Plants the world over are absorbing about 31% more carbon dioxide than previously thought, according to a new assessment developed by scientists. The research, detailed in the journal Nature, is expected to improve Earth system simulations that scientists use to predict the future climate, and spotlights the importance of natural carbon sequestration for greenhouse gas mitigation.
The amount of CO2 removed from the atmosphere via photosynthesis from land plants is known as Terrestrial Gross Primary Production, or GPP. It represents the largest carbon exchange between land and atmosphere on the planet. GPP is typically cited in petagrams of carbon per year. One petagram equals 1 billion metric tons, which is roughly the amount of CO2 emitted each year from 238 million gas-powered passenger vehicles.
A team of scientists led by Cornell University, with support from the Department of Energy's Oak Ridge National Laboratory, used new models and measurements to assess GPP from the land at 157 petagrams of carbon per year, up from an estimate of 120 petagrams established 40 years ago and currently used in most estimates of Earth's carbon cycle. The results are described in the paper, "Terrestrial Photosynthesis Inferred from Plant Carbonyl Sulfide Uptake."
Researchers developed an integrated model that traces the movement of the chemical compound carbonyl sulfide, or OCS, from the air into leaf chloroplasts, the factories inside plant cells that carry out photosynthesis. The research team quantified photosynthetic activity by tracking OCS. The compound largely follows the same path through a leaf as CO2, is closely related to photosynthesis and is easier to track and measure than CO2 diffusion. For these reasons, OCS has been used as a photosynthesis proxy at the plant and leaf levels. This study showed that OCS is well suited to estimate photosynthesis at large scales and over long periods of time, making it a reliable indicator of worldwide GPP.
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