构建城市生态与自然生态之间的桥梁

萨斯基娅·萨森/Saskia Sassen

前言

现阶段所进行的大规模的城市化进程，不可避免地成为未来环境问题的核心。人类通过城市和庞大的城市群不断地占据着地球表面的空间，并且通过城市来协调人类和各类环境资源的关系、以及人类与环境资源循环的关系。城市，曾是一个非常有限的区域，而如今却是一个全球化的区域。随着全球经济的扩张，为了支撑有限的产业和场所，我们占据了世界上越来越多的空间。在此，我着重强调城市的多尺度性：即多样的地域和领域，有些领域甚至影响到那些满足城市发展需求的未城市化地区。同时，我也对城市的生态特性做出强调：即多系统性和循环性，这些特性使城市的发展进程及其最终结果相互关联，随之产生了城市生态与自然生态之间的联系。

1. 将形式与内容区分的必要

城市化对自然生态的影响不断加剧，影响到包括气候、物种多样性和海洋净化等方面。它还产生了许多新的环境问题，如热岛、臭氧洞、沙漠化和水污染的产生。我们已经进入了一个新的阶段：那就是人类第一次成为所有重要生态系统中的主要消费者，而城市化则是进入该阶段的一个主要途径。目前，出现了一系列空前的全球化生态状况，暨大城市已经成为影响全球的、不同形态的社会生态系统。城市对于传统农村经济，以及该种经济同生物多样性的长期适应性具有显著的影响。农村人口已经成为由工业经济制造出的产品的消费者。农村环境逐渐演变成为一种与生物多样性无关的新型的社会关系体系。这些发展均表明，城市环境将成为所有未来环境问题的主要根源。这一切引发了人类与地球上其他物种之间关系的巨大改变。

但是，环境问题究竟来自城市化本身，还是来自于我们已经建构的特定的城市体系及产业进程？也就是说，城市形态究竟是以什么为标志，是城市自身所具有的聚集性和密集性，还是在历史进程中城市所选择的发展方式？全球生态环境问题是城市聚集和密集的产物，还是由不同城市中某些系统引起的？例如，我们所发展的交通、垃圾处理、建筑、供热、制冷、食物供应等系统，还包括提取、种植、制造、包装、分配等产业，以及我们饮食、服务及材料的处理所采用的系统。

毫无疑问，答案是后者，即我们所建构的特定的城市体系。今天，当我们再次关注这些主要城市，一个突出的特征是，这些城市在环境可持续发展方面存在着巨大差异。这种差异是由城市不同的政策、经济基础、生活习俗、文化差异等造成的。在所有这些差异中，有一些本质差异正不断影响甚至支配着我们做事的方式。其中之一就是人类经济发展中，在开发自然能源与材料的同时，回馈给自然界的却是污染和废弃物。这已经使自然资源的流动产生断裂，尽管一些城市正在努力避免这种断裂的产生，但无论是城市还是农村，几乎在所有的经济形态中，都存在着这种断裂。它给城市所带来的复杂影响和负面效应特别明显，这使城市成为大多数环境破坏和一些最难解决的损害的根源。但同时，也恰恰是城市的复杂性为解决问题提供了途径[1]。

现在迫切需要将城市以及城市化作为环境问题解决的途径之一。我们需要利用和依赖这些城市特性，使它们能够对城市中有组织的生态系统与自然体系产生积极的影响。这些影响，以及它们所涵盖的各个领域，将成为联系城市与自然生态的一种社会生态系统。我们所能做的就是尽可能地让这些对环境有积极影响的结果产生。这些可供利用并能产生积极影响的特征包括：规模经济、稠密度、资源高效利用及其他相关方面的潜力，另外还包括非常重要但却常常被忽略的密集型信息交流网络，它可有助于促进城市实施一些环境保护方面的措施。从理论上说，城市是由各种各样的进程构成的，包括空间、时间、场地以及自然等进程。同时，它也包含这些进程中可能存在着的突变，比如，当时间因素成为环境保护措施的关键：生态经济学可以让我们认识到，如果用环境标准来衡量，那些根据市场标准在短期价值框架下是无效的或贬值的措施，长远来看却是积极有效的。

2. 城市的复杂性和全球规划

正如所记载的那样，城市一直以来都是创新、发展、建构复杂物质系统和组织系统的场所。所以，我们必须在城市这个复杂体系中找到解决环境破坏问题的方法，并重新建构城市化进程中的社会生态系统。城市所拥有的网络以及信息圈使沟通和传递信息变得更加便利，通过这些可以说服业主、政府和企业去支持那些对环境影响敏感的项目，并投身到能从根本上转变体制的建设中来。

城市体系同样包含支撑目前城市结构的社会关系系统。为了达到更高的环境敏感度和有效性，除采取一些措施（如废弃物回收）外，社会关系系统本身也需要有所改变。比如，其中一个关键问题是，世界范围内的大项目和大规模的投资对环境产生的危害。例如，我们所熟知的大规模森林砍伐和水坝的修筑。这些项目的投资规模，和其全球化、私有化的特征表明，无论是市民，还是政府或非政府组织，都不具备能够改变这种投资模式的能力。但在今天，一些由经济形态搭建的平台，可以对这些强大的集团企业产生作用，并与之抗衡。经济全球化布局在涉及到全球经济运作的管理、协作、金融与服务时，虽不够全面但却是具有战略意义的。这种战略性布局对探讨规范和管理全球经济的可能性是至关重要的。如果处在全球化战略布局网络中的城市，把密集型经济运转与高层管理机制相结合，就会产生战略性布局的决策。同样，我们也可以将此视为对环境损害负有责任的战略性布局。因为，庞大的权力集中于少数跨国企业和全球金融市场，而全球经济的特征也决定了它们必然集中在某些区域，而不是分散开来的。相应的，这使得对环境损害所承担的责任也相对集中了，投资标准也随之发生了改变。制约企业总部的行为，与制约数千万的矿井和工厂、以及数百万同类全球企业的服务出口相比，是完全不同的。如今，消费者、政客以及媒体对环境危机的认知有助于促使对企业总部的牵制，而数百万当地小企业对大多数环境破坏应承担的责任则被忽略了。尽管如此，通过国家管制以及当地政府的干预，对小企业的控制也是极有可能被实现的。

