The urban ecology model
Developed by Abel Wolman and Peter Newman
Emphasizes the way in which the city itself resembles an environmental system and hence should integrate waste, water and nutrient recycling as key aspects of its urban management
Urban resources - inclusive of air, water, infrastructure, food and fuel - should be utilized in a closed-loop, rather than linear, system wherein a significant proportion of the city's outputs are recycled within the city energy system to create value and sustain its growth.