Planting a trillion trees will not cool the planet. Planting the right trees, in the right places, will — and in the wrong places, new tree cover can actually make things warmer.
That second half is the part the tree-planting pledges leave out. Trees are one of the most powerful cooling technologies on Earth, but "cooling" is not automatic and it is not everywhere. Whether a newly forested acre nets to cooling or warming depends on where it sits. Get this right and afforestation is a genuine climate tool; get it wrong and you spend money to warm a landscape while telling yourself you helped.
yes — trees really do cool, powerfully
Start with the good news, because it is real. A tree cools its surroundings two ways: it shades surfaces from direct sun, and it transpires, converting absorbed sunlight into water vapor instead of heat. That evaporative cooling is enormous — roughly 70 kilowatt-hours per 100 liters a tree moves, comparable to running two air conditioners. Street trees can drop nearby air temperature by a few degrees and surface temperature far more, and a mature canopy keeps soil moist and streams cold.
So where forests already stand — especially in the tropics — they are cooling machines, and cutting them is one of the fastest ways to heat a region. If the story ended there, "plant everywhere" would be right.
the catch: trees are dark, and dark absorbs heat
Here is the physics the pledges skip. A forest is darker than the snow, sand, or pale dry grass it often replaces. Darker surfaces reflect less sunlight — they have lower albedo — so they absorb more heat. Every forest therefore runs a tug-of-war between two effects:
| effect | direction | strongest where |
|---|---|---|
| evapotranspiration + shade | cooling | warm, wet, sunlit — the tropics |
| low albedo (dark canopy) | warming | cold/snowy or bright/dry — boreal, drylands |
Which side wins is set mostly by latitude and moisture:
| where you plant | what usually wins | net result |
|---|---|---|
| tropical | strong evapotranspiration | year-round cooling |
| mid-latitude | cooling in summer, warming in winter | mild net cooling |
| boreal / snow-covered | dark canopy over bright snow | often net warming |
| drylands / native grassland | albedo penalty, weak evapotranspiration | frequently net-negative for climate |
Researchers put the "latitude of zero net effect" — the line where a new forest flips from cooling to warming — somewhere around 30 to 56°N (Lawrence et al., 2022). Above it, in snow country, planting can backfire. And in drylands, a landmark Science study found the albedo penalty cancels roughly 70% of the carbon benefit of afforestation (Rohatyn et al., 2022) — before counting the water it costs or the native grassland it can wreck.
Planting a forest over snow can warm the climate even as it stores carbon. That single fact is why counting only carbon gets nature's cooling wrong.
this is exactly why a carbon-only lens misleads
A pure carbon-tonnage view says: trees store carbon, carbon is good, plant trees anywhere. It cannot see albedo, it cannot see evapotranspiration, and it cannot see place. So it will happily fund planting in the boreal and the desert — the two places the science says are most likely to warm or waste the effort.
A place-based, biophysical view — the one that asks "what will this actually do to temperature and water here?" — does not make that mistake. It is more honest precisely because it refuses to reduce a living system to a single number.
so what actually cools — a practical ranking
- Protect intact forest first. A standing tropical or temperate forest cools on every channel with no albedo gamble. Avoided deforestation is the highest-confidence cooling move there is — nothing you plant beats keeping what already works.
- Restore where it's climate-positive. Reforest degraded tropical and mid-latitude land, and use albedo-aware maps to steer planting toward locations that genuinely cool (Hasler et al., 2024).
- Don't afforest the wrong biomes. Skip snow-dominated high latitudes and native drylands/grasslands as "climate" planting — the albedo penalty, high tree mortality, and biodiversity harm make it a poor bet.
- Add non-forest cooling. Wetlands, riparian shade, functioning grasslands, and urban canopy all cool through water and shade without the boreal-albedo problem.
how the right planting gets funded — and kept honest
The reason bad planting keeps happening is that the money follows the carbon number, and the carbon number is blind to place. ensurance prices cooling as a real, place-specific asset and measures the outcome in temperature and water — land-surface temperature, evapotranspiration, canopy cover, stream temperature — not only in tonnes. That accounting funds protection first and steers restoration toward locations that actually cool, because a certificate tied to measured local cooling has no reason to reward a forest that warms its own valley.
For an investor or funder, that is the difference between buying a story and buying an outcome.
taking action
- See the funding model. Explore how cooling and other ecosystem outcomes are priced and funded at
ecosystem servicesandgeneral ensurance. - Fund a specific place. Directed, asset-level funding lives at
specific ensurance. - Start upstream. Read deforestation is how the planet loses its air-conditioning for the cooling case behind protection.
- Talk it through. For siting a real project honestly, reach us at
contact.