構建城市生態與自然生態之間的橋梁

薩斯基婭·薩森/Saskia Sassen

前言

現階段所進行的大規模的城市化進程，不可避免地成為未來環境問題的核心。人類通過城市和龐大的城市群不斷地占據著地球表面的空間，并且通過城市來協調人類和各類環境資源的關系、以及人類與環境資源循環的關系。城市，曾是一個非常有限的區域，而如今卻是一個全球化的區域。隨著全球經濟的擴張，為了支撐有限的產業和場所，我們占據了世界上越來越多的空間。在此，我著重強調城市的多尺度性：即多樣的地域和領域，有些領域甚至影響到那些滿足城市發展需求的未城市化地區。同時，我也對城市的生態特性做出強調：即多系統性和循環性，這些特性使城市的發展進程及其最終結果相互關聯，隨之產生了城市生態與自然生態之間的聯系。

1. 將形式與內容區分的必要

城市化對自然生態的影響不斷加劇，影響到包括氣候、物種多樣性和海洋凈化等方面。它還產生了許多新的環境問題，如熱島、臭氧洞、沙漠化和水污染的產生。我們已經進入了一個新的階段：那就是人類第一次成為所有重要生態系統中的主要消費者，而城市化則是進入該階段的一個主要途徑。目前，出現了一系列空前的全球化生態狀況，暨大城市已經成為影響全球的、不同形態的社會生態系統。城市對于傳統農村經濟，以及該種經濟同生物多樣性的長期適應性具有顯著的影響。農村人口已經成為由工業經濟制造出的產品的消費者。農村環境逐漸演變成為一種與生物多樣性無關的新型的社會關系體系。這些發展均表明，城市環境將成為所有未來環境問題的主要根源。這一切引發了人類與地球上其他物種之間關系的巨大改變。

但是，環境問題究竟來自城市化本身，還是來自于我們已經建構的特定的城市體系及產業進程？也就是說，城市形態究竟是以什么為標志，是城市自身所具有的聚集性和密集性，還是在歷史進程中城市所選擇的發展方式？全球生態環境問題是城市聚集和密集的產物，還是由不同城市中某些系統引起的？例如，我們所發展的交通、垃圾處理、建筑、供熱、制冷、食物供應等系統，還包括提取、種植、制造、包裝、分配等產業，以及我們飲食、服務及材料的處理所采用的系統。

毫無疑問，答案是后者，即我們所建構的特定的城市體系。今天，當我們再次關注這些主要城市，一個突出的特征是，這些城市在環境可持續發展方面存在著巨大差異。這種差異是由城市不同的政策、經濟基礎、生活習俗、文化差異等造成的。在所有這些差異中，有一些本質差異正不斷影響甚至支配著我們做事的方式。其中之一就是人類經濟發展中，在開發自然能源與材料的同時，回饋給自然界的卻是污染和廢棄物。這已經使自然資源的流動產生斷裂，盡管一些城市正在努力避免這種斷裂的產生，但無論是城市還是農村，幾乎在所有的經濟形態中，都存在著這種斷裂。它給城市所帶來的復雜影響和負面效應特別明顯，這使城市成為大多數環境破壞和一些最難解決的損害的根源。但同時，也恰恰是城市的復雜性為解決問題提供了途徑[1]。

現在迫切需要將城市以及城市化作為環境問題解決的途徑之一。我們需要利用和依賴這些城市特性，使它們能夠對城市中有組織的生態系統與自然體系產生積極的影響。這些影響，以及它們所涵蓋的各個領域，將成為聯系城市與自然生態的一種社會生態系統。我們所能做的就是盡可能地讓這些對環境有積極影響的結果產生。這些可供利用并能產生積極影響的特征包括：規模經濟、稠密度、資源高效利用及其他相關方面的潛力，另外還包括非常重要但卻常常被忽略的密集型信息交流網絡，它可有助于促進城市實施一些環境保護方面的措施。從理論上說，城市是由各種各樣的進程構成的，包括空間、時間、場地以及自然等進程。同時，它也包含這些進程中可能存在著的突變，比如，當時間因素成為環境保護措施的關鍵：生態經濟學可以讓我們認識到，如果用環境標準來衡量，那些根據市場標準在短期價值框架下是無效的或貶值的措施，長遠來看卻是積極有效的。

