Atmospheric Chemistry Unlocks Hidden Climate Benefits of Global Forest Restoration

Efforts to restore forests have long been promoted as a nature-based solution to climate change. The conventional understanding is simple: trees absorb carbon dioxide, lock it into biomass, and help offset greenhouse gas emissions. Yet, a new study published in Communications Earth & Environment reveals that this is only part of the story. The atmosphere itself — through complex chemical reactions triggered by forest emissions — may significantly enhance the climate benefits of tree restoration.

Researchers Robert J. Allen, Yu-Chi Lee, and Antony Thomas (2025) show that when atmospheric chemistry is accounted for, the climate cooling potential of global reforestation becomes stronger than previously estimated. This insight could reshape the way policymakers and climate initiatives design restoration strategies, moving beyond a narrow focus on carbon storage.

Why Trees Do More Than Store Carbon

The scientific and policy debate around tree planting often centers on carbon sequestration. But forests also influence climate through several other pathways:

• Albedo effects: Replacing bright surfaces (such as snow or grasslands) with darker tree canopies can reduce reflectivity, trapping more heat.
• Evapotranspiration: Trees release water vapor, influencing local cooling and precipitation patterns.
• Biogenic volatile organic compounds (BVOCs): Forests emit a range of gases — sometimes described as the "perfume of trees" — which interact with other atmospheric chemicals.

It is this last element, the role of BVOCs, that Allen and colleagues place at the center of their study. Their findings suggest that ignoring these interactions risks underestimating the full climate potential of forest restoration.

Modeling Forests and the Atmosphere Together

The team conducted advanced coupled simulations, integrating climate models with detailed atmospheric chemistry modules. They compared two scenarios:

1. Without chemistry: Restoration effects limited to carbon storage, albedo changes, and evapotranspiration.
2. With chemistry: Restoration also includes BVOC emissions and their transformation into ozone and aerosols.

The scenarios simulated ambitious large-scale restoration projects, akin to proposals aiming to return global forest cover toward preindustrial levels.

The analysis tracked global surface temperature, radiation fluxes, oxidant concentrations, tropospheric ozone, and secondary organic aerosols. By contrasting these variables, the study was able to isolate the additional contribution of chemistry-driven processes to global cooling.

Key Findings: Invisible Chemistry, Tangible Cooling

The study reveals three critical mechanisms through which forests cool the planet beyond carbon uptake:

1. Secondary Aerosols Formation: When BVOCs react with oxidants, they form tiny airborne particles. These scatter sunlight, producing a "natural parasol" effect.
2. Reduction of Tropospheric Ozone: Ozone at ground level is both a pollutant and a greenhouse gas. Forest chemistry helps lower its concentration, yielding climate and health benefits.
3. Regional Balances: While high-latitude restoration can cause warming due to albedo loss, tropical restoration benefits are amplified by atmospheric chemistry, reinforcing carbon storage gains.

Quantitatively, media coverage of the study highlighted that global-scale restoration could reduce global mean temperature by several tenths of a degree Celsius — with cited figures around 0.34 °C in comparable scenarios. While modest compared to fossil fuel reductions, this effect is still meaningful for meeting climate targets.

"Atmospheric chemistry enhances the mitigation potential of restoration beyond what carbon storage alone suggests," the authors note, underscoring the importance of moving past simplified models.

Implications for Climate Policy and Practice

These results carry direct implications for governments, NGOs, and global restoration programs:

• Smarter climate accounting: Carbon offset markets and national restoration pledges must integrate atmospheric chemistry into their climate benefit assessments.
• Tropical priority: Regions like the Amazon, Congo Basin, and Southeast Asia offer compounded benefits — high carbon uptake plus strong chemical cooling effects.
• Biodiversity matters: Not all trees emit the same BVOCs. Species choice influences atmospheric chemistry, making diverse, native forests a better climate strategy than monocultures.
• Limits in high latitudes: In northern regions, albedo-related warming can outweigh benefits, suggesting restoration should be carefully balanced with local climate realities.

Conclusion: Forests as Atmospheric Engineers

The study by Allen, Lee, and Thomas (2025) broadens the scientific lens on restoration. Forests are not passive carbon sinks — they are active chemical players in the climate system. By shaping the air we breathe, they indirectly shape the climate we live in.

For policymakers, the message is clear: tree restoration is more powerful when atmospheric chemistry is included in the equation. But this must go hand in hand with biodiversity protection, ecological integrity, and — most importantly — the urgent reduction of fossil fuel emissions.

Call to action: Tree planting campaigns and climate policies should evolve beyond counting carbon. Incorporating atmospheric chemistry into restoration planning can unlock hidden climate benefits and ensure that restoration delivers its full potential.

Topics of interest

Climate

Reference: Allen RJ, Lee YC, Thomas A. Atmospheric chemistry enhances the climate mitigation potential of tree restoration. Commun Earth Environ [Internet]. 2025 May 13;6(1) Article 2343. Available on: https://doi.org/10.1038/s43247-025-02343-9