从文化和心理学意义上讲，城市荒野的审美启智功能让人类探索未知的天性得以释放—这正是推动文明进步的原动力。于我看来，东西方哲人的深邃思考和智慧大多来源于荒野：如释迦摩尼的菩提树、穆罕默德的希拉山洞、王阳明的龙场山洞，以及梭罗的瓦尔登湖等。生态心理学认为，人与自然的日益分离将有损人类健康，而人类的健康源于地球的健康，疗愈人类身心疾病有赖于人与自然关系的修复，以及自然生态系统的修复。景观感知的相关研究表明，景观的复杂性和可探索性决定了自然环境的美感。相较而言，园艺化的景观（如修剪整齐的草坪）显得索然无味—它们纵然代表着文明进步、能令人获得须臾的喜悦和激动，却唤不起人类的探索欲望和冲动，也难以传达诗情画意的美感。谈及“荒野”，我的思绪不由地回到了儿时的两处秘境—一处是村子最南边的风水林，那里葬着祖先的遗骨，林冠蔽日、蘑菇遍地、野花隐约，时而有野兽出没；另一处是我家半亩宅院里的水塘，杂草丛生、鱼鳖藏匿，萤火虫和着各种虫鸣翻飞— 它们时刻吸引着我去探寻并收获惊喜，就像鲁迅的百草园。拥有这样的荒野秘境，是我不幸童年的最大幸事。遗憾的是，它们都在我告别童年后相继消失了。先是风水林被园田化的水渠和机耕路切割开，随后林中的树木被砍伐殆尽，黄土深处的蛇洞被挖开，整整一窝赤链蛇（Lycodon rufozonatus ）曝尸路面，原先见过的许多鸟兽也从此绝迹；而后，我宅院中的水塘逐渐干涸，最终被填平并盖上了房子。好在这两处荒野秘境尚能偶尔出现在梦境之中，给我带来无限的欢愉。
来到北京求学后，我也曾迷恋过一处荒野，那就是圆明园遗址公园中的废墟。几乎在整个20世纪80年代，这里都是我的最爱，也是我恋爱时流连忘返的去处。深浅不一的坑塘与土丘交错分布，乱石散落其间，零星的精美石雕露出水面，水岸边被芦苇（Phragmites australis ）、野慈姑（Sagittaria trifolia ）和香蒲（Typha orientalis ）等植被覆盖，走近时会有鱼蛙受惊，搅动起“啪啦”的水声。早春时节，遍地的苦荬菜（Ixeris polycephala ）、毛地黄（Digitalis purpurea ）、诸葛菜（Orychophragmus violaceus ）、点地梅（Androsace umbellata ）和紫花地丁（Viola philippica ）给枯黄的土地铺上绚烂的彩色；此后，山桃（Prunus davidiana ）、毛樱桃（Prunus tomentosa ）、鼠李（Rhamnus davurica ）、黄刺玫（Rosa xanthina ）等相继开花。夏天的荫凉来自杨、柳、榆、槐、椿等乡土乔木，每一种乔木都因地势之高低和土地的不同湿度而统治着各自的群落，喜鹊（Pica pica）、灰喜鹊（Cyaponica cyanus ）、乌鸦（Corvus sp.）和各种啄木鸟（Picidae spp.）栖息其间。秋天则被黄栌（Cotiuns coggygria ）、山杏（Prunus sibirica ）、银杏（Ginkgo biloba ）和芦苇抢了风头，饱含野性的花青素让树叶红得热烈。我尤其喜爱冬天里的漫步—听冰裂的回声，看乌鸦在白杨树梢盘旋、苇穗在寒风中颤动，细赏残雪下的碑刻和悄悄觅食的麻雀。
但就在2008年北京奥运会举办前夕，为了向世界展示北京的文明和城市化水平，在“高雅化”和“美化”的名义下，这处举世无双的遗迹和最具北京特色的城市荒野，几乎在一夜之间被铲除：湖底铺上了防渗膜；荒野不再，取而代之的是光鲜的草坪与牡丹（Paeonia suffruticosa）、月季花（Rosa chinensis ）等各色园艺花木，以及喜庆的灯笼。
Urban Wildness as Another Civilization
Urban wildness has become the lost pearl in the industrialized city built with metal and glass. Human civilization continuously advances due to humans’ instincts of curiosity and exploration—from African savannahs to Asian jungles, European tundra, and to American deserts.... Gradually, the rough ores were polished into jades and clay was made into porcelains; the sparks lighted by firestones burned away wild plains; wildflowers were cultivated into horticultural flowers in aristocratic gardens; free-running rivers turned into canals; marshes occupied for urban and rural developments…. With fossil energy and mechanical technology, cities, farmlands, and gardens have been constantly displacing the nature, and the wildness is disappearing. Henceforth, “smooth,” “exquisite,” “elegant,” and “docile” now become “synonyms” of modern civilization. Modern cities magnifying the advance of civilization have evolved into a bright, beautiful, and clean palace built with plastic, metal, and glass, where however weed and insect habitats are increasingly eliminated; the nature and wildness, instead, only exists as virtual reality presented by electronic devices. Human beings lost their instinct of wildness, as lonely and dispirited tigers living in the glass cages of fancy hotels. It is time to call for the wildness.
