Urban Park Design
Large, native vegetation green spaces like urban parks are critical to biodiversity because they provide habitats for many species, many of which are not suited to survival in typical urban settings. Reviews of park statistics across multiple countries conclude that park size is positively correlated with species richness., In addition to park area, park distribution is an important consideration because park isolation has an inverse relationship with species richness.
Terratopia’s city design draws from the following sample designs to strike a balance between large park size and even park distribution.
Parkscore is a nonprofit tool that rates cities based on the distribution of their parks, namely the amount of people within ten minute walking distance to a public access park. This metric is a suitable proxy for the guiding criteria of even distribution and minimized isolation. The top rated city on the tool is Minneapolis, MN. Therefore, this low isolation design best demonstrates optimal park distribution. The area of Minneapolis is 53.97 square miles, 15% of the city land is dedicated to parks and recreation, and the city contains 269 parks in total., This places the average size of each park at around .03 square miles. Incidentally, Minneapolis has a higher average park size than the other top five scoring cities, making it a model example for park area as well.
Beyond these high proximity parks, to make sure that a sufficiently large habitat is preserved, the city will maintain a one square mile central park in the city center. The feasibility of this is modeled after the existence of the much larger Central Park in New York City.
Cost of Park Maintenance
While there is a high variability in maintenance costs, averages across cities remain useful. According to a review of 40 municipalities in the Veneto, Italy (1997) park maintenance costs averaged 1.10 euros per square meter and varied between € 0.39 to 2.73 per square meter.
A separate study in 2002 reviewed 15 parks in the United Kingdom, reporting a variation between € 0.28 to € 1.34 per square meter. Finally a 2018 study of urban parks in São Paulo, Brazil reports maintenance costs of about $2.10 per square meter. By adjusting for inflation and currency differences, the resulting range of costs across these reviews is $0.40 to $5.08 per square meter per year.,
Connectivity is another crucial element to greenified city planning as it allows gene flow between larger greenspaces like natural parks, making urban animal populations more resilient. Connectivity can come in many forms, providing many opportunities for city specific planning.
Urban Tree Cover
Tree cover is a very versatile form of connectivity that has a large impact without requiring major structural change to the city layout. Most impactful to birds, high tree density throughout urban areas can bolster native bird populations by providing stopping points between more substantial green spaces.
A powerful sample design, the city of Tampa has the highest tree cover of the cities evaluated by the MIT tool Treepedia. With 21% of land area having right of way (publicly provided) tree cover, this design is within feasibility for Terratopia.
Cost of Tree Cover Projects
According to a 2018 study from the University of Massachusetts at Amherst, the cost of planting white and red oak trees with direct planting is $4.38/tree. According to another study, per-tree maintenance costs range from $0.17 to $6.84 in 2006, or $0.10 to $4.00 in 1999. Averaged and adjusted for inflation, these values result in a planting cost of $4.60/per tree and between $0.22-$8.98 per tree per year for maintenance in 2020.
Park Connecting Corridors
The West Loop Park Connector is a corridor that connects several parks in Singapore, allowing both pedestrian movement as well as animal movement due to the intentionally heavy vegetation density. Begun in 1995 and currently a work in progress, it will eventually become 300 kilometers in length. As of the 2021 budget, the projected total cost of the project is $154,613,000, which translates to a cost of around $515,400 per kilometer.
Roadside corridors take advantage of the existing need for human mobility to integrate animal mobility in the city network. Because roads are a major culprit of urban fragmentation, this transformation is particularly impactful. The guiding concept is a stretch of dense trees parallel to the road, so the cost is largely represented by the cost of trees.
Small Green Space Design
Smaller greenspaces such as green walls, native vegetation lawns, and green roofs provide stopping points along corridors, strengthening connectivity. They can also provide habitats for smaller taxa like arthropods, reptiles, and amphibians.
Additionally, there are many opportunities to implement small greenspaces in locations with government jurisdiction, making small greenspaces highly viable for smaller public projects.
Some green rooftop projects in Singapore attracted as many as 32 species of butterflies and 24 species of birds. Beyond their utility for biodiversity, these green roofs have been demonstrated to capture and re-use approximately 12% of the rain water run-off.
As a relatively new urban phenomenon, green roofs have highly variable prices, particularly between intensive and extensive styles. Between Illinois, Germany, Brazil, and Portugal, the prices range significantly from 21.59 euros per square meter (in 2003) to 185.9 euros per square meter (in 2016) for extensive roofs. The inflation and currency adjusted range is $33.94 per square meter to $221.72 per square meter.,
Green walls are another relatively new urban design. In Genoa, Italy, direct green facades can cost between 30 and 45 euros per square meter, an indirect green facade can cost between 26 and 215 euros per square meter, and a modular green wall can be 315 euros per square meter (all in 2013).
According to an analysis of green wall economic sustainability, extensive or indirect green walls are often more economically sustainable. The currency and inflation adjusted range of indirect facade wall installation is $45.18 per square meter to $67.77 per square meter.
The most common public jurisdiction buildings are public schools and universities, making them excellent candidates for small greenspace implementation. The Virginia Department of Education guidelines for public school facilities describes classroom space requirements which indicate that there will be at least one external wall of around 9 square meters and at least one segment of rooftop of around 37 square meters.
These designs represent the best of the greenification efforts of various cities. Put together as a unified, comprehensive plan for expanding cities, these projects can initiate an impactful shift toward urban biodiversity preservation. When applied to the urban expansion model of Las, Vegas, the feasibility of large scale implementation is revealed. Human development does not have to be unsustainable, but can be successfully integrated with the present wildlife. This is the aim of Terratopia.