由此，引出一个重要的问题，即损害产生的尺度，以及随之可能出现的干预或改变，它有别于产生损害的程度和区域。就这点而言，城市是一个无比复杂的实体。举例来说：城市多元的系统性，形成了与之相关的环境动态，反之又影响到城市，而且不同的政策，从地方层面到国际层面，都可被实施；更进一步来说，大多数全球化城市中的特定网络，是建立全球性网络的关键子系统，可被视为对全球经济活动负责的区域网络。

引起和造成我们环境损害的社会法律体系和利益关系，恰恰是城市可持续发展不可回避的，这使得城市的复杂性和多样性进一步扩大。城市可持续问题的解决，必然要触动城市的主要系统，这些系统在国家之间、南北差异之间也都有所不同。虽然在一些其他的环境领域中，可以通过科技手段来解决问题，但在处理城市的环境问题时科技手段却并不适用。非科技因素是城市问题的关键部分：能源、贫穷与贫富差距、思想体系和文化偏好等问题，是导致问题的根源，但同时也是解决问题的途径。当前的一个主要趋势是全球化和市场化，向着越来越公共化的领域扩展。发展城市可持续的关键是采取政策导向以及提高参与的积极性，包括要求人们去支持垃圾回收、去追究那些对环境破坏影响巨大的生产工序和全球企业的责任。

3. 尺度

那些与城市相关联的生态条件在多种尺度上产生作用。重要的是，城市包含了一系列的尺度，不同尺度所对应的特定生态条件在该尺度上起到相应的作用。并使城市自身的尺度得以显现。另外，城市也使生态系统的多尺度特性显现出来，并被市民所认知。城市的这种特性，由于它在地区、国家甚至全球层面上的重要性越来越强，也应当予以重视并得到发展和加强。大多数探讨城市环境管理方面的文章认为，区域尺度是战略性的尺度；而另一些长期讨论的观点则认为，城市的生态章程已经不再能从更宽泛的全球化管理中分离出来。它同样也是对于非城市地区关于“经济及环境”分析的一种长期立场。

城市是实施大范围环境友好政策的关键尺度，同时也是不同社会经济阶层用以争取生活环境质量的场所。空气、噪声以及水污染问题都可以在城市里部分得到解决，即使所涉及的政策牵扯到国家或区域层面时也是如此。不可否认，世界范围内数千个城市都已经制定了它们自己的环境政策，虽然其中有些内容有悖于国家法律，但却是不得已而为之，仅限于国家政府对有害空气或污水等潜在的灾难无法作出相应的应急反应时的一种选择。当前，经济全球化给城市带来直接压力，这使得在城市层面原本已经非常脆弱的环境问题更加严峻。其中一个例子就是以迪拜为缩影的全球企业对建筑环境类型的极端需求。另一种压力则来源于对运输以及基础物流（如大量木材、水泥、不可再生资源、航空、货运、船运等）需求的急剧增加。当前环球企业经济所引起的另一个问题是，相对于世贸组织中“自由”全球贸易这个“必要条件”来说，环境标准则是次要的。最终，私有化和管制的撤销削弱了政府职能，尤其是对于国家层面来说，这最终削弱了其对于环境标准方面的控制力。

城市作为一个战略性空间，巨大的环境破坏力与急增的生存环境需求之间产生了直接的、严酷的交锋。我们不断提到的全球环境挑战，在城市中已经形成，情况迫在眉睫。国际和国家标准将在城市层面的[2]范围内被强制执行，城市层面可以实现很多切实的目标，但对于资金非常有限的南半球当地政府而言，它也存在着一些限制。然而，当地政权作为服务的直接或间接提供者，作为管理者、领导者、合作者以及社区资源[3]的使用者，应有能力去完成可持续发展的目标。每种要素的组合都是独特的，并且有机地嵌入到当地及区域的生态系统中。从这种独特性里可以得出对场地的认知，并可以在尺度上升级，从而有助于对全球状况的理解。臭氧洞的例子就对这种尺度的升级做出了阐释：环境损害是在汽车、户主、工厂、建筑等微观层面中产生的，但其整体影响却是在地球极地才可被看到和评估的，然而那里既没有建筑物，也没有汽车。

一场自1990年代开始且至今未解决的争论是：全球与区域尺度相比较，哪种对于环境保护行动而言更具有战略意义。雷德克利夫特（Redclif t，1996）的观点是我们不能在全球尺度上管理环境。全球问题是由生产与消耗综合造成的，而这些问题多数集中于世界的城市中心。雷德克利夫特认为：我们首先要在区域层面实现可持续化，而仓促制定的以管理环境为目的的国际协定与机构，对改善环境的进程来说意义不大。但有人提出反对意见，如萨特思韦特（Satterthwaite，1999）认为：我们需要建立国际协定对全球负责。洛（Low，2000）也认为：我们有一个日益壮大的由城市管理层所组成的全球合作系统，这个跨国合作系统将为地球的生存与毁灭担负越来越多的责任。全球性的环境公平问题是当今发展的焦点，说起来，这本应是早期工业时代国家层面的问题。

