05 December 2011

Human Ecosystem

Definition: The ecosystem concept was originally defined as a biological community, consisting of plants, animals, and microbes, interacting with a physical environmental complex, consisting of soils, water, air, and physical conditions such as temperature and wind, all in a specified area.  The human ecosystem combines these components traditionally recognized by ecologists with the built environment and the social characteristics, structures, and interactions in the area of interest (Fig 1).  The key aspects of ecosystems are 1) the spatial boundary, 2) the physical, biological, social, and engineered and built components, 3) the interactions among the components, and 4) the feedbacks and controls that result from the interactions within the ecosystem or which are imposed by conditions that exist outside the ecosystem boundary.

Examples: Human ecosystems are now the predominant kind of ecological system on the Earth.  A grazing landscape containing cattle, and dominated by grasses, in which a there may be occasional fences or roads, but in which few people may be present permanently, is a human ecosystem because the influences and management effects of people are still part of the system.  Of course, cities are human ecosystems in the fullest sense of the term, with humans densely present along with their buildings, roads, pipes and other infrastructure.  Beyond these obvious features, cities as human ecosystems contain other organisms, ranging from pets, to garden plants, to wildlife, to disease causing bacteria, to microbes that process nutrients in the soil.  Ecological processes of temperature regulation, flow and storage of water, nutrients, and carbon are also features of the human ecosystem of cities. 


Figure 1. (Human Ecosystem 1).  A conceptual diagram of the human ecosystem, building on the original biophysical definition from ecology.  Adapted from Pickett and Grove 2009.

Why important: Considering urban areas to be human ecosystems reminds us that connections, sometimes subtle and hidden, among the various components are crucial to the functioning and management of cities, suburbs, and the surrounding exurban areas.  Understanding that nature and natural processes are part of cities, suburbs, and exurbs can also enrich people’s experience of their most familiar environment – the places where they live.

For more information:
Spirn, A. W. 1984. The granite garden: urban nature and human design. Basic Books, New York.
Hough, M. 1995. Cities and natural process. Routledge, London.
Pickett, S. T. A. and J. M. Grove. 2009. Urban ecosystems: what would Tansley do? Urban Ecosystems 12:1-8.

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