城市生物多樣性

城市并非只是給生物多樣性帶來威脅，人工與自然相互協(xié)調(diào)的城市生態(tài)系統(tǒng)也會(huì)為保護(hù)生物多樣性提供機(jī)遇。人們普遍認(rèn)為城市化是導(dǎo)致自然生態(tài)系統(tǒng)退化、生物多樣性下降的直接原因。然而，城市生態(tài)系統(tǒng)同樣擁有適應(yīng)其復(fù)雜環(huán)境的本土物種，并且能夠通過營(yíng)造近自然的、穩(wěn)定的棲息地來鼓勵(lì)新的物種前來定居。此外，經(jīng)過對(duì)城市生態(tài)系統(tǒng)進(jìn)行科學(xué)的規(guī)劃和修復(fù)，城市發(fā)展過程最初喪失的物種也有可能重新回到城市中來。近年來，北京通過大面積恢復(fù)濕地與林地生境、優(yōu)化生態(tài)基礎(chǔ)設(shè)施布局等措施，其生物多樣性水平已位居世界大都市前列。就連曾經(jīng)數(shù)量銳減的北京城“土著物種”雨燕，也在逐步適應(yīng)北京的變遷，種群數(shù)量穩(wěn)定在7 000余只，再現(xiàn)“舊時(shí)王謝堂前燕，飛入尋常百姓家”的情景。

風(fēng)景園林學(xué)科能通過理論和實(shí)踐為城市生物多樣性保護(hù)做出重要貢獻(xiàn)。

首先，通過建立完善的生態(tài)基礎(chǔ)設(shè)施網(wǎng)絡(luò)來保障城市生物多樣性。許多動(dòng)物可以在城市和郊區(qū)繁衍生息，這需要合理規(guī)劃它們棲息的空間體系——城市生態(tài)基礎(chǔ)設(shè)施網(wǎng)絡(luò)。從數(shù)量的角度，城市綠地和水體是生物多樣性的重要載體，只有足夠的面積才能有效地保護(hù)城市的生物多樣性；從結(jié)構(gòu)的角度，加強(qiáng)生態(tài)廊道系統(tǒng)的建設(shè)，提升綠地的連通性，相當(dāng)于增加動(dòng)物到達(dá)棲息地的途徑，有利于生物之間的遷徙與交流。也需要考慮到城市中建筑、道路橋梁、管道等灰色基礎(chǔ)設(shè)施的分割作用，設(shè)置有助于生物遷徙的結(jié)構(gòu)設(shè)施。

其次，通過營(yíng)建多樣化生境和構(gòu)建多級(jí)生物鏈提升城市生物多樣性。準(zhǔn)確識(shí)別城市生境類型及空間分布規(guī)律、探明生物多樣性本底，有助于增加生物多樣性保護(hù)的生態(tài)邊界劃定以及生物多樣性動(dòng)態(tài)監(jiān)控的科學(xué)性，進(jìn)而持續(xù)營(yíng)建生境和生物鏈。德國(guó)等歐洲國(guó)家廣泛開展城市生境單元制圖的理論與應(yīng)用研究，此類探索能有力支持不同地區(qū)生物多樣性的定向景觀規(guī)劃與管理。構(gòu)成生態(tài)基礎(chǔ)設(shè)施的植物生境是可供鳥類、昆蟲和其他動(dòng)物繁殖、居住和捕食的棲息地，合理選擇能夠承載復(fù)雜生物鏈的植物作為骨干樹種，在城市中構(gòu)建野生動(dòng)物友好的生態(tài)鏈條。在美國(guó)巴爾的摩市，橡樹能夠?yàn)轺[翅目昆蟲的幼蟲、鳥類、水生無脊椎動(dòng)物、魚類等多達(dá)537類物種提供食物或棲息地，被認(rèn)為是對(duì)野生動(dòng)物非常友好的樹種之一，因此當(dāng)?shù)匾?guī)定1/2以上的種植喬木必須是橡樹。提升城市生物多樣性的策略對(duì)城市建設(shè)有廣泛的借鑒意義。

再者，通過構(gòu)建人與自然的聯(lián)系，提升生物多樣性價(jià)值對(duì)于人類社會(huì)的積極效益。作為與城市中的動(dòng)植物共同生活的城市居民，在日常生活中都會(huì)不經(jīng)意間接觸到城市中的自然——街道的樹蔭、頭頂?shù)镍B群、草叢間的麻雀或者夏日傍晚的蟬鳴。越來越多研究證據(jù)表明此類與自然的接觸會(huì)影響人們的健康、態(tài)度和行為，未來需要將研究領(lǐng)域擴(kuò)展至生物多樣性與社會(huì)功能關(guān)系的層面，剖析不同程度的生物多樣性對(duì)城市居民產(chǎn)生影響的機(jī)制。通過持續(xù)發(fā)掘生物多樣性對(duì)人與社會(huì)的影響力，構(gòu)建不同的城市生物多樣性模式，提升人類居住空間品質(zhì)，為城市居民營(yíng)造詩意棲居地。

