China’s vast campaign to expand tree cover has long been presented as one of the world’s most important nature-based responses to climate change. The country is the largest national source of carbon dioxide emissions, yet it has also become a global center of forest restoration and tree planting. New research shows that the climate value of those efforts depends strongly on where the trees are growing and what happened on the land before they appeared. From 1986 to 2019, forests recovering after disturbance—reforestation—captured more carbon than forests established on land that had not recently been forested, a process known as afforestation. The distinction matters because the two pathways may look similar in satellite images while behaving very differently as carbon sinks.
The study, published in Nature Geoscience, reconstructs China’s forest carbon balance at a spatial resolution of 30 meters over more than three decades. The researchers combined locally derived aboveground biomass accumulation curves with a spatially explicit bookkeeping model. This approach allowed them to estimate how quickly carbon accumulated in different forest types and locations, while also accounting for carbon losses caused by disturbances such as harvesting, fire, and other forms of forest degradation. Rather than treating all newly visible tree cover as equivalent, the analysis separated forests returning after disturbance from trees established on previously non-forested land. That distinction provided a more detailed picture of how China’s changing landscapes have influenced the atmosphere.
The researchers first developed biomass growth curves for each one-degree grid cell across China. These curves describe how aboveground carbon increases as forests grow, incorporating regional differences in climate, vegetation, and growth conditions. Aboveground biomass includes the carbon stored in trunks, branches, and leaves, but not necessarily the full carbon balance of soils or dead organic matter. By applying these locally calibrated relationships to annual changes in forest cover, the team could estimate carbon uptake over time instead of relying only on a single average growth rate for the entire country. The model then tracked carbon gains from newly growing forests alongside emissions associated with disturbances, creating an annual ledger for China’s forest biomass.
Across the full study period, China’s forest biomass absorbed an average of 0.139 petagrams of carbon per year, with an uncertainty of 0.052 petagrams. One petagram equals one billion metric tons, making this a substantial national-scale carbon sink. The annual sink strengthened markedly over time. During the 1990s, forests absorbed approximately 0.1 ± 0.015 petagrams of carbon per year, while the average rose to about 0.2 ± 0.012 petagrams per year in the 2010s. The increase reflects the expanding area of forests and the continued growth of stands established or restored in earlier decades. It also demonstrates why the timing of planting and recovery is central to climate accounting: a forest may occupy the same area for decades while its rate of carbon uptake changes as the trees mature.
Afforestation expanded more rapidly in area than reforestation during the period examined. The study estimates that afforested tree cover increased by about 1.31 million hectares per year, compared with approximately 1.06 million hectares per year of reforestation following disturbance. On the surface, those figures might suggest that afforestation should have made the larger contribution to the carbon sink. However, carbon uptake is determined not only by how much land is covered by trees, but also by how efficiently vegetation accumulates biomass. Forests regenerating after disturbance displayed a mean sequestration rate of 1.47 ± 0.42 metric tons of carbon per hectare per year. Afforestation sites accumulated carbon more slowly, at about 0.96 ± 0.28 metric tons per hectare per year.
That difference in growth rate made reforestation the dominant contributor to China’s forest biomass carbon sink over the three decades. In ecological terms, forests recovering after disturbance may benefit from surviving roots, seed banks, established soil structure, and nearby sources of natural regeneration. Even when a disturbance removes much of the visible forest, biological legacies can remain below ground or in the surrounding landscape. Afforestation on non-forested land can face a different starting point. Newly planted trees may need to establish root systems, compete with grasses or other vegetation, and tolerate local water and soil constraints before they begin accumulating biomass rapidly. The study does not imply that afforestation is ineffective; rather, it shows that its carbon benefits should not automatically be assumed to match those of natural or assisted forest recovery.
The distinction also changes how forest policies should be evaluated. Counting increases in tree-covered area alone can obscure the fact that a hectare of recovering forest and a hectare of newly planted forest may have different carbon trajectories. A policy that protects a disturbed forest from further conversion may preserve an existing recovery pathway and avoid future emissions, while a planting program may create a new sink that develops more gradually. The researchers’ bookkeeping framework captures these pathways separately, helping identify which landscapes are gaining carbon, which are losing it through disturbance, and where restoration or protection could have the greatest effect. Such information can improve national greenhouse-gas inventories, which require estimates of both carbon removal and emissions.
The findings arrive as China pursues its goal of achieving carbon neutrality by the 2060s. Forests are expected to play an important role in that strategy, but their capacity to offset emissions is not unlimited or uniform. Carbon stored in living biomass can be released if forests burn, are harvested, or experience severe degradation. In addition, the rate at which a forest removes carbon from the atmosphere generally changes as it ages. A young, rapidly growing stand may absorb carbon quickly, while a mature forest can hold a large stock even if its annual net uptake is lower. This means that climate planning must distinguish between protecting existing carbon stocks, encouraging continued growth, and establishing new forests in places where they can survive without creating unintended ecological costs.
The study’s high-resolution, time-explicit approach offers a way to move beyond broad national averages, although the authors’ estimates remain subject to uncertainty. Satellite observations can reveal changes in tree cover, but they do not directly measure every component of carbon storage, and biomass relationships vary among forest types and regions. The analysis focuses on forest biomass, so it should not be interpreted as a complete accounting of soil carbon, harvested wood products, or all greenhouse gases associated with land management. Even so, combining observations with locally derived growth curves provides a stronger basis for comparison than treating every forest expansion event as identical. It also makes it possible to examine how disturbance and recovery interact across space and time.
The central message is both encouraging and cautionary: China’s forests have become a growing carbon sink, but the most powerful contributor has not been tree planting alone. Forests returning after disturbance sequestered carbon faster than afforestation sites and supplied the larger share of the sink from 1986 to 2019. Future climate strategies could therefore benefit from protecting forests that are already regenerating, reducing repeated disturbance, and targeting afforestation to landscapes where trees are ecologically suitable and likely to persist. For carbon neutrality, the research suggests that the question is no longer simply how many hectares of trees China can add. It is how each hectare came to be forested, how quickly it stores carbon, how long that carbon remains secure, and how accurately those changes are counted.
Subject of Research: China’s forest carbon sink, reforestation, afforestation, forest disturbances, and biomass carbon accumulation.
Article Title: Reforestation dominated China’s forest carbon sink from 1986 to 2019
Article References: Xu, W., Liu, Z., Ciais, P. et al. “Reforestation dominated China’s forest carbon sink from 1986 to 2019.” Nature Geoscience (2026). https://doi.org/10.1038/s41561-026-02074-2
Image Credits: AI Generated
DOI: https://doi.org/10.1038/s41561-026-02074-2
Keywords: China, forest carbon sink, reforestation, afforestation, carbon sequestration, biomass carbon, forest disturbances, carbon neutrality, remote sensing, climate change.
