Nowhere on earth is the challenge for ecological understanding greater, and yet more urgent, than in those parts of the globe where human activity is most intense - cities. The majority of the world's people live in or near cities, and the percentage is increasing.
Urbanization is one of the major environmental changes that people are causing on a global scale.
Urban areas concentrate enormous amounts of energy and resources, creating unique ecosystems and causing innumerable impacts to adjacent and distant lands and waters. People need to understand how cities work as ecological systems to take control of the vital links between human actions and environmental quality. Furthermore, city dwellers' lives are enriched through appreciating and understanding their local environment. By seeing cities as ecosystems, with physical, biological and social structure and function, we bring urban areas into the realm of ecology and ecological understanding into the service of urban planners, managers, educators and citizens. Developing broad understanding of cities as ecosystems faces numerous challenges, both intellectual and practical.