关于这个争论我有以下两个观点：首先，我们所说的区域层面可能不止一个尺度，如跨国企业分散在全球多处进行采矿或生产活动，并在更高的组织层面进行整合，最后发展为全球范围的行动。大部分的环境净化及预防措施的确需要针对每个当地的环境破坏现状来采取行动，但同样也需要全球性组织参与其中。同样，全球经济一体化下城市间的相互竞争，使城市决策者往往关注于建立单个完善的全球化城市，而忽略了建立城市网络对全球经济的重要性和迫切性。因此，城市间特定的网络是跨国城市联盟的天然平台，它可以满足全球性企业的需求。城市间达成国际协定的最大益处在于，可以防止某些国家或城市，从那些正在建立环保政策的国家和城市中获益。实施环保政策长远来看可能会提升国家的竞争力，但由于环保而增加的成本却在当前降低了 “竞争力”。无论在国内还是国际范围，实施这些政策的城市没理由为没有实施的城市去负担成本。这就需要建立相关政策[4]，以防环境成本转移到其他地区。

其次，在涉及可持续发展的城市文献中，焦点大多集中在以人和家庭为单位的消费行为怎样破坏环境。这样在衡量城市时，不可避免地将为数众多的个人与家庭作为研究对象，显然，这种方式是具有明显缺陷的。按照政策，以家庭为单位的回收行为成了重点关注对象，而对于那些响应环境的产品，则被忽略在经济体制下的价格模式中。在这种情况下，城市的可持续发展将容易忽略那些在家庭和个别企业层面上未能实现，却是全球经济与生态系统中更深层面的相互影响。例如，坚持在局部层面控制温室气体排放的观点，从许多角度来说是正确的，但也需要从更宏观的经济层面来考量。

4. 结论：多尺度的生态城市分析

这些不同的问题可以被看作是尺度问题。尺度可以作为一种方式去划定非此即彼的状态，如区域性与全球性，市场机制与非市场机制，绿色环境与贫瘠环境。生态学家正在从事的一些尺度方面的分析工作，我认为将城市尺度化是非常有启发性的。复合系统是多尺度系统，而不是多层次系统，其复合性是表现在跨尺度的关联上的，这种观点非常重要。“当许多包罗万象的事物在细节上密切关联，该系统就需要被作为一个复合系统来对待。” 学者发现：在尺度之间的紧密关联是复合生态系统的一种特征，也是城市明显具有的一种状态。充分理解城市尺度之间如何紧密关联，有助于分析由城市化带来的环境破坏，以及帮助城市从根本上解决环境问题。“直到生态学家善于处理尺度上的问题，城市生态学才有可能突破对单一层次的详细描述。另一方面，试图去处理同一层次上的所有内容，是不明智和混乱的”。对于城市问题也会出现这样的争论，尤其对只强调区域范围的研究和实施时。

这里所涉及的一个重要的分析手段是以时空尺度来看待研究对象。这需要把研究对象从情境变量中辨别出来，对城市来说可能是人口、经济基础等方面。进行这种分析将帮助我们避免抱有“城市”承担环境破坏罪行的谬论，消除城市不一定能解决环境危机的错误观念。我们需要了解那些具体的政治系统、经济系统、交通系统等所能起到的作用和可能性，这些系统导致了哪些不利于环境资源利用的模式，我们可以发现并改变。各种系统在城市构成中整合，是一个从相关系统中分析与辨别各种系统的条件。辨别特定系统的背景或情境变量，让我们避免把“城市”看作一个容器或一个边界封闭的单元。在我的城市和全球化研究之中，我通过多维的高度专业化的跨境经济循环使城市概念化成为一个多尺度系统。这一想法可以应用于城市和环境动态。在这种情况下，城市是一个多重特定的社会——生态循环中的多尺度系统。它不是一个封闭的系统。城市是多重“损害”循环、“修复”循环和“策略”循环的混合。

通过针对一系列生态系统具体问题的研究之后，我们发现大量关于环境条件和政策的分析，这有助于我们理解城市与城市化进程。其中最关键的是，我们应该努力去理解和假设在城市范畴内的各种环境动态模式，并制定针对性的策略。因为只有在制定补救政策或进行环境治理的过程中，我们才能更加清晰地认识到要去做什么。但是，将城市理解为一个更广泛的系统却会产生新的难题，因为城市是由多种尺度构成的，它既是一种分散功能的系统，也是一个政治经济和法律行政的系统。这就是说，单个的家庭、企业或政府单位可以把废弃物循环再造，但不能有效地解决更为宽泛的问题（如过量消耗稀缺资源等）；国际协议能够号召全球采取措施以减少温室气体排放，但这是要靠国家、城市、家庭和企业来具体落实的；政府虽然可以授权制定环保标准，但要根据其经济实力和资源供应系统而定。分析问题的关键一步是：当我们面对一种特定的环境条件时（不论正面还是负面），应该考虑哪种尺度的生态、社会、经济、政策等因素，并且采取相应的措施。另一个分析步骤是考虑时间尺度或各种城市状态和动态的框架，如人工环境循环、经济循环、生活基础设施和某种投资的周期等。这两个步骤的结合有助于我们将现有的复杂情况进行解构，并将构成条件放在更高层次的综合系统中（空间、时间、管理）来分析。

在生态进程中显现的空间和时间尺度的联系可应用于处理在城市方面的问题。那些可能在小空间尺度或短时期内表现为负面的事物，却可能在更大尺度或更长时期显现出积极的一面。对于一系列既定的干预，不同的时空尺度可能会从生态系统引发不同的反应。举一个生态例证：局部的森林可能会出现或消失，但这个区域的总体的森林覆盖率却可以相对保持稳定。这就引出了另一个问题，即一个城市是否需要一个更大的系统去中和城市内部的主要干预带给城市总体系统的影响。该领域的生态学家得出以下研究成果：即跨尺度运动所引起的主体变化不仅是一个变大或变小的问题，而是本质上的变化。不稳定的系统变得被视为稳定，自下而上的控制变成自上而下的控制，竞争变得不那么重要。这给城市本身可以作为解决各种环境损害的源头的思想以启发：在某些尺度上，我们认为城市是有利于解决环境危机的。

