urban green spaces come with many benefits, especially for children and elderly POPULATIONS in society.
Studies on urban green spaces have reached the same conclusion - it is crucial for the well-being of urban dwellers. A few of the benefits are listed below.
For children, growing up in cities is associated with a risk of psychiatric disorders in adulthood. Green spaces lower the risk. [Source]
For older adults and the elderly, green space visits has been consistently linked with a lower risk of cardiovascular disease, slower cognitive decline, slower decline in walking speed, lower mortality, better life satisfaction and less stress. [Source#1][Source#2]
For cities, green spaces have shown to reduce temperatures (preventing heat stress) and ground level ozone. Often, they serve as biodiversity hotspots, absorb air particulates, prevent soil erosion and buffer noise pollution.
As is well documented, green spaces imbue a sense of "ecological awareness" within concrete jungles, so that residents do not lose touch with nature (and hence are aware of their relationship with and impact on natural processes). Their aesthetic value, too, cannot be ignored.
So, how much space is required?
The amount of green space required in a particular city or area depends on factors such as population, population density, climate and others. One important metric is urban green space per capita, the total area of green space divided by population of that particular area (Gholami-Karzaei, 2003).
The WHO recommends 9 m² of safe, accessible and function green space for every person. [Source]
Countries across the EU follow different standards for UGS availability. [Source]
Majnounian (1995) has said that standard UGS per capita is between 15 to 50 m².
Reports by the Planning Committee of the Iranian Ministry of the Interior quote that per capita green space in a residential area should not be less than 30 to 50 m².
Standard United Nations Environment has determined a standard per capita of 20 to 25 m² for Iran.
Goel Cohen (1992) has stated that standard per capita green space is at least 10 to 15 m² due to each country's climate. Elsewhere, he has introduced this standard to be 20 percent of the urban area.
Due to the controversy surrounding the standard value, we chose 20 percent of the area as the standard for our tool. That is, areas with ratio of 0.2 and above are scored an 'A' irrespective of their location. We plan to refine this standard in future versions.
Space near people
Having sufficient green space area is not enough. A WHO report states "...urban residents should be able to access public green spaces of atleast 0.5 - 1 hectare (5000 - 10,000 m²) within 300 m linear distance (~5 min walking time) of their homes." To account for this, we introduced the Your Location version. As opposed to the City Address or Center version, this utilizes the user's coordinates to detect green space area within a selected "distance" (radius). The user's location becomes the central point. As a result, they will be able to estimate if they meet the recommendation stated above.