文章来源：俞孔坚, 萨拉·雅各布斯, 张健. "大脚"度量的集聚与混合[J]. 景观设计学, 2016(2):6.
要理解人类的城市，必须从理解人是社会性动物及其需求开始。在外星人的眼里，人类与蚂蚁、蜜蜂、猴子和狒狒实际上没有多大区别：白天每个个体分头忙碌，晚上纷纷回巢，分享收获，交流聚会，抱团取暖；从高空用高倍望远镜看地球上的城市，就如同我们用肉眼看蜂巢和蚁穴一样，难怪近年来“蜗居”和“蚁族”被用来形容城中村的人居状态。辉煌一时后被铲平的北京唐家岭，本地人口不足3 000人，近些年却集聚了超过5万的外来人口，其中大学毕业生占三分之一；两年前，我曾带领研究生对与唐家岭毗邻的一个村落进行了调查，当地居民只有不足2 000人，却集聚了2万人在此栖居，南腔北调，摩肩接踵，虽嘈杂拥挤，却活力无比；我也曾“冒着生命危险”深入世界上最大的蚁居城市—巴西里约热内卢近郊的Favela（俗称贫民窟），那里集聚了30多万人口，里面的景象与媒体报道的负面形象并不完全一致，那里有着自由组织的街道，空间利用高效，生活井然秩序，到处生机勃勃。只要不随意拍照、不去招惹带枪的毒品贩子，实际上并无危险，那里甚至已经被开发成为旅游目的地。
集聚的密度和功能混合的程度却随着个体日常出行方式及远足能力的变化而变化。在工业革命之前，天足的脚力是衡量空间聚集程度的量度，所以，中国广大乡村的集市之间的距离大约为5~10km，定时流动，当街为市，用来满足个体的各种日常需求。马车定义了欧洲中世纪城市的尺度和街道格局；霍华德的田园城市（Garden City，1898）模式是基于蒸汽机动力的首个经过规划的、理想的、集聚和满足居民一切需要的、功能混合的城市模式，尺度约2km2，从城市边缘到中心约1km，街区尺度不足百米，居住人口3万人，另外有2 000人散居在乡间。30多年之后，柯布西耶提出了新的集聚的城市模式，即光明城市（The Radiant City，1935），但其尺度是田园城市的百倍，人口规模也是数以百万计，街区尺度则是上千米了，已经完全不再是人的步行尺度。这时候，所谓集聚和混合都只有通过汽车轮子来实现了，城市被理解为由各种功能体块组装起来的机器，只留下了不能步行的集聚—百万人和千万人规模的集聚。几乎在同时，另一位欢呼和拥抱汽车时代的建筑大师弗兰克·劳埃德·赖特则将这种汽车轮子上的城市推演到了极致，提出了顷宅城（Broad Acre City），这里人的步行空间被压缩在每家的4 000m2的后院之内，所有出行都依赖于汽车，包括买酱油、理发、看电影和约会。
美国的郊区化因此如脱缰野马，以“美国梦”的名义和“消失的城市”（The Disappearing City，1932）的欢呼，蔓延开来。美国中西部的大部分城市沿快速路网延伸，形成大面积的城镇化的低密度郊区，并围绕一个高楼林立的CBD核心。这样的城市形态以巨大的能源、土地、环境成本以及社区交流和家庭生活的牺牲为代价，维持着每个个体对集聚与混合的需求。所以，早在50年代后期，这种城市形态就已经被“外行”的人文主义学者简·雅各布斯所痛斥，并把汽车作为罪魁祸首。这样的质疑一直到20世纪80年代，才被城市规划设计界所广泛认同，于是，以新都市主义（New Urbanism）为代表的步行的、高密度的、混合型的城市形态的回归思潮应运而生，一直延续到今天。然而，要想刹住这基于汽车的惯性蔓延谈何容易！
Aggregation and Integration, Measured by Big Feet
My mentor, Professor Richard Forman, developed an ideal ecological landscape pattern, what he called an “Aggregate-with-Outliers” (1995). In his view, this was the best possible pattern for biodiversity protection. The same pattern is true for the urban morphology of human life and work.
To understand the city, humans must be seen as social animals. From the eyes of an extraterrestrial, human beings would be no different from ants, bees, monkeys or baboons; they move as individuals in the daytime and return to their nests in the night to share, communicate and warm each other. From a high-powered telescope, our cities are much like a beehive or an ant colony. No wonder people use similar phrases to describe the residential urban villages. As an example, the once-flourishing and then torn down area of Tangjialing, Beijing, with a population of 3,000, swells to over 50,000 people, one third of which are college students. Two years ago, I conducted research with my graduate students in a village adjacent to Tangjialing. At that time, 20,000 people from around the country crowded into the little village of fewer than 2,000 local residents. The atmosphere was noisy yet vibrant. At another time, I “risked my life” to sneak into one of the world’s largest ant tribe cities, Rio De Janeiro. Visiting the favela of 300,000 people felt very different from how these areas are represented. Instead, I saw organized streets, efficiently used spaces, and ordered daily lives. The environment was full of life. The favela has even been developed into a type of tourism destination.