2. 城市的復雜性和全球規劃

正如所記載的那樣，城市一直以來都是創新、發展、建構復雜物質系統和組織系統的場所。所以，我們必須在城市這個復雜體系中找到解決環境破壞問題的方法，并重新建構城市化進程中的社會生態系統。城市所擁有的網絡以及信息圈使溝通和傳遞信息變得更加便利，通過這些可以說服業主、政府和企業去支持那些對環境影響敏感的項目，并投身到能從根本上轉變體制的建設中來。

城市體系同樣包含支撐目前城市結構的社會關系系統。為了達到更高的環境敏感度和有效性，除采取一些措施（如廢棄物回收）外，社會關系系統本身也需要有所改變。比如，其中一個關鍵問題是，世界范圍內的大項目和大規模的投資對環境產生的危害。例如，我們所熟知的大規模森林砍伐和水壩的修筑。這些項目的投資規模，和其全球化、私有化的特征表明，無論是市民，還是政府或非政府組織，都不具備能夠改變這種投資模式的能力。但在今天，一些由經濟形態搭建的平臺，可以對這些強大的集團企業產生作用，并與之抗衡。經濟全球化布局在涉及到全球經濟運作的管理、協作、金融與服務時，雖不夠全面但卻是具有戰略意義的。這種戰略性布局對探討規范和管理全球經濟的可能性是至關重要的。如果處在全球化戰略布局網絡中的城市，把密集型經濟運轉與高層管理機制相結合，就會產生戰略性布局的決策。同樣，我們也可以將此視為對環境損害負有責任的戰略性布局。因為，龐大的權力集中于少數跨國企業和全球金融市場，而全球經濟的特征也決定了它們必然集中在某些區域，而不是分散開來的。相應的，這使得對環境損害所承擔的責任也相對集中了，投資標準也隨之發生了改變。制約企業總部的行為，與制約數千萬的礦井和工廠、以及數百萬同類全球企業的服務出口相比，是完全不同的。如今，消費者、政客以及媒體對環境危機的認知有助于促使對企業總部的牽制，而數百萬當地小企業對大多數環境破壞應承擔的責任則被忽略了。盡管如此，通過國家管制以及當地政府的干預，對小企業的控制也是極有可能被實現的。

由此，引出一個重要的問題，即損害產生的尺度，以及隨之可能出現的干預或改變，它有別于產生損害的程度和區域。就這點而言，城市是一個無比復雜的實體。舉例來說：城市多元的系統性，形成了與之相關的環境動態，反之又影響到城市，而且不同的政策，從地方層面到國際層面，都可被實施；更進一步來說，大多數全球化城市中的特定網絡，是建立全球性網絡的關鍵子系統，可被視為對全球經濟活動負責的區域網絡。

引起和造成我們環境損害的社會法律體系和利益關系，恰恰是城市可持續發展不可回避的，這使得城市的復雜性和多樣性進一步擴大。城市可持續問題的解決，必然要觸動城市的主要系統，這些系統在國家之間、南北差異之間也都有所不同。雖然在一些其他的環境領域中，可以通過科技手段來解決問題，但在處理城市的環境問題時科技手段卻并不適用。非科技因素是城市問題的關鍵部分：能源、貧窮與貧富差距、思想體系和文化偏好等問題，是導致問題的根源，但同時也是解決問題的途徑。當前的一個主要趨勢是全球化和市場化，向著越來越公共化的領域擴展。發展城市可持續的關鍵是采取政策導向以及提高參與的積極性，包括要求人們去支持垃圾回收、去追究那些對環境破壞影響巨大的生產工序和全球企業的責任。

