Wolfe R E et al. Remote sensing of the urban heat island effect across biomes in the continental USA[J]. , 2010, 114(3): 504-513.
We find that ecological context significantly influences the amplitude of summer daytime UHI (urban–rural temperature difference) the largest (802°C average) observed for cities built in biomes dominated by temperate broadleaf and mixed forest. For all cities combined, ISA is the primary driver for increase in temperature explaining 70% of the total variance in LST. On a yearly average, urban areas are substantially warmer than the non-urban fringe by 2.902°C, except for urban areas in biomes with arid and semiarid climates. The average amplitude of the UHI is remarkably asymmetric with a 4.302°C temperature difference in summer and only 1.302°C in winter. In desert environments, the LST's response to ISA presents an uncharacteristic “U-shaped” horizontal gradient decreasing from the urban core to the outskirts of the city and then increasing again in the suburban to the rural zones. UHI's calculated for these cities point to a possible heat sink effect. These observational results show that the urban heat island amplitude both increases with city size and is seasonally asymmetric for a large number of cities across most biomes. The implications are that for urban areas developed within forested ecosystems the summertime UHI can be quite high relative to the wintertime UHI suggesting that the residential energy consumption required for summer cooling is likely to increase with urban growth within those biomes.
GeorgescuM, MoustaouiM, MahalovA, et al.An alternative explanation of the semiarid urban area “oasis effect”[J]. , 2011, 116(D24113):1-13.
LazzariniM, MoliniA, Marpu P R et al. Urban climate modifications in hot desert cities: The role of land cover, local climate, and seasonality[J]. , 2015, 42(22):9980-9989.
Abstract Urban climate modifications like the urban heat island (UHI) have been extensively investigated in temperate regions. In contrast, the understanding of how urbanization relates to climate in hot, hyperarid environments is still extremely limited, despite the growing socioeconomic relevance of arid lands and their fast urbanization rate. We explore here the relationship between land cover and temperature regime in hot desert cities (HDCs) based on estimates of land surface temperature, normalized difference vegetation index, and impervious surface areas inferred from Moderate Resolution Imaging Spectroradiometer and Landsat satellite products. Our analysis shows that HDCs display common climatic patterns, with downtown areas on average cooler than suburbs during the daytime (urban cool island) and warmer at night (classical UHI). The observed diurnal cool island effect can be largely explained by relative vegetation abundance, percentage of bare soil, and local climatic conditions and calls for a more in deep investigation of the physical processes regulating boundary layer dynamics in arid regions.
[WeiJianbing, XiaoDuning, XieFuju.Evaluation and regulation principles for the effects of human activities on ecology and environment. , 2006, 25(2): 36-45.]
PengJ, TianL, Liu YXet al. Ecosystem services response to urbanization in metropolitan areas: Thresholds identification[J]. , 2017, 607-608: 706-714.
Abstract Ecosystem service is the key comprehensive indicator for measuring the ecological effects of urbanization. Although various studies have found a causal relationship between urbanization and ecosystem services degradation, the linear or non-linear characteristics are still unclear, especially identifying the impact thresholds in this relationship. This study quantified four ecosystem services (i.e. soil conservation, carbon sequestration and oxygen production, water yield, and food production) and total ecosystem services (TES), and then identified multiple advantageous area of ecosystem services in the peri-urban area of Beijing City. Using piecewise linear regression, the response of TES to urbanization (i.e., population density, GDP density, and construction land proportion) and its thresholds were detected. The results showed that, the TES was high in the north and west and low in the southeast, and there were seven multiple advantageous areas (distributed in the new urban development zone and ecological conservation zone), one single advantageous area (distributed in the ecological conservation zone), and six disadvantageous areas (mainly distributed in the urban function extended zone). TES response to population and economic urbanization each had a threshold (229personkm -2 and 107.15millionyuankm -2 , respectively), above which TES decreased rapidly with intensifying urbanization. However, there was a negative linear relationship between land urbanization and TES, which indicated that the impact of land urbanization on ecosystem services was more direct and effective than that of population and economic urbanization. It was also found that the negative impact of urbanization on TES was highest in the urban function extended zone, followed in descending order by that in the new urban development zone and ecological conservation zone. According to the detected relationships between urbanization and TES, the economic and population urbanization should be strengthened accompanied by slowing or even reducing land urbanization, so as to achieve urban ecological sustainability with less ecosystem services degradation. Copyright 脗漏 2017 Elsevier B.V. All rights reserved.
Nelson AC, MooreT.Assessing urban growth management: The case of Portland, Oregon, the USA’s largest urban growth boundary[J]. , 1993, 10(4): 293-302.
Many states in the USA attempt to manage urban growth so that development is directed to urban areas equipped to accommodate development, and rural lands are preserved for resource and other non-urban uses. The state of Oregon is entering its third decade of what many commentators describe as the nation's most aggressive urban growth management programme administered statewide. This article reports a recent evaluation of the effectiveness of the state urban growth management policies as they are implemented by the metropolitan Portland area. The metropolitan Portland area contains the largest population, employment and land base within a single urban growth boundary in the USA. Using primary data collection and analysis, the effectiveness of the urban growth management and resource land preservation effort is assessed. Nearly all regional development has been directed to the urban growth boundary and away from resource lands. Many problems with administration are found, however. Policy implications are suggested.
KühnM.Greenbelt and green heart: Separating and integrating landscapes in European city regions[J]. , 2003, 64(1-2): 19-27.
Regarding the relationship of city and landscape, two main positions of planning have to be distinguished: at the one side, landscape is seen as a separating element of city and suburbia. According to this view, Greenbelts are designed to protect a compact urban form. At the other side, landscape is seen as a connecting element in city regions, integrating them to regional cities. According to this view, landscape is seen as a Green middle. This article presents two contrasting case studies of planning approaches in European city regions, which represent a reversed relationship of city and landscape: the Regional Parks Berlin-Brandenburg, forming a Greenbelt around the German capital and the Green Heart as a Middle of the Dutch Randstad. In comparing both cases, the conclusion is drawn, that a negative definition of landscape form, which is derived as an urban containment, can hardly be successful to protect open spaces in growing city regions. Instead landscape has to have a positive definition, basing on the uses and perception by people.
Jongman R HG, Bouwma IM, GriffioenAet al. The pan European ecological network: PEEN[J]. , 2011, 26(3): 311-326.
AbstractThe pan European biological and landscape diversity strategy (PEBDLS) was developed under the auspices of the Council of Europe in order to achieve the effective implementation of the convention of biological diversity (CBD) at the European level. A key element of PEBLDS has been the development of the Pan European Ecological Network (PEEN) as a guiding vision for coherence in biodiversity conservation. PEEN has been developed in three subprojects: Central and Eastern Europe, completed in 2002; South-eastern Europe, completed in 2006; and Western Europe, also completed in 2006. The methodology of the development of the three maps has been broadly comparable but data availability, differences in national databases, technical developments and geographical differences caused variations in the detailed approach. One of the challenges was to find common denominators for the habitat data in Europe; this was solved differently for the subprojects. The project has resulted in three maps that together constitute the PEEN. They differ in terms of ecological coherence and the need for ecological corridors; for example, in Central and Western Europe corridors are essential to provide connectivity, while in Northern, Eastern and South-eastern Europe larger, coherent natural areas still exist. The future steps in developing PEEN should include the implementation of national ecological networks and, in particular, the pursuit of international coherence through the development of trans-European ecological corridors. The big challenge is to develop a common approach among the over 100 European-wide agencies that are responsible for biodiversity conservation.
HongW, YangC, Chen L et al. Ecological control line: A decade of exploration and an innovative path of ecological land management for megacities in China[J]. , 2017, 191: 116-125.
