San Francisco, California
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Most maps tell you where the parks are. Few tell you whether a city’s nature is actually alive.
So we read San Francisco through three lenses — who lives here, what the street looks like, and how green space is used.
A measure of urban nature not by acreage, but by life: Implied Urban Nature Vitality.
Interactive Project · Urban Vitality & Environmental Justice
Most maps tell you where the parks are. Few tell you whether a city's nature is actually alive — seen, used, and felt by the people around it. This project proposes a measure for exactly that, read across San Francisco through three very different lenses.
The question
Conventional green-space studies map distribution in two dimensions — acres, polygons, buffers. But a vibrant tree-lined street and a fenced, empty lawn can look identical from above. Implied Urban Nature Vitality (IUNV) reframes urban nature as a human–urban–nature interaction: not merely where green exists, but how vital it is to the people who live with it.
Three lenses
Who lives here
Nine socio-economic variables from the ACS 2016–2020 (CDC Social Vulnerability Index): population, poverty, education, age, and ethnicity — summarized for every census tract.
What the street looks like
26,810 Google Street View images sampled every 10 m along the road network, segmented with the ADE20K model (~150 classes) into the share of trees, sky, buildings, and road.
How it's actually used
Geotagged Flickr photos of the city's green spaces (2013–2022), labelled by the Google Vision API and grouped by hierarchical clustering into recurring scenes.
The method
OSM road network & land use, Google Street View imagery, ACS census data, and Flickr photos.
GIS, computer-vision segmentation, and unsupervised hierarchical clustering of image labels.
Pearson correlation, multilevel OLS, Moran's I, and a spatial error model to find what moves IUNV.
12 vitality types
Hierarchical clustering of 3,434 cleaned Flickr photos surfaced twelve recurring kinds of urban-nature life — from waterfronts and leisure parks to cultural performances and sacred green spaces. Bars show how often each scene appeared.
Reading the map
Switch between Photos, Street view, and Census in the interactive map above to read the city three ways at once. Comparing the social-media scenes against the census layer reveals where social, environmental, and behavioural signals reinforce one another — and where access to vibrant urban nature falls short. Younger neighbourhoods such as South Beach and Mission Bay register higher IUNV, while lower educational attainment tracks with lower vitality.
What we found
Accessibility, land-use mix, road density, and population density were the dominant drivers of IUNV — the city's structure sets the stage.
Among visual features, trees and sculptures were the two most powerful — greenery and public art consistently lifted vitality.
More visible people, walls, and fences correlated negatively; open, sittable space (chairs) correlated positively.
Younger areas showed higher vitality; education and economic constraints emerged as limiting factors.
A near-zero Moran's I (−0.0136) means vitality doesn't cluster neatly by geography — it is stitched together block by block.
Why it matters
By isolating the levers that actually move vitality — canopy, public art, and accessible, sittable open space — the IUNV framework helps planners allocate green investment where it yields the most liveability and equity, rather than counting hectares alone.
Project
San Francisco Nature Vitality maps where residents, greenery, and everyday activity converge across the city. By combining census demographics, street-view greenery, and geotagged social-media activity, the project builds an implied measure of urban nature vitality — and surfaces where access to vibrant green space is unevenly distributed across neighbourhoods.
Team
A Nature AI Lab project.
Publication
Chen, M., Cai, Y., Guo, S., Sun, R., Song, Y., Shen, X. (2024). Evaluating implied urban nature vitality in San Francisco: An interdisciplinary approach combining census data, street view images, and social media analysis. Urban Forestry & Urban Greening.
Use & Credit
The visualizations on this page may be reused in any publication provided that:
For more information, mingze.chen@ubc.ca