Urban Ecology, from my point of view, is concerned urbanism under long-term span which is the sustainability, the aim of which is to meet the needs of the present without compromising the ability future generations to meet their own.  The object that urban ecology is concerned may contain nature, human, society, culture, economy and whatever interacts with human and nature, just as Ian Douglas pointed out, “an ‘integrated bio-socio-systems’”. The city is not only an ecosystem, but also an economic system, a culture system and a social system. Urban ecology is to fulfill the task of maintain the various systems in homeostasis for recent and for the future; the stability is not contributed by conserving, but updating heritage to modern society, running in more energy efficient ways, maintaining systems in a healthy cycle, and etc., then the roots of which are back to raw materials and nature. Thus, the context of urban ecology is defined into physical and social eco-system. 
1. Hough, Michael. Urban Ecology: a basis for shaping cities. Routledge Press, 2004.
2. Downton, Paul. Ecopolis: Architecture and cities for changing climate. Springer Science & Business Media. 2008