城市時(shí)代下的風(fēng)景園林規(guī)劃與設(shè)計(jì)

撰文：（美國(guó)）杰克·艾亨

翻譯：黃伊偉

城市時(shí)代下的風(fēng)景園林規(guī)劃與設(shè)計(jì)

撰文：（美國(guó)）杰克·艾亨

翻譯：黃伊偉

城市化進(jìn)程將會(huì)在世界各個(gè)領(lǐng)域以不同的速度發(fā)生，而且主要將發(fā)生在發(fā)展中國(guó)家。作者基于“城市的成功或失敗將決定千年發(fā)展目標(biāo)的實(shí)現(xiàn)”，在文章中討論了以下4個(gè)方面：城市動(dòng)態(tài)的類型學(xué)；將蔓生的城市作為城市實(shí)驗(yàn)室（以上海為例）；城市生態(tài)系統(tǒng)服務(wù)的重要性和衡量標(biāo)準(zhǔn)；以及在綠道和綠色基礎(chǔ)設(shè)施中實(shí)現(xiàn)監(jiān)控生態(tài)系統(tǒng)服務(wù)的方法。文章強(qiáng)調(diào)了當(dāng)代城市發(fā)展中，風(fēng)景園林設(shè)計(jì)師和城市規(guī)劃師所面臨的機(jī)遇和挑戰(zhàn)。

城市化；生態(tài)系統(tǒng)服務(wù)；城市可持續(xù)性；綠色基礎(chǔ)設(shè)施

本文是作者在舉辦于馬薩諸塞大學(xué)阿莫斯特分校的2013年法布士風(fēng)景園林與綠道規(guī)劃國(guó)際會(huì)議上發(fā)表的演講的要點(diǎn)概述。

1 全球城市化進(jìn)程的趨勢(shì)及挑戰(zhàn)

在20世紀(jì)初，大約10%的世界人口居住在城市中。而21世紀(jì)之所以被人們稱為城市的時(shí)代，是因?yàn)樵?007年，城市人口在歷史上第一次達(dá)到了世界人口的50%。在接下來(lái)的數(shù)十年中，世界總?cè)丝趯?0億增加到100億，其中大部分增長(zhǎng)都將在城市中發(fā)生[1]。重要的是，城市人口增長(zhǎng)的趨勢(shì)將在本世紀(jì)持續(xù)，并預(yù)計(jì)在2050年達(dá)到63億，在2100年則達(dá)85億[2]。城市化進(jìn)程會(huì)在世界各個(gè)領(lǐng)域以不同的速度發(fā)生，但主要將發(fā)生在發(fā)展中國(guó)家。城市人口增長(zhǎng)這一現(xiàn)象將主要發(fā)生在當(dāng)代大學(xué)生以及規(guī)劃與設(shè)計(jì)專業(yè)的應(yīng)屆畢業(yè)生的職業(yè)生涯中。如果這個(gè)擁有超級(jí)城市的新世界想要實(shí)現(xiàn)可持續(xù)發(fā)展，那么它的城市就必須實(shí)現(xiàn)可持續(xù)——這是一個(gè)巨大的挑戰(zhàn)，尤其是對(duì)城市與風(fēng)景園林規(guī)劃和設(shè)計(jì)領(lǐng)域的挑戰(zhàn)。

到2100年，亞洲地區(qū)將發(fā)生城鎮(zhèn)人口的最大增幅，從2010年的18億，到2050年的33億，最后增加到38億（聯(lián)合國(guó)人類發(fā)展報(bào)告，2012）。通過大眾媒體的傳播，中國(guó)被廣泛誤解為一個(gè)超級(jí)城市國(guó)家。事實(shí)上，在2011年，中國(guó)的城市人口比例（50.6%）遠(yuǎn)低于美國(guó)（82%）和荷蘭（83%）[3]。然而，中國(guó)目前正在經(jīng)歷一個(gè)巨大的、前所未有的城市遷移過程。在未來(lái)的25年里，中國(guó)將會(huì)建造更多人口超百萬(wàn)的城市，甚至超過美國(guó)目前百萬(wàn)人口城市數(shù)目的總和。在中國(guó)，這種農(nóng)村向城市的人口遷移正在有條不紊地進(jìn)行，僅僅在接下來(lái)的12年中，就有2.5億人口涌入中國(guó)現(xiàn)有的或者新建的城市[4]。從這一點(diǎn)來(lái)說(shuō)，中國(guó)將可以成為一個(gè)實(shí)驗(yàn)室，讓世界其他國(guó)家學(xué)習(xí)如何以可持續(xù)發(fā)展的方式來(lái)規(guī)劃和設(shè)計(jì)城市，適應(yīng)新的城市人口。

