Cities have always set the pace for human progress. From the Greek polis and medieval cities to contemporary megacities like Mexico City, Shanghai and New York, cities have traditionally been the center of art and culture, trade and industry, science and technology. Some 50 percent of global economic output is generated in the world’s 600 biggest cities alone. Yet the negative effects of progress have also been most evident in cities: noise, over-crowding, environmental pollution and traffic congestion.

In the past cities were the exceptional oases of human civilization. Today they are the norm. Two hundred years ago, only three percent of the world’s population lived in cities. Today the total has grown to over half, and the trend is accelerating. Urban problems have also kept pace with this growth. Cities now produce 80 percent of the world’s greenhouse gas emissions and consume 75 percent of all energy produced. Keep reading →