在生态研究中关于尺度的重要问题是，层次和尺度常常被混淆：有时候表现为尺度变化，而实际上却是层次之间的转换。尺度变化往往导致新的相互作用和关联，转换为另一个不同的体系。而层次则是在等级组织体系中的一个相对位置。因此，层次上的变化有数量或大小之说，却不是实体的改变。组织体系的层次不是尺度，即使它有尺度或在某一个尺度之中。尺度和层次是两个不同的维度。

通过上文对城市的分析和辨别，我可以用4种方式来看待城市的多尺度：首先是关注其改变事物性质的特点，特别是量的计算。个体的存在不同于整合的结果，整合不代表个体在数量上的累计，它们是不同的事物。城市中的个体和整合可以通过一个环境损害的程度来界定，拿不同的尺度和不同来源的城市污染来说：微型汽车或单个家庭的燃煤单位值虽然小，但是所产生的CO2总量却导致严重的空气污染，导致全市的CO2排放量超标。空气和水中的微生物引发家庭和个体尺度的小范围疾病，但是城市的高密度引发病毒成倍增长并发展成流行疾病，直接影响那些不具备疾病防御能力的企业运营的不稳定。将城市作为多尺度的第2种方式是关注环境损害产生的地理区域：这些破坏有的发生在大气层，有的则在城市人工环境的内部（如大量的污水或疾病），还有一些在全球的偏远地区（森林砍伐）。

第3种方式是城市对资源的跨国开采和加工布局，这种方法是采取对分布在全球各地的各个地区的资源进行采集的模式。这种世界范围的开采分布在城市内部，并以特定的、具体的形式进行着（如：家具、珠宝、机器和燃料），城市处于这种全球化开采的战略时刻。第4种看待城市多尺度的方法是城市政策级别的多样性。非常关键的一点就是要注意政策范围（国际级、国家级、区域级和地方级），并实施相应的程序、规章、处罚等规定。这些具体实施的结果不同于政府颁布与实施的其他级别的政策。

另外，很重要的一点是，应该把可能在空间尺度上产生的冲突考虑在内。一方面，环保主义者在更广阔的时空范围内采取行动，从宏观角度来观察各地方的一系列活动所带来的影响，例如，全球变暖、酸雨的形成以及基础资源的全球掠夺。环保主义者在执行中经常会受到执行时间短，实施水平有限的限制。而在特定地区追求清洁和补救的措施，相对于更大范围的影响往往是收效甚微的，同时，这也影响并削弱了资源消耗问题的迫切性，并使应急反应更加滞后。另一方面，那些经济学家或企业，则更倾向于强调将他们在特定时间段内对特定区域的利益最大化。

城市在消耗和产生废物的布局方面是个复杂的系统，它同时也是产生解决方案的关键。某些在城市内响应环境的行为部署也适用于全球。在前部分提到的全球城市网络可以成为全球化的投资管理空间，且有可能把具有环境破坏性的全球资本投资转变成为环境和谐型投资。这个网络系统不仅包含了最具破坏性行为的地区，也包括极力要求这些破坏者负责的地区。该网络的尺度远大于组成这个网络的单个城市尺度。

以上从多方面阐述了城市尺度的问题。城市的多尺度系统从两方面得到体现：多尺度城市空间结构和城市中实施的多尺度（国家级、国际级、区域级的）政策框架。循环经济环境保护主义者们希望能够将可循环利用这一理念引入到城市功能中，使其最大化从而减少浪费，并在不同尺度的空间内得以循环实施。其中一部分用于家庭内部，另一部分则广泛用于城市以及全球的其他地方。□（包延慧，乔悦 译；吉宁，刘舒 校）

注释：

[1] 并非城市化本身在损害环境，而是要追溯到近代之前的农村社会城市化模式，由于采用了对环境有害的生产程序所造成的。一直到近期，一些环境可持续的经济实践仍然存在，如轮作以及非化学方法施肥和控制虫害。此外，我们的极端资本主义使贫穷地区，尤其是地球南方更加贫穷，这导致贫穷地区的人们开始从事对环境有害且会导致沙漠化的开发行为。

[2] 一些国际协议很关键，例如：当限制各国家稀有能源的消费以及环境污染时，部分具有消极意义的协议误导了碳交易市场——使企业无需改变他们的方式，而只要花钱让别人承担污染的责任。这使得污染现象并没有下降趋势。

[3] 可持续消费逻辑的建构可以通过一系列的手段来实现：区域或更加细化的分区控制、建立规程、建筑规范、交通/水及废水规划、城市更新及城市扩张、提升当地税收（环境税、费用、征税），或者引进环境因素等方式。（参见 Satterthwaite及其他研究者网站）。

[4] 举例来说，为发展商业性农业生产，在印尼的森林里会用火烧出大片空地（在此事例里为面向世界市场的棕榈油种植园）而会定期向新加坡上空排放浓烟。而新加坡是一个为严格控制空气污染而对居民与企业收取高税的国家。

萨斯基娅·萨森，哥伦比亚大学社会学教授，同时也是哥伦比亚大学全球思考委员会成员，她最近出版了《领土、权威和权利：从中世纪到全球聚集》（Territory,Authori ty, Rights: From Medieval to Global Assemblages, Princeton University Press,2006）和《全球化社会学》（A Sociology of Global ization,Nor ton,2007），她同时也是《2006年威尼斯双年展建筑目录》（2006 Venice Biennale of Archi tecture Catalogue）的作者，她刚刚在来自30多个国家的研究人员的帮助下，完成了一个联合国教科文组织的5年项目，这个项目是关于人类定居可持续性方面的，此项目的调研结果已经作为《生命维持系统（维生系统）百科全书》（Encyclopedia of Life Support Systems, Oxford,UK: EOLSS Publishers）的一卷由“英国牛津：维持生命系统百科全书出版社”出版。她的作品被翻译成21种语言，她的一些观点和评论也在《卫报》、《纽约时报》、《民主开放网》、《外交界》、《国际先驱论坛报》、《国际新闻周刊》、《金融时报》等媒体上有过阐述。《全球城市》（The Global City）这本书的中文译本也已被上海社科院社会科学出版社出版。她的《世界经济下的城市》（Cities in a World Economy）也将于2010年由译林出版社出版发行。