此前， 聯(lián)合國(guó)千年系統(tǒng)評(píng)估提出了一個(gè)激進(jìn)的論點(diǎn)，那就是：“‘城市的成功或者失敗’將決定千年發(fā)展目標(biāo)的實(shí)現(xiàn)”[5]。這一主張是基于城市化和社會(huì)經(jīng)濟(jì)發(fā)展之間的聯(lián)系，包括城市發(fā)展對(duì)于城市周邊農(nóng)村環(huán)境的影響、提供為農(nóng)村發(fā)展和支持農(nóng)村經(jīng)濟(jì)的源動(dòng)力。這個(gè)大膽的論點(diǎn)，在全球范圍內(nèi)掀起了對(duì)于城市規(guī)劃者和設(shè)計(jì)者的基本挑戰(zhàn)，即“如何以可持續(xù)的方式，擴(kuò)張現(xiàn)有城市規(guī)

模、建設(shè)新城市，以滿足新城市人口的巨大需求，并同時(shí)管理景觀和生態(tài)，讓城市和居民賴以生存的生態(tài)系統(tǒng)正常服務(wù)？”

2 城市動(dòng)態(tài)的類型學(xué)

城市化的動(dòng)態(tài)可以理解為基于人口增長(zhǎng)和建成城市環(huán)境的密度水平的類型學(xué)（圖02）。蔓生的城市會(huì)在人造環(huán)境密度高，人口增長(zhǎng)迅速的情況下出現(xiàn)。隨著城市的持續(xù)發(fā)展，它們會(huì)從城市中心開始，通常沿著交通干線，向外擴(kuò)張。在蔓生的城市，由于城市空間的激烈經(jīng)濟(jì)競(jìng)爭(zhēng)，城市開放空間變得格外稀缺。規(guī)劃的有效性也往往由于緊急的新發(fā)展以及現(xiàn)有的難以更改的密度而受到限制。然而，實(shí)踐和實(shí)驗(yàn)創(chuàng)新的城市發(fā)展和綠色基礎(chǔ)設(shè)施的動(dòng)力和機(jī)會(huì)是巨大顯著的。人們對(duì)于城市擴(kuò)張的普遍反應(yīng)是遏制，或者精明增長(zhǎng)——讓城市在一個(gè)可以提供生態(tài)系統(tǒng)功能的、相互鏈接的網(wǎng)絡(luò)開放空間結(jié)構(gòu)下，從容發(fā)展。

穩(wěn)定的城市擁有中度到高度的建成環(huán)境，并且有一個(gè)穩(wěn)定的人口。這些城市往往已經(jīng)建立了城市開放空間系統(tǒng)。而這些建成的城市開放空間，在城市空間競(jìng)爭(zhēng)激烈的背景下，與新的或者重新開發(fā)的綠地相鏈接的概率，比正在增長(zhǎng)的城市要低。在穩(wěn)定的城市中，城市規(guī)劃會(huì)是目的性與機(jī)會(huì)性并存，而對(duì)于常規(guī)二次開發(fā)的建筑和基礎(chǔ)設(shè)施的需求，為推行綠色建筑和綠色基礎(chǔ)設(shè)施提供了機(jī)會(huì)。因?yàn)槌鞘忻扛魩资甓家潞椭亟?，這樣的重建提供了可持續(xù)改造的機(jī)會(huì)。比如說(shuō)主要的道路一般在每20年需要重鋪/重建。而在這一過程中，重建的道路可改造成一條綠色街道，適當(dāng)?shù)靥砑涌蓾B透性、高反照率的鋪裝，配上自行車道、綠化帶以及野生動(dòng)物地下通道。

新的/計(jì)劃的城市發(fā)生在人口增長(zhǎng)速度快，但建成環(huán)境密度低的國(guó)家或區(qū)域范圍內(nèi)。新的城市通常建立在農(nóng)業(yè)區(qū)域，需要重新安置時(shí)，將現(xiàn)有的建設(shè)少、環(huán)境相對(duì)干凈的區(qū)域設(shè)為“綠地”，而將之前經(jīng)濟(jì)活動(dòng)留下來(lái)的污染土地但擁有較少人口的地方設(shè)為“棕地”。新的/計(jì)劃的城市為大膽的、富有遠(yuǎn)見的規(guī)劃和設(shè)計(jì)提供了最大機(jī)會(huì)——在落實(shí)高效的土地利用和交通的同時(shí)，包含了人為設(shè)計(jì)的、可提供生態(tài)系統(tǒng)服務(wù)的城市開放/綠地空間系統(tǒng)?！吧鷳B(tài)城市”運(yùn)動(dòng)展現(xiàn)了探索創(chuàng)新模式和城市化概念的新型城鎮(zhèn)化的潛力。

萎縮的城市有以下特征：人口不斷下降，最終形成密度越來(lái)越低的建成環(huán)境。城市萎縮發(fā)生在宏觀經(jīng)濟(jì)變化和缺乏就業(yè)和公共收入的背景下。在萎縮的城市中蘊(yùn)含著獨(dú)特的更新和重建機(jī)會(huì)，通過謹(jǐn)慎“編輯”未被利用/未被充分利用城市發(fā)展——引入可持續(xù)的填充式發(fā)展，結(jié)合城市交通和開放空間資源。萎縮的城市具有重塑自己的身份、經(jīng)濟(jì)以及物理形態(tài)——包括其城市/綠地結(jié)構(gòu)——的潛力，這同時(shí)也是一種挑戰(zhàn)。

