Planting timber helps cool the planet, however not all areas ship the identical advantages.
New analysis reveals that tropical forests are the true local weather champions — pulling in carbon, releasing cooling water vapor, and even serving to to suppress fires. Whereas planting at increased latitudes can typically lure extra warmth than it prevents, tropical timber provide the strongest returns for each local weather stability and hearth resistance, making them nature’s best frontline defenders.
Tropical Planting Brings Largest Local weather Advantages
Planting extra timber can assist decrease world temperatures and scale back hearth threat, however the largest advantages come when they’re grown within the tropics, in keeping with new analysis from UC Riverside.
The examine, printed in npj Local weather and Atmospheric Science, confirms that planting timber is mostly good for the local weather as a result of they take away warming carbon dioxide from the air. But the native temperature results differ vastly relying on the place the timber are planted. In increased latitudes, forests can typically create a slight warming impact, whereas in tropical areas they have an inclination to offer stronger cooling.
Why Tropics Are the Candy Spot for Tree Progress
“Our examine discovered extra cooling from planting in heat, moist areas, the place timber develop year-round. Tropical timber not solely pull carbon dioxide from the air, in addition they cool whereas releasing water vapor,” stated examine first writer and UCR graduate pupil James Gomez. “It’s not that planting elsewhere doesn’t assist – it does – however the tropics provide the strongest returns per tree.”
These outcomes align with an earlier UCR investigation suggesting that tree planting may cool Earth’s floor greater than scientists as soon as thought. That earlier work targeted on the chemical methods timber work together with the environment, whereas the brand new examine highlights the bodily processes that contribute to cooling.
The Cooling Energy of Tree ‘Sweating’
These results embody “tree sweating,” or evapotranspiration. Tree roots pull water from the soil, which then travels up by means of the trunk and into the leaves. When pores within the leaves open up so the tree can soak up carbon dioxide for photosynthesis, some of the water in the leaves evaporates into the air. This process cools the air on Earth’s surface and cools the tree, too.
“It’s just like the way sweating cools your body,” Gomez said. “In the tropics, there is constantly water available for trees, and that increases transpiration.”
Clouds, Humidity, and Sunlight Blocking
Trees can also reduce the amount of sunlight that reaches the planet’s surface. As they give off water vapor, the air can become more humid. More humidity can mean more clouds, and water vapor itself can soak up some sun. Both of these effects reduce the amount of sun that reaches the ground, giving a cooling effect.
The physical effects of the added trees yield weak global mean cooling of 0.01° F, although this cooling does become significant in the tropics at about 0.1° F, with some tropical regions like central Africa experiencing cooling up to 0.8° F.
Carbon Storage Adds Even More Cooling
Accounting for the carbon sequestration of the added trees is expected to amplify these cooling effects by about 0.15° F globally. The researchers note that better estimates of the carbon sequestration effects will be explored in a future study, where both the physical and carbon cycle effects of establishing new forests are interactively simulated.
“Though the non-CO2 effects are small, it is good news that they are not warming, which prior studies have indicated is likely,” Gomez said.
A Realistic Scenario for Global Tree Planting
For this study, the researchers also used a relatively realistic scenario, planting trees in places where they have been removed, avoiding deforestation, and limiting new trees to places where they would not displace people or too much agricultural land. In addition, the experiment used data from 12 climate models commonly used for international policy analysis, so the results would be more reliable than relying on a single model.
The researchers also found that, in some cases, trees can have a fire suppression effect. “In tropical savannahs, and in other places around the world, trees are much more fire resistant than grasses,” Gomez said.
However, the study found that in parts of Canada and the northeastern U.S., trees would likely cause more fires and reduce cooling by absorbing too much sun.
Finding the Goldilocks Zone for Forests
“This is not an invitation to get rid of the trees growing there! They provide multiple benefits for ecosystems and diversity, reducing CO2 and cooling the surrounding areas,” Gomez said.
“What we need is a Goldilocks zone of trees in each region. Just the right amount to have the strongest and most positive climate effects.”
Reference: “Climate effects of a future net forestation scenario in CMIP6 models” by James L. Gomez, Robert J. Allen, Larry W. Horowitz, Steven T. Turnock, Rosie A. Fisher, Olivia E. Clifton, Bryan K. Mignone, Elena Shevliakova and Sergey Malyshev, 8 August 2025, npj Climate and Atmospheric Science.
DOI: 10.1038/s41612-025-01127-4
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