3. 尺度

那些與城市相關聯的生態條件在多種尺度上產生作用。重要的是，城市包含了一系列的尺度，不同尺度所對應的特定生態條件在該尺度上起到相應的作用。并使城市自身的尺度得以顯現。另外，城市也使生態系統的多尺度特性顯現出來，并被市民所認知。城市的這種特性，由于它在地區、國家甚至全球層面上的重要性越來越強，也應當予以重視并得到發展和加強。大多數探討城市環境管理方面的文章認為，區域尺度是戰略性的尺度；而另一些長期討論的觀點則認為，城市的生態章程已經不再能從更寬泛的全球化管理中分離出來。它同樣也是對于非城市地區關于“經濟及環境”分析的一種長期立場。

城市是實施大范圍環境友好政策的關鍵尺度，同時也是不同社會經濟階層用以爭取生活環境質量的場所。空氣、噪聲以及水污染問題都可以在城市里部分得到解決，即使所涉及的政策牽扯到國家或區域層面時也是如此。不可否認，世界范圍內數千個城市都已經制定了它們自己的環境政策，雖然其中有些內容有悖于國家法律，但卻是不得已而為之，僅限于國家政府對有害空氣或污水等潛在的災難無法作出相應的應急反應時的一種選擇。當前，經濟全球化給城市帶來直接壓力，這使得在城市層面原本已經非常脆弱的環境問題更加嚴峻。其中一個例子就是以迪拜為縮影的全球企業對建筑環境類型的極端需求。另一種壓力則來源于對運輸以及基礎物流（如大量木材、水泥、不可再生資源、航空、貨運、船運等）需求的急劇增加。當前環球企業經濟所引起的另一個問題是，相對于世貿組織中“自由”全球貿易這個“必要條件”來說，環境標準則是次要的。最終，私有化和管制的撤銷削弱了政府職能，尤其是對于國家層面來說，這最終削弱了其對于環境標準方面的控制力。

城市作為一個戰略性空間，巨大的環境破壞力與急增的生存環境需求之間產生了直接的、嚴酷的交鋒。我們不斷提到的全球環境挑戰，在城市中已經形成，情況迫在眉睫。國際和國家標準將在城市層面的[2]范圍內被強制執行，城市層面可以實現很多切實的目標，但對于資金非常有限的南半球當地政府而言，它也存在著一些限制。然而，當地政權作為服務的直接或間接提供者，作為管理者、領導者、合作者以及社區資源[3]的使用者，應有能力去完成可持續發展的目標。每種要素的組合都是獨特的，并且有機地嵌入到當地及區域的生態系統中。從這種獨特性里可以得出對場地的認知，并可以在尺度上升級，從而有助于對全球狀況的理解。臭氧洞的例子就對這種尺度的升級做出了闡釋：環境損害是在汽車、戶主、工廠、建筑等微觀層面中產生的，但其整體影響卻是在地球極地才可被看到和評估的，然而那里既沒有建筑物，也沒有汽車。

一場自1990年代開始且至今未解決的爭論是：全球與區域尺度相比較，哪種對于環境保護行動而言更具有戰略意義。雷德克利夫特（Redclif t，1996）的觀點是我們不能在全球尺度上管理環境。全球問題是由生產與消耗綜合造成的，而這些問題多數集中于世界的城市中心。雷德克利夫特認為：我們首先要在區域層面實現可持續化，而倉促制定的以管理環境為目的的國際協定與機構，對改善環境的進程來說意義不大。但有人提出反對意見，如薩特思韋特（Satterthwaite，1999）認為：我們需要建立國際協定對全球負責。洛（Low，2000）也認為：我們有一個日益壯大的由城市管理層所組成的全球合作系統，這個跨國合作系統將為地球的生存與毀滅擔負越來越多的責任。全球性的環境公平問題是當今發展的焦點，說起來，這本應是早期工業時代國家層面的問題。

關于這個爭論我有以下兩個觀點：首先，我們所說的區域層面可能不止一個尺度，如跨國企業分散在全球多處進行采礦或生產活動，并在更高的組織層面進行整合，最后發展為全球范圍的行動。大部分的環境凈化及預防措施的確需要針對每個當地的環境破壞現狀來采取行動，但同樣也需要全球性組織參與其中。同樣，全球經濟一體化下城市間的相互競爭，使城市決策者往往關注于建立單個完善的全球化城市，而忽略了建立城市網絡對全球經濟的重要性和迫切性。因此，城市間特定的網絡是跨國城市聯盟的天然平臺，它可以滿足全球性企業的需求。城市間達成國際協定的最大益處在于，可以防止某些國家或城市，從那些正在建立環保政策的國家和城市中獲益。實施環保政策長遠來看可能會提升國家的競爭力，但由于環保而增加的成本卻在當前降低了 “競爭力”。無論在國內還是國際范圍，實施這些政策的城市沒理由為沒有實施的城市去負擔成本。這就需要建立相關政策[4]，以防環境成本轉移到其他地區。