城市動(dòng)態(tài)的類型學(xué)提供了一個(gè)結(jié)構(gòu)化的系統(tǒng)，根據(jù)城市地區(qū)的人口增長(zhǎng)和城市形態(tài)密度進(jìn)行分類。類型學(xué)暗示了內(nèi)在的一種特定類型的城市動(dòng)態(tài)的特定的機(jī)會(huì)和挑戰(zhàn)。在這個(gè)“城市的時(shí)代”，最具挑戰(zhàn)性和最重要的類型也許是蔓生的城市。

3 蔓生的城市作為城市實(shí)驗(yàn)室

上海是一個(gè)典型的蔓生的城市。它有著悠久的城市歷史，目前正處于開發(fā)熱潮之中。這個(gè)包含上海和長(zhǎng)三角在內(nèi)的特大型區(qū)域?yàn)檠芯刻峁┝穗y得的機(jī)會(huì)。上海市城市化生態(tài)過程與生態(tài)恢復(fù)重點(diǎn)實(shí)驗(yàn)室（以下簡(jiǎn)稱為SHUES）已經(jīng)由華東師范大學(xué)建立，以期解決共生的挑戰(zhàn)和機(jī)遇問題。

SHUES是由包括中國(guó)國(guó)家自然科學(xué)基金委員會(huì)在內(nèi)的多源資助的一個(gè)跨學(xué)科研究小組。它在以下3個(gè)方面開展研究：1）復(fù)雜的城市和農(nóng)村生態(tài)系統(tǒng)；2）規(guī)劃管理和設(shè)計(jì)城市與區(qū)域生態(tài)系統(tǒng)；3）生態(tài)工程設(shè)計(jì)。SHUES運(yùn)用其研究來(lái)解決城市環(huán)境和生態(tài)問題。在象偉寧教授的領(lǐng)導(dǎo)下，SHUES已成為一個(gè)使用城市區(qū)域作為實(shí)驗(yàn)室的典范，他們監(jiān)測(cè)和管理數(shù)據(jù)庫(kù)，隨時(shí)間的推移記錄城市狀況。在許多方面上，SHUES都類似于美國(guó)亞利桑那州鳳凰城和馬里蘭州巴爾的摩的城市長(zhǎng)期研究中心。但是，因?yàn)樯虾Ｊ鞘澜缟献畲蟮某鞘兄?，并有望在未?lái)繼續(xù)擴(kuò)張，因此SHUES可以使用“從實(shí)踐中學(xué)習(xí)”的方法來(lái)理解復(fù)雜的城市生態(tài)環(huán)境問題，并設(shè)計(jì)和監(jiān)測(cè)創(chuàng)新和實(shí)驗(yàn)性的解決方案①。

4 衡量城市生態(tài)系統(tǒng)服務(wù)

生態(tài)系統(tǒng)服務(wù)的概念在千年生態(tài)系統(tǒng)評(píng)估報(bào)告中被廣泛推廣。它有4類服務(wù)類型：支持、供應(yīng)、監(jiān)管和文化。這些都是為人類利益而提供的自然生態(tài)系統(tǒng)的服務(wù)和功能。為便于闡述，可以將它們分為3大類：非生物類，生物類以及文化類[6]。非生物類型是無(wú)生

命體的服務(wù)，它們來(lái)自于物理環(huán)境，例如水文學(xué)，這也許是在城市生態(tài)規(guī)劃與設(shè)計(jì)中最重要的一環(huán)。

生物生態(tài)系統(tǒng)則是與生活和生命系統(tǒng)相關(guān)。生態(tài)系統(tǒng)為野生動(dòng)物物種提供棲息地和行動(dòng)走廊。空氣污染減排及污染防治可以通過城市森林實(shí)現(xiàn)。偉大的哲學(xué)家和科學(xué)家，比如利奧波德（Aldo Leopold）提醒我們，保護(hù)生物多樣性是明智的，因?yàn)槲覀儫o(wú)法知道在未來(lái)，哪一些物種將會(huì)被證明有多么重要。馬薩諸塞大學(xué)教授德里克·洛夫利發(fā)現(xiàn)了生活在華盛頓特區(qū)波托馬克河的沉積物中的地桿菌。這種細(xì)菌能代謝和穩(wěn)定有毒廢物。這就是一個(gè)表面看似毫無(wú)價(jià)值，但最終被證明價(jià)值非凡的生物體的例子。如果我們想要實(shí)現(xiàn)城市的可持續(xù)發(fā)展，我們就要使它們成為生物多樣性的中心——而不是生物多樣性的沙漠！

