Trees alone won't save us: New study says forestation has less potential to fix the climate

Planting trees is seen as a cornerstone of efforts to avert climate breakdown. But a major new study in Science finds their potential has been drastically overstated and relying on forests to offset carbon emissions could distract from the urgent need to cut fossil fuel use.

- HEIKO BALZTER

The researchers, a team of scientists mostly based in China, looked at both afforestation (creating new forests) and reforestation (restoring cleared ones). Unlike earlier studies, they carefully limited the land assumed to be available to avoid unintended consequences.

For instance, planting trees in snowy regions darkens the surface, since trees are darker than snow. This reduces reflectivity and can actually lead to further warming. Forests can also compete with grassland for water or threaten biodiversity.

Previous studies varied hugely in the area of land that they thought was suitable for planting trees, ranging from 200 million to 2,000 million hectares. Once those unsuitable areas are removed, the new study calculates just 389 million hectares worldwide were left suitable for forestation.