Urban villages such as Tangjialing in Beijing and high-density, integrated settlements such as favelas in Rio indicate the human heart of a city’s formation. Humans need to gather and be social. Abraham Maslow’s “Hierarchy of Needs,” classified human behavior into five levels of needs: physiological, safety, love and belonging, esteem and self-actualization. In order to meet these needs, an individual must be part of a social group. It is these needs that tie individuals first to communities and then to cities. The cities of the Middle Ages or the bazaars of vast Chinese countryside are examples of the human need to organize socially. They reflect a density of aggregation and integration that humans can achieve in the most economical and efficient ways.
The intensity of transportation aggregation and integration are, however ever-changing, based on the individual body. Before the Industrial Revolution, our feet were the measurement of spatial aggregation. This explains why an enormous number of Chinese village markets are five to ten kilometers from each other. The markets occur on the street, and move periodically to meet different individual needs. The horse carriage defined the city scale and pattern of the European cities in the Middle Ages. Ebenezer Howard’s Garden City (1898) was the first mixed-use city planned for the intentional gathering and meeting of residents. The Garden City was around 200 hectares, and the distance from the cities edge to center was around one kilometer. The neighborhood scale was less than 100 meters, which supported a residential population of 30,000, with 2,000 more scattered in countryside. Over three decades later, Le Corbusier proposed a new aggregation city model, the Radiant City (1935). With the Radiant City, the scale grew to one hundred times the size of the Garden City and the population reached one million with the neighborhood scale at over 1,000 meters. The city was no longer imagined through the scale of human feet. Aggregation and integration was now realized through car wheels, and the city became a machine of unwalkable, mono-functional blocks. At the same time that Le Corbusier was planning the Radiant City, Frank Lloyd Wright was also planning new urbanisms for the automobile age. His conceptual plan for Broad Acre City compressed walking spaces to a half hectare backyard; going out for shopping or social activities would rely on automobiles.
The suburbanization of America sprawled like a runaway wild horse under the guise of the American Dream and The Disappearing City (1932). In many midwestern cities, low-density suburbs began to populate the landscape around a central business district consisting of mostly high-rise buildings. These urban patterns required huge amounts of land and resources and had lasting effects on the environment, in addition to neighborhood communication and family lives. In the late 1950s, the “amateur” humanistic scholar Jane Jacobs sharply criticized the automobile as the chief culprit of American suburbanization and lack of urban life. Jacob’s criticism has been widely acknowledged in urban planning and design, and was a major influence for the New Urbanism movement of the 1980’s and 1990’s, which advocated for pedestrian-friendly, high-density, mixed-use cities. This, however, has not stopped the momentum of the automobile.
While the United States was desperately trying to amend its twentieth century suburbanization, China started its own process of urbanization. Here there was a chance for China to learn from countries who had already experienced modern urbanization, but rather than design and advocate for truly high-density, mixed-use urban systems at a human scale, Chinese urbanization followed the American urbanization train. With the same inertia as the United States in the 1950’s and 1960’s, China created its own death trap. As the roads were widen, ancient village were razed in order for town to “gain” new land for urban expansion. The standards for city streets and blocks became larger and larger making walking or cycling no longer an option. Single-functional development blindly expanded into suburban areas, and Chinese cities went down the road of no return! I foresaw this tragedy ten years ago in a book titled Urban Landscape Road — Communicating with Mayors. In it, I summarized the complication of China’s rapid urbanization as being caused by a feudal centralized power split between the nouveau riche and the peasant class. I am not boasting in referencing myself, I do not feel proud for foretelling the tragedy. In contrast, I would like to imagine a positive vision for China’s urbanization: China’s future aggregation and integration patterns will include expanded metropolises and revived villages, propelled by the momentum of urbanization and forming “aggregate-with-outliers.”
This vision — a spiral of the Garden City and the Chinese traditional village — must be based on the human foot, but also must be understood through high-density and mixed-use aggregation patterns. Some Chinese villages will be revived, while others that have lost their natural or cultural features will decline or vanish. In an “aggregate-with-outliers,” the expanded metropolis and revived villages will be repeated to create a pattern of urban form. This vision depends on five conditions:
1. Human nature requires a mix of aggregation and integration as we are social animals.
2. Escapes from the big city in favor of more livable environments will be a need for most people. We can expect another round of “Down to the Countryside,” with increasing numbers of retired or financially secure urban populations traveling to the countryside along high-speed railway. We have a limited time to realize the potential consequences of a countryside revival.
3. High-speed rail and developed internet network will make escaping from big cities possible and accessible through technologies other than the automobile. Rail connects the walkable and beautiful countryside, while wireless networks make working and communicating possible from even far away urban infrastructures. Together, new transportation and new technology can achieve aggregate and mixed-use neighborhoods.
4. An ecological civilization will need to become a national strategy, which, together with restrictions on energy and environmental extraction, will help re-recognize the charm of thinking at the scale of our feet.
5. The new economy encourages growth in the design industry, as the beautiful countryside at the urban fringes and along high-speed railways will become sites for new urbanization.
Even with foresight, China risks getting lost in the momentum of urban construction.