In land use planning, urban open space is open space areas for "parks", "green spaces", and other open areas. The landscape of urban open spaces can range from playing fields to highly maintained environments to relatively natural landscapes. They are commonly open to public access, however, urban open spaces may be privately owned. Areas outside city boundaries, such as state and national parks as well as open space in the countryside, are not considered urban open space. Streets, piazzas, plazas and urban squares are not always defined as urban open space in land use planning.
The term "urban open space" can describe many types of open areas. One definition holds that, "As the counterpart of development, urban open space is a natural and cultural resource, synonymous with neither 'unused land' nor 'park and recreation areas." Another is "Open space is land and/or water area with its surface open to the sky, consciously acquired or publicly regulated to serve conservation and urban shaping function in addition to providing recreational opportunities." In almost all instances, the space referred to by the term is, in fact, green space. However, there are examples of urban green space which, though not publicly owned/regulated, are still considered urban open space.
From another standpoint public space in general is defined as the meeting or gathering places that exist outside the home and workplace that are generally accessible by members of the public, and which foster resident interaction and opportunities for contact and proximity. This definition implies a higher level of community interaction and places a focus on public involvement rather than public ownership or stewardship.
Generally considered open to the public, urban open spaces are sometimes privately owned. Some examples of such places include higher education campuses, neighborhood/community parks/gardens, and institutional or corporate grounds. These areas still function to provide "aesthetic and psychological relief from urban development". Nevertheless, most commonly the term is used to reference spaces that are public and "green".
The benefits that urban open space provides to citizens can be broken into three basic forms; recreation, ecology, and aesthetic value.
Urban open space is often appreciated for the recreational opportunities it provides. Recreation in urban open space may include active recreation (such as organized sports and individual exercise) or passive recreation, which may simply entail being in the open space. Time spent in an urban open space for recreation offers a reprieve from the urban environment.
The conservation of nature in an urban environment has direct impact on people for another reason as well. A Toronto civic affairs bulletin entitled Urban Open Space: Luxury or Necessity makes the claim that "popular awareness of the balance of nature, of natural processes and of man’s place in and effect on nature – i.e., "ecological awareness" – is important. As humans live more and more in man-made surroundings – i.e., cities – he risks harming himself by building and acting in ignorance of natural processes." Beyond this man-nature benefit, urban open spaces also serve as islands of nature, promoting biodiversity and providing a home for natural species in environments that are otherwise uninhabitable due to city development.
In a sense, by having the opportunity to be within a natural urban green space people gain a higher appreciation for the nature around them. As Bill McKibben mentions in his book The End of Nature, people will only truly understand nature if they are immersed within it. He follows in Henry David Thoreau's footsteps when he isolated himself in the Adirondack Mountains in order to get away from society and the overwhelming ideals it carries. Even there he writes how society and human impact follows him as he sees airplanes buzzing overhead or hears the roar of motorboats in the distance.
The aesthetic value of urban open spaces is self-evident. People enjoy viewing nature, especially when it is otherwise extensively deprived, as is the case in urban environments. Therefore, open space offers the value of "substituting gray infrastructure."
One researcher states how attractive neighborhoods contribute to positive attitudes and social norms that encourage walking, while having close access to recreational facilities such as parks increases the likelihood that people will translate walking intentions into actual action.
The value of urban open space can also be considered with regards to the specific functions it provides. For example, the Bureau of Municipal Research in Toronto lists these functions as the nature function, urban design function, economic function, social retreat function, and outdoor recreation function. Another study categorizes the values open space offers from a sociological viewpoint, listing: civic and social capital, cultural expression, economic development, education, green infrastructure, public health, recreation, and urban form. These studies reiterate the same core benefits of urban open spaces and none of the options create any inconsistencies with the others.
Additional beneficial aspects of urban open space can be factored into how valuable it is compared to other urban development. One study categorizes these measures of value into six groups: utility, function, contemplative, aesthetic, recreational, and ecological. These categories account for the value an urban open space holds to the development of the city in addition to just those things citizens consciously appreciate. For example, the "function value" of an open space accounts for the advantages an urban open space may provide in controlling runoff. The final three values listed, aesthetic, recreational, and ecological, are essentially the same as the values that make urban open spaces consciously valuable to citizens. Of course, there are several different ways to organize and refer to the merit of open space in urban planning.
A study conducted in Australia provided insight into how there is a correlation between community development/community safety and natural open space within the community. Open areas allow community members to engage in highly social activities and facilitate the expansion of social networks and friendship development. As people become more social they decrease the perceptions of fear and mistrust allowing a sense of community bondage.
Despite improvements in medical technology that allow humans to heal from numerous diseases and medical conditions, research shows that contact with the green environment still offers great benefits to mental health and psychological well-being. Within a population, whether it is in the scale of a town or a state, researchers are continuing to find evidence of increased health benefits from a green environment that provides abundant vegetation. When physical activity of an individual is coupled with green environments, the health benefits are observed to be amplified.
Psychological benefits gained by visitors to urban green spaces increased with their biodiversity, indicating that 'green' alone is not sufficient; the quality of that green is important in delivering the health benefits.
Interacting with nature can have a restorative effect on attention/focus levels, through providing the brain a break from overstimulation.
A research study showed that women who spent six hours in the woods for two days showed an increase in white blood cells. This increase was also recorded to have stayed for seven days afterwards.