Urban wildness is encroached in civilization and urbanization processes, exactly like the trees, clumps of weeds, or streams in the tiger cages. In a phylogenetic sense, urban wildness exists as primary nature in forms of debris of natural patches or corridors, such as remained wetlands (e.g., Harbin Qunli Stormwater Park), and as secondary nature which is free from human intervention, such as the natural vegetation growing in the abandoned gray infrastructure (e.g., the previous site of the High Line in New York). In addition to such wildscapes, urban wildness also includes the natural process or creatures (such as the natural runoffs, soils and microbes, spontaneous plants, weeds in concrete cracks, shrubs growing tenaciously on the stone walls of drains, leaves growing and falling seasonally, and cocks and frogs singing in different weathers) that are free from human intervention.
Ecologically, urban wildness is key to sustaining a healthy urban ecosystem as it can work with the laws of nature and the internal deep order as a natural ecosystem, which provides ecosystem services critical to human society, including air and water purification, microclimate regulation, and the maintenance of local biodiversity.
Urban wildness is also of cultural and psychological significance. Inspired by the aesthetics of urban wildness, humans explore the unknown world by their instinct, which is the motivity to civilization advancing. The wildness is also considered inspiration source of both eastern and western philosophers, such as the Bodhi tree for Sakyamuni Buddha, the Cave of Hira for Muhammad, the Longchang Cave for Wang Yangming, and the Walden Pond for Henry David Thoreau. Ecological psychology believes that human beings separated from the nature may suffer from health problems, which could be alleviated by re-establishing the human–nature harmony and restoring the natural ecosystem. Research on landscape perception also proves that complex and explorable landscapes contribute to creating beautiful natural environments. Their horticultural counterparts (such as well-manicured lawns) are dull—no matter how civilized or pleasant they are, they can neither attract humans to explore, nor convey a poetic aesthetic sense.
Speaking of “wildness,” I could not help but reminisce about two fairylands in my childhood—one was the Fengshui forest in the south of my village, where the ancestors’ remains were entombed, with mushrooms growing under the trees, and scattered wildflowers and wild animals around; the other was the pond in my courtyard, which covered an area of about 300 m2 and homed fish and turtles, with overgrown weeds and dancing fireflies with other insects. For me, they were as attractive and explorative as the Baicao Garden for Lu Xun, which dispelled the gloom in my childhood. Unfortunately, they all disappeared years later: the Fengshui forest was substituted by farmlands with channels and roads, trees cut down, snake holes excavated and dead Lycodon rufozonatus saw everywhere, and native birds and beasts vanishing; soon after, the courtyard pond dried up and was eventually filled up to build a house. Till now, I could still dream about these fairylands of wildness, bringing me much pleasure.