其次，在涉及可持續發展的城市文獻中，焦點大多集中在以人和家庭為單位的消費行為怎樣破壞環境。這樣在衡量城市時，不可避免地將為數眾多的個人與家庭作為研究對象，顯然，這種方式是具有明顯缺陷的。按照政策，以家庭為單位的回收行為成了重點關注對象，而對于那些響應環境的產品，則被忽略在經濟體制下的價格模式中。在這種情況下，城市的可持續發展將容易忽略那些在家庭和個別企業層面上未能實現，卻是全球經濟與生態系統中更深層面的相互影響。例如，堅持在局部層面控制溫室氣體排放的觀點，從許多角度來說是正確的，但也需要從更宏觀的經濟層面來考量。

4. 結論：多尺度的生態城市分析

這些不同的問題可以被看作是尺度問題。尺度可以作為一種方式去劃定非此即彼的狀態，如區域性與全球性，市場機制與非市場機制，綠色環境與貧瘠環境。生態學家正在從事的一些尺度方面的分析工作，我認為將城市尺度化是非常有啟發性的。復合系統是多尺度系統，而不是多層次系統，其復合性是表現在跨尺度的關聯上的，這種觀點非常重要。“當許多包羅萬象的事物在細節上密切關聯，該系統就需要被作為一個復合系統來對待。” 學者發現：在尺度之間的緊密關聯是復合生態系統的一種特征，也是城市明顯具有的一種狀態。充分理解城市尺度之間如何緊密關聯，有助于分析由城市化帶來的環境破壞，以及幫助城市從根本上解決環境問題。“直到生態學家善于處理尺度上的問題，城市生態學才有可能突破對單一層次的詳細描述。另一方面，試圖去處理同一層次上的所有內容，是不明智和混亂的”。對于城市問題也會出現這樣的爭論，尤其對只強調區域范圍的研究和實施時。

這里所涉及的一個重要的分析手段是以時空尺度來看待研究對象。這需要把研究對象從情境變量中辨別出來，對城市來說可能是人口、經濟基礎等方面。進行這種分析將幫助我們避免抱有“城市”承擔環境破壞罪行的謬論，消除城市不一定能解決環境危機的錯誤觀念。我們需要了解那些具體的政治系統、經濟系統、交通系統等所能起到的作用和可能性，這些系統導致了哪些不利于環境資源利用的模式，我們可以發現并改變。各種系統在城市構成中整合，是一個從相關系統中分析與辨別各種系統的條件。辨別特定系統的背景或情境變量，讓我們避免把“城市”看作一個容器或一個邊界封閉的單元。在我的城市和全球化研究之中，我通過多維的高度專業化的跨境經濟循環使城市概念化成為一個多尺度系統。這一想法可以應用于城市和環境動態。在這種情況下，城市是一個多重特定的社會——生態循環中的多尺度系統。它不是一個封閉的系統。城市是多重“損害”循環、“修復”循環和“策略”循環的混合。

