The study, published in Nature Ecology & Evolution, focuses on mature forests, which account for approximately 72 percent of forested area in the conterminous United States. These ecosystems are particularly important in the global carbon cycle because they cover extensive landscapes and contain large stores of carbon in trunks, branches, roots and other living biomass. Their contribution is also scientifically difficult to measure. Young forests can show obvious changes as trees grow rapidly and canopy cover expands, but older forests may continue to gain carbon through slower increases in tree diameter, the growth of taller individuals, recruitment into larger size classes and changes in stand structure that are not easily translated into total biomass by satellite sensors.

The researchers compared several independent ways of detecting forest change, including satellite-derived biomass estimates, lidar observations, forest inventories and ecosystem models. Lidar, short for light detection and ranging, measures the time required for laser pulses to travel from an instrument to vegetation and back. By sampling the vertical arrangement of leaves, branches and stems, lidar can reveal forest structure, including canopy height and changes in the distribution of vegetation through the forest profile. Forest inventories provide another form of evidence by repeatedly measuring trees at established locations, recording characteristics such as species, diameter and height. Ecosystem models use observations and ecological relationships to estimate how carbon moves through forests over time. Together, these approaches provide a way to test whether a satellite signal reflects real biological change or simply reaches the limits of the measurement system.

The contrast between the measurements was striking. Satellite estimates indicated that biomass in mature forests had undergone nearly neutral change over recent decades, implying little overall gain or loss. Forest inventories, by comparison, estimated that mature forests were accumulating about 102 teragrams of carbon each year. A teragram is one million metric tonnes, so the estimated increase represents a substantial annual transfer of carbon into forest biomass across the United States. The agreement between inventory evidence, repeat lidar measurements and ecosystem models suggests that the apparent lack of growth in satellite records does not necessarily mean that mature forests have stopped accumulating carbon. Instead, it points to an observational gap concentrated in the forests that contain much of the country’s existing woody biomass.

That gap becomes especially clear when canopy height is considered. The analysis found that satellite estimates detected little additional biomass increase once canopy height rose above approximately 16 metres. This does not mean that forests taller than 16 metres cease to grow. Rather, it indicates that the satellite-based relationship between what the sensor observes and how much biomass is actually present becomes unreliable after forests reach a certain structural stage. Once the canopy is closed, additional carbon may be added through thickening trunks and branches, growth in large trees, understory development or subtle changes in vertical structure. Those changes can increase carbon stocks without producing a proportionate change in the broad canopy signal that many satellite biomass products rely on.

The problem is not simply that satellites are incapable of observing forests. Earth-observation systems are powerful tools for mapping forest cover, disturbance and large-scale structural differences, and they provide consistent measurements across enormous areas. The difficulty is that different forest processes leave different signatures in remotely sensed data. A forest can lose biomass through tree mortality, harvesting, fire or other disturbances, producing a detectable reduction in canopy structure. Gains in mature forests may be more gradual and distributed across many trees, making them harder to distinguish from measurement uncertainty, seasonal variation or natural differences between stands. The researchers describe this as an asymmetric bias: the observations are more likely to register losses than gains, which can make forests appear to be weaker carbon sinks than they are.

This asymmetry matters because carbon-cycle calculations depend not only on detecting dramatic changes, but also on measuring persistent, incremental accumulation. If a satellite product records a decline clearly but overlooks an equivalent or larger increase spread through mature stands, the resulting estimate will be biased downward. At continental and global scales, even a modest bias repeated across extensive forest areas can alter assessments of how much carbon terrestrial ecosystems remove from the atmosphere. The issue is particularly important for mature forests because they occupy most of the forest area examined in the study. Their growth may be slow compared with that of regenerating forests, but the carbon involved is distributed across a much larger existing stock and may continue year after year.

The findings also challenge a simplified view of forest carbon dynamics in which mature ecosystems rapidly approach saturation and then contribute little additional carbon storage. Forests are not storage tanks with a single fixed capacity that is reached when canopies close. Carbon enters through photosynthesis, as trees convert atmospheric carbon dioxide into organic matter, and it leaves through respiration, decomposition, mortality and disturbance. A mature forest’s net carbon balance depends on the difference between these processes. Even when overall canopy appearance changes very little, trees can continue to add wood, redistribute carbon among living tissues and replace carbon lost through mortality. The study does not imply that all mature forests accumulate carbon indefinitely or that their carbon stores are immune to disturbance. It shows instead that the observational tools used to estimate change may fail to capture widespread gains in structurally complex, already tall forests.

