俞孔堅：氣候適應和韌性

▼江西省南昌魚尾洲公園（2021年12月5日攝）? 土人設計

在位于長江中下游洪澇頻發的南昌市，一個55hm2的粉煤灰堆放地和遭受污染的漁塘一同被改造為一座具有洪澇調節功能的海綿公園——一片能調節雨洪100萬方，同時凈化面源污染、修復鳥類棲息地，并提供多種休憩功能的美麗綠洲。該項目為城市如何應對季風性氣候以及全球氣候變化影響下的洪澇問題提供了一個可復制的模式。這個項目也是設計者試圖在建成環境中引入自然，以此適應諸如季風降雨等自然過程，同時滿足人們對開放空間的使用需求的一次探索。

氣候適應和韌性

俞孔堅

北京大學建筑與景觀設計學院教授；

美國藝術與科學院院士

原文刊發時間：2021年12月

為應對全球氣候變化，數十年來，國際社會做出了巨大的努力，無非兩條途徑：一是減排，二是適應。然而，全世界的目光似乎大多聚焦于減排或碳中和。直到最近，更兇猛的洪水淹沒了街道并沖毀了房屋，更猛烈的火災吞噬了山林，更干旱的天氣讓農民顆粒無收，更嚴酷的城市熱浪威脅著人的生命……人們似乎才強烈地意識到，闊談減排來實現氣候的回歸已經成為遙不可及的夢想。我們迫切需要擺脫眼前的困境，于是，2021年1月25~26日，聯合國首屆氣候適應峰會（以下簡稱“峰會”）在線上召開，全球的目光投向了適應，這“應對氣候不能被忽略的另一半”^[1]。

據《巴黎協定》所設定的目標，為了避免造成嚴重后果，全球氣溫升幅較工業化前水平必須控制在2℃以內，并向將升幅控制在1.5℃以內的目標努力。^[2]為此，必須在2050年前實現碳中和^[3]。然而，根據大自然保護協會（The Nature Conservancy）的測算，即使全球政府和企業已經采取了加快向清潔能源轉型、提高能源利用效率的相關減排行動，我們也難以實現2℃的溫控目標，更無從奢談1.5℃^[4]。但具有諷刺意義的是，近年來，全世界在氣候領域的絕大部分投資都投向了此類節能減排技術^[5]，卻幾乎忽視了基于自然的減排途徑——如果動員及時，那么經濟的、基于自然的減排途徑（保護、恢復和改良全球森林，濕地和農業用地的土地管理行動）有望在2017~2030年間貢獻37%的減排量，將全球氣溫升幅保持在2℃以下^[6]。

根據峰會報告，氣候相關的災難在過去三年中給全球造成了6 500億美元的損失，超過了此間全球GDP的0.25%；而且預計到2100年時，如果全球氣溫上升2℃，將可能帶來高達69萬億美元的損失^[7]~[9]。地球的氣候韌性投資每提高1美元，便可以為其他方面節省6美元^[1]。聯合國環境規劃署（UNEP）2021年發布的《氣候適應差距報告》指出，2019年，僅發展中國家每年的氣候適應成本就高達約796億美元；2030年時，這一數字將升至1 400~3 000億美元，2050年將達到2 800~5 000億美元^[10]。這些天文數字告訴我們，建設具有氣候韌性的人居環境需要付出多大的努力；也告訴我們，基于自然、適應自然的建設途徑具有多大的潛力！

正是在此背景下，基于自然的綠色基礎設施和氣候適應的海綿城市得到了空前的關注。UNEP、世界各地政府、各大銀行也開始把注意力轉向氣候適應的對策和行動。尤其值得注意的是，近幾年來，帶有強烈中國特色的“海綿城市”概念和相關實踐成為熱點。Google搜索中“sponge city”的檢索結果竟多達1億條，幾乎是“孔子”（Confucius）的兩倍。而世界各大銀行——包括世界銀行、亞洲基礎設施投資銀行、歐洲復興開發銀行——都開始將目光轉向基于自然的氣候適應基礎設施的投資，包括建設海綿城市和生態基礎設施。僅僅在過去的兩年時間中，我本人應邀為上述三大銀行做了八場關于基于自然的氣候適應、海綿城市和海綿星球的專題報告。