通過針對一系列生態系統具體問題的研究之后，我們發現大量關于環境條件和政策的分析，這有助于我們理解城市與城市化進程。其中最關鍵的是，我們應該努力去理解和假設在城市范疇內的各種環境動態模式，并制定針對性的策略。因為只有在制定補救政策或進行環境治理的過程中，我們才能更加清晰地認識到要去做什么。但是，將城市理解為一個更廣泛的系統卻會產生新的難題，因為城市是由多種尺度構成的，它既是一種分散功能的系統，也是一個政治經濟和法律行政的系統。這就是說，單個的家庭、企業或政府單位可以把廢棄物循環再造，但不能有效地解決更為寬泛的問題（如過量消耗稀缺資源等）；國際協議能夠號召全球采取措施以減少溫室氣體排放，但這是要靠國家、城市、家庭和企業來具體落實的；政府雖然可以授權制定環保標準，但要根據其經濟實力和資源供應系統而定。分析問題的關鍵一步是：當我們面對一種特定的環境條件時（不論正面還是負面），應該考慮哪種尺度的生態、社會、經濟、政策等因素，并且采取相應的措施。另一個分析步驟是考慮時間尺度或各種城市狀態和動態的框架，如人工環境循環、經濟循環、生活基礎設施和某種投資的周期等。這兩個步驟的結合有助于我們將現有的復雜情況進行解構，并將構成條件放在更高層次的綜合系統中（空間、時間、管理）來分析。

在生態進程中顯現的空間和時間尺度的聯系可應用于處理在城市方面的問題。那些可能在小空間尺度或短時期內表現為負面的事物，卻可能在更大尺度或更長時期顯現出積極的一面。對于一系列既定的干預，不同的時空尺度可能會從生態系統引發不同的反應。舉一個生態例證：局部的森林可能會出現或消失，但這個區域的總體的森林覆蓋率卻可以相對保持穩定。這就引出了另一個問題，即一個城市是否需要一個更大的系統去中和城市內部的主要干預帶給城市總體系統的影響。該領域的生態學家得出以下研究成果：即跨尺度運動所引起的主體變化不僅是一個變大或變小的問題，而是本質上的變化。不穩定的系統變得被視為穩定，自下而上的控制變成自上而下的控制，競爭變得不那么重要。這給城市本身可以作為解決各種環境損害的源頭的思想以啟發：在某些尺度上，我們認為城市是有利于解決環境危機的。

在生態研究中關于尺度的重要問題是，層次和尺度常常被混淆：有時候表現為尺度變化，而實際上卻是層次之間的轉換。尺度變化往往導致新的相互作用和關聯，轉換為另一個不同的體系。而層次則是在等級組織體系中的一個相對位置。因此，層次上的變化有數量或大小之說，卻不是實體的改變。組織體系的層次不是尺度，即使它有尺度或在某一個尺度之中。尺度和層次是兩個不同的維度。

通過上文對城市的分析和辨別，我可以用4種方式來看待城市的多尺度：首先是關注其改變事物性質的特點，特別是量的計算。個體的存在不同于整合的結果，整合不代表個體在數量上的累計，它們是不同的事物。城市中的個體和整合可以通過一個環境損害的程度來界定，拿不同的尺度和不同來源的城市污染來說：微型汽車或單個家庭的燃煤單位值雖然小，但是所產生的CO2總量卻導致嚴重的空氣污染，導致全市的CO2排放量超標。空氣和水中的微生物引發家庭和個體尺度的小范圍疾病，但是城市的高密度引發病毒成倍增長并發展成流行疾病，直接影響那些不具備疾病防御能力的企業運營的不穩定。將城市作為多尺度的第2種方式是關注環境損害產生的地理區域：這些破壞有的發生在大氣層，有的則在城市人工環境的內部（如大量的污水或疾病），還有一些在全球的偏遠地區（森林砍伐）。

第3種方式是城市對資源的跨國開采和加工布局，這種方法是采取對分布在全球各地的各個地區的資源進行采集的模式。這種世界范圍的開采分布在城市內部，并以特定的、具體的形式進行著（如：家具、珠寶、機器和燃料），城市處于這種全球化開采的戰略時刻。第4種看待城市多尺度的方法是城市政策級別的多樣性。非常關鍵的一點就是要注意政策范圍（國際級、國家級、區域級和地方級），并實施相應的程序、規章、處罰等規定。這些具體實施的結果不同于政府頒布與實施的其他級別的政策。

