Can trees save the climate? Not with misleading maps, experts warn

New global maps reveal that realistic reforestation opportunities are 71-92% smaller than previously believed. By fixing data flaws and addressing social and environmental risks, scientists found just 195 million hectares are safely restorable.

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Reforestation has long been considered a major solution to climate change. Planting trees can absorb carbon dioxide, cool the planet, and restore damaged ecosystems. But a new international study published in Nature has revealed that most global maps showing where reforestation could happen are flawed, overly optimistic, or dangerously misleading.

Reforestation matters but maps have misled the world

These old maps have been used to set global goals like the “Trillion Trees” movement. But the new research, based on the most advanced data and local realities, shows that only 195 million hectares (Mha) of land are truly available for responsible and effective reforestation. That’s up to 92% less than previous global estimates.

How the new study corrected the past

A team of researchers reviewed 89 reforestation maps published between 2011 and 2022. They found that previous maps suffered from:

Loose definitions: Including grasslands, open woodlands, and savannas that shouldn't be covered with trees.

Poor data: Using low-resolution or outdated maps that ignored existing trees or local land use.

Lack of safeguards: Ignoring food security, land rights, biodiversity, and even situations where planting trees could worsen global warming (due to changes in land reflectivity or albedo).

To fix these issues, the researchers:

• Narrowed the definition of forest to areas that can support at least 60% tree cover.
• Removed areas where frequent fires, croplands, cities, wetlands, or peatlands exist.
• Used high-resolution global datasets and fire history to rule out unsuitable zones.

What’s really possible: 195 million hectares

After applying all corrections and safeguards, the researchers found that only 195 Mha of land can be reforested in a socially and environmentally responsible way. This could help remove 2,225 teragrams of CO₂ equivalent per year for 30 years, making it a powerful, but limited, climate tool.

This new area is a massive drop compared to previous estimates, which ranged up to 2,500 Mha. The downsizing is mostly due to removing croplands and ecologically important areas where reforestation could do more harm than good.

Not one map fits all: Real-world reforestation scenarios

The study presents different scenarios for reforestation, based on practical or ethical priorities:

Avoiding social conflicts: Focusing only on countries with land rights and strong governance

Avoiding regions where reforestation would hurt rural or indigenous livelihoods

Maximizing ecosystem services: Targeting areas with nearby forests to boost biodiversity

Reforesting slopes and floodplains for better water quality and climate resilience

Aligning with government policies: Restoring forests in protected zones

Prioritizing countries with official forest restoration commitments

But here’s the catch: Only 15 Mha of land meet 7 out of 8 of these conditions. A tiny 0.5 Mha meets all 8. This means there's no one-size-fits-all solution, local context matters more than ever.

Why this matters for global climate action

This study is a wake-up call for the world. Countries and NGOs can no longer rely on overly ambitious tree-planting targets without understanding local realities and trade-offs. Overestimating land availability could lead to deforestation elsewhere, harm to rural communities, or even policies that backfire.

Yet, all is not lost. The study shows that we can reforest vast areas safely and effectively, especially if efforts focus on zones with strong local governance, secure land rights, and minimal social disruption.

Key takeaway: Smarter, not just bigger, reforestation

The world still has room to grow forests and fight climate change, but the space is smaller and more complicated than we thought. Quality over quantity is now the motto. As one of the authors put it, “We must reforest the right places, for the right reasons, with the right people.”