Introduction

The massive processes of urbanization under way today are inevitably at the center of the environmental future. It is through cities and vast urban agglomerations that humankind is increasingly present in the planet and through which it mediates its relation to the various stocks and f lows of environmental capital. The urban hinterland, once a most ly confined geographic zone, is today a global hinterland. With the expansion of the global economy we have raised our capacity to annex growing portions of the world to support a limited number of industries and places. Here I address the multi-scalar character of cities: the diverse terrains and domains, many non-urban, onto which they project their ef fects and f rom which they meet their needs. And I address their ecological character: the multiple mechanisms and feedback loops that articulate urban processes and their consequences, and, fur thermore, the emergent articulations between these urban ecologies and nature’s ecologies.

1. The need to distinguish format f rom content

The enormously distinctive presence that is urbanization is changing a growing range of nature’s ecologies, from the climate to species diversity and ocean purity. And it is creating new environmental conditions－heat islands, ozone holes, desertification,and water pol lution. We have entered a new phase:for the first time humankind is the major consumer in al l the significant ecosystems. And urbanization has been a major instrument. There is now a set of global ecological conditions never seen before. And major cities have become distinct socio-ecological systems with planetary reach. Cities have a pronounced ef fect on traditional rural economies and their long-standing cul tural adaptation to biological diversity. Rural populations have become consumers of products produced in the industrial economy, one much less sensitive to biological diversity. The rural condition has evolved into a new system of social relations, one that does not work wi th biodiversity. These developments all signal that the urban condition is a major factor in any environmental future. It all amounts to a radical transformation in the relation between humankind and the rest of the planet.

But is it urbanization per se or the particular types of urban systems and industrial processes we have instituted? That is to say, is it the urban format marked by agglomeration and density dynamics, or the contents we have historical ly and col lectively produced par t ly through a processes of pathdependence which kept eliminating options as we proceeded. Are these global ecological conditions the result of urban agglomeration and density or are they the result of the specific types of urban systems we have develop to handle transport, waste disposal,building, heating and cooling, food provision, and the industrial process through which we extract, grow,make, package, distribute, and dispose of al l the foods, services and materials we use?

It is, doubtless, the latter－the specific urban systems we have made. One of the outstanding features when one examines a range of major cities today is their sharp differences in environmental sustainability.These dif ferences resul t f rom diverse government policies, economic bases, cultures of daily life, and so on. Across al l these differences are a few foundational elements that now increasingly dominate our way of doing things. One of these is the fact that the entire energy and material f lux through the human economy returns in altered form as pol lution and waste to the ecosphere. The rupture at the heart of this set of f lows is made and can, thus, be unmade －and some cities are working on this. This rupture is present in just about al l economic sectors, from urban to nonurban. But it is in cities where it takes on its most complex interactions and cumulative ef fects. This makes cities a source of most of the environmental damage, and some of the most intractable conditions feeding the damage. But it is also the complexity of cities that is part of the solution.[1]

It is now urgent to make cities and urbanization part of the solution: we need to use and build upon those features of cities that can re-orient the material and organizational ecologies of cities towards positive interact ions with nature’s ecologies. These interactions, and the diversity of domains they cover,are themselves an emergent socio-ecological system that bridges the city’s and nature’s ecologies. Part of the ef fort is to maximize the chances that it has positive environmental outcomes. Specific features of cities that help are economies of scale, density and the associated potential for greater ef ficiency in resource use, and, important but of ten neglected,dense networks of communication that can serve as facilitators to institute environmentally sound practices in cities. More theoretically, one can say that in so far as cities are constituted through various processes that produce space, time, place and nature, cities also contain the transformative possibilities embedded in these same processes. For example, the temporal dimension becomes critical in environmental ly sound initiatives: thus ecological economics al lows us to recognize that what is inef ficient or value-losing according to market criteria with short temporal evaluation frames, can be positive and value-adding using environment driven criteria.

2. The complexity and global projection of cities

As has been much documented, cities have long been sites for innovation and for developing and instituting complex physical and organizational systems. It is within the complexity of the city that we must find the solutions to much environmental damage and the formulas for reconfiguring the socio-ecological system that is urbanization. Cities contain the networks and in format ion l oops that may faci l i tate communicating, informing, and persuading households,governments, and firms to support and participate in environmental ly sensitive programs and in radical ly transformative institution building.

Urban systems also entail systems of social relations that support the current configuration.Beyond adoption of practices such as waste recycling,it will take a change in this system of social relations itsel f to achieve greater environmental sensitivity and ef ficiency. For instance, a crucial issue is the massive investment around the wor ld promoting large projects that damage the environment. Deforestation and construction of large dams are perhaps among the best known cases. The scale and the increasingly global and private character of these investments suggest that citizens, governments, NGOs, all lack the power to alter these investments patterns. But there are today structural platforms for acting and contesting these power ful corporate actors (Sassen 2005). The geography of economic globalization is strategic rather than al l-encompassing and this is especially so when it comes to the managing, coordinating, servicing and financing of global economic operations. The fact that it is strategic is significant for a discussion about the possibilities of regulating and governing the global economy. There are sites －the network of global cities-in this strategic geography where the density of economic transactions and top-level management functions come together and represent a strategic geography of decision-making. We can see this also as a strategic geography for demanding accountability about environmental damage. It is precisely because the global economic system is characterized by enormous concentration of power in a limited number of large multinational corporations and global financial markets that makes for concentrated (rather than widely dispersed) sites for accountability and for changing investment cr i ter ia. Engaging the headquarters is a very dif ferent type of action from engaging the thousands of mines and factories, and the mil lions of service outlets of such global firms.This engagement is today facilitated by the recognition,among consumers, politicians and the media, of an environmental crisis. For sure, it leaves out mil lions of smal l local firms responsible for much environmental damage, but these are more likely to be control lable through national regulations and local activisms.

