How will a warming world impact the Earth’s ability to offset our carbon emissions?
Plants in the terrestrial biosphere perform a ‘free service’ to us, by taking between a quarter and a third of humanity’s carbon emissions out of the atmosphere. Will they be able to keep this up?
IMAGE: IMAGE OF A MONITORING STATION TOWER IN SHENANDOAH NATIONAL PARK. view more
CREDIT: PHOTOGRAPH IS COURTESY OF NOAA.
Washington, DC—As the world heats up due to climate change, how much can we continue to depend on plants and soils to help alleviate some of our self-inflicted damage by removing carbon pollution from the atmosphere?
New work led by Carnegie’s Wu Sun and Anna Michalak tackles this key question by deploying a bold new approach for inferring the temperature sensitivity of ecosystem respiration—which represents one side of the equation balancing carbon dioxide uptake and carbon dioxide output in terrestrial environments. Their findings are published in Nature Ecology & Evolution.
“Right now, plants in the terrestrial biosphere perform a ‘free service’ to us, by taking between a quarter and a third of humanity’s carbon emissions out of the atmosphere,” Michalak explained. “As the world warms, will they be able to keep up this rate of carbon dioxide removal? Answering this is critical for understanding the future of our climate and devising sound climate mitigation and adaptation strategies.”
Photosynthesis, the process by which plants, algae, and some bacteria convert the Sun’s energy into sugars for food, requires the uptake of atmospheric carbon dioxide. This occurs during daylight hours. But through day and night, these same organisms also perform respiration, just like us, “breathing” out carbon dioxide.
Being able to better quantify the balance of these two processes across all the components of land-based ecosystems—from soil microbes to trees and everything in between—and to understand their sensitivity to warming, will improve scientists’ models for climate change scenarios.
In recent years, researchers—including Carnegie’s Joe Berry—have developed groundbreaking approaches for measuring the amount of carbon dioxide taken up by plants through photosynthesis, such as using satellites to monitor global photosynthetic activity and measuring the concentration of the atmospheric trace gas carbonyl sulfide.
But, until now, developing similar tools to track respiration at the scale of entire biomes or continents has not been possible. As a result, respiration is often indirectly estimated as the difference between photosynthesis and the overall uptake of carbon dioxide.
“We set out to develop a new way to infer how respiration is affected by changes in temperature over various ecosystems in North America,” said Sun. “This is absolutely crucial for refining our climate change projections and for informing mitigation strategies.”
Michalak, Sun, and their colleagues developed a new way to infer at large scales how much respiration increases when temperatures warm using measurements of atmospheric carbon dioxide concