The current and potential role of urban metabolism studies to analyze the role of food in urban sustainability

Food supply chains are essential for urban sustainability. To reflect on the state of knowledge on urban food flows in urban metabolism research, and the actual and potential role of urban metabolism studies to tackle food sustainability in cities, we systematically review scientific research on food from an urban metabolism perspective and apply statistical and thematic analyses. The analysis of 89 studies provides insights as to the relation between food supply and (environmental and social dimensions of) urban sustainability. First, food is an important contributor to urban environmental impacts, if a consumption-based approach is adopted. Secondly, the social impacts of urban food supply remain scarcely studied in urban metabolism research, but emerging results on public health, malnutrition, and food waste appear promising. In parallel, we find that the findings of the studies fail to engage with debates present in the broader literature, such as that of food justice. Our analysis shows that most studies focus on large cities in high-income, data-rich countries. This limits our understanding of global urban food supply. Existing studies use innovative mixed-methods to produce robust accounts of urban food flows in data-scarce contexts; expanding these accounts is necessary to get a better understanding of how urban food supply and its diverse impacts in terms of environmental and social sustainability may vary across cities, a necessary step for the urban metabolism literature to contribute to current debates around food sustainability and justice.     

城市碳代谢过程研究进展

碳代谢过程分析是城市代谢研究的重要环节,而通过土地利用/覆盖的空间调整优化城市碳代谢过程已成为区域可持续发展的关键。利用城市代谢思想,本文综述了城市碳代谢过程核算、碳代谢网络模拟、碳代谢过程与土地利用/覆盖变化关系分析、碳代谢空间格局演替等方面的内容,并指出了当前研究中存在着空间属性表达缺乏、核算/模拟结果较难直接应用于实践调控、自然和社会经济代谢过程难以并重考虑等问题。在此基础上,提出了此领域未来发展预期:(1)基于土地流转,将碳排放/碳吸收垂向流映射到碳存量变化的水平流,以"存量"变化推导出网络"流量"分布,实现节点、流互动关系的空间表达,构建时空维度碳代谢网络模型;(2)强调自然节点在城市碳代谢网络中的重要作用,形成社会经济节点与自然节点并重的生态网络模型,有效服务于城市规划及设计。     

基于景观生态学的城市人居环境代谢研究范式与研究框架建构

人居环境建设已经成为中国城市发展和当代生态学研究的新兴命题,基于物质代谢研究成果,系统剖析城市人居环境问题,提升城市化过程的生态文明水准成为推动新型城市化发展的重要路径选择。通过对人居环境视角和社会代谢视角的城市研究进行简要回顾,认为两种视角的有机整合可以弥补各自的理论和方法论缺陷,进而凝练出新的城市生态学研究思路。利用景观生态学理论和概念体系,建构了多层次、多维度的城市人居环境代谢研究范式和基本研究框架。这一范式可以从多尺度和多维度反映城市人居环境代谢的过程特征,厘清城市人为活动和各种资源环境问题的关联关系,整合多学科的知识和技术手段,解析城市人居环境的时空动态演化过程及其驱动机制,为城市人居环境研究学科的发展创造有利条件。通过建构基于景观生态学的城市人居环境物质能量代谢研究框架,还可以有效推进城市人居环境物质能量代谢中的格局-过程-尺度耦合问题,数据采集、储存与分析问题和效应调控与过程管理问题的研究,对于完善城市代谢研究方法,促进城市人居环境建设具有重要的参考和借鉴意义。     

A new physical accounting model for material flows in urban systems with application to the Stockholm Royal Seaport District

Sustainable urbanization requires streamlining of resource management in urban systems which in turn requires understanding of urban metabolism (UM). Even though various methods have been applied for UM analysis, to date there is no standardized method for comprehensive accounting of material flows in urban systems. Moreover, the accounting of material flows is rarely implemented with a bottom‐up approach that can provide a thorough analysis of UM. This article presents the Urban Accounting Model (UAM) which aims to allow comprehensive accounting of urban material flows based on a bottom‐up approach. The model comprises two interlinked sub‐models. The first was developed by integrating a new physical input output table (PIOT) framework for urban systems into a three‐dimensional structure. The second comprises a set of physical accounts for systematic accounting of material flows of each economic sector in the system in order to support the compilation of the PIOTs. The functions of the UAM were explored through its application to two urban neighborhoods in the Stockholm Royal Seaport district. The application highlighted that the UAM can describe the physical interactions between the urban system and the environment or other socioeconomic systems, and capture the intersectoral flows within the system. Moreover, its accounts provide information that allow an in‐depth analysis of the metabolism of specific sectors. Overall, the UAM can function as a useful tool for UM analysis as it systematizes data collection and at the same time depicts the physical reality of the urban system.     

面向环境管理的城市代谢物质实体空间研究评述

城市代谢是适应当前全球环境问题研究需要而出现的理论研究,与国家制定的环境管理目标具有内在一致性.本文对城市代谢概念进行解析,并指出城市代谢物质实体研究的意义;概述了城市代谢研究的主要方法并进行优缺点比较;解读了城市代谢物质实体空间研究的系统边界、内涵和研究方法等;总结城市物质实体空间代谢的应用研究进展,提出城市代谢研究存在概念体系、基础理论体系、交叉学科综合理论体系不完善,导致研究发展速度难以满足当前发展的需要、典型案例研究数量有限的不足;建议未来研究可加强在国家间进行实证研究案例的综合比较,以及城市生态系统演化规律、典型城市代谢的优化模式和以实体城市为基本研究单元的环境管理决策支持系统研究.     

Integrating strategic environmental assessment and material flow accounting: a novel approach for moving towards sustainable urban futures

Purpose

The population living in urban areas of the world continues to grow rapidly. It is, thus, a great priority for the planning practice to embed sustainability concept in their urban development endeavors. Currently, development and expansion of urban systems stress the need to control consumption of resources, especially non-renewable ones. There is also a need to reduce related environmental impacts, while stimulating a sustainable pathway for the population and urban growth.

Methods

Strategic environmental assessment (SEA) is useful for policy design to build an integrated method for supporting the development of a sustainable society. It undertakes territorial assessments and describes urban flows and impacts related to them by using a variety of tools, including material flow accounting (MFA). This study employs MFA, as it fits well within the scope of SEA and supports the growing environmental attention in the urban metabolism approach. Although helpful, MFA has not been systematically applied in the urban development context; for this reason, this paper proposes the integration of SEA and MFA.

Results and discussion

Integration of SEA and MFA generates a new framework for sustainable development planning. The framework is structured in phases oriented to the continual improvement based on the Deming cycle (i.e., plan, do, check, act), a key management approach mainly used in businesses for improving the effectiveness of an organization. It can also be implemented at the urban system level. In order to maintain normative compliance, each process (urban planning, strategic environmental assessment with urban metabolism approach, participatory processes) is standardized in line with a common and mandatory approach. While the processes are integrated among them, highlighting the reciprocal contact points, the results are combined in a holistic perspective. The framework, hence, transforms the voluntary MFA tool into a mandatory process.

Conclusions

The proposed SEA-MFA framework has the potential to unify and standardize the processes of categorizing and quantifying data in order to improve the understanding of urban metabolic principles and scale effects. It also supports management and policy development and meets the requirements of different stakeholders. The framework, thus, generated a novel approach for sustainable urban development planning by providing solutions for specific policy problems and ensuring urban ecological balance and sustainable urban futures.

     

Surveying the Environmental Footprint of Urban Food Consumption

Assessments of urban metabolism (UM) are well situated to identify the scale, components, and direction of urban and energy flows in cities and have been instrumental in benchmarking and monitoring the key levers of urban environmental pressure, such as transport, space conditioning, and electricity. Hitherto, urban food consumption has garnered scant attention both in UM accounting (typically lumped with “biomass”) and on the urban policy agenda, despite its relevance to local and global environmental pressures. With future growth expected in urban population and wealth, an accounting of the environmental footprint from urban food demand (“foodprint”) is necessary. This article reviews 43 UM assessments including 100 cities, and a total of 132 foodprints in terms of mass, carbon footprint, and ecological footprint and situates it relative to other significant environmental drivers (transport, energy, and so on) The foodprint was typically the third largest source of mass flows (average is 0.8 tonnes per capita per annum) and carbon footprint (average is 2.1 tonnes carbon dioxide equivalents per capita per annum) in the reviewed cities, whereas it was generally the largest driver of urban ecological footprints (average is 1.2 global hectares per capita per annum), with large deviations based on wealth, culture, and urban form. Meat and dairy are the primary drivers of both global warming and ecological footprint impacts, with little relationship between their consumption and city wealth. The foodprint is primarily linear in form, producing significant organic exhaust from the urban system that has a strong, positive correlation to wealth. Though much of the foodprint is embodied within imported foodstuffs, cities can still implement design and policy interventions, such as improved nutrient recycling and food waste avoidance, to redress the foodprint.     

城市能源代谢生态网络分析研究进展

运用生态网络分析方法研究城市能源代谢可以打破以往研究中的"黑箱模式",有助于考察城市内部能源的代谢过程和代谢路径。对研究城市能源代谢的一般方法进行了分析和对比,发现在探究城市能源代谢方面,生态网络分析相较于其他方法更具优越性;因此,全面整理和阐述了生态网络分析方法的主要内容,并系统综述了该方法在城市能源代谢中的应用。在此基础之上,指出在未来城市能源代谢的生态网络分析中应从研究尺度、上升性分析和环境元分析的结合应用以及增加不同模型精细度的对比研究3个方面做出改进。     

A general multi-trait-based framework for studying the effects of biodiversity on ecosystem functioning

Environmental change is as multifaceted as are the species and communities that respond to these changes. Current theoretical approaches to modeling ecosystem response to environmental change often deal only with single environmental drivers or single species traits, simple ecological interactions, and/or steady states, leading to concern about how accurately these approaches will capture future responses to environmental change in real biological systems. To begin addressing this issue, we generalize a previous trait-based framework to incorporate aspects of frequency dependence, functional complementarity, and the dynamics of systems composed of species that are defined by multiple traits that are tied to multiple environmental drivers. The framework is particularly well suited for analyzing the role of temporal environmental fluctuations in maintaining trait variability and the resultant effects on community response to environmental change. Using this framework, we construct simple models to investigate two ecological problems. First, we show how complementary resource use can significantly enhance the nutrient uptake of plant communities through two different mechanisms related to increased productivity (over-yielding) and larger trait variability. Over-yielding is a hallmark of complementarity and increases the total biomass of the community and, thus, the total rate at which nutrients are consumed. Trait variability also increases due to the lower levels of competition associated with complementarity, thus speeding up the rate at which more efficient species emerge as conditions change. Second, we study systems in which multiple environmental drivers act on species defined by multiple, correlated traits. We show that correlations in these systems can increase trait variability within the community and again lead to faster responses to environmental change. The methodological advances provided here will apply to almost any function that relates species traits and environmental drivers to growth, and should prove useful for studying the effects of climate change on the dynamics of biota.     

Using spatially explicit commodity flow and truck activity data to map urban material flows

To analyze and promote resource efficiency in urban areas, it is important to characterize urban metabolism and particularly, material flows. Material flow analysis (MFA) offers a means to capture the dynamism of cities and their activities. Urban‐scale MFAs have been conducted in many cities, usually employing variants of the Eurostat methodology. However, current methodologies generally reduce the study area into a “black box,” masking details of the complex processes within the city's metabolism. Therefore, besides the aggregated stocks and flows of materials, the movement of materials—often embedded in goods or commodities—should also be highlighted. Understanding the movement and dispersion of goods and commodities can allow for more detailed analysis of material flows. We highlight the potential benefits of using high‐resolution urban commodity flows in the context of understanding material resource use and opportunities for conservation. Through the use of geographic information systems and visualizations, we analyze two spatially explicit datasets: (1) commodity flow data in the United States, and (2) Global Positioning System‐based commercial vehicle (truck) driver activity data in Singapore. In the age of “big data,” we bring advancements in freight data collection to the field of urban metabolism, uncovering the secondary sourcing of materials that would otherwise have been masked in typical MFA studies. This brings us closer to a consumption‐based, finer‐resolution approach to MFA, which more effectively captures human activities and its impact on urban environments.     

中国城市家庭代谢及其影响因素分析

家庭是可持续消费研究的主要对象,为了分析家庭消费的环境影响,荷兰的HOMES项目将代谢的概念引入家庭,提出了家庭代谢的概念。目前家庭代谢分析是评价家庭消费活动环境影响的主要方法,它通过对家庭系统中物质和能量流动过程的描述,来识别家庭消费的环境结果。本文首先介绍了家庭代谢的概念模型,该模型中包含着代谢流的方向、流量和速度3个要素,水资源、能源和物质代谢是家庭代谢的主要内容。应用这一模型,对中国城市家庭近20a的水资源和能源代谢进行描述,对家庭代谢的经济及人口社会因素进行了分析。结果表明,中国城市家庭的代谢量在可预见的短-中期时间内,将继续保持增加的趋势。     

Evaluation Approaches for Advancing Urban Water Goals

Urban areas (especially cities) are challenged in meeting their direct water needs from local sources. They also exert strain on global water resources through their indirect (virtual) water use. Agencies concerned with urban water management have visions and goals for managing direct water use, but indirect use is only inferred in more global visions for sustainable consumption. There is limited quantification of “urban water performance” at the macro urban scale (whole of city) to monitor progress toward these goals. It is constrained by a lack of clarity about the evaluation approaches that best serve them. We ask, How can the evaluation approaches described in literature advance urban water management goals? We reviewed the utility of eight evaluation approaches, including urban water system modeling, urban metabolism (territorial and mass balance), consumption (life cycle assessment, water footprinting, and input‐output analysis), and complex systems (ecological network analysis and systems dynamics) approaches. We found that urban metabolism based on water mass balance is a core method for generating information to inform current goals for direct urban water use, with potential for being “coupled” with the other approaches. Consumption approaches inform the management of indirect water use. We describe this in a framework for urban water evaluation to give greater clarity to this field and flag the further research that would be needed to progress this. It includes the recommendation to differentiate the evaluation of direct and indirect urban water, but to also interpret them together.     

城市代谢研究评述:内涵与方法

随着城市发展面临的生态问题日益显著,部分研究者试图通过对自然生态系统进行类比来寻求解决途径,城市代谢理论应运而生。当以系统科学来研究城市生态系统时,哲学思想的引入为探索和城市及城市代谢的内涵提供了最原始的桥梁。因此,在介绍城市代谢内涵与研究进展的基础上,融合产业、家庭、社会等多尺度代谢理论,对城市代谢的边界进行扩展,将其分为狭义与广义两类,结合亚里士多德的"四因说"对其质料因(组分)、形式因(结构)、动力因(驱动力)和目的因(功能)进行识别分析,据此将城市代谢研究方法归纳为质料、形式和混合研究方法三类,并提出未来研究的主要动向和解决手段。城市代谢"四因图"可为相关研究者提供参考。     

城市住宅建筑系统流量-存量动态模拟——以北京市为例

地面建筑物的累积与更新是城市化过程的结果与显性特征之一。城市建筑系统在不同层面上与外部环境系统进行着物质能量交换,对这种交互产生的资源压力与环境胁迫的关注,使其成为城市代谢研究领域中的热点问题。系统分析与模拟城市建筑物流量-存量的动态变化过程及其资源环境响应,对于揭示城市建筑系统代谢机理,提高城市总体规划精准性、强化资源系统韧性管理、提升废弃物处置效率等宏观战略具有重要意义。以北京市为例,基于Stella建模平台,构建了城市居民住宅建筑系统流量-存量的动态模拟模型,定量模拟了不同管理情景下钢材需求量与建筑拆除垃圾产生量的变化区间。结果表明:(1)基准情景下,北京住宅建筑新建流量前期增速较快,2005年达到峰值3024.1万m~2,而拆除流量约于2057年达到峰值,拆除面积为2073.14万m~2;城市住宅建筑存量最高值出现在2075年左右,面积为7.51亿m~2;(2)与基准情景相比,如果人均住宅建筑面积提高到45 m~2,从现在到模拟期结束(2019—2100)将增加钢铁需求量3251.65万t;而如果延长住宅建筑寿命至设计值,同期可减少钢铁需求量3022.9万t;(3)基准情景、大面积情景以及长寿命情景下,北京市城镇住宅建筑拆除垃圾峰值产生量分别为0.29亿t、0.39亿t、0.20亿t,政府管理部门应采取有针对性的应对措施,提前做出综合利用和处理处置方案。     

食物源CNP的城市代谢特征——以厦门市为例

基于元素流分析原理,将食物源碳氮磷3种元素在城市系统中的代谢特征进行耦合分析,追踪以"食物消费"、"废物处置"、"人体代谢"为主要环节的食物碳氮磷代谢过程,发掘其中共同的代谢环节,明晰3种元素代谢路径、代谢通量及其影响因素的差异,并对厦门市1991—2010年食物源碳氮磷城市代谢进行案例分析。结果表明,食物源碳氮磷城市代谢中通量最大的代谢路径是"食物—食物摄入—人体粪尿—未还田粪尿—污水处理—污泥—污泥填埋—土壤";食物源碳氮磷城市代谢主要引起土壤和水体的环境负荷加重;厨余垃圾中碳氮磷占食物源的比例分别为13.7%、32.2%、70.3%,在整个代谢过程中具有最大的减量管理潜力。提出优化代谢过程、减少碳氮磷环境负荷的若干对策建议,包括增大食物的有效食用比例、资源化利用污泥和厨余垃圾等。     

城市建筑代谢研究方法及其展望

建筑代谢是当前城市代谢研究领域中的一个新兴热点问题,其研究着重关注建筑系统中物质能量流动可能对周围环境产生的压力及其有害影响。本文在阐明城市建筑代谢内涵的基础上,综述了国内外建筑代谢研究方法的进展情况,分析了目前城市建筑代谢研究方法的适用范围及其特点,指出了城市建筑代谢研究方法在未来应从以下几个方面发展:开发跨城市边界的代谢研究方法;注重建筑代谢中非物质性代谢流研究;制定适合乡土建筑地域特点的代谢研究方法;综合物质量和价值量的建筑代谢研究,全面认识和评价建筑的可持续性。     

城市代谢效率研究的热点识别与综合效率实证研究

城市代谢是城市可持续发展研究的重要部分,其有序运行为城市发展与居民生活提供重要保障,代谢效率的提高有助于缓解资源利用与环境保护间的矛盾。通过分析国内外近30年的城市代谢效率的研究进展,整合代谢效率研究热点选取综合效率评估所需指标,并以深圳市为案例研究,结合数据包络分析（DEA）模型对城市物质代谢综合效率进行评估。结果表明：（1）近30年城市代谢研究处于蓬勃发展阶段,中国在相关研究领域中的影响力凸显,而城市代谢效率研究主要关注能源、水资源、碳氮元素及耐用物质（主要为建筑材料）等要素及其环境效应;（2）基于上述要素对深圳城市代谢的综合效率进行评估,其综合效率在2005-2017年间呈波动状态,多数年份城市代谢过程取得了高效运行（效率值大于1）,但仍存低效年份,包括2006（0.96）、2007（0.76）、2011（0.85）和2013（0.97）年,研究期间综合效率提高不明显。在资源投入与效益产出方面,深圳市在水资源利用效率方面需进一步提高;在当前资源消耗水平下经济效益仍有提高潜力;在减少碳氮元素的环境排放及建筑垃圾产生的效率方面有一定程度的提高。（3）通过城市代谢效率研究的热点识别,可明晰目前城市代谢综合效率评估所需涵盖的要素,由此建立评估体系可用于综合效率评估的实践,通过案例分析研究其反映城市资源利用效率动态的可行性,以期为城市可持续发展评估提供科学参考。     

From the urban metabolism to the urban immune system

Urban areas face mounting risks from many sources. Cities pursue myriad tactics to resist, recover from and adapt to shocks and stresses, but little is known about how these approaches relate across the scales of a city nor how cities compare in their abilities. Part of the challenge in addressing these gaps is that the risk to cities is typically studied with an emphasis on one or a few hazards or through the lens of a singular sector. This paper proposes a framework, dubbed the Urban Immune System (UIS) to coalesce and expand industrial ecology research on urban risk management. In the same way that Urban Metabolism (UM) is a unifying framework for urban environmental sustainability, UIS can be a unifying framework for urban resilience, especially related to climate change. Herein, UIS is defined, its many capabilities are dissected and linked to disparate studies; and opportunities for application of the concept are provided. The paper concludes by examining the relationship between UIS and climate change and by identifying those attributes of the UIS that are expected to be of increasing importance under climate change.     

Linking ecological and social systems in cities: urban planning in Finland as a case

The loss of urban green space as a result of urbanization threatens the overall biodiversity of urban areas, and prompts us to consider the importance of existing urban nature more carefully. Because urban ecological systems are in intense interaction with human-social systems, it is fruitful to create an interdisciplinary research and planning framework to ensure the maintenance of biodiversity in urban areas. For this purpose, we adapted a suitable theoretical and conceptual scheme for the setting of Finnish urban development, which provides an example of a situation where a lot of nature has so far remained inside and around urban area. The adapted scheme focuses on the land use change as a result of urban land use planning and development, and may provide a way to address the important variables and feedback mechanisms between information flowing from ecological systems and drivers from the social system. Furthermore, we outlined a more specific framework around the Finnish urban detailed planning process in order to study the interactions between these systems further. After addressing ecology-oriented questions of quantity, quality and needs of urban nature, and human-oriented drivers, such as flow and incorporation of information, knowledge, values and institutions, we identified several challenges in integrating the components of ecological and social systems. Creating common conceptual ground for different actors and disciplines, improving communication in the process, matching contradictory values and perceptions, and improving stakeholder participation would be in the best interest of nature and people of urban areas.     

城市生物多样性分布格局研究进展

城市生物多样性分布格局由自然生态环境和城市化过程所决定;其动态和机理与自然生态系统迥然不同.城市生物多样性为城市生态系统提供了诸多生态系统功能和服务,对改善城市环境、维持城市可持续发展有着重要的意义和作用.城市化过程深刻改变了城市的生物多样性分布格局,导致了诸如本地物种多样性降低、外来物种多样性增加、物种同质化等一系列问题.近年来,城市生物多样性受到学界高度关注,大量研究结果既回答了一些关键性问题,又提出了诸多新的论题和挑战.分析了当前城市生物多样性分布格局研究的若干热点问题,总结了影响城市生物多样性格局的主要因素,探讨了城市生物多样性格局研究方法的关键问题,指出了未来城市生物多样性研究的发展方向,特别强调了城市生物多样性的生态系统功能研究在未来城市生物多样性研究中的重要地位.