Where We Plant Trees Matters as Much as Planting Them in the Fight Against Global Warming

We know that planting trees and increasing green spaces are beneficial in combating climate change, but a new study has shown that where we plant trees is just as important as planting them. According to the research published in the journal Nature Communications, in some cases, planting too many trees in an area can lead to the Earth absorbing more heat due to less sunlight being reflected from the Earth's surface.
While some scientists have discovered that restoring forest cover could lead to changes in albedo (the amount of solar radiation reflected from the planet's surface), experts have only recently been able to identify this particular phenomenon.

Simply put, albedo refers to the ability of a surface to reflect sunlight. Light-colored surfaces reflect a large portion of the light back into the atmosphere, indicating they have a high albedo. Forested areas tend to be darker compared to other surfaces, meaning they absorb more sunlight, retain heat, and have a lower albedo. Therefore, some experts argue that forests can trap unwanted heat and thereby contribute to global warming.
The authors of the study used new maps to investigate the cooling effect of trees and the warming caused by decreased albedo. They found that many previous studies on afforestation failed to account for albedo. As a result, the research concluded that additional tree planting could provide climate benefits ranging from 20% to 80%.

Scientists emphasize the need to consider not only the benefits of trees in carbon storage but also the albedo effect of forests. However, despite the drawbacks of albedo, the research team reminds us that more trees mean better ecosystems, increased clean air, and water levels. Additionally, the maps they used offer hope for the future of reforestation by helping to determine where trees should be planted for maximum positive impact on the climate.

Reference: Hasler, N., Williams, C.A., Denney, V.C. et al. Accounting for albedo change to identify climate-positive tree cover restoration. Nat Commun 15, 2275 (2024).