Abstract Ecological control line is a system innovation in the field of ecological environment protection in China and it has become as an important strategy of national ecological protection. Ten years have passed since the first ecological control line in Shenzhen was delimited in 2005. This study examines the connotations of ecological control line and the current study status in China and abroad, and then takes a brief description about the delimitation background and existing problems of the ecological control line in Shenzhen. The problem-solving strategy is gradually transforming from extensive management to refined management. This study proposes a differential ecological space management model that merges the space system, management system, and support system. The implementation paths include the following five aspects: delimiting ecological bottom lines to protect core ecological resources; formulating access systems for new construction projects to strictly control new construction; implementing construction land inventory reclamation assisted by market means; regulating boundary adjusting procedures and processes; and constructing ecological equity products by using multiple means to implement rights relief. Finally, this study illustrates the progress of the implementation and discusses the rigorousness and flexibility problems of ecological control line and calls for the promotion of the legislation. The management model and implementation paths proposed in this study have referential significance for developing countries and megacities to achieve ecological protection and sustainable development. Copyright 2017 Elsevier Ltd. All rights reserved.
[LiYangfan, LinJingyu, SunXiang.An early warning method on ecological risk and its application to improve landscape ecological security pattern regulation. , 2017, 36(3): 485-494.]
JonesB, O’Neill B C, McDaniel L et al. Future population exposure to US heat extremes[J]. , 2015, 5(7): 652-655.
Extreme heat events are likely to become more frequent in the coming decades owing to climate change. Exposure to extreme heat depends not only on changing climate, but also on changes in the size and spatial distribution of the human population. Here we provide a new projection of population exposure to extreme heat for the continental United States that takes into account both of these factors. Using projections from a suite of regional climate models driven by global climate models and forced with the SRES A2 scenario and a spatially explicit population projection consistent with the socioeconomic assumptions of that scenario, we project changes in exposure into the latter half of the twenty-first century. We find that US population exposure to extreme heat increases four- to sixfold over observed levels in the late twentieth century, and that changes in population are as important as changes in climate in driving this outcome. Aggregate population growth, as well as redistribution of the population across larger US regions, strongly affects outcomes whereas smaller-scale spatial patterns of population change have smaller effects. The relative importance of population and climate as drivers of exposure varies across regions of the country.
LelieveldJ, Evans JS, Fnais M et al. The contribution of outdoor air pollution sources to premature mortality on a global scale[J]. , 2015, 525(7569): 367-371.
Abstract Assessment of the global burden of disease is based on epidemiological cohort studies that connect premature mortality to a wide range of causes, including the long-term health impacts of ozone and fine particulate matter with a diameter smaller than 2.5 micrometres (PM2.5). It has proved difficult to quantify premature mortality related to air pollution, notably in regions where air quality is not monitored, and also because the toxicity of particles from various sources may vary. Here we use a global atmospheric chemistry model to investigate the link between premature mortality and seven emission source categories in urban and rural environments. In accord with the global burden of disease for 2010 (ref. 5), we calculate that outdoor air pollution, mostly by PM2.5, leads to 3.3 (95 per cent confidence interval 1.61-4.81) million premature deaths per year worldwide, predominantly in Asia. We primarily assume that all particles are equally toxic, but also include a sensitivity study that accounts for differential toxicity. We find that emissions from residential energy use such as heating and cooking, prevalent in India and China, have the largest impact on premature mortality globally, being even more dominant if carbonaceous particles are assumed to be most toxic. Whereas in much of the USA and in a few other countries emissions from traffic and power generation are important, in eastern USA, Europe, Russia and East Asia agricultural emissions make the largest relative contribution to PM2.5, with the estimate of overall health impact depending on assumptions regarding particle toxicity. Model projections based on a business-as-usual emission scenario indicate that the contribution of outdoor air pollution to premature mortality could double by 2050.
SunY, ZhangX, Zwiers F W et al. Rapid increase in the risk of extreme summer heat in Eastern China[J]. , 2014, 4(12): 1082-1085.
