Dear Colleagues,

In 1900, only about 13% of the world’s population lived in cities; now the figure has increased to over 50%, and is expected to reach 60% by populations in cities and suburban areas, developing countries are still in the process of urbanization. Every day, hundreds and thousands of people move to the city. Why do we choose to concentrate ourselves in cities? What is the value of cities? What do cities offer us?

To understand the value of cities is to understand the nature of human beings as a biological species, as social animals and as cultural organisms. Food, warmth, clean water and air, safety, cultural identity and social status— these are the needs and desires we seek in cities. But often we find that the city turns against our will. Pollution and environmental degradation, poverty, unaffordable housing, crime, immobility, lose of health, loss of cultural identity or no sense of community, etc. become the common issues that occur side-by-side in urbanization worldwide. More currently issues such as climate change, and the dangers of nuclear power as demonstrated by the aftermath of the recent Japanese earthquake, etc. has further dampened our dreams for cities.

How can we design our cities to overcome the dark sides of urbanization while pursuing the full benefits of city life, so that the value of cities can be fully realized? This issue of Challenges will focus on both the scientific analysis and case studies concerning the relationship between the physical design of cities and their function as resilient organisms that can adapt to ever-changing environments, provide multiple ecosystem services, give cultural identity and facilitate social justice.

Prof. Dr. Kongjian Yu
Guest Editor

• agricultural urbanism
• eco-city
• ecological infrastructure
• ecological urbanism
• green infrastructure
• green urbanism
• landscape architecture
• landscape urbanism
• livable city
• resilient city
• urban design
• urban ecology