風(fēng)景園林學(xué)是以協(xié)調(diào)人與自然之間的關(guān)系為宗旨，保護(hù)和恢復(fù)自然環(huán)境，營(yíng)造健康優(yōu)美人居環(huán)境的學(xué)科?！渡锒鄻有怨s》第十五次締約方大會(huì)（COP15）提出“生態(tài)文明：共建地球生命共同體”主題，為風(fēng)景園林學(xué)科開展城市生物多樣性保護(hù)提供了重大機(jī)遇。通過拓展以城市生物多樣性保護(hù)為特征的學(xué)科理論，并推廣應(yīng)用到城市生態(tài)保護(hù)修復(fù)、適應(yīng)氣候變化的城市生態(tài)基礎(chǔ)設(shè)施建設(shè)等具體行動(dòng)中，從不同層面有意識(shí)地提升城市韌性并促進(jìn)城市生物多樣性保護(hù)規(guī)劃，實(shí)現(xiàn)人與自然和諧共生的美好愿景。

Urban Biodiversity

Cities are not only a kind of menace to biodiversity, but also an opportunity for biodiversity in the urban ecosystem where manpower and nature inter-coordinate. It is widely believed that urbanization is the direct cause of natural ecosystem degradation and biodiversity decline. However, the urban ecosystem is similarly provided with native species adapted to their complex environments, and is able to create stable habitats close to nature to encourage new species to settle. In addition, with scientific planning and restoration of urban ecosystems, the species initially lost during urban development may be able to return to cities. Of recent years, Beijing has ranked among the world’s largest metropolises in terms of biodiversity through extensive restoration of wetland and woodland habitats and optimization of eco-infrastructure.Even swifts, the “indigenous species” of Beijing, whose number has once reduced sharply, have gradually adapted themselves to the changes in the city, and its population has stabilized at over 7,000,recreating the scene that “the swifts who lived under the eaves of Wang Xie’s hall are flying into ordinary people’s homes.”

The discipline of landscape architecture can make an important contribution to the protection of urban biodiversity through theory and practice.

Firstly, safeguard urban biodiversity by building up a sound eco-infrastructure network. Many animals can propagate in urban and suburban areas and it requires us to rationally plan the spatial system where they inhabit - the urban eco-infrastructure network.The green spaces and waters in the city are the important carriers of biodiversity from the quantitative perspective. Only with the sufficient area can urban biodiversity be effectively protected.From the structural perspective, consolidating the construction of eco-corridor systems and bettering the connectivity of green spaces amount to increasing the ways for animals to reach their habitats, conducive to migration and exchange among organisms.Consideration must also be given to the segmentation of gray infrastructure like buildings, roads, bridges and pipelines in the cities, and the structural facilities making for biological migration be built up.

Secondly, increase urban biodiversity through the creation of diverse habitats and the formation of multi-level bio-chains. The types of urban habitats and the patterns of spatial distribution should be identified accurately and the background of biodiversity ascertained, which can help improve the scientificity of delimiting the ecological boundary for biodiversity conservation and dynamically monitoring biodiversity, and thus sustain the building of habitats and bio-chains. Theoretical and applied research on mapping of urban habitat unit is widely conducted in Germany and other European countries. Such exploration can strongly support biodiversity-oriented landscape planning and management in different regions. The plant habitats that form eco-infrastructure are the homes where birds, insects and other animals can breed,live and feed. The plants that can carry complex bio-chains should be reasonably selected as backbone tree species to build wildlifefriendly eco-chains in the cities. In Baltimore, one of American cities, oak trees can provide food or habitats for over 537 species such as larvae of lepidopteran insects, birds, aquatic invertebrates and fishes, being considered one of the wildlife-friendly wood species, so more than 1/2 of the planted trees must be oak trees according to the local regulations. The strategy of improving urban biodiversity is of extensive reference significance for urban construction.

Thirdly, enhance the positive benefits of biodiversity value for human society by building a connection between people and nature. As the city dwellers who live with animals and plants in our cities, we are all inadvertently exposed to the urban nature in our daily lives - the shadows of trees on both sides of streets, flocks of birds overhead, sparrows among the grasses, or the chirping of cicadas on summer evenings. There is growing research evidence that such contact with nature will affect people’s health, attitudes and behaviors. The future research needs to be extended to the relationship between biodiversity and social function, dissecting the mechanism for the impact of different levels of biodiversity on urban residents. The impact of biodiversity on people and society should be explored ceaselessly and different models of urban biodiversity constructed to improve the quality of human living spaces and create poetic habitats for urban residents.

As a discipline that aims to harmonize the relationship between humans and nature, landscape architecture is to protect and restore the natural environment, and create a healthy and beautiful living environment. At the 15th Conference of the Parties (COP15) of theConvention on Biological Diversitywas brought forward the theme of “Ecological Civilization: Building a Community of Life on Earth”, which provides a major opportunity for this discipline to carry out urban biodiversity protection.Through extending its theories that feature the protection of urban biodiversity and applying them to concrete actions such as ecological protection and restoration of cities, and construction of urban eco-infrastructure for climatization, the urban persistence can be consciously enhanced and the planning of protecting urban biodiversity promoted at different levels so as to achieve a nice vision of harmonious coexistence between human beings and nature.

Editor-in-Chief: Professor ZHENG Xi

December 31, 2021