A crucial issue raised by al l the above is the question of the scales at which damage is produced and intervention or change should occur. These may in turn differ from the levels and sites for responsibility and accountability. The city is, in this regard, an enormously complex entity. Cities are multi-scalar systems where many of the environmental dynamics that concern us are constituted and in turn constitute what we cal l the city, and where dif ferent policy levels, f rom the supra-to the sub-national, get implemented. Further, specific networks of most ly global cities, also constitute a key component of the global scale and hence can be thought of as a network of sites for accountability of global economic actors.

Urban complexity and diversity are fur ther augmented by the fact that urban sustainability requires engaging the legal systems and profit logics that underlie and enable many of the environmental ly damaging aspects of our societies. The question of urban sustainability cannot be reduced to modest interventions that leave these major systems untouched. And the actual features of these systems vary across countries and across the North-South divide.While in some of the other environmental domains it is indeed possible to confine the treatment of the subject to scientific knowledge, this is not the case when dealing with cities. Non-scientific elements are a crucial part of the picture: questions of power, of pover ty and inequality, ideology and cul tural preferences, are al l part of the question and the answer. One major dynamic of the current era is globalization and the spread of markets to more and more institutional realms. Questions of policy and proactive engagement possibilities are a critical dimension of treatments of urban sustainability,whether they involve asking people to support garbage recycling or demanding accountability f rom major global corporations known to have environmental ly damaging production processes.

3. Scaling

City-related ecological conditions operate at a diversity of geographic scales. Importantly, cities incorporate a range of scales at which a given ecological condition functions, and in that sense cities make visible the fact itself of scaling. Further, cities make the multiscalar property of ecological systems present and recognizable to its residents. This urban capacity to make visible should be developed and strengthened as it wil l become increasingly critical for policy matters not only of cities, but also at the regional, national and global level. For the majority of those writing about environmental regulation in and of cities, the strategic scale is the local one (Habitat II; Local Agenda 21). Others have long argued that the ecological regulation of cities can no longer be separated from wider questions of global governance (Low, 2000);this is also a long-standing position in general, nonurban, analyses about the “economy and the environment” (e.g. Etsy, 1998; 1999).

Beyond regulation, the city is a also key scale for implementing a broad range of environmental ly-sound policies and also a site for struggles over environmental quality of life for dif ferent socio-economic classes.Air, noise, and water pol lution can al l be partly addressed inside the city, even when the policies involved may originate at the national or regional level. And indeed thousands of cities wor ldwide have initiated their own de fact environmental policies to the point of going against national law, not because of ideals but because they had to, in a way that national governments are far more removed f rom the immediate catastrophic potentials of poisoned air and f loods.The acuteness of environmental chal lenges at the urban level has been further sharpened by the current phase of economic globalization which puts direct pressures on cities. One example of these pressures is the global corporate demand for the extreme type of buil t-environment epitomized by Dubai. The other side of this is the sharply increased demand for inputs,transport and the inf rastructure for mobility: the enormous demand for wood, cement, non-renewable energy, airf light, trucking, shipping, and so on. A second element that the current global corporate economy has brought with it is the Wor ld Trade Organization’s subordination of environmental standards to what are presented as “requisites” for“f ree” global trade. Final ly, privatization and deregulation reduce the role of government, especial ly at the national level, and hence weaken its mandatory powers regarding environmental standards.

The city becomes a strategic space for the direct and brutal encounter between forces enormously destructive of the environment and increasingly acute needs for environmental viability. Much of what we keep describing as global environmental chal lenges becomes concrete and urgent in cities. International and national standards are likely to have to be implemented and enforced at the urban scale.[2]There are limits to the urban level, especial ly in the Global South where local governments have limited funds.But it is one of the scales at which many concrete goals can be achieved. Local authorities are in a strong position to pursue the goals of sustainable development as direct or indirect providers of services, as regulators,leaders, partners, and as mobilizers of community resources.[3]Each urban combination of elements is unique, and so is its mode of insertion within local and regional ecosystems. Out of this specificity comes place-based knowledge, which can the be scaled-up and cont ribute to the understanding of global conditions. The case of ozone holes il lustrates this scale-up: the damage is produced at the microlevel of cars, households, factories, buildings, but its full impact becomes visible/measurable over the poles, where there are no cars and buildings.

A debate that gathered heat beginning in the 1990s and remains unresolved pits the global against the local as the most strategic scale for action. Redclift(1996) argued that we cannot manage the environment at the global level. Global problems are caused by the aggregation of production and consumption, much of it concentrated within the world’s urban centers. For Redclif first we need to achieve sustainability at the local level; he argues that the f lurry of international agreements and agencies are international structures for managing the environment that bear litt le or no relat ion to the processes through which the environment is being transformed. Not everyone agrees. Thus Satterthwaite has long argued that we need global responsibilities and cannot do that without international agreements (Satterthwaite 1999). And Low (2000) adds that we have a global system of corporate relations of which city administrations are increasingly part. This complex cross-border system is increasingly responsible for the health and destruction of the planet. Today’s processes of development bring into focus the question of environmental justice at the global level, a question that , if asked, would have been at the national level in the early industrial era.

