The city stands as one of man's most intriguing inventions. Though certainly not ancient in the time scale of human evolution, the idea of the city has come to be regarded as his highest development.

It is not by chance that man chose to associate himself with other men and with plants and other animals. The inhabitants of cities, however, do not usually consider them biological communities. To be sure, in one sense the history of the city can be regarded as a history of architecture or engineering: and our modern cities are truly marvels of engineering and technology—so much so that to a large extent the nonengineering and the nontechnical aspects of cities have come to be forgotten or ignored, in some instances with catastrophic consequences.

It is the nonengineering, nonarchitectural, nontechnical components of cities that make them comparable wherever they are found. These factors are the ecological and biological components of cities that are now the great concern of environmental designers. Clean air, clean water, food, clothing, and shelter are the common requisites of all men, in cities and out. Providing these commodities while providing the environment for the technical activity of man is in essence the function of the city. It is in the ecological relations of man—his environment and his work—that the true forms of the city are to be found. This preliminary discussion on the ecology of the city is intended, therefore, to be a reminder to engineers, city planners, and architects that, while virtually any conditions can be engineered, the goal of their efforts should be the establishment of the most favorable conditions for man, and these most favorable conditions can best be achieved through ecological understanding and management.

This recognition that every city functions as a biological community will oblige city planners to reconcile human needs for greenery, clean air, and space with the purely technical solutions to city problems. Faster traffic flow or expanded office and manufacturing facilities must not preempt the need to preserve favorable living conditions for the human organism. The city-limit signs that outline a community also define a distinct ecological setting, which must be managed as an ecosystem if it is to continue to function for the benefit and productivity of its inhabitants.