The summer of 2013 was the hottest on record in Eastern China. Severe extended heatwaves affected the most populous and economically developed part of China and caused substantial economic and societal impacts. The estimated direct economic losses from the accompanying drought alone total 59 billion RMB (ref. ). Summer (June-August) mean temperature in the region has increased by 0.82 C since reliable observations were established in the 1950s, with the five hottest summers all occurring in the twenty-first century. It is challenging to attribute extreme events to causes. Nevertheless, quantifying the causes of such extreme summer heat and projecting its future likelihood is necessary to develop climate adaptation strategies. We estimate that anthropogenic influence has caused a more than 60-fold increase in the likelihood of the extreme warm 2013 summer since the early 1950s, and project that similarly hot summers will become even more frequent in the future, with fully 50% of summers being hotter than the 2013 summer in two decades even under the moderate RCP4.5 emissions scenario. Without adaptation to reduce vulnerability to the effects of extreme heat, this would imply a rapid increase in risks from extreme summer heat to Eastern China.
ZhaoL, LeeX, Smith R B et al. Strong contributions of local background climate to urban heat islands[J]. , 2014, 511(7508): 216-219.
The urban heat island (UHI), a common phenomenon in which surface temperatures are higher in urban areas than in surrounding rural areas, represents one of the most significant human-induced changes to Earth's surface climate. Even though they are localized hotspots in the landscape, UHIs have a profound impact on the lives of urban residents, who comprise more than half of the world's population. A barrier to UHI mitigation is the lack of quantitative attribution of the various contributions to UHI intensity (expressed as the temperature difference between urban and rural areas, ΔT). A common perception is that reduction in evaporative cooling in urban land is the dominant driver of ΔT (ref. 5). Here we use a climate model to show that, for cities across North America, geographic variations in daytime ΔT are largely explained by variations in the efficiency with which urban and rural areas convect heat to the lower atmosphere. If urban areas are aerodynamically smoother than surrounding rural areas, urban heat dissipation is relatively less efficient and urban warming occurs (and vice versa). This convection effect depends on the local background climate, increasing daytime ΔT by 3.0 ± 0.3 kelvin (mean and standard error) in humid climates but decreasing ΔT by 1.5 ± 0.2 kelvin in dry climates. In the humid eastern United States, there is evidence of higher ΔT in drier years. These relationships imply that UHIs will exacerbate heatwave stress on human health in wet climates where high temperature effects are already compounded by high air humidity and in drier years when positive temperature anomalies may be reinforced by a precipitation-temperature feedback. Our results support albedo management as a viable means of reducing ΔT on large scales.
Martin-Mikle CJ, Beurs K MD, Julian JPet al. Identifying priority sites for low impact development (LID) in a mixed-use watershed[J]. , 2015, 140: 29-41.
Low impact development (LID), a comprehensive land use planning and design approach with the goal of mitigating land development impacts to the environment, is increasingly being touted as an effective approach to lessen runoff and pollutant loadings to streams. Broad-scale approaches for siting LID have been developed for agricultural watersheds, but are rare for urban watersheds, largely due to greater land use complexity. Here, we introduce a spatially-explicit approach to assist landscape architects, urban planners, and water managers in identifying priority sites for LID based exclusively on freely available data. We use a large, mixed-use watershed in central Oklahoma, the United States of America, as a case-study to demonstrate our approach. Our results indicate that for one sub-catchment of the Lake Thunderbird Watershed, LID placed in 11 priority locations can facilitate reductions in nutrient and sediment loading to receiving waters by as much as 16% and 17%, respectively. We had a high rate of correctly identified sites (94卤5.7%). Our systematic and transferable approach for prioritizing LID sites has the potential to facilitate effective implementation of LID to lessen the effects of urban land use on stream ecosystems.
Fostering resilience in the face of environmental, socioeconomic, and political uncertainty and risk has captured the attention of academics and decision makers across disciplines, sectors, and scales. Resilience has become an important goal for cities, particularly in the face of climate change. Urban areas house the majority of the world's population, and, in addition to functioning as nodes of resource consumption and as sites for innovation, have become laboratories for resilience, both in theory and in practice. This paper reviews the scholarly literature on urban resilience and concludes that the term has not been well defined. Existing definitions are inconsistent and underdeveloped with respect to incorporation of crucial concepts found in both resilience theory and urban theory. Based on this literature review, and aided by bibliometric analysis, the paper identifies six conceptual tensions fundamental to urban resilience: (1) definition of 榰rban; (2) understanding of system equilibrium; (3) positive vs. neutral (or negative) conceptualizations of resilience; (4) mechanisms for system change; (5) adaptation versus general adaptability; and (6) timescale of action. To advance this burgeoning field, more conceptual clarity is needed. This paper, therefore, proposes a new definition of urban resilience. This definition takes explicit positions on these tensions, but remains inclusive and flexible enough to enable uptake by, and collaboration among, varying disciplines. The paper concludes with a discussion of how the definition might serve as a boundary object, with the acknowledgement that applying resilience in different contexts requires answering: Resilience for whom and to what? When? Where? And why?
