Establishing forests can capture carbon and boost biodiversity — but some biomes are a better bet than others, a recent study about afforestation and reforestation finds. Forest restoration has emerged as a top nature-based solution to mitigate climate change, with numerous high-profile initiatives launched over the past few decades. And while there’s enthusiasm for replanting degraded forest areas, or reforestation, there’s also a growing unease that establishing forests in ecosystems that historically had little of them, or afforestation, could harm biodiversity, demonstrating the importance of intentional, well-researched efforts.

The question about is, how can we pinpoint the best places for afforestation and reforestation, on a global scale? A number of studies have tackled this challenge. For example, a 2025 Nature Communications study found that 195 million hectares (482 million acres) of land is suitable for reforestation when climate goals, nature, and people were taken into account by afforestation and reforestation efforts. Though this represents an area the size of Mexico, it’s far smaller than previous estimates.

Now, a recent study in Environmental Research Letters describes a different way of gauging the potential of afforestation and reforestation across 13 biomes. The study finds that overall, many areas within the tropical and subtropical moist broadleaf forest biome offer the highest compatibility with biodiversity conservation and carbon sequestration goals. However, there’s significant variation between areas, even within the same biome. In contrast, the study finds that all grasslands, shrublands and savanna biomes are poorly suited to afforestation and reforestation.

Areas with high carbon sequestration potential are attractive for climate change mitigation projects involving afforestation and reforestation, but could be risky for biodiversity, says Pavithra Rangani Wijenayake, a research associate at the National Institute for Environmental Studies in Japan and the study’s first author.

“[W]e need to detect these kinds of locations, especially on this global scale, to avoid massive plantation projects,” Wijenayake says.

For their study, the researchers define afforestation as the establishment of trees in areas that were unforested for at least 30 years, while reforestation refers to the establishing trees on more recently cleared or degraded forested land. The analysis also assumed native species were used in afforestation and reforestation, something that isn’t always the case on the ground.

Read the full article about afforestation and reforestation by Ruth Kamnitzer at Mongabay.