文化和社會(huì)生態(tài)系統(tǒng)服務(wù)在城市可持續(xù)發(fā)展中同樣重要。公園是重要的，當(dāng)然有對(duì)人類娛樂的方面，但它也支持著人類健康，為健康的社會(huì)交往提供場(chǎng)所。我們正在創(chuàng)造21世紀(jì)城市的新的性質(zhì)，以提供一整套的生態(tài)系統(tǒng)服務(wù)：非生物類，生物類以及文化類。上述以及其他概念共同定義和肯定著一項(xiàng)，那就是，生態(tài)系統(tǒng)服務(wù)對(duì)人類健康和福祉的各個(gè)方面都至關(guān)重要。生態(tài)系統(tǒng)功能是人類賴以生存在一個(gè)可持續(xù)發(fā)展的世界的保障。可持續(xù)性的挑戰(zhàn)在21世紀(jì)的城市中成功與否，就取決于城市所提供的生態(tài)系統(tǒng)服務(wù)。因此，我們可以認(rèn)為，生態(tài)系統(tǒng)服務(wù)是城市可持續(xù)發(fā)展的指標(biāo)。

生態(tài)系統(tǒng)服務(wù)可以作為聯(lián)系城市形態(tài)（模式）和城市過程（生態(tài)系統(tǒng)服務(wù)）的考核指標(biāo)。一旦對(duì)其進(jìn)行了了解、測(cè)量和映射，生態(tài)系統(tǒng)服務(wù)便可成為城市可持續(xù)發(fā)展規(guī)劃的目標(biāo)和基準(zhǔn)。在規(guī)劃和設(shè)計(jì)可持續(xù)發(fā)展的城市中，風(fēng)景園林師已經(jīng)從生態(tài)學(xué)家那里學(xué)習(xí)到保護(hù)及恢復(fù)城市綠地和生境的大、小斑塊之間連通性的重要性。綠道具有提供廣闊的城市區(qū)域生態(tài)系統(tǒng)服務(wù)套件的潛能。綠色基礎(chǔ)設(shè)施是另一種為城市提供生態(tài)系統(tǒng)服務(wù)的現(xiàn)代的理念[6]。生態(tài)設(shè)計(jì)的概念，包括綠道和綠色基礎(chǔ)設(shè)施，得到人們的日益理解和重視。隨著全球城市化進(jìn)程推進(jìn)，設(shè)計(jì)師在測(cè)量和記錄其所設(shè)計(jì)的項(xiàng)目所能提供的生態(tài)系統(tǒng)服務(wù)時(shí)，將面臨更大的挑戰(zhàn)。

5 綠道和綠色基礎(chǔ)設(shè)施中的生態(tài)系統(tǒng)功能監(jiān)測(cè)

生態(tài)系統(tǒng)功能的概念被越來(lái)越多地理解為城市可持續(xù)性的重要目標(biāo)和指標(biāo)。設(shè)計(jì)領(lǐng)域的下一個(gè)挑戰(zhàn)將會(huì)是提倡以提供特定生態(tài)系統(tǒng)功能為目標(biāo)的項(xiàng)目，并對(duì)其實(shí)施監(jiān)測(cè)。在設(shè)計(jì)領(lǐng)域中，并沒有支持監(jiān)測(cè)系統(tǒng)的傳統(tǒng)。如果監(jiān)測(cè)可以在小尺度的、安全失敗的設(shè)計(jì)實(shí)驗(yàn)中實(shí)施，那么失敗的風(fēng)險(xiǎn)將能被降到最低，而創(chuàng)造成功的潛力將達(dá)到最大化[7]。

城市森林的其中一項(xiàng)預(yù)期效益是增加生物多樣性。測(cè)量鳥類的多樣性可以用“點(diǎn)測(cè)法”實(shí)現(xiàn)（圖06），通過一個(gè)或多個(gè)專業(yè)培訓(xùn)的/專家觀測(cè)者進(jìn)入一個(gè)城市森林，并記錄下在特定時(shí)間段所觀察到的或聽到的鳥類數(shù)量和種類，然后對(duì)不同觀測(cè)者的結(jié)果，包括觀測(cè)時(shí)間、觀測(cè)的地點(diǎn)進(jìn)行比較和計(jì)算。這一方法在生物領(lǐng)域被廣泛認(rèn)知，卻很少在設(shè)計(jì)領(lǐng)域中運(yùn)用。這些數(shù)據(jù)將用于記錄特定城市森林的種植和組態(tài)所產(chǎn)生的生物多樣性效益。如果風(fēng)景園林師可以增加生物多樣性的監(jiān)測(cè)，他們就可以與“設(shè)計(jì)實(shí)驗(yàn)”科學(xué)家們合作，學(xué)習(xí)如何提供城市所需的生態(tài)系統(tǒng)服務(wù)。

屋頂綠化能提供多元的生態(tài)系統(tǒng)服務(wù)：能源節(jié)約、雨水蓄洪、改善水質(zhì)、延長(zhǎng)建筑物屋頂?shù)母鼡Q，并對(duì)生物多樣性——尤其是益蟲的支持。在高度城市化的環(huán)境下，綠色空間和棲息地有限，屋頂綠化可以成為傳粉昆蟲寶貴的棲息地。為城市蔬菜、樹木和花卉授粉的蜜蜂可以在綠色屋頂中找到棲息地。而蜂種的存在性和多樣性可以通過多種陷阱裝置來(lái)測(cè)量?！跋葳邋仭笔怯命S色的平底鍋，裝滿肥皂水，吸引和捕捉蜜蜂的裝置。通過定期收集和調(diào)度監(jiān)測(cè)陷阱裝置，我們可以了解蜜蜂的種類有多少，哪些是存在于綠色屋頂——為周圍社區(qū)提供授粉服務(wù)。“馬萊茲陷阱”是更大一些的帳篷狀裝置，可以捕捉更廣泛多樣的飛蟲。和“陷阱鍋”一樣，“馬萊茲陷阱”可以進(jìn)行定期采樣和記錄，從而了解哪些昆蟲存在于綠色屋頂（圖07）。

人造濕地通常被廣泛用于提供生態(tài)系統(tǒng)功能。浮動(dòng)濕地一種獨(dú)特的綠色基礎(chǔ)設(shè)施，它可以在城市水域建設(shè)人工浮動(dòng)棲息地，以提供棲息地并改善水質(zhì)。由于浮動(dòng)濕地可以在大型水面移動(dòng)，因此很難用常規(guī)方法對(duì)其進(jìn)行監(jiān)測(cè)。圖08描述了傳統(tǒng)的監(jiān)測(cè)方法，它采用GPS相聯(lián)的傳感器將濕地位置、水溫以及水質(zhì)等參數(shù)數(shù)據(jù)報(bào)告到衛(wèi)星上。因?yàn)檫@個(gè)系統(tǒng)與遙感相連，它可以在已知坐標(biāo)的不同位置，連續(xù)地報(bào)告水質(zhì)的數(shù)據(jù)。

雨水花園是較常見的一種綠色基礎(chǔ)設(shè)施，它可以提供與水有關(guān)的生態(tài)系統(tǒng)服務(wù)，包括雨水滯留、滲透以及水質(zhì)改善。不幸的是我們很少對(duì)雨水花園進(jìn)行監(jiān)測(cè)。但是，如果在建造雨水花園前就決定對(duì)其進(jìn)行監(jiān)測(cè)，那么安裝一個(gè)簡(jiǎn)易的監(jiān)測(cè)井就十分容易，所需成本也十分低廉。監(jiān)測(cè)井可以用來(lái)收集于雨水花園下不同深度穿過的水樣品，并通過實(shí)驗(yàn)室對(duì)樣品進(jìn)行分析，以測(cè)量選定樣本的水質(zhì)參數(shù)（即硝酸鹽，磷）的效果（圖09）。如果在建設(shè)雨水花園時(shí)沒有安裝監(jiān)測(cè)井，那么后期再進(jìn)行安裝的將會(huì)變得非常具有破壞性，而且成本昂貴。

這些示例演示了綠道和綠色基礎(chǔ)設(shè)施的未來(lái)生態(tài)系統(tǒng)服務(wù)，并如何對(duì)其進(jìn)行準(zhǔn)確的監(jiān)測(cè)。如果以標(biāo)準(zhǔn)認(rèn)可的方法進(jìn)行數(shù)據(jù)收集，就可以科學(xué)地對(duì)數(shù)據(jù)進(jìn)行分析，并了解不同的綠道或綠色基礎(chǔ)設(shè)施的配置或整改對(duì)生態(tài)系統(tǒng)服務(wù)的不同影響。當(dāng)監(jiān)測(cè)成為一種慣例，每個(gè)城市建設(shè)都可以看成一個(gè)實(shí)驗(yàn)，在一個(gè)自適應(yīng)的設(shè)計(jì)過程中，計(jì)劃和設(shè)計(jì)都可被視為一種機(jī)會(huì)去探索和開發(fā)新研究，并對(duì)這些想法進(jìn)行測(cè)試。這是一種不同于采用標(biāo)準(zhǔn)解決方案的專業(yè)規(guī)劃和設(shè)計(jì)實(shí)踐的新的方式。

6 總結(jié)

在這個(gè)城市的世紀(jì)，可持續(xù)發(fā)展將在現(xiàn)有和未來(lái)的城市中成功或失敗。城市可持續(xù)發(fā)展可以被理解為，甚至計(jì)量為，城市中特定的支持人口增長(zhǎng)的生態(tài)系統(tǒng)功能，和人類賴以生存的生物多樣性。設(shè)計(jì)專業(yè)領(lǐng)域可以通過在城市規(guī)劃和設(shè)計(jì)整合生態(tài)系統(tǒng)服務(wù)，納入基礎(chǔ)設(shè)施、環(huán)境和綠色系統(tǒng)來(lái)促進(jìn)城市可持續(xù)發(fā)展。由于這是一個(gè)全新的、具體的挑戰(zhàn)，且在每個(gè)城市都不盡相同，設(shè)計(jì)師們必須找到和測(cè)試新的想法，以“從實(shí)踐中學(xué)習(xí)”的方式，測(cè)試這些想法在特定條件和位置下是如何隨時(shí)間推移而作用的。如果規(guī)劃者和設(shè)計(jì)者可以有效地實(shí)踐適應(yīng)性設(shè)計(jì)，他們會(huì)意識(shí)到從城市化的過程中學(xué)習(xí)與獲益的可能性。這樣的話，城市化進(jìn)程將能夠從一個(gè)已察覺的人類問題開始轉(zhuǎn)變——轉(zhuǎn)變成新思路和新實(shí)踐的源頭，而這個(gè)源頭將可能會(huì)對(duì)城市可持續(xù)發(fā)展的解決方案產(chǎn)生重大意義。