Certain benefits may be derived from exposure to virtual versions of the natural environment, too. For example, people who were shown pictures of scenic, natural environments had increased brain activity in the region associated with recalling happy memories, compared to people that were shown pictures of urban landscapes.
Studies done on physically active adults middle aged and older show there are amplified benefits when the physical activities are coupled with green space environments. Such coupling leads to decreased levels of stress, lowers the risk for depression as well as increase the frequency of participation in exercise. Degree of intensity of exercises don't impact degree of benefit from green space. Casual group walks in a green environment (nature walks) increase one's positive attitude and lower stress levels as well as risk of depression. Research shows that when open spaces are attractive and accessible, people are more likely to engage in physical activity, which has obvious inherent health benefits. Accessibility has been shown to increase open space use, which drops dramatically for distances longer than a five-minute walk (about 400 m). Neighbourhood layouts such as the Oglethorpe Plan for Savannah, GA or the contemporary Fused Grid achieve high degree of accessibility. It is important to note that according to a different study, physical exercise in natural environments do not necessarily elevate one's health state such as treating depression, but rather benefit in the forms of preventing the decrease of one's mental well-being such as risk of depression or distress. Also, regular use of non-natural, in particular sporting environments, was positively and significantly associated with greater well-being in terms of physical health, but no such correlation was found with regular use of any of the natural environments from the study. This suggests that greener environments and their positive benefits on human health is limited to mental health and well-being.
A large epidemiological study  concluded that wealthier individuals were generally healthier than individuals with a lower income, explained by the pattern that wealthier individuals reside in areas more concentrated with green space. There was a positive correlation with increased green space and improvement in health. Also, from equal exposure to green space, everyone benefited but the lowest income group benefited the most (see chart). These striking results based on an exceptionally large sample confirm unambiguously the health-related effects of green space and suggest its importance as an element in neighbourhood layouts. Not only would it reduce health disparities between incomes but it would also promote general health and well-being.
The basis for many urban open spaces seen today across Europe and the West began its process of development in London in the 17th and 18th centuries. What would eventually become urban open green space began as paved public plazas. Though they were intended to be open to the public, these spaces began to be re-designated as private parks around the late eighteenth century. It was during this period that the areas became pockets of green in the urban environment, commonly modelled after the natural wild of the countryside.
The first parks to reverse the trend of privatization and again be opened to the public were England’s royal parks in the nineteenth century. This was done in response to the extensive and unexpected population movement from the country into cities. As a result, "the need for open space was socially and politically pressing… The problems, to which the provision of parks was expected to offer some relief, were easy to describe: overcrowding, poverty, squalor, ill-health, lack of morals and morale, and so on". Such sentiments again received significant popular support during the "City Beautiful" movement in America during the 1890s and 1900s. Both trends focused on providing the public an opportunity to receive all of the perceived health and lifestyle benefits of having access to open space within urban environments.
Segmentation of urban open spaces was particularly prominent in America during the twentieth century. Since the late 1800s romantic park systems, open space designers have been concerned with guiding, containing or separating urban growth, distributing recreation, and/or producing scenic amenity, mostly within the framework of geometric abstractions." Such segmentation was especially prominent in the 1990s, when urban open spaces took a path similar to that of parks, following the modernization trend of segmentation and specialization of areas. As modernity stressed "increased efficiency, quantifiablity, predictability, and control… In concert with the additional social divisions" (Young 1995), open spaces grew more specific in purpose. Perhaps this increase in division of social classes’ use of open space, demonstrated by the segmentation of the spaces, displays a situation similar to the privatization of London parks in the eighteenth century, which displayed a desire to make classes more distinct.
Today, places like Scandinavia, which do not have a significant history of outdoor recreation and gathering places, are seeing a proliferation of urban open spaces and adopting a lifestyle supported by the extra urban breathing room. An example of this can be seen in Copenhagen where an area closed to car traffic in 1962 developed, in just a few decades, a culture of public political gatherings and outdoor cafes emerged. Not only is appreciation for and use of urban open spaces flourishing in locations that historically lacked such traditions, the number of urban open spaces is increasing rapidly as well.
Properties near urban open space tend to have a higher value. One study was able to demonstrate that, “a pleasant view can lead to a considerable increase in house price, particularly if the house overlooks water (8–10%) or open space (6–12%).” When it comes to proximity to the park edge, while there is a premium attached to apartments in close vicinity to the park, a negative premium is attached to this attribute for single-family houses, which may be due to the potential negative externalities that may surround parks, particularly in the evenings.
Urban open space is under strong pressure. Due to increasing urbanization, combined with a spatial planning policy of densification, more people face the prospect of living in less green residential environments, especially people from low economic strata. This may lead to environmental inequality with regard to the distribution of (access) to public green space. This is especially the case in California, leading to concern regarding open space accessibility in California.
One study, which compared public open spaces between high socioeconomic neighborhoods and low socioeconomic neighborhoods, found that urban open space in the highest socioeconomic neighborhoods had more amenities (e.g. picnic tables, drink fountains and toilets) than open spaces in lower socioeconomic neighborhoods. Urban open spaces in higher socioeconomic neighborhoods were more likely to have trees that provided shade, a water feature (e.g. pond, lake and creek), walking and cycling paths, lighting, signage regarding dog access and signage restricting other activities as well.