U.S. forests have sequestered more carbon over the past two decades than at any other period in the last century, according to a new study published on January 20, 2026, in the Proceedings of the National Academy of Sciences. The research, led by Brent Sohngen of Ohio State University, examines how both natural environmental changes and human activities influence forest carbon storage across the United States.
The study analyzed six primary drivers of forest carbon sequestration: temperature, precipitation, atmospheric carbon dioxide levels, forest management practices, forest age composition, and total forest area. Natural factors such as rising temperatures and changing precipitation patterns played a significant role, contributing an estimated 66 million metric tons of additional carbon storage per year between 2005 and 2022.
Human activity showed mixed results. Deforestation reduced forest carbon storage by roughly 31 million metric tons annually, while reforestation and tree planting added approximately 23 million metric tons per year. The largest contributor, however, was forest age structure. The expansion of older, mature forests accounted for about 89 million metric tons of carbon locked in each year, making it the most significant single factor identified in the study.
Forests and Their Role in Climate Mitigation
Forests are widely recognized as critical carbon sinks that absorb carbon dioxide from the atmosphere and help slow climate change. Large tropical forests such as those in the Amazon and Congo Basin function primarily as passive carbon sinks, meaning they absorb substantial amounts of carbon without extensive human intervention.
In contrast, temperate forests in the United States often require active management to maintain and enhance their carbon sequestration potential. Practices such as conservation, reforestation, and sustainable forest management play an important role in ensuring these ecosystems continue to absorb more carbon than they release.
Scientists also warn that forest carbon sinks may not remain reliable indefinitely. Increasing wildfires, droughts, and land use pressures have weakened forest carbon uptake in many regions worldwide. These climate-driven disturbances raise concerns about whether forests can continue offsetting a meaningful share of global carbon emissions in the future.
Policy Implications and Carbon Accounting
The findings highlight the importance of improving the measurement and reporting of forest carbon. Distinguishing between carbon gains driven by natural processes and those resulting from human intervention is critical for accurate national carbon accounting and effective climate policy.
Researchers emphasize that while natural factors are currently boosting forest carbon storage, relying on these trends alone would be risky. Long term climate strategies will require sustained forest protection, responsible land management, and policies that support both carbon sequestration and ecosystem resilience.
As governments pursue net-zero emission targets, understanding the true role of forests in locking in carbon emissions will be essential. This study offers a clearer framework for integrating forest carbon dynamics into broader climate and decarbonization efforts.