This article is a summary of the keynote presentation given by the author at the 2013 Fábos Landscape Planning and Greenway Conference, University of Massachusetts Amherst

1 Trends and Challenges of Global Urbanization

At the start of the 20thCentury approximately 10 percent of the world's population lived in cities. The 21stCentury has already been called the century of the city because, in 2007 for the first time in history, the world's population became more than 50% urban. In the coming decades the world’s total population is expected to rise from 7 billion to 10 billion, with much of that increase occurring in the world's cities[1]. Importantly, this trend towards an urban population is expected to continue throughout the century, reaching 6.3 billion urban inhabitants by 2050 and 8.5 billion by 2100[2]. This urbanization is expected to occur at different rates around the world but will mostly occur in the developing countries. Much of this increase in urban population will occur during the professional careers of the current generation of university students and recent graduates in planning and design. If this new hyper-urban world is to be sustainable, its cities must be sustainable -

and that represents a profound challenge, especially for urban and landscape planning and design professions.

By the year 2100, the Asian region will see the world's largest increase in urban population from 1.8 billion in 2010 to 3.3 billion in 2050 to 3.8 billion (UN ESA 2012). Through the popular media, China is widely misunderstood as a hyperurban country. In 2011 China's population was far less urban (50.6%) than the United States (82%), or The Netherlands 83%[3]. However, China is in the process of a massive, unprecedented urban migration. In the next 25 years, China will build more cities with more than one million people than total of current cities with over one million population in United States. In China, this ruralto-urban migration is well underway, with 250 million additional Chinese planned to move into new and existing cities in the next 12 years alone![4]In this respect China has the potential to become a laboratory from which the rest of the world can learn how to plan and design cities to accommodate this new urban population in a sustainable manner.

The United Nation's Millennium Assessment raised the radical proposition that "the struggle to achieve the Millennium Development Goals will be `won or lost in cities'"[5]. This proposition is based on the link between urbanization and socioeconomic development including the effect of urban development on the rural environments around cities, providing engines for rural development and supporting the rural economy. This bold proposition, in a global context, raises a basic challenge for urban planners and designers "How can existing cities be expanded, and new cities created - in a sustainable manner, to meet the crushing demands of the new urban population while managing landscapes and ecosystems to provide the ecosystem services that the cities, and their residents depend on?

2 A Typology of Urban Dynamics

The dynamics of urbanization can be understood with a typology based on the level of population growth and the density of the built urban environment (Fig.02). Sprawling Cities occur where high rates of population growth occur in the context of a high-density built environment. Because these cities continue to grow they expand from the center, typically along transportation routes. In sprawling cities, urban open space becomes scarce due to the intense economic competition for urban space. The effectiveness of planning is often limited by the exigency for new development, and the existing density that limits change through planning. However, the motivation and opportunity to implement and test innovative urban development and green infrastructure is substantial. The common response to sprawl is containment, or smart growth - allowing the city grow in a more deliberate way crafting a connected, networked open space structure to provide ecosystem services.

Stable cities have a moderate to high density of built environment, but a stable population. These cities often have established urban open space systems, and the opportunity to include new green space in conjunction with new or redevelopment because the competition for urban space is moderate to low in comparison with sprawling cities. In stable cities urban planning can be intentional and opportunistic, and the need for routine re-development of buildings and infrastructure provides opportunity to implement green building and infrastructure. Because cities need to be rebuilt every few decades, that rebuilding creates the opportunity for sustainability retrofits. Take the example of major roads that generally need repaving/rebuilding every 20 years. During rebuilding a road can become a green street with permeable, high-albedo paving materials, bicycle lanes, tree planting belts, and wildlife underpasses added where appropriate.

New/Planned cities occur in national or regional contexts where population growth is high, but the existing density of the built environment is low. New cities are often located in agricultural regions, requiring resettlement, in "greenfields" where existing development is minimal and the environment is relatively clean, and "brownfields" where prior economic activity left a contaminated environment, but existing population is low. New/ Planned cities provide the greatest opportunity for bold, visionary planning and design - employing the best practices for efficient land use and transportation while including an intentional urban open/green space system to deliver ecosystem services. The "eco-city" movement demonstrates the potential for new urbanization to explore innovative models and urbanization concepts.

Shrinking cities are defined by a declining population and eventually produce a low, or lower density of built environment. Shrinking cities occur because of macroeconomic changes and suffer from lack of employment and public revenues. Shrinking cities provide unique opportunities to renew and rebuild through deliberate "editing" of un/underused urban development - by introducing sustainable infill developments, integrated with urban transportation and open space resources. Shrinking cities hold the potential and the challenge to reinvent their identity and economy, and physical form - including their urban/green space structure.