而當到了具體實施層面，我們又不得不需要對一些習以為常、甚至被認為是“先進”的理念和行動提出質問。比如，當科學告訴我們，森林和濕地在應對氣候變化方面非常有效，我們卻遇到了“河道管理范圍內禁止種樹”的規范，原因竟是樹木會阻礙行洪，河道必須裁彎取直以保證高效的過洪斷面；又比如，科學告訴我們，農林間作有利于促進農業生產，特別是生態農業需要有多樣化的生境同時存在，我們卻遇到了“永久基本農田禁止種樹、挖塘”的規定，如此等等。于是，河流廊道失去了能適應氣候和調節流量的濕地和河漫灘森林，田園失去了自我調節旱澇、截留和凈化面源污染的濕地，維持生態平衡的生物棲息地和生物多樣性也隨之消失。第二次全國濕地資源調查結果顯示，2009~2013年，中國自然濕地面積減少了337.62萬公頃，減少率近10%^[11]。而根據本人主持的北京大學研究團隊在安徽、重慶和云南的實際調查，中國廣大鄉村和農田景觀中的陂塘和坑塘濕地消失了約30%。這意味著季風氣候下，中國大地的氣候適應能力相應下降，由此造成的損失不言而喻。

因此，如何基于自然、利用自然、適應自然，用科學的精神和系統的途徑設計適應氣候變化且富有韌性的綠色基礎設施，有賴于跨越地理、農業、水利、市政等各個專業界面的協同設計。而這也正是景觀設計所面臨的重大挑戰和機遇。

 以下為文章英文版本   引用格式及所在主題刊詳細信息見文末 

Climate Adaptation and Resilience

YU Kongjian

Professor of College of Architecture and Landscape, Peking University; 

Member of the American Academy of Arts and Sciences

Published in December 2021

The international community has made great efforts over the past decades to cope with global climate change via two major countermeasures: carbon emission reduction and adaptation. At present, the world’s most attention is attached to carbon emission reduction or carbon neutrality. As more violent floods engulf roads and houses, stronger fire disasters rage across forests, more droughty weather steals harvests from farmers, and harsher urban heat waves threaten lives, we come to realize that carbon emission reduction helps little stop climate change. We are in urgent need to address climate change from a new perspective. As Climate Adaptation Summit 2021 (the Summit hereafter), the first of its kind hosted by the United Nations, held online on January 25 and 26, the international community shifted to the approaches of adaptation, since “adaptation cannot be the neglected half of the climate equation”^[1].

The Paris Agreement highlighted the exigency of “holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 °C above pre-industrial levels” to significantly reduce the risks and impacts of climate change.^[2] To this end, humans need to take efforts for the goal of carbon neutrality by 2050^[3]. However, predicted by The Nature Conservancy, governments and enterprises across the globe to date have been focused on accelerating the transition to clean energy and improving energy efficiency, yet the corresponding action “still lags far behind what is necessary to keep the planet below 2 °C threshold of warming, and nowhere near what is required to stay below the 1.5 °C target”^[4]. Ironically, such mitigation projects have made up the vast majority of global total climate finance in last decades^[5], while nature-based mitigation approached have been neglected. If mobilized in time, the research points out that cost-effective natural climate solutions—conservation, restoration, and improved land management actions across global forests, wetlands, grasslands, and agricultural lands—can offer 37% of mitigation needed between 2017 and 2030 to keep global temperature rise below 2 °C.^[6]

The Summit reported that over the past three years, climate-related disasters have cost the world USD 650 billion, more than 0.25 percent of global GDP for those years, and the costs of damages from warming in 2100 for 2 °C will be USD 69 trillion^[7]~[9]. An assessment figures out that “for every dollar invested in climate resilient infrastructure, six dollars can be saved”^[1]. Adaptation Gap Report 2021 by United Nations Environment Programme (UNEP) notes that climate finance flows to developing countries (for both mitigation and adaptation) reached USD 79.6 billion in 2019. It is estimated that the annual costs of adaptation in developing countries could be USD 140 ~ 300 billion by 2030 and 280 ~ 500 billion by 2050^[10]. These astonishing figures signify the huge potential of and enormous efforts required in building a climate-resilient living environment through nature-based and nature-adapted approaches!

Against this background, nature-based green infrastructures and climate-adaptive sponge cities are receiving unprecedented attention. UNEP, governments, and major banks across the globe start to put forward climate adaptation measures and actions. The concept of Sponge City that has distinctive Chinese characteristics become particularly a widely-discussed interest among international researchers and practitioners over the past few years. There are over 10 million pieces of Google search results of “sponge city,” almost twice that of “Confucius.” Major banks, including World Bank, Asian Infrastructure Investment Bank, and European Bank for Reconstruction and Development, have set about investing in nature-based climate adaptation infrastructures such as sponge cities and ecological infrastructures. Over the past two years, I have delivered eight lectures on nature-based climate adaptation, sponge city, and sponge planet upon the invitation from above banks.