另外，很重要的一點是，應該把可能在空間尺度上產生的沖突考慮在內。一方面，環保主義者在更廣闊的時空范圍內采取行動，從宏觀角度來觀察各地方的一系列活動所帶來的影響，例如，全球變暖、酸雨的形成以及基礎資源的全球掠奪。環保主義者在執行中經常會受到執行時間短，實施水平有限的限制。而在特定地區追求清潔和補救的措施，相對于更大范圍的影響往往是收效甚微的，同時，這也影響并削弱了資源消耗問題的迫切性，并使應急反應更加滯后。另一方面，那些經濟學家或企業，則更傾向于強調將他們在特定時間段內對特定區域的利益最大化。

城市在消耗和產生廢物的布局方面是個復雜的系統，它同時也是產生解決方案的關鍵。某些在城市內響應環境的行為部署也適用于全球。在前部分提到的全球城市網絡可以成為全球化的投資管理空間，且有可能把具有環境破壞性的全球資本投資轉變成為環境和諧型投資。這個網絡系統不僅包含了最具破壞性行為的地區，也包括極力要求這些破壞者負責的地區。該網絡的尺度遠大于組成這個網絡的單個城市尺度。

以上從多方面闡述了城市尺度的問題。城市的多尺度系統從兩方面得到體現：多尺度城市空間結構和城市中實施的多尺度（國家級、國際級、區域級的）政策框架。循環經濟環境保護主義者們希望能夠將可循環利用這一理念引入到城市功能中，使其最大化從而減少浪費，并在不同尺度的空間內得以循環實施。其中一部分用于家庭內部，另一部分則廣泛用于城市以及全球的其他地方。□（包延慧，喬悅 譯；吉寧，劉舒 校）

注釋：

[1] 并非城市化本身在損害環境，而是要追溯到近代之前的農村社會城市化模式，由于采用了對環境有害的生產程序所造成的。一直到近期，一些環境可持續的經濟實踐仍然存在，如輪作以及非化學方法施肥和控制蟲害。此外，我們的極端資本主義使貧窮地區，尤其是地球南方更加貧窮，這導致貧窮地區的人們開始從事對環境有害且會導致沙漠化的開發行為。

[2] 一些國際協議很關鍵，例如：當限制各國家稀有能源的消費以及環境污染時，部分具有消極意義的協議誤導了碳交易市場——使企業無需改變他們的方式，而只要花錢讓別人承擔污染的責任。這使得污染現象并沒有下降趨勢。

[3] 可持續消費邏輯的建構可以通過一系列的手段來實現：區域或更加細化的分區控制、建立規程、建筑規范、交通/水及廢水規劃、城市更新及城市擴張、提升當地稅收（環境稅、費用、征稅），或者引進環境因素等方式。（參見 Satterthwaite及其他研究者網站）。

[4] 舉例來說，為發展商業性農業生產，在印尼的森林里會用火燒出大片空地（在此事例里為面向世界市場的棕櫚油種植園）而會定期向新加坡上空排放濃煙。而新加坡是一個為嚴格控制空氣污染而對居民與企業收取高稅的國家。

薩斯基婭·薩森，哥倫比亞大學社會學教授，同時也是哥倫比亞大學全球思考委員會成員，她最近出版了《領土、權威和權利：從中世紀到全球聚集》（Territory,Authori ty, Rights: From Medieval to Global Assemblages, Princeton University Press,2006）和《全球化社會學》（A Sociology of Global ization,Nor ton,2007），她同時也是《2006年威尼斯雙年展建筑目錄》（2006 Venice Biennale of Archi tecture Catalogue）的作者，她剛剛在來自30多個國家的研究人員的幫助下，完成了一個聯合國教科文組織的5年項目，這個項目是關于人類定居可持續性方面的，此項目的調研結果已經作為《生命維持系統（維生系統）百科全書》（Encyclopedia of Life Support Systems, Oxford,UK: EOLSS Publishers）的一卷由“英國牛津：維持生命系統百科全書出版社”出版。她的作品被翻譯成21種語言，她的一些觀點和評論也在《衛報》、《紐約時報》、《民主開放網》、《外交界》、《國際先驅論壇報》、《國際新聞周刊》、《金融時報》等媒體上有過闡述。《全球城市》（The Global City）這本書的中文譯本也已被上海社科院社會科學出版社出版。她的《世界經濟下的城市》（Cities in a World Economy）也將于2010年由譯林出版社出版發行。

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