The typology of urban dynamics offers a structured system to classify urban regions based on their population growth and density of urban form. The typology suggests the particular opportunities and challenges that are inherent in a particular type of urban dynamic. In this "Century of the City" perhaps the most challenging and important type are the sprawling cities.

3 Sprawling Cities as Urban Laboratories

Shanghai is a quintessential sprawling city.

It has a long urban history and is currently in the midst of a development boom. This mega-regional context of Shanghai and the Yangtze River Delta provides a unique opportunity for research. The Shanghai Key Lab for Urban Ecological Processes and Eco-restoration (SHUES) at East China Normal University has been organized to address the simultaneous challenge and opportunity.

SHUES is an interdisciplinary research group funded by the Natural Science Foundation of China, among other sources. SHUES conducts research in three areas: 1) complex urban and rural ecosystems, 2) planning managing and design of the urban and regional ecosystem and 3) ecological engineering. SHUES applies its research to solve urban environmental and ecological problems. Under the Direction of Xiang, Wei-ning, SHUES has become a model for using an urban region as a laboratory where monitoring and data base management can document urban conditions over time. In many respects SHUES is similar to the Urban Long Term Research Centers in Phoenix Arizona and Baltimore Maryland in the US. However, because Shanghai is one of the world’s largest cities, and is expected to expand into the future, SHUES has a unique opportunity to "learn-by-doing" in understanding complex urban ecological issues, and designing and monitoring innovative and experimental solutions①.

4 Measuring Urban Ecosystem Services

The concept of ecosystem services was popularized in the Millennium Ecosystem Assessment. There are four categories of services, supporting, provisioning, regulatory and cultural. These are the services and functions provided by natural ecosystems to the benefit of humans. I've organized them into three broad categories for the sake of illustration: Abiotic, Biotic and Cultural[6]. The abiotic are the non-living services that come from the physical environment, for example hydrology, which is perhaps the most important process in the urban ecology planning and design.

The biotic ecosystem services are related to life and living systems. Ecosystems provide habitat and movement corridors for wildlife species. Air pollution mitigation and remediation can be provided by urban forests. Great philosophers and scientists like Aldo Leopold remind us that it is wise to protect biodiversity, because we don't know how important any species may prove to be in the future. A professor at the University of Massachusetts, Derek Lovley, discovered the geobacter bacteria living in the sediment of the Potomac River in Washington. This bacteria can metabolize and stabilize toxic waste. Here is an example of an organism with no apparent value that has proven to be highly valuable. If our cities are to be sustainable, we need them to be centers of biodiversity - not biodiversity deserts!

Cultural and social ecosystem services are equally important for urban sustainability. Parks are important, of course for human recreation, but also to support human health and to provide places for healthy social interaction. We are creating a new nature in 21stCentury cities and we need this new nature to provide a broad suite of ecosystem services, abiotic, biotic and cultural. These, and other concepts both define the term and affirm that ecosystem services are essential for all aspects of human health and well-being. Ecosystem services are what humans depend on for survival in a sustainable world. If the challenge for sustainability will be won or lost in 21stCentury cities, it will depend on the ecosystem services that cities provide. Ecosystem services can therefore be understood as the metrics of urban sustainability.

Ecosystem services can serve as assessment metrics to link urban form (pattern) with urban process (ecosystem services). Once understood, measured, and mapped, ecosystem services can become the goals and benchmarks of planning for urban sustainability. In planning and designing sustainable cities, landscape architects have learned from ecologists of the importance of protecting and restoring connectivity between large, and small patches of urban green spaces and habitats. Greenways are understood for their potential to provide a broad suite of ecosystem services in urban areas. Green infrastructure is another contemporary concept for providing urban ecosystem services[6]. Ecological design concepts including greenways and green infrastructure are increasingly understood and valued. As urbanization advances globally, designers will be increasingly challenged to measure and document the ecosystem services that their plans actually provide.

5 Monitoring Ecosystem Services in Greenways and Green Infrastructure

The concept of ecosystem services is increasingly understood as a useful goal and metric for urban sustainability. The next challenge for design professionals is to advocate for and practice monitoring of projects that aim to provide particular ecosystem services. Design professions do not have a tradition of supporting monitoring. If monitoring can be conducted on small-scale, safeto-fail design experiments, the risk of failure can be minimized and the potential to earn success can be maximized[7].

I have developed methods for monitoring specific ecosystem services associated with greenways and green infrastructure with landscape architecture students at the University of Massachusetts Amherst. We developed a “toolbox”of methods that landscape architects and planners can readily build into projects that intend to provide ecosystem services.

One of the expected benefits of urban forests is to increase biodiversity. Measuring of bird diversity can be conducted with the “point count” method where one or more trained/expert observers visit an urban forest or neighborhood and record the number and type(s) of birds seen and heard in a specific observation time(Fig. 06). The results between multiple observers, observation dates, and locations can be compared and averaged. This method is well-known in biology but is rarely practiced by design professionals. These data serve to document the biodiversity benefits of particular types of urban forest plantings and configurations. If landscape architects can learn to promote biodiversity monitoring they can become partners with scientists in "design experiments" to learn how to provide ecosystem services in cities.