The authors’ conclusion is therefore both a warning and a roadmap for improving carbon accounting. Satellite biomass products remain essential for monitoring forests, but their estimates need to be integrated with measurements that are sensitive to structural change beyond canopy closure. Repeat lidar can help identify growth in height and vertical complexity, while inventories provide detailed ground-based evidence of changes in individual trees and stands. Ecosystem models can connect these observations to carbon fluxes and test whether estimated changes are consistent with forest ecology. Combining these sources should make it possible to distinguish genuine stability from growth that is hidden by the limitations of a particular sensor or algorithm. More accurate observations will be increasingly important as researchers assess the future of the land carbon sink and determine how forests respond to climate change, disturbance and management.

The central message is that the world’s mature forests may be quietly doing more carbon-storage work than satellite records currently acknowledge. Their canopies can look stable from above while their trunks, branches and internal structure continue to accumulate carbon. Because these forests cover such a large fraction of the US forest landscape, overlooking that growth can distort the national picture of carbon exchange and weaken estimates of the terrestrial sink. The study does not remove the uncertainty surrounding forests’ future role: warming, drought, fire, pests and other disturbances can all alter carbon balances. But it identifies a specific and correctable source of uncertainty. To understand how much carbon forests are storing, researchers must look beyond whether a canopy appears to change and measure how the entire forest structure evolves over time.

At its core, photosynthesis is the process by which trees assimilate atmospheric carbon dioxide (CO2) and convert it into organic compounds using sunlight. It has been widely accepted that this carbon fixation necessarily translates to tangible increases in trunk diameter, branch thickness, and root volume—the woody structures that represent long-term carbon storage. Yet, the new study’s intensive measurements depict a nuanced reality: photosynthesis continues late into the year; however, the physiological growth of the trees—measured by the expansion of trunk girth—ceases by midsummer in eastern U.S. oaks and stops by August in Californian variants. This decoupling shakes the foundational assumptions of carbon cycle models that factor tree growth as a primary carbon sink.

This finding holds profound implications for climate modeling and forest management. Models currently employed to predict global carbon dynamics often assume a tight coupling between photosynthesis and biomass accumulation. As atmospheric CO2 levels rise due to anthropogenic emissions, these models hypothesize enhanced photosynthetic rates, resulting in accelerated tree growth and greater carbon storage. However, if photosynthesis does not directly lead to increased wood production, the capacity of forests to act as long-term carbon sinks may be substantially overestimated, thereby impacting forecasts of climate change mitigation.

The research team, led by ecoclimatologist Mukund Palat Rao from the Lamont-Doherty Earth Observatory at Columbia Climate School, employed an integrative approach involving satellite-based photosynthesis assessments, in situ CO2 flux monitoring, and precise dendrometric measurements from trunk sensors. These sensors captured minute changes in tree diameter, allowing the team to track real-time growth activity. Their analysis extended over multiple sites across eastern United States and California, leveraging over seven decades of growth ring data and regional temperature records to contextualize observed patterns.

Notably, trees exhibit daily cycles of expansion and contraction, influenced by water uptake and transpiration. The trunks expand during nighttime when roots absorb water, swelling the wood and cells. Conversely, daylight hours induce slight shrinkage due to transpiration-driven water loss. Despite these fluctuations, genuine growth—reflecting cell division and expansion leading to increased woody biomass—occurs only during defined seasonal windows. The data reveal that the crucial growth window for eastern U.S. oaks spans May through July, while in California, it predominantly occurs from December to April, both ceasing well before photosynthetic activity tapers off.

This temporal mismatch becomes particularly apparent during periods of water limitation. Trees require adequate internal water pressure to sustain cell growth; thus, dry, hot conditions promptly halt growth activity. Intriguingly, photosynthesis proves more resilient, continuing at moderate levels despite reduced soil moisture, albeit at a slightly diminished rate. This physiological decoupling may be attributed to the distinct cellular processes governing carbon fixation versus cell expansion and biomass formation, highlighting an intricate regulatory mechanism in plant metabolism.

