The study published in the journal Nature reveals that plants around the world are absorbing 31% more carbon dioxide than previously thought. Terrestrial Gross Primary Production (GPP), the amount of CO2 removed from the atmosphere by land plants, is now estimated at 157 petagrams of carbon per year, up from the previous estimate of 120 petagrams. This new assessment is crucial for improving Earth system simulations used to predict future climate change and underscores the significance of natural carbon sequestration in mitigating greenhouse gas emissions.
A team of scientists led by Cornell University and Oak Ridge National Laboratory used new models and measurements to calculate GPP. They introduced an integrated model that tracks the movement of the chemical compound carbonyl sulfide (OCS) from the air into plant cells, where photosynthesis occurs. OCS serves as a proxy for photosynthesis, and the study demonstrated that it is effective in estimating photosynthetic activity at large scales and over extended periods of time. By improving the understanding of photosynthesis processes, researchers were able to refine estimates of global GPP.
The study drew on plant data from various sources, including the LeafWeb database established at Oak Ridge National Laboratory. To validate their model, researchers compared the results with high-resolution data from environmental monitoring towers, rather than relying solely on satellite observations. The focus was on improving representations of mesophyll diffusion, the process by which OCS and CO2 move from leaves to chloroplasts for carbon fixation. This understanding is crucial for assessing plant efficiency in conducting photosynthesis and predicting their response to changing environments.
The research team, which included photosynthesis expert Lianhong Gu from Oak Ridge National Laboratory, developed a mesophyll conductance model as part of the project. Gu emphasized the importance of accurately estimating global GPP to enhance representations of the Earth’s carbon cycle in large-scale models. The study revealed that pan-tropical rainforests made the biggest difference in GPP estimates, indicating that they play a more significant role in carbon sequestration than previously thought. These findings shed light on the importance of accurate measurements to improve climate change predictions.
To improve future predictions of tropical forest carbon cycle response to climate change, the study emphasizes the need to incorporate key processes like mesophyll conductance into model representations of photosynthesis. The results are expected to inform new model development under the DOE’s Next Generation Ecosystem Experiments in the Tropics program, reducing uncertainty in projections of tropical forest GPP. Collaborators on the project included institutions such as Wageningen University, Carnegie Institution for Sciences, and NASA Jet Propulsion Laboratory, with support from Cornell, the National Science Foundation, and the DOE’s Office of Science Biological and Environmental Research program.
