Attempts to determine the value added by parks date at least back to the 1860s, when Frederick Law Olmsted attempted to calculate the increase in Manhattan real estate values generated by the creation of Central Park. That the park increased the value of the land adjacent to it was obvious, but Olmsted might have considered several other key questions, such as:
- Even if a park increases values, do those increases outweigh the the value that would have been gained from leaving the land available for development?
- Alternatively, could the same or approximately similar increases in value be achieved with a reduction in park acreage (and thus an increase in developable land)?
- Are values better served by a small number of large parks or many small parks, bearing in mind that many small parks are more expensive to maintain than a few large ones?
- Do certain types of park programming and design increase values more than others?
One of the best resources on the topic is a 2001 MIT Department of Architecture thesis, which was guided by several urbanist eminences including Andrés Duany and Eran Ben-Joseph. Although I'd encourage you to check out this paper on your own, some of the author's most important findings include:
- Homes adjacent to parkland receive a 22% price premium, but the premium rapidly drops off for properties beyond 600 feet from the park.
- Large parks do confer greater premiums than small parks, but the premium is small compared to the effect of being close to a small park.
- Smaller lots place a higher value on park proximity than large lots.
The intended use of a park also has a large impact on the effect the park will have on surrounding properties, according to the Trust for Public Land. Space devoted exclusively to athletics, for instance, may actually harm adjacent property values; open space designed as a wildlife corridor or for stormwater runoff can also be a disamenity where an unlit and forested area is perceived to pose safety issues. Large parks may also suffer from safety issues resulting from lack of use. Certain common purposes for open space, therefore, may not coincide with the objective of improving surrounding property values.
None of this, I think, would come as a surprise to Jane Jacobs, who through personal observation and study reached many of the same conclusions:
"Conventionally, neighbourhood parks or parklike open spaces are considered boons conferred on the deprived populations of cities. Let us turn this thought around, and consider city parks deprived places that need the boon of life and appreciation conferred upon them. This is more nearly in accord with reality, for people do confer use on parks and make them successes – or else withhold use and doom parks to rejection and failure."Even more to the point:
"City districts with relatively large amounts of generalized park ... seldom develop intense community focus on a park and intense love for it. ... Parks intensely used in generalized public-yard fashion tend to have four elements in their design which I shall call intricacy, centering, sun and enclosure."Jacobs, in Death and Life of Great American Cities, was reacting the common tendency of planners in her era to dedicate excessive amounts of land for open space, such that the space became an obvious disamenity, and a liability, rather than a benefit. Planning decisions about parks are going to revolve around more than the mathematical calculations of a developer, but having the tools to think about parks in a more objective way can aid in the creation of parks that are both successful and financially beneficial.