When studying in Beijing, I was fascinated by the ruins and wildness of Yuan-ming Yuan, which was the dreamland in my twenties, as well as a dating place with my beloved. Ponds, mounds, and rocks scattered on the site, and exquisite stone carvings stood in the lake. Phragmites australis, Sagittaria trifolia, and Typha orientalis grew on the lakesides; When approached by people, fish and frogs splashed in the water. In early spring, Ixeris polycephala, Digitalis purpurea, Orychophragmus violaceus, Androsace umbellate, and Viola philippica brought colors and vibrancy to the land; since then, Prunus davidiana, Prunus tomentosa, Rhamnus davurica, and Rosa xanthina bloomed one after another. Native dominant trees with leafy shade in summer, such as poplars, willows, elms, locust trees, and trees of heaven, formed vegetation communities with varied terrain and moisture conditions, where Pica pica, Cyaponica cyanus, Corvus sp., and several Picidae species inhabited. Colored-leaf trees such as Cotiuns coggygria, Prunus sibirica, and Ginkgo biloba, as well as Phragmites australis, together created an alluring autumn wildscape. In winter, I loved walking on the frozen river surface, enjoying echoes of ice cracking, watching crows hovering over the poplar trees and reeds trembling in the wind, and appreciating the inscription covered by snow and the quietly foraging sparrows.
Sadly, on the eve of the 2008 Summer Olympics in Beijing, the world-level stunning heritage of urban wildness manifesting historic characteristics of Beijing was almost eliminated in the name of beautification. The lakebeds were covered with anti-seepage geotextile; wild plants were removed and replaced with Paeonia suffruticosa, Rosa chinensis, and other colorful horticultural species, ornamented with festive lanterns.
At the same time, scholars all over the country set off a “protest” movement to defend the relics and the wildness of Yuan-ming Yuan. This nationwide debate, initiated by ecologists and environmentalists and supported by public media, highlighted Yuan-ming Yuan’s symbolic significance in human civilization and urban wildness. The original site of the park was a natural marsh in front of mountain, and then reclaimed as a rice field, forming a landscape of agricultural civilization reputed as the “Watertown of North China”; during the reigns of Kangxi and Qianlong from the 17th to 18th century, the park was expanded into an imperial grand garden that imitated the remarkable poetic landscapes in lower reaches of Yangtze River; afterwards, the park was destroyed by the war between the rising western industrial civilization and the collapsing Chinese agricultural civilization; over the past century, natural succession dominated the site again and made the park an urban wildness with rich cultural and natural heritage.
It is worth mentioning that when Yuan-ming yuan—the pearl of Chinese gardening art—was ruined, western philosophers were exploring the implications of wildness: “What we call wildness is a civilization other than our own.” The “civilization of our own” mentioned by Thoreau here undoubtedly referred to the industrial civilization fanatically pursued by the western world. However, nearly 150 years later, the fight against the prevalent beautification and urbanization happened. This defense of urban wildness is exactly a “conflict between two civilizations.” Today, a new civilization that embraces wildness—ecological civilization—is rising.
I still remember the days when I walked alone along the Walden Pond 29 years ago. During my immersing in the wildness, the ideas of Thoreau echoed in my head—“In wildness is the preservation of the world,” “the most alive is the wildest.” It is exactly my understanding of urban wildness. For me, “the most alive” here can not only refer to a person per se, but also to a certain group, city, nation, country, and even the entire human race and human civilization. Therefore, defending urban wildness is the only way for humans to move toward a higher level of civilization.
 Roszak, T. (2001). The Voice of the Earth: An Exploration of Ecopsychology. Newburyport, MA: Red Wheel / Weiser.
 Kaplan, R., & Kaplan, S. (1989). The Experience of Nature: A Psychological Perspective. Cambridge, England: Cambridge University Press.
 Yu, K. (2003). Be Kind to the Ruins of Yuan-ming yuan—Speech at the Symposium of “Restorative Planning for Yuan-ming yuan”. Beijing Planning Review, Supplement, 53-55.
 Thoreau, H. D. (1906). The Writings of Henry D. Thoreau. Boston, MA: Houghton Mifflin and Company.
 Yu, K. (2020). The Conflict between Two Civilizations: On Nature-Based Solutions. Landscape Architecture Frontiers, 8(3), 4-9.