Green roofs are advocated for the multiple ecosystem services they provide: energy savings, stormwater retention, water quality improvement, extending building roof replacement, and supporting biodiversity - particularly of beneficial insects. In highly urbanized environments where green space and habitat is limited, green roofs may become valuable habitats for pollinating insects. The bees that pollinate urban vegetables, trees and flowers can find habitat on green roofs. The presence and diversity of bee species can be measured by several types of traps. The "pantrap" deploys yellow pans filled with soapy water that attracts and captures the bees. The traps can be collected and monitored on a regular schedule to learn how many individuals and which species of bees are present on the green roof - and providing pollination services to the surrounding neighborhood. Malaise traps are larger tent-like structures that can capture a wide diversity of flying insects. As with pan traps, malaise traps can be sampled and recorded on a regular basis to learn which insects are present on the green roof(Fig. 07).

Created wetlands are commonly used to provide ecosystem services. Floating wetlands are a unique type of green infrastructure that constructs

artificial floating habitats on urban waters to provide habitat and water quality improvements. Because floating wetlands can move across large water surfaces, they are difficult to monitor by conventional methods. Figure 8 illustrates a monitoring method that employs GPS-linked sensors to report data to satellites on the floating wetland location, water temperature and water quality parameters. Because this system works with remote sensing it can report data continuously on water quality at different locations with known coordinates(Fig. 08).

Rain gardens are one of the more common types of green infrastructure to provide waterrelated ecosystem services including stormwater retention, infiltration and water quality improvement. Unfortunately monitoring is rarely conducted in rain gardens. However, if a commitment to monitoring is made before the rain garden is constructed, simple monitoring wells can be easily installed at low cost. The wells can be used to gather water samples at multiple depths beneath the rain garden to measure the effect of the substrate on selected water quality parameters (i.e. Nitrate, Phosphorous) through laboratory analysis of the samples(Fig. 09). If these wells are not installed during installation they become very disruptive and expensive to install.

These examples demonstrate how the ecosystem services intended and expected from greenways and green infrastructure can be accurately monitored. If the data are collected with standard accepted methods, it can be scientifically analyzed to learn the differential effects of alternative greenway or green infrastructure configurations or treatments on ecosystem services. When monitoring becomes a regular practice, every urban construction can be understood as an experiment, in an adaptive design process where plans and designs are conceived as opportunities to explore and develop new research, and to test ideas. It’s a different way of thinking about professional planning and design practice than conventional work that tends to apply standard solutions.

6 Summary

In this century of the city, sustainability will be won-or-lost in existing and future cities. Urban sustainability can be understood, and measured, as the specific ecosystem services provided in cities to support human populations and the biodiversity on which humans depend. Design professionals can contribute to urban sustainability by integrating ecosystem services into plans and designs for infrastructure, settlements and green systems in cities. Because this is a new challenge, and is specific and different in every city, designers must develop and test new ideas and "learn-by-doing" how these ideas perform over time under specific conditions and locations. If planners and designers can effectively practice adaptive design, they may realize the possibility to learn from, and benefit by the process of urbanization. In this way urbanization can change from a perceived human problem - to the source of new ideas and practices that can be important to the solution for urban sustainability.

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注釋：

①資料參考自上海市城市化生態(tài)過程與生態(tài)恢復(fù)重點(diǎn)實(shí)驗(yàn)室網(wǎng)站：http://www.shues.org/

杰克·艾亨/博士/美國(guó)風(fēng)景園林師協(xié)會(huì)常任理事/美國(guó)馬薩諸塞大學(xué)阿莫斯特分校風(fēng)景園林專業(yè)教授/國(guó)際項(xiàng)目副教育長(zhǎng)

譯者簡(jiǎn)介：

黃伊偉/美國(guó)馬薩諸塞大學(xué)阿莫斯特分校風(fēng)景園林專業(yè)研究生、助教

Biography

Jack AHERN, FASLA, Ph.D, is a Professor of Landscape Architecture in the University of Massachusetts Amherst, USA. He is also the Vice Provost for International Programs.

About the translator:

HUANG Yi-wei is a graduate student and teaching assistance of Landscape Architecture in the University of Massachusetts Amherst, USA.

Landscape Planning and Design in the Century of the City

Text by: Jack AHERN (US)
Translation by: HUANG Yi-wei

Urbanization is expected to occur at different rates around the world but will mostly occur in developing countries. Based on the challenges that “the struggle to achieve the millennium development goals will be won or lost in cities”, the author discusses four aspects in this paper: urban dynamics typology, using sprawling cities as urban laboratories(taking Shanghai as an example), the significance and measurement of urban ecosystem services, and methods to monitor ecosystem services in greenways and green infrastructures. The paper emphasizes the opportunities and challenges of contemporary urban development that landscape architects and urban planners confront.

Urbanization; Ecosystem Services; Urban Sustainability; Green Infrastructure

TU984.3

A

1673-1530（2014）01-0120-08

2014-01-17

修回日期：2014-02-16