Recently, the research team led by Prof. DU Yun at the Innovation Academy for Precision Measurement Science and Technology (APM), in collaboration with the GFZ Helmholtz Centre for Geosciences, the Joint Research Centre, Lancaster University, and other institutions, developed region-specific forest regeneration carbon accumulation models by integrating pantropical moist forest change products with LiDAR-derived biomass footprint data. These models incorporated climatic and environmental conditions to quantify carbon sequestration from different types of natural forest regeneration, as well as carbon emissions from deforestation and forest degradation across the moist tropics over the past four decades. The study revealed that previously overlooked natural forest expansion represents a larger carbon sink than secondary forests, underscoring its important role in mitigating global climate change. The findings were recently published in Nature Geoscience.

Understanding the carbon dynamics associated with forest disturbance and recovery has become a frontier topic in global change research. Tropical moist forests, which are widely distributed across the tropics, play essential roles in maintaining biodiversity, regulating the terrestrial carbon cycle, and mitigating climate change. However, over recent decades, extensive deforestation driven by human activities, together with increasing forest degradation caused by fires, extreme droughts, and selective logging, has turned tropical forests into one of the major global sources of carbon emissions. Natural forest regeneration is regarded as one of the most cost-effective nature-based solutions for removing atmospheric carbon dioxide. It mainly includes three recovery pathways: secondary forests, degraded forests, and forest expansion. Previous studies have shown that the regrowth of secondary and degraded forests provides substantial carbon sinks that can partially offset carbon emissions from disturbances in primary tropical forests. Nevertheless, although existing datasets suggest that the area of natural forest expansion in moist tropical regions slightly exceeds that of secondary forests, its carbon sink capacity has not yet been quantified, creating considerable uncertainty in assessing the contribution of tropical forest regeneration to climate change mitigation.

Modelled region-specific AGC accumulation for naturally regenerating forests. Climatic Regions I and II for the tropical Americas (a), Africa (d) and Asia (g). Modelled AGC accumulation curves for natural forest expansion (b, c), secondary forest (e, f) and degraded forest (h, i) in Region I and II across the three tropical regions

To address this knowledge gap, the research team integrated the Joint Research Centre Tropical Moist Forest (JRC TMF) change product with NASA GEDI LiDAR biomass footprint data to derive fine-resolution spatial distributions of forest age for pantropical forest regeneration, including natural forest expansion, secondary forests, and degraded forests, from 1985 to 2022. Using the classical “space-for-time” substitution approach, the researchers developed above-ground carbon (AGC) accumulation models for different climate zones and recovery pathways, and further investigated the climatic and environmental drivers influencing forest carbon accumulation and prediction. Based on these models, they quantified and compared carbon accumulation rates and carbon sink capacities among the three types of naturally regenerating forests across the tropical America, Africa, and Asia under different climatic conditions. The study also evaluated their contributions to offsetting carbon emissions caused by forest degradation and deforestation. In addition, future carbon sink potentials of the three natural forest regeneration pathways by 2030 were projected under five forest restoration scenarios.

Pantropical carbon stocks of natural forest expansion (a), secondary forest (b) and degraded forest (c) using region-specific AGC accumulation models

The study found that the area of natural forest expansion across moist tropical regions is 6% larger than that of secondary forests, while exhibiting comparable AGC accumulation rates as secondary forests, particularly in the tropical Americas. Compared with secondary and degraded forests, AGC accumulation in natural forest expansion is more sensitive to climatic and environmental changes, possibly because these forests are generally located in drier regions farther from intact old-growth forests. Across the pantropical region, the total AGC uptake from natural forest expansion reached 795±132 Tg C, which is 5.4% greater than that of secondary forests (754±105 Tg C). Natural forest expansion additionally offset 2.4±0.6% of carbon emissions resulting from forest deforestation and degradation, whereas regrowth of secondary and degraded forests offset 2.3±0.5% and 13.6±2.1%, respectively. These findings suggest that the capacity of natural forest regeneration to offset disturbance-related carbon emissions remains limited, and that reducing deforestation and forest degradation should remain the highest priority for mitigating global climate change. At the same time, the study highlights natural forest expansion as an overlooked pan-tropical carbon sink with substantial climate mitigation potential, particularly if sustainably managed alongside the effective protection of old-growth and regenerating forests.

The study, entitled “Natural forest expansion is a larger carbon sink than secondary forests in moist tropics,” was published in Nature Geoscience. APM is the first affiliated institution. Prof. DU Yun, Prof. LI Xiaodong, Prof. ATKINSON Peter, and Dr. WANG Xia are co-authors of the study. Dr. ZHANG Yihang is the first author, while Dr. ZHANG Yihang, Dr. HEINRICH Viola H. A., and Dr. BOURGOIN Clément served as co-corresponding authors.

This work was supported in part by the National Natural Science Foundation of China, the Key Research Program of Frontier Sciences, Chinese Academy of Sciences, the Hubei Provincial Natural Science Foundation of China for Distinguished Young Scholars, the Young Top-notch Talent Cultivation Program of Hubei Province.

Link to the article: https://www.nature.com/articles/s41561-026-01984-5