Philadelphia's missing shade
The city lost 5.9% of its tree canopy between 2008 and 2018. The neighborhoods that lost the most green are the same ones with the highest heat-vulnerability scores — and the lowest median incomes. A scroll through the compounding geography of heat, trees, and who bears both.
🌳 Beat 1 of 5 · tree canopy
Every tree counted
Philadelphia's 2018 tree inventory covered roughly 2700 hex cells across the city. The deepest green on the map clusters in the Northeast, Chestnut Hill, and the Wissahickon valley. The grey voids — barely any canopy at all — are concentrated in North and West Philadelphia.
Each hex covers roughly the same area of city. The difference in coverage isn't distance from the park system — it's decades of planting decisions, property vacancy, and disinvestment that accumulate block by block.
📉 Beat 2 of 5 · canopy change
A decade of loss
Between 2008 and 2018, Philadelphia lost a net 5.9% of its tree canopy. That's 21.3 million square feet gone — against only 13.7 million square feet gained. The map has flipped: what was green is now shown in brick, and the losses aren't scattered randomly.
Kensington, North Philly, parts of West Philadelphia — the same grid squares that appear in overdose maps, code-violation maps, abandoned-property maps. Trees don't survive when buildings are demolished and lots stay vacant. They also don't get replanted there at the same rate as elsewhere.
🌡️ Beat 3 of 5 · heat vulnerability
When green disappears, heat arrives
The map just changed from hex tree cells to census tract boundaries — but notice how little the geography changed. The tracts scoring highest on Philadelphia's Heat Vulnerability Index are the same places that just showed up dark red on the canopy-loss map.
The HVI is a composite score combining heat exposure (urban heat island intensity, impervious surface) and heat sensitivity (age, poverty, housing type, AC access). Of Philadelphia's 384 census tracts, 40% score in the top 40% of heat vulnerability. Almost none of them are the tracts that still have deep canopy.
💵 Beat 4 of 5 · income context
Who pays the price
The Pearson correlation between tract-level median household income and HVI score is 0.00. A correlation of −1.0 would mean every dollar of income perfectly predicts lower heat risk. At 0.00 it's not perfect — but it's close enough that the scatterplot below looks almost like a straight line.
Each dot = one Philadelphia census tract
0 Philadelphia census tracts sit in the upper-right quadrant: high heat vulnerability and household income below the city median of $59k. These aren't two separate problems. They're one geography, layered.
📍 Beat 5 of 5 · north philadelphia
Where it compounds
The map has flown to North Philadelphia. The deep orange-red cluster anchored around Kensington, Strawberry Mansion, and Hunting Park is where all three signals converge: least canopy, most canopy lost since 2008, highest heat vulnerability scores.
| Tract | Heat score | Median income |
|---|
A heat score of +8 is eight standard deviations above the city average. These aren't modestly elevated tracts — they're outliers, in the statistical sense and in what that means for the people who live there during a heat event. Philadelphia's Department of Public Health identifies heat as the leading cause of weather-related death in the city. The tracts on this table are where that risk concentrates.
📊 Data: top heat-vulnerable tracts (screen reader / fallback)
| Tract | HVI score (σ) | Median income |
|---|