Private property and conventional markets work reasonably well for the allocation of goods and services (table on right).
Ecosystem services are public goods - they are neither bought or sold. From an economic theory perspective, they are considered non-excludable and non-rival (Costanza et. al 2014). Excludability refers to whether or not people can be prevented form consuming or accessing a good or service. Rivalry refers to whether a good or service can be used by only one person at a time, and whether or not it diminishes after use.
Common pool resources, known as “the commons”, are also nonmarket goods. They are non-excludable and rival resources such as open grazing pastures, made famous by Garret Hardin's article "Tragedy of the Commons" (1968). Nobel prize winning economist Elinor Ostrom popularized research on the commons focused on natural resource systems such as fisheries and forests (Ostrom 1990). Recent studies have looked at urban permutations of the commons in urban public space and planning; dog parks; community gardens; and urban lakes.
An important lesson charted by Colding and Barthel (2013) is that by conceptualizing green space as commons, we can foster a culture of environmental stewardship and civic participation in urban land management that may help bridge the human-nature gap in cities. This may be of concern to cities as they transition to sustainability.
Links to urban commons research
Ostrom in the City
Article on the "Co-City" by Christian Iaione
Confluence Park - Denver, CO
Confluence Park in downtown Denver, Colorado is a good example of "The Commons" in a highly urbanized area. Many types of people congregate on the banks of Cherry Creek and the Platte River: tourists, homeless people, local families, and shoppers. Image by AboutColorado.