The carbon absorbed during these late photosynthetic phases appears to be allocated towards non-structural functions. Instead of contributing to woody tissue, it supports the synthesis of foliage and root structures or feeds metabolic pathways that maintain cell viability through dormancy phases. Some of this carbon serves as starch reserves that enable rapid bud and shoot growth in subsequent seasons. Beyond the tree itself, a portion of this assimilated carbon is released into the rhizosphere, where it sustains microbial communities essential for nutrient cycling and pathogen defense.

Quantifying the exact fraction of carbon locked into long-lived woody biomass remains challenging. Current evidence suggests that a significant share is diverted into short-term physiological roles rather than permanent sequestration. This revelation necessitates reevaluation of carbon budget models that rely heavily on tree growth as a proxy for forest carbon storage capacity—particularly under future climate scenarios marked by increased CO2 concentrations and extreme weather variability.

Moreover, the research highlights that in years characterized by erratic local climate—oscillating between drought and precipitation extremes—the disconnect between photosynthesis and growth intensifies. Such fluctuations are anticipated to become more frequent in a warming world, potentially exacerbating the divergence between carbon uptake and wood production. This insight signals an urgent need to refine predictive models to incorporate the complex interactions of hydrological stress, phenological shifts, and metabolic allocation.

Future research directions are already underway, spearheaded by Rao and collaborators, seeking to determine whether this decoupling phenomenon extends beyond oak species to other tree taxa and ecosystems globally. Preliminary expectations suggest variance across forest types and climatic zones, potentially influenced by species-specific physiology and environmental constraints. Clearly, this line of inquiry opens a new frontier in understanding forest carbon dynamics, with critical repercussions for managing natural carbon reservoirs amid accelerating climate change.

In summary, this study reveals that photosynthesis and tree growth, long assumed synonymous, are mechanistically independent under certain conditions. This paradigm challenges existing climate models and urges the scientific community to rethink estimates of forest carbon sequestration. As forests remain a cornerstone of global carbon management strategies, deeper insights into these physiological processes are indispensable to accurate forecasting and effective climate policy development. The discovery underscores the complexity inherent in ecological systems and the ongoing need for integrative, high-resolution research methodologies.

Subject of Research: Not applicable
Article Title: New Research Indicates That in the Future, Trees May Store Less Carbon Than Expected
News Publication Date: 12-Jun-2026
Web References: http://dx.doi.org/10.1126/sciadv.ady7139
References: Palat Rao, M., et al. “New Research Indicates That in the Future, Trees May Store Less Carbon Than Expected.” Science Advances, 12 June 2026.
Image Credits: Not specified

Keywords: Carbon cycle, Biogeochemistry, Biogeochemical cycles, Dendrochronology, Photosynthesis, Plant physiology, Plant respiration, Climate change

Forests serve as one of the planet’s most vital carbon sinks, absorbing large quantities of CO2 through photosynthesis and storing it in biomass and soil. However, deforestation, fragmentation, and human-induced disturbances have severely compromised these natural repositories. The study by Fu and colleagues focuses on the differential carbon sequestration benefits accrued when protected areas in China are subject to stronger conservation regimes compared to their less regulated counterparts. By adopting advanced monitoring techniques and comprehensive data analysis, the authors provide a granular understanding of the spatial and temporal dynamics of carbon accumulation within these regions.

The researchers utilized a combination of satellite remote sensing data, ground-based biomass inventories, and advanced ecological modeling to quantify carbon stocks across varying levels of protection intensity. Notably, their approach incorporated high-resolution time series to track changes in forest cover, biomass growth rates, and carbon flux over multiple decades. This methodological rigor allowed for robust attribution of carbon gains directly to enhanced protection measures rather than confounding environmental or anthropogenic variables.

One of the pivotal findings of the study is that intensified protection efforts—characterized by stricter enforcement against illegal logging, habitat restoration initiatives, and ecological management policies—resulted in significantly amplified forest carbon sequestration rates. Specifically, areas transitioning from minimal protection to stringent conservation status demonstrated carbon gains exceeding 20% over a ten-year period. This trend underscores the potential scalability of targeted protection policies, reinforcing their value not just for biodiversity preservation but also as climate action pillars.