When it comes to implementation, we have to question the ideas or actions that are widely accepted or even “advanced” as so called. For instance, scientific knowledge proves that forests and wetlands are effective for mitigation of climate change, but existing regulations forbid to plant trees within the management areas of river courses (as trees could hinder flood drainage); It evidences that the combination of forest- and field-crops helps boost agricultural production (which is particularly true for eco-agriculture sites suffering from the loss of habitat diversity), which is also illegal under regulations such as tree planting and pond digging are not allowed in the permanent prime farmland. As a result, wetlands or floodplain forests that can contribute to climate adaptation and runoff regulation are being erased from river courses. Also, wetlands that help regulate droughts and floods and intercept and purify non-point-source polluted water bodies are being eliminated in farmlands, along with the disappear of wildlife habitats and biodiversity that are key to keeping ecological equilibrium. According to the Second Survey on National Wetlands^[11], in China, the area of natural wetland reduced by 3,376,200 hectares, a nearly 10% dropping from 2009 to 2013. The field investigation in Anhui, Chongqing, and Yunnan made by researchers from Peking University, led by the author, showed that ponds and pond wetlands in China’s rural areas and farmlands reduced by approximately 30%. Consequently, China’s climate adaptation capacity is dwindling, causing huge losses.

Therefore, collaborative design with experts from the fields of Geography, Agriculture, Hydraulic Engineering, and Civil Engineering is required to develop resilient climate-adaptive green infrastructures by scientifically and systematically leveraging the power of nature. This poses great challenges and opportunities for landscape architects.

^參考文獻

^{[1] Guterres, A. (2021). Remarks to the Climate Adaptation Summit. UN Headquarters. Retrieved from https://www.un.org/sg/en/content/sg/ speeches/2021-01-25/remarks-climate-adaptation-summit}

^{[2] United Nations. (2015). Paris Agreement. Retrieved from https://unfccc.int/sites/default/files/english_paris_agreement.pdf}

^{[3] Guterres, A. (2021). Remarks to the Climate Adaptation Summit. Carbon neutrality by 2050: The world’s most urgent mission. Retrieved from https://www. un.org/sg/en/content/sg/articles/2020-12-11/carbon-neutrality-2050-the-world%E2%80%99s-most-urgent-mission}

^{[4] The Nature Conservancy. (n. d.). Playbook for Climate Action. Author. Retrieved from https://www.nature.org/content/dam/tnc/nature/en/documents/TNC_ PlaybookClimateAction.pdf}

^{[5] Lamy, Y. S., Leijonhufvud, C., & O’Donohoe, N. (2021). The Next 10 Years of Impact Investment. Stanford Social Innovation Review. Retrieved from https:// doi.org/10.48558/XFK2-6N65}

^{[6] Griscom, B. W., Adams, J., Ellis, P. W., Houghton, R. A., Lomax, G., Miteva, D. A., … Fargione, J. (2017). Natural climate solutions. Proceedings of the National Academy of Sciences, 114(44), 11645–11650. doi:10.1073/pnas.1710465114}

^{[7] Moomaw, W., Law, B., Ripple, W., Verkooijen, P., Huq, S., & Gordon, C. (2021). Global Scientists Call for Economic Stimulus to Address Climate Adaptation and Covid. Global Center on Adaptation. Retrieved from https://www.preventionweb.net/news/global-scientists-call-economic-stimulus-address-climate-adaptation-and-covid}

^{[8] DiChristopher, T. (2019, Feburary 14). Climate disasters cost the world $650 billion over 3 years—Americans are bearing the brunt: Morgan Stanley. CNBC. Retrieved from https://www.cnbc.com/2019/02/14/climate-disasters-cost-650-billion-over-3-years-morgan-stanley.html}

^{[9] Hoegh-Guldberg, O., Jacob, D., Taylor, M., Bindi, M., Brown, S., Camilloni, I., ... Zhou, G. (2018). Impacts of 1.5°C Global Warming on Natural and Human Systems. In V. Masson-Delmotte, P. Zhai, H.-O. Portner, et al. (Eds.), Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. In Press. Retrieved from https://www.ipcc.ch/sr15/chapter/chapter-3/}

^{[10] United Nations Environment Programme. (2021). The Gathering Storm Adapting to climate change in a post-pandemic world. Author. Retrieved from https://www.unep.org/resources/adaptation-gap-report-2021)}

^{[11] National Forestry and Grassland Administration. (2014). Main Results of the Second Survey on National Wetlands (2009-2013). Author. Retrieved from http://www.forestry.gov.cn/main/65/20140128/758154.html}

^Source:

^{Yu, K. (2021). Climate Adaptation and Resilience. Landscape Architecture Frontiers, 9(6), 4-7. https://doi.org/10.15302/J-LAF-1-010021}

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