An integral part of the success of our urban systems in cities is predicated on the placement and arrangement of our zoning and land use. In particular land-use diversity can help to promote sustainable development by allowing citizens close proximity to where they can work, shop and live as well as giving them the infrastructure to connect to the wider city. But how diverse is Toronto’s Land use and how does this effect our daily lives. In this blog I will use Shannon’s Index and Moran’s I to evaluate Toronto’s land use diversity using Toronto’s Zoning By-Law data taken from Toronto’s Open Data Catalogue.
Shannon’s Diversity Index
A Shannon’s Index is a quantitative measure that reflects the variation of types in a community while also looking at how evenly these types are distributed. This is commonly used in ecology to evaluate the diversity of species such as trees within a certain area, but can also be used for text strings and in this case land-use type. The equation of Shannon Index is as follows: pi the proportion of the individual in the community is multiplied by the log of pi which is them summed with the other proportions of species in that community and then multiplied by negative 1 to produce a Shannon Index value. The higher the number the more diverse the community where equal diversity of all species produces a value of ln(R). Conversely, the lower the value the less diverse with only one type in the community equating to a value of zero.
Instead of looking at the proportion of species in a community Shannon’s Index will be used to look at the proportion of each land use type within a community by using the total area of each land use type divided by the total community area to calculate pi, which can then be used to give a Shannon Index Value for different areas of the city.
Procedure
Above is a map of Toronto’s Zoning By-law categorized by land-use type. In order to look at the diversity of different areas across Toronto I overlaid a two square kilometer hexagon grid across the city which was clipped by Toronto’s municipal boarder so that no empty space factored into the proportion along communities bordering the city. After the grid was overlaid I used the Tabulate Intersection tool to find the proportion of each land-use type per hexagon in that area. Finally the table was converted to an excel spreadsheet to complete the Shannon Index calculations for each area before being spatially joined back into the hexagon grid to display areas of low and high zoning diversity.
Results of Shannon’s Index and Moran’s I
When Shannon’s Index was used to calculate the diversity of Zoning land-use throughout Toronto it showed many hot spots across the city of both low (dark blue) and high zoning diversity (red). The first and most notable area of high diversity can be seen on the lower east side of Toronto around the Beaches and East York area. Shannon Index values in this area ranged from 1.31 to 1.79 indicating high diversity mainly due to the areas mix of low and high density residential, industrial employment, green space as well as small pockets of commercial spaces in the Beaches area. Other areas of high zoning diversity in Toronto were centered around Toronto’s regional shopping centers of: Sherway Gardens, Yorkdale, and Scarborough Town Center due to these areas mix of Industrial, Commercial and Residential zoning along with Utility and Transportation land use due to the regional highway network.
Along with areas of high zoning diversity Shannon’s Index also revealed areas of low zoning diversity throughout Toronto. Disregarding Rouge National Park and The Waterfront which was classified as undefined the most notable area of low diversity land use was in an area just west of Yonge Street continuing down south of Allen Road. In this area Shannon Index values ranged from 0.00 to 0.67 indicating very low zoning diversity due to large areas mainly comprised of low density residential housing. Two other areas in Toronto that also had low Shannon Index values were Pearson Airport zoned almost exclusively and Industrial Employment and low density residential communities surrounding the downtown core mainly on the east side of downtown such as: St. James Town, Regent Park, Corktown, and Cabbage Town South created during the small urban renewal movement of the late 1960s in Toronto which was centered around large housing complexes and separation of land uses.
Along with using Shannon’s Index to calculate zoning diversity Moran’s I was also used to calculate the spatial auto correlation of the Shannon Index values to determine if these areas are dispersed or clustered throughout Toronto. When compared to an expected index of -0.002 a value of 0.381 indicated significant clustering of low and high zoning diversity areas throughout the city. Moreover, when testing for statistical significance a z-score of 12.38 coupled with a p-value of 0.00 indicates a less the 1% chance that this the result of a random spatial process. As a result the significant clustering of these high and low diversity areas has made Toronto more auto-dependent in suburban areas as citizen in lower diversity areas have to travel further distances in order to complete daily tasks such as travel to and from work especially with a lack of high-quality public transportation connecting these areas. In addition travel to large single-use employment areas like Pearson Airport can compound this problem of auto-dependency as most of these areas are only accessible by car.
Conclusion
In conclusion, while the use of Shannon’s Index to identify zoning diversity throughout the city showed that Toronto is more diverse and mixed use in its allocation of land use zoning than a typical sprawling city such as Chicago and Atlanta. However, the significant clustering of these high and low diversity areas coupled with a lack of public transportation has made Toronto just as auto-dependent.
References
City of Toronto Open Data Catalogue. (2014). Zoning By-Law (WGS84) [Data set]. Retrieved from:
Alex tabascio GIS 