The age of the world’s forests plays a critical and complex role in regulating the global carbon cycle and, by extension, Earth’s climate system. While young forests are known for their rapid growth rates and ability to absorb atmospheric carbon dioxide (CO₂), they are fundamentally different from mature forests in their capacity to store carbon over the long term. In groundbreaking research recently published in Nature Ecology & Evolution, an international team of scientists has quantified how the global distribution of forest ages is shifting, and what these shifts mean for the net carbon balance of terrestrial ecosystems.
Mature forests, often referred to as old-growth stands, accumulate vast amounts of biomass carbon over centuries, acting as important carbon reservoirs that stabilize atmospheric CO₂ concentrations. Conversely, young and regenerating forests, while dynamic carbon sinks due to their rapid growth and photosynthetic activity, store comparatively less carbon at any given moment. This distinction is critical, particularly as global forest landscapes are continuously disturbed by natural events such as wildfires, storms, and insect outbreaks, as well as by human activities including logging and land-use change.
The new study, led by Dr. Simon Besnard of the GFZ Helmholtz Centre for Geosciences in Germany, has harnessed cutting-edge remote sensing technologies combined with field inventory data to build the Global Age Map of Forests v2.0 (GAMI v2.0). This high-resolution, global dataset charts forest age distributions with unprecedented accuracy and spatial detail. By integrating GAMI v2.0 with satellite-derived carbon stock assessments and atmospheric CO₂ measurements, the research team has developed a comprehensive understanding of how changes in forest age influence carbon storage at both regional and global scales.
By conducting a detailed analysis of forest age transitions between 2010 and 2020, the researchers identified distinct geographic patterns of forest ageing and disturbance. Regions including Europe, parts of North America, and China are predominantly experiencing forest ageing, indicative of forests that are maturing and potentially increasing their carbon storage capacity. In stark contrast, vast stretches of tropical forests and Siberian boreal woodlands are undergoing widespread rejuvenation due to disturbances, leading to net decreases in carbon stocks from biomass.
This research reveals a troubling global trend: the ongoing replacement of mature forests with younger stands is contributing to a net annual loss of approximately 140 million tonnes of carbon from aboveground biomass alone. Such carbon losses exacerbate the challenge of mitigating climate change by releasing sequestered carbon back into the atmosphere. While young forests provide invaluable climate benefits through carbon uptake during regrowth, these benefits cannot fully compensate for the long-term carbon storage capacity lost when mature forests are disturbed or destroyed.
The implications of these findings extend beyond simple carbon accounting. Forest age structure influences not only carbon dynamics but also biodiversity, ecosystem resilience, and hydrological cycles. Mature forests support unique species assemblages and complex ecological interactions that cannot be easily restored in younger stands. The gradual shift toward younger forest age classes could, therefore, have cascading effects on ecosystem services critical to sustaining human societies.
Dr. Besnard and colleagues underscore the importance of nuanced forest management strategies that balance protection and regrowth. Protecting old-growth forests is imperative to preserving existing carbon reservoirs and maintaining ecological integrity. Concurrently, managing younger forests to optimize their carbon sequestration potential through careful silviculture can maximize climate benefits during regrowth phases. Achieving this balance necessitates integrating local disturbance histories, forest age structures, and landscape-scale carbon dynamics into policy and land management decisions.
Technologically, this study exemplifies the power of combining multiple data streams—including satellite imagery, forest inventory data, and atmospheric CO₂ observations—to enhance our understanding of terrestrial carbon fluxes. Earth observation platforms such as NASA’s GEDI and ESA’s Sentinel satellites have revolutionized forest monitoring by providing detailed three-dimensional structural data and enabling near-real-time assessments of forest disturbance and recovery. The application of machine learning algorithms in parsing these complex datasets further refines estimates of forest age and biomass, enabling policy-relevant insights at global scales.
This research also aligns with global climate goals, such as those articulated in the Paris Agreement, by informing accurate carbon accounting and identifying key forest regions where conservation and restoration efforts can yield the highest climate mitigation returns. Understanding the spatial patterns of forest age transitions allows stakeholders to target interventions that simultaneously enhance carbon sequestration, biodiversity conservation, and sustainable land use.
Overall, this study shifts the paradigm from viewing forests solely as ambivalent carbon sinks or sources toward appreciating the nuanced roles forest age dynamics play in the terrestrial carbon cycle. It highlights the urgent need for holistic forest conservation strategies that acknowledge temporal changes in forest structure and composition to sustain and enhance their vital role in climate regulation.
As natural and anthropogenic disturbances continue to sculpt forest landscapes globally, continuous monitoring and adaptive management become paramount. The integration of emerging technologies and data-driven models, as demonstrated by the GAMI v2.0 dataset and corresponding analyses, will be essential tools in navigating the challenges ahead. By leveraging such insights, the global community can better safeguard the planet’s forests — the lungs of the Earth — to mitigate climate change and preserve ecological heritage for future generations.
Subject of Research: Not applicable
Article Title: Global covariation of forest age transitions with the net carbon balance
News Publication Date: 19-Aug-2025
Web References: https://doi.org/10.1038/s41559-025-02821-5
References: Besnard, S., Heinrich, V.H.A., Carvalhais, N. et al. Global covariation of forest age transitions with the net carbon balance. Nature Ecology & Evolution (2025).
Image Credits: CC BY 4.0 Besnard et al. (2021); Mapping global forest age from forest inventories, biomass and climate data, Earth Syst. Sci. Data, 13, 4881–4896
Keywords: Earth sciences, Climatology, Earth systems science, Earth climate, Environmental monitoring
