Urban Green Space

Urban green space, which is related to, but not necessarily the same as, an urban ecosystem and green infrastructure, comes in a variety of forms and serves a variety of purposes in the urban landscape (see the first set of photos). Various types of urban green space are recognized in the literature: planned or unplanned remnant intact patches of vegetation embedded in the urban matrix, planned spaces such as parks or restored areas, and abandoned or derelict sites that are slowly being colonized by pioneer plant species. The definition might reasonably be expanded to include freshwater and marine environments. Thus, urban green space includes iconic sites such as London's Hyde Park and New York's Central Park, large expanses of seminatural vegetation such as Perth's Kings Park and Botanic Garden, and abandoned sites such as can be found in all cities. Irrespective of their form, urban green spaces are perceived in many ways by those who encounter and use them. For many people urban green spaces are places that enhance physical and psychological well-being by providing contact with the “natural” world, yet for others they are places of fear or spaces that serve to reinforce social boundaries. This entry first defines ecology in cities and the ecology of cities and examines the contributions urban green spaces can make in terms of environmental services, engineered urban green space, social and cultural services, and health and well-being. Negative outcomes and perceptions of urban green space are then examined. The entry concludes with a look at the future of the many forms of urban green space.

Homo sapiens is rapidly becoming a predominantly urban(ized) species. At the beginning of the 20th century, only 10% of the world's people lived in urban areas; that number now stands at more than 50% and continues to grow. Ongoing urbanization and the growth of megacities pose threats to biodiversity, dramatically alter climatic and hydrologic processes in urban environments and the surrounding landscapes, and threaten to isolate humans living in cities from “nature” as urban green spaces are lost to development and infilling. Nevertheless, many urban areas contain a surprising amount of green space. These “urban green spaces,” in their many forms, provide a wide range of environmental and sociocultural services to city dwellers, including those related to health, education, and recreation. Such spaces are playing an increasingly central role in integrated regional and urban planning and design.