Gaffin SR, Rosenzweig RC, Kong AY.Adapting to climate change through urban green infrastructure[J]. , 2012, 2(10): 704-704.
To the Editor — Jones et al.1 lay out the strong case for the many virtues of using 'ecoysytem-based approaches to adaptation' (EbA) to address current and future climate change. However, their article did not mention the burgeoning use of this approach within cities to address climate-related impacts and other environmental…
Jones HP, Hole DG, Zavaleta ES.Harnessing nature to help people adapt to climate change[J]. , 2012, 2(7): 504-509.
Adapting to climate change is among the biggest challenges humanity faces in the next century. An overwhelming focus of adaptation strategies to reduce climate change-related hazards has been on hard-engineering structures such as sea walls, irrigation infrastructure and dams. Closer attention to a broader spectrum of adaptation options is urgently needed. In particular, ecosystem-based adaptation approaches provide flexible, cost-effective and broadly applicable alternatives for buffering the impacts of climate change, while overcoming many drawbacks of hard infrastructure. As such, they are a critical tool at adaptation planners' disposal for tackling the threats that climate change poses to peoples' lives and livelihoods.
Kuang WH, Chen LJ, Liu J Y et al. Remote sensing-based artificial surface cover classification in Asia and spatial pattern analysis[J]. , 2016, 59(9): 1720-1737.
Abstract Artificial surfaces, characterized with intensive land-use changes and complex landscape structures, are important indicators of human impacts on terrestrial ecosystems. Without high-resolution land-cover data at continental scale, it is hard to evaluate the impacts of urbanization on regional climate, ecosystem processes and global environment. This study constructed a hierarchical classification system for artificial surfaces, promoted a remote sensing method to retrieve subpixel components of artificial surfaces from 30-m resolution satellite imageries (GlobeLand30) and developed a series of data products of high-precision urban built-up areas including impervious surface and vegetation cover in Asia in 2010. Our assessment, based on multisource data and expert knowledge, showed that the overall accuracy of classification was 90.79%. The mean relative error for the impervious surface components of cities was 0.87. The local error of the extracted information was closely related to the heterogeneity of urban buildings and vegetation in different climate zones. According to our results, the urban built-up area was 18.18104 km2, accounting for 0.59% of the total land surface areas in Asia; urban impervious surfaces were 11.65104 km2, accounting for 64.09% of the total urban built-up area in Asia. Vegetation and bare soils accounted for 34.56% of the urban built-up areas. There were three gradients: a concentrated distribution, a scattered distribution and an indeterminate distribution from east to west in terms of spatial pattern of urban impervious surfaces. China, India and Japan ranked as the top three countries with the largest impervious surface areas, which respectively accounted for 32.77%, 16.10% and 11.93% of the urban impervious surface area of Asia. We found the proportions of impervious surface and vegetation cover within urban built-up areas were closely related to the economic development degree of the country and regional climate environment. Built-up areas in developed countries had relatively low impervious surface and high public green vegetation cover, with 50170% urban impervious surfaces in Japan, South Korea and Singapore. In comparison, the proportion of urban impervious surfaces in developing countries is approaching or exceeding 80% in Asia. In general, the composition and spatial patterns of built-up areas reflected population aggregation and economic development level as well as their impacts on the health of the environment in the sub-watershed.
Kuang WH, Liu JY, Dong J W et al. The rapid and massive urban and industrial land expansions in China between 1990 and 2010:A CLUD-based analysis of their trajectories, patterns and drivers[J]. , 2016, 145: 21-33.