A new study reveals that the carbon stored by plants globally is more transient and more vulnerable to the impacts of climate change than previously thought. Led by Dr Heather Graven of Imperial College London, the research shows that current climate models significantly underestimate the amount of CO2 absorbed by vegetation each year and overestimate how long it is retained, suggesting that carbon is released into the atmosphere earlier than expected. This indicates the need for rapid reductions in fossil fuel emissions and suggests limits to the effectiveness of natural carbon removal strategies, such as large-scale tree planting.
New research indicates that plants absorb and release carbon dioxide faster than previously thought, calling into question the effectiveness of natural carbon removal strategies and highlighting the urgency of reducing fossil fuel emissions to fight climate change.
Global carbon stored by plants is more ephemeral and more sensitive to climate change than previously thought, according to a new study. These findings have significant implications for our understanding of the role of nature in climate change mitigation, particularly for natural carbon removal projects like mass tree planting initiatives.
The research, carried out by an international team led by Dr Heather Graven from Imperial College London and published in Sciencereveals that existing climate models underestimate the amount of carbon dioxide (CO2) which is absorbed by the world’s vegetation each year, while overestimating the length of time this carbon remains there.
Dr Graven, Reader in Climate Physics at Imperial’s Department of Physics, said: “Plants around the world are actually more productive than we thought. »
The results also mean that although carbon is taken up by plants faster than previously thought, carbon is also locked up for a shorter period of time, meaning carbon from human activities will be released into the atmosphere earlier than expected.
Dr Graven added: “Many strategies developed by governments and businesses to combat climate change rely on plants and forests to reduce global warming.2 and lock it into the ecosystem.
“But our study suggests that the carbon stored in living plants doesn’t stay there as long as we thought. It emphasizes that the potential for such nature-based carbon removal projects is limited and that fossil fuel emissions must be reduced quickly to minimize the impact of climate change.
Use carbon
So far, the rate of CO utilization by plants2 produce new tissues and other parts on a global scale – a measure known as net primary productivity – has been approximated by augmenting data from individual sites. But the scarcity of sites with comprehensive measurements means it has not been possible to accurately calculate net primary productivity on a global scale.
Plant productivity has been increasing since the early 1900s and more CO2 is currently absorbed by plants before being released into the air. Researchers know that around 30% of CO2 Emissions from human activities are therefore stored each year in plants and soils, thus reducing climate change and its impacts.
Video summary. Credit: Heather Graven /
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However, the details of how this storage occurs and its stability in the future are not yet well understood.
In this study, radiocarbon (14C) – a radioactive isotope of carbon – was combined with model simulations to understand how plants use CO2 on a global scale, paving the way for valuable information on the interaction between the atmosphere and the biosphere.
Tracking carbon from bomb tests
Radiocarbon is produced naturally, but nuclear bomb testing in the 1950s and 1960s increased the level of radiocarbon. 14C in the atmosphere. This supplement 14C was available to plants around the world, giving researchers a good tool to measure how quickly they could assimilate it.
By examining the accumulation of 14C in power plants between 1963 and 1967 – a period when there were no significant nuclear detonations and the total 14C in the Earth system was relatively constant – the authors were able to assess how quickly carbon moves from the atmosphere to vegetation and what happens to it once it’s there.
The results show that current, widely used models that simulate how land and vegetation interact with the atmosphere underestimate the net primary productivity of plants on a global scale. The results also show that the models overestimate the duration of carbon storage in plants.
Role of the biosphere
Co-author Dr Charles Koven, from Lawrence Berkeley National Laboratory, US, said: “These observations date from a unique moment in history, just after the peak of atomic weapons testing in the world. atmosphere in the 1960s.
“Observations show that plant growth at the time was faster than current climate models estimate. The significance is that this implies that carbon cycles between the atmosphere and the biosphere are faster than we thought, and that we need to better understand and account for this faster cycling in climate models.
The authors say the research demonstrates the need to improve theories about how plants grow and interact with their ecosystems, and to adjust global climate models accordingly, to better understand how the biosphere mitigates climate change.
Co-author Dr Will Wieder, from the US National Center for Atmospheric Research, said: “Scientists and policymakers need improved estimates of historical terrestrial carbon uptake to inform projections of this critical ecosystem service in the decades to come. Our study provides critical insights into the dynamics of the terrestrial carbon cycle, which can inform models used for climate change projections.
The work highlights the usefulness of radiocarbon measurements to help understand the complexities of the biosphere. Among the authors of the study are German physicist Ingeborg Levin, a pioneer in radiocarbon and atmospheric research who sadly died in February.
Reference: “Bombard radiocarbon evidence for high global carbon uptake and turnover of terrestrial vegetation” by Heather D. Graven, Hamish Warren, Holly K. Gibbs, Samar Khatiwala, Charles Koven, Joanna Lester, Ingeborg Levin , Seth A. Spawn-Lee and Will Wieder, June 20, 2024, Science.
DOI: 10.1126/science.adl4443