Terrestrial ecosystems are vital to regulating Earth’s climate by removing carbon dioxide (CO2) from the atmosphere through photosynthesis. This process, known as gross primary production (GPP), represents the largest carbon flux on Earth and serves as the foundation of the global carbon cycle. However, accurately quantifying GPP has been a longstanding challenge due to uncertainties in its global magnitude, spatial distribution, and variability over time.
For decades, scientists relied on indirect methods such as remote sensing to estimate global GPP at around 120 petagrams of carbon (PgC) per year. However, new research, published in Nature, suggests this figure may be significantly underestimated. According to updated findings, terrestrial plants could absorb as much as 157 PgC annually—a 31% increase over previous calculations. This revelation has profound implications for understanding the global carbon cycle and predicting future climate scenarios.
A team led by Cornell University, in partnership with Oak Ridge National Laboratory (ORNL), developed an innovative approach to estimate GPP using carbonyl sulfide (OCS). Unlike CO2, which is released back into the atmosphere during respiration, OCS uptake during photosynthesis is irreversible. This makes OCS a more reliable indicator of photosynthetic activity. The researchers created a model that tracks the movement of OCS from the atmosphere into plant chloroplasts, overcoming limitations associated with traditional satellite-based methods, which are often obscured by cloud cover in regions like tropical rainforests.
One of the study’s breakthroughs was incorporating mesophyll diffusion into their models. Mesophyll diffusion describes how gases like OCS and CO2 move into leaves and chloroplasts, a process often oversimplified in earlier models. By integrating detailed mesophyll conductance into the National Center for Atmospheric Research’s Community Land Model version 5 (CLM5), the team improved the accuracy of GPP simulations. These adjustments were validated using field measurements from sites such as Harvard Forest in the United States and Hyytiälä Forest in Finland.
The findings revealed several critical insights. Nighttime OCS uptake accounted for 20–30% of daily totals, highlighting its previously underappreciated role. Seasonal and spatial patterns of GPP were also influenced by mesophyll conductance, which varies with environmental conditions and plant growth stages. These results emphasize the need for detailed physiological processes to be incorporated into global carbon cycle models to better capture the complexity of terrestrial photosynthesis.
The study also demonstrated that tropical rainforests are significantly more productive as carbon sinks than satellite data had previously indicated. This underscores the importance of combining satellite observations with ground-based methods, such as OCS tracking, to improve accuracy. As tropical forests play a critical role in the global carbon cycle, refining these models is essential for predicting their responses to climate change and rising CO2 levels.
Supported by institutions like the Department of Energy and leveraging databases like LeafWeb, this research represents a major advancement in carbon cycle science. By providing a robust framework for understanding GPP dynamics, it not only refines predictions of climate trajectories but also informs conservation strategies. Accurate modeling of the global carbon cycle is crucial to addressing climate challenges and ensuring a sustainable future.
https://www.thebrighterside.news/post/major-study-reveals-plants-now-absorbing-30-more-co2-worldwide