Moreover, the study highlights the heterogeneity in carbon gain responses across different forest types and geographical regions. Subtropical and temperate forests in southern and eastern China exhibited particularly robust carbon sequestration improvements when protection was intensified. These biomes’ higher productivity and resilience may partly explain the amplified carbon accumulation, suggesting that region-specific management strategies could maximize conservation outcomes.

The implications of these findings extend beyond national borders, providing a compelling case for integrating forest protection metrics into carbon accounting frameworks such as REDD+ (Reducing Emissions from Deforestation and Forest Degradation). By demonstrating that enhanced legal and institutional frameworks can lead to measurable increases in carbon stocks, the research reinforces the effectiveness of policy interventions in achieving durable climate benefits.

Further technical insights from the study reveal the interplay between forest structure complexity and carbon storage capacity. The researchers observed that areas under stronger protection developed greater vertical stratification and species diversity, factors correlated with higher biomass density and carbon retention. Such ecological sophistication implies that conservation efforts yield synergistic effects, enhancing ecosystem resilience while securing carbon sequestration.

Importantly, Fu et al. also examined the temporal lag often associated with forest recovery dynamics. While some regions showed rapid carbon stock improvements following protection upgrades, others exhibited gradual but steady increases over decades. This temporal dimension elucidates the necessity of long-term commitment and continuous monitoring to fully realize the carbon sequestration potential of protected forests.

In the context of accelerating global climate change effects, the study touches on the threats posed by climate-induced disturbances such as increased wildfire frequency, pest outbreaks, and extreme weather events. By reinforcing protection mechanisms, China’s forest management authorities appear to have bolstered ecosystem stability against these challenges, indirectly sustaining carbon sequestration capacities amid environmental stresses.

Another technical aspect explored involves soil organic carbon dynamics, an often overlooked component of total forest carbon budgets. Enhanced protection reduced soil disturbance and erosion, promoting accumulation of organic carbon in upper soil horizons. This finding emphasizes the multidimensional benefits of forest protection extending beyond aboveground biomass.

The research team also contextualizes their findings within China’s ambitious ecological civilization policies and carbon neutrality commitments by 2060. They propose that optimizing the management of existing protected areas via reinforced governance could be one of the most cost-effective strategies to align national forestry practices with international climate goals.

From a broader ecological perspective, the expansion and reinforcement of protected areas have cascading effects on biodiversity conservation. By fostering habitat integrity, these areas support species that contribute directly or indirectly to forest productivity and carbon cycling, creating a positive feedback loop synergistic with sequestration objectives.

Fu and colleagues’ study leverages state-of-the-art data integration and machine learning techniques to assess carbon stock changes at unprecedented scales and resolutions. This technological advancement enables policymakers to pinpoint priority zones for enhanced protection and allocate resources more efficiently. The study’s methodological innovations thus set new standards for environmental monitoring.

In conclusion, this comprehensive analysis presented in Nature Communications offers compelling empirical evidence that stronger protection of forest reserves in China catalyzes significant increases in carbon sequestration potential. The study harmonizes ecological theory with pragmatic policy implications, advocating for reinforced conservation frameworks not only as a biodiversity imperative but as a linchpin for climate mitigation. As global carbon budgets tighten, such insights pave the way toward more informed, effective environmental stewardship and climate resilience strategies.

The remarkable scale and depth of this research underscore the transformative power of combining rigorous science with policy innovation. As countries worldwide grapple with meeting their emission reduction targets, the findings from Fu et al. suggest that fortifying protected areas represents an untapped reservoir of natural climate solutions. This paradigm shift reinforces hope that ecological preservation and climate action can proceed hand in hand to safeguard planetary health.

Subject of Research: Forest carbon sequestration enhancement through strengthened protection of protected areas in China.

Article Title: Enhanced forest carbon gains from stronger protection in China’s protected areas.

Article References:

Fu, Y., Li, W., Niu, Z. et al. Enhanced forest carbon gains from stronger protection in China’s protected areas.
Nat Commun (2026). https://doi.org/10.1038/s41467-026-69505-x

Image Credits: AI Generated