Plants Release Carbon Sooner Than Expected

New research indicates that plants absorb and release carbon dioxide faster than previously thought, challenging the effectiveness of nature-based carbon removal strategies and underscoring the urgency to cut fossil fuel emissions to combat climate change.

According to a new study, the global carbon stored by plants is more short-lived and susceptible to climate change than previously believed. These findings have significant implications for our understanding of nature’s role in mitigating climate change, particularly for nature-based carbon removal projects like mass tree-planting initiatives.

The research, carried out by an international team led by Dr. Heather Graven at Imperial College London and published in Science, reveals that existing climate models underestimate the amount of carbon dioxide (CO₂) that is taken up by vegetation globally each year, while overestimating how long that carbon remains there.

Dr Graven, a Reader in Climate Physics in Imperial’s Department of Physics, said: “Plants across the world are actually more productive than we thought they were.”

The findings also mean that while carbon is taken up by plants quicker than thought, the carbon is also locked up for a shorter time, meaning carbon from human activities will be released back into the atmosphere sooner than previously predicted.

Dr Graven added: “Many of the strategies being developed by governments and corporations to address climate change rely on plants and forests to draw down planet-warming CO₂ and lock it away in the ecosystem.

“But our study suggests that carbon stored in living plants does not stay there as long as we thought. It emphasizes that the potential for such nature-based carbon removal projects is limited, and fossil fuel emissions need to be ramped down quickly to minimize the impact of climate change.”

Using carbon

Until now, the rate at which plants use CO₂ to produce new tissues and other parts globally – a measure known as Net Primary Productivity – has been approximated by scaling up data from individual sites. But the sparsity of sites with comprehensive measurements means it has not been possible to accurately calculate Net Primary Productivity globally.

Plants’ productivity has been increasing since the early 1900s and more CO₂ is currently taken up by plants than is released back into the air. Researchers know that approximately 30% of CO₂ emissions by human activities are therefore stored in plants and soils each year, reducing climate change and its impacts.

Video abstract. Credit: Heather Graven / DOI: 10.1126/science.adl4443