Major study reveals plants now absorbing 30% more CO2 worldwide
Scientists find plants absorb 31% more CO2 than earlier estimates, using innovative carbonyl sulfide tracking to redefine global photosynthesis rates. (CREDIT: Jeffrey Warren/ORNL, U.S. Dept. of Energy)
New research reveals plants absorb 31% more CO2 than estimated, reshaping climate predictions and highlighting natural carbon sequestration.
Published Jan 12, 2025 11:07 AM PST Joshua Shavit
Terrestrial ecosystems play a critical role in 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, driving the terrestrial carbon cycle. However, for decades, scientists have struggled to accurately quantify GPP due to uncertainties in its global magnitude, spatial distribution, and temporal variability.
Traditional estimates pegged global GPP at around 120 petagrams of carbon (PgC) per year since the 1980s. This figure, derived from remote sensing and other indirect methods, has been widely used to model Earth’s carbon cycle. However, recent research challenges this estimate, suggesting that plants globally absorb as much as 157 PgC annually—a 31% increase over previous calculations.
This finding, published in Nature, has significant implications for predicting future climate scenarios and understanding the role of terrestrial ecosystems in mitigating greenhouse gas emissions.
A team led by Cornell University, with support from Oak Ridge National Laboratory (ORNL), introduced a novel approach to estimating GPP using carbonyl sulfide (OCS), a trace gas closely linked to photosynthetic activity. Unlike CO2, which is released back into the atmosphere during plant respiration, OCS uptake is irreversible, making it a reliable proxy for measuring photosynthesis.
The researchers developed a model that traces the movement of OCS from the atmosphere into plant chloroplasts—the cellular structures where photosynthesis occurs. This approach leverages OCS’s unique properties to overcome limitations of traditional methods, such as satellite-based measurements, which can be obstructed by cloud cover, particularly over tropical rainforests.
“Figuring out how much CO2 plants fix each year is a conundrum that scientists have been working on for a while,” said Lianhong Gu, a distinguished staff scientist at ORNL and co-author of the study. “It’s important that we get a good handle on global GPP since that initial land carbon uptake affects the rest of our representations of Earth’s carbon cycle.”
Key to the new GPP estimate is a better representation of mesophyll diffusion—the process by which OCS and CO2 move from leaves into chloroplasts. Mesophyll layers act as significant barriers to gas movement, influencing how efficiently plants conduct photosynthesis. Previous models often neglected this process or used simplified assumptions, leading to underestimates of GPP.