Where should the next 40 trees go?
CoolBlock turns a heat grant into a plan a city can defend: which public sites get trees, what each one costs, and who it cools. Built on real public data for Edison–Eastlake, Phoenix.
This is the heat
Summer afternoon surface temperature across the neighborhood, measured by 63 Landsat passes and sharpened to 10-metre detail by a model.
A city can plant in 773 places
Every public street edge, park and lot with room for a tree. Found by mapping 2,844 buildings, the roads and the parking lots, and keeping the open ground that’s left.
$20,000 plants 46 trees at these 4 sites
Placed where each dollar of shade reaches the most people at risk from heat: older and very young residents, renters, people without a car, and people with asthma or heart disease. Total cost $19,925.
Same money, five ways to spend it
Cities already pick tree sites somehow. We ran the common ways against CoolBlock on the same budget and the same public sites, and measured how much cooling reaches the people who need it.
3.4×the cooling of the next-best way, at $20,000
- CoolBlockMost cooling per dollar for the people most at risk
- Tree Equity Score rankingPlant in the blocks with the lowest score first
- Squeaky wheelRequests weighted toward higher-income blocks
- Split evenlyThe same dollars for every census block group
- Hottest spots firstRank sites by surface temperature alone
Cooling is counted in person-degree-hours: the modeled temperature drop at each home, times the people living there and the hours they spend exposed to heat, weighted toward those most at risk. Every strategy spends the same budget on the same public-land tree sites. The lead is smallest at $50,000 (1.4×) and largest at $20,000 (3.4×).
View as table
| Strategy | $20,000 | $50,000 | $100,000 |
|---|---|---|---|
| CoolBlock | 4,057 | 11,775 | 18,179 |
| Tree Equity Score ranking | 1,182 | 8,182 | 7,220 |
| Squeaky wheel | 0 | 6,719 | 6,762 |
| Split evenly | 67 | 275 | 807 |
| Hottest spots first | 44 | 46 | 46 |
How it decides
- 2,844buildings mapped, with every road and parking lot
- 1,450places with room for a tree
- 773of them on public land a city can plant
- 6heat-risk factors weigh who each tree would cool
- 46 treesat 4 sites for $19,925
The cooling each tree would give is calibrated on this neighborhood’s own temperature readings, not borrowed from a national average. Then a solver picks the set of sites that cools the most at-risk people for the money — and for a plan this size it proves, in about two seconds, that no other set of sites does better.
What it can’t tell you
- It ranks places; it doesn’t forecast degrees. The heat model passed 2 of its 3 validation checks, so treat its numbers as priorities, not promises.
- Trees are only compared with trees. A cool roof lowers the temperature of the roof; a tree cools the air around people. Those aren’t the same measurement, so the app never ranks one against the other.
- One neighborhood so far. Everything here is Edison–Eastlake, Phoenix.
- Not modeled yet: which species to plant, how much water they need, and how wind moves cool air down a street.
What it stands on
- The tree cover and temperature disparity in US urbanized areas: quantifying the association with income across 5,723 communitiesPLOS ONE
- Trees halve urban heat island effect globally but unequal benefits only modestly mitigate climate-change warmingNature Communications
- Increasing tree canopy lowers urban air temperature by up to 1.5 °C in heat-prone areasnpj Urban Sustainability
- Street trees provide an opportunity to mitigate urban heat and reduce risk of high heat exposureScientific Reports
- Urban Heat EquityAmerican Forests, Tree Equity Score