I would make two observations here. One is that what we refer to or think of as the local level may actual ly entail more than one scale. For instance, the operations of a mining or manufacturing multinational corporation involve mul tiple localities, scattered around the globe. Yet these localities are integrated at some higher organizational level into what then reemerges as a global scale of operations. Much cleanup and preventive action wil l indeed have to engage each local ly produced set of damages. But the global organizational structure of the corporation involved needs to be engaged as wel l. Along these same lines,the focus on individual cities promoted by notions of inter-city competition in a global corporate economy,has kept analysis and pol itical leaders f rom understanding the extent to which that global economy needs networks of cities, not just one perfect global city. Hence, specific networks of cities are natural platforms for cross-border city-al liances that can confront the demands of global firms. One key benefit for cities of international agreements is to prevent some countries and cities f rom taking advantage of others that are instituting environmental ly sound policies. Implementing such policies is likely to raise costs, at least for the short term thereby possibly reducing the “competitiveness” of such cities and countries, even if in the long term this is likely to enhance their competitiveness. Cities that succeed in instituting such policies should not carry the costs of the absence of such policies in other cities, whether at the national or international level. This wil l at times require policies that restrain the transfer of environmental costs to other locations.[4]

The second observation is that an enormous share of the attention in the literature on urban sustainability has been on how people as consumers and as householdlevel actors damage the environment. When measuring cities, inevitably individuals and households are by far the most numerous units of analysis. Yet there are clearly shortcomings to this focus. In terms of policy it leads to an emphasis on household recycling activities without addressing the fundamental issue of how an economic system prices modes of production that are not environmental ly sound. In this regard, an urban focus can easi ly leave out global economic and ecological systems that are deeply involved yet cannot be addressed at the level of households or even many individual firms. For instance, those who insist that greenhouse gas emissions will have to be control led at the local level are, in many ways right. But these emissions wil l also have to be addressed at the broader macro levels of our economic systems.

4. Conclusion: Towards a multi-scalar ecological urban analysis

These various questions can be analytical ly conceived of as questions of scale. Scaling can be seen as one way of handling what are now of ten seen as either/or conditions: local vs. global, markets vs.non-ma r ke t mechani sms, g reen vs. b rown environmentalism. I have found some of the analytic work on scaling being done among ecologists very illuminating in the ef fort to conceptualize the city in this context. Of particular relevance is the notion that complex systems are multi-scalar systems as opposed to multilevel systems, and that the complexity resides precisely in the relations across scales. “When broad overarching events appear to be closely related to details, a system requires treatment as a complex system.” These authors find that tension among scales is a feature of complex ecological systems, a condition that would cer tainly seem to hold for cities.Understanding how tensions among scales might be operating in the context of the city might strengthen the analysis of environmental damages associated with urbanization, and the ways in which cities are also the source for solutions. “Until ecologists become adept at addressing the scale issue, the discipline will remain stuck in detailed descriptions at one level.Trying to deal with everything at one level, on the other hand, is unwieldy and messy”. One could clearly make a paral lel argument for the case of cities,particularly in the insistence on emphasizing the local scale for research and implementation.

A crucial analytic operation involved here is giving spatio-temporal scaling to the object of study. This also entails distinguishing that object of study from contextual variables, which in the case of cities might be population, economic base, etc. Executing such analytic operations would help us avoid the fal lacy of holding “the city” guilty of environmental damage.Eliminating cities would not necessarily solve the environmental crisis. We need to understand the functioning and the possibilities for changing specific systems of power, economic systems, transportation systems, and so on, which entail modes of resource use that are environmental ly unsound. The fact that these various systems amalgamate in urban formations is an analytical ly distinct condition from the systems involved. The distinction between specific systems and background or contextual variables also helps us avoid the fal lacy of seeing “the city” as a container,and a bounded closed unit. In my research on cities and globalization, I instead conceptualize the city as a multiscalar system through which multiple highly specialized cross-border economic circuits circulate.This idea can be applied to cities and the environmental dynamic. In this case, the city is a multiscalar system through which mul tiple specific socio-ecological circuits traverse. It is not a closed system. Cities are amalgamations of mul tiple “damage” circuits,“restoration” circuits and policy circuits.

There are a set of specific issues raised by research on ecological systems that point to possibly fruit ful analytic strategies to understand cities and urbaniza t ion p rocesses bo th in te rms o f environmental conditions and in terms of policy.One of the reasons this may be helpful is that we are stil l struggling to understand and situate various types of environmental dynamics in the context of cities and how to engage policy. When it comes to remedial policy and clean-up there is greater clarity in understanding what needs to be done. But understanding the city as a broader system poses enormous di f ficul ties precisely because of the mul tiple scales that are constitutive of the city,both as a system of distributed capabilities and as a political-economic and juridical-administ rative system. That is to say, the individual household or f irm or government of f ice can recycle waste but cannot address ef fectively the broader issue of excess consumpt ion of scarce resources; the international agreement can cal l for global level measures to reduce greenhouse emissions but depends on individual countries and individual cities and individual households and firms to implement many of the necessary steps; and the national government can mandate environmental standards but it depends on systems of economic power and systems of weal th production. A key analytic step is to decide which of the many scaled ecological,social, economic, policy processes are needed to explain a specific environmental condition (whether negative or positive) and design a specific action or response. Another analytic step is to factor in the temporal scales or frames of various urban conditions and dynamics: cycles of the buil t environment, of the economy, the l ife of inf rast ructures and of cer tain types of investment inst ruments. The combination of these two steps helps us deconstruct a given situation and to locate its constitutive conditions in a broader grid of spatial, temporal,and administrative scales.

The connection between spatial and temporal scales evident in ecological processes may prove analytical ly useful to approach some of these questions in the case of cities. What may be found to be negative at a smal l spatial scale, or a short-time frame, may emerge as positive at a larger scale or longer time frame. For a given set of disturbances, different spatiotemporal scales may elicit dif ferent responses from ecosystems. Using an il lustration from ecology, we can say that individual forest plots might come and go but the forest cover of a region overal l can remain relatively constant. This raises a question as to whether a city needs a larger system in place that can neutralize the impact on the overal l city system of major disturbances inside the city. One outcome of the research by ecologists in this domain is that movement across scales brings about change which is the dominant process: it is not only a question of bigger or smaller,but rather that the phenomenon itsel f changes.Unstable systems come to be seen as stable; bottomup control turns into top-down control; competition becomes less important. This also is suggestive for thinking about cities as the solution to many types of environmental damage: what are the scales at which we can understand the city as contributing solutions to the environmental crisis.

An important issue raised by scaling in ecological research is the frequent confusion between levels and scales: what is sometimes presented as a change of scales is actual ly a translation between levels. A change of scale results in new interactions and relationships,of ten a dif ferent organization. Level, on the other hand, is a relative position in a hierarchically organized system. Thus a change in levels entails a change in a quantity or size rather than the forming of a different entity. A level of organization is not a scale, even if it can have scale or be at a scale. Scale and level are two dif ferent dimensions.

Relating some of these analytic distinctions to the case of cities suggests that one way of thinking of the city as multi-scalar is to note that some of its features, notably density, alter the nature of an event.The individual occurrence is distinct from the aggregate outcome; it is not merely a sum of the individual occurrences, i.e. a greater quantity of occurrences. It is a dif ferent event. The city contains both, and in that regard can be described as instantiating a broad range of environmental damage that may involve very dif ferent scales and origins yet get constituted in urban terms: CO2emissions produced by the microscale of vehicles and coal burning by individual households becomes massive air pol lution covering the whole city with ef fects that go beyond CO2emission per se. Air and water borne microbes materialize as diseases at the scale of the household and the individual body and become epidemics thriving on the multiplier ef fects of urban density and capable of destabilizing operations of firms whose machines have no intrinsic susceptibility to the disease. A second way in which the city is mul tiscalar is in the geography of the environmental damages it produces. Some of it is atmospheric, some of it internal to the bui l t environment of the city, as might be the case with much sewage or disease, and some of it in distant locations around the globe, as with deforestation.

A third way in which the city can be seen as multiscalar is that its demand for resources can entail a geography of extraction and processing that spans the globe, though it does so in the form of a collection of confined individual sites, albeit sites distributed worldwide. This wor ldwide geography of extraction instantiates in particular and specific forms (e.g.furniture, jewelry, machinery, fuel) inside the city.The city is one moment—the strategic moment—in this global geography of extraction, and it is different from that geography itsel f. And a fourth way in which the city is multiscalar is that it instantiates a variety of policy levels. It is one of the key sites where a very broad range of policies—supranational, national,regional and local—materialize in specific procedures,regulations, penalties, forms of compliance and types of violations. These specific outcomes are dif ferent f rom the actual policies as they get designed and implemented at other levels of government.

Important also is the need to factor in the possibility of conflicts in and between spatial scales.Environmentalists can operate at broad spatial and temporal scales, observing the ef fects of local activities on macro-level conditions such as global warming, acid rain formation and global despoliation of the resource base. Environmentalists with a managerial approach of ten have to operate at very short time frames and confined levels of operation,pursuing clean ups and remedial measures for a particular locality, remedial measures that may do litt le to af fect the broader condition involved and may, indeed, diminish the sense of urgency about larger issues of resource consumption and thereby delay much needed responses. On the other hand,economists or f i rms, wi l l tend to emphasize maximizing returns on a particular site over a specific period of time.

Cities are complex systems in their geographies of consumption and of waste-production and this complexity also makes them crucial to the production of solutions. Some of the geographies for sound environmental action in cities wil l also operate wor ldwide. The network of global cities described in the preceding section becomes a space at the global scale for the management of investments but also potent ial ly for the re-engineer ing of envi ronmental ly dest ruct ive global capi tal investments into more responsible investments. It contains the sites of power of some of the most destructive actors but potential ly also the sites for demanding accountability of these actors. The scale of the network is dif ferent f rom the scale of the individual cities constituting this network.

Al l of the above brings out the multiple ways in which the city scale is present. The city is a multiscalar system in the double sense of what instantiates there and of the dif ferent policy f rameworks that operate in cities—national, supranational, subnational. The circular logic environmentalists want to introduce in the functioning of cities, i.e. maximum re-use of outputs to minimize waste, will entail spatial circuits that operate at different scales. Some wil l be internal to households, others wil l be city wide and yet others wil l go beyond the city and run through places around the globe. □

Notes:

[1] That it is not urbanization per se that is damaging but the mode of urbanization also is signaled by the adoption of environmental ly harmful production processes by pre-modern rural societies. Until recently these had environmental ly sustainable economic practices, such as crop rotation and no use of chemicals to fertilize and control insects. Further, our extreme capitalism has made the rural poor, especial ly in the Global South, so poor that for the first time many now are also engaging in environmental ly destructive practices, notably practices leading to desertification.

[2] Some kinds of international agreements are crucial－for instance, when they set enforceable limits on each national society’s consumption of scarce resources and their use of the rest of the world as a global sink for their wastes. Other such agreements I find problematic, notably the market for carbon trades which has negative incentives: firms need not change their practices insofar as they can pay others to take on their pol lution. At the limit, there is no absolute reduction in pol lution.

[3] For instance, instituting a sustainable consumption logic can be aided by zoning and subdivision,regulations, building codes, planning for transport,for water and waste, recreation and urban expansion,local revenue raising (environmental taxes, charges,levies) and through the introduction of environmental considerations when designing budgets, purchases,contracting and bidding (see Satterthwaite’s and other researchers’ work on the IIED website for one of the most detailed and global data sets on these issues).

[4] For instance, the vast fires to clear big tracts of the Indonesian forests in order to develop commercial agriculture (in this case, palm oil plantations geared to the wor ld market) have regular ly produced thick smoke carpets over Singapore, a city-state that has implemented very stringent air pol lution controls at often high tax costs to its inhabitants and firms.

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http://www.iied.org/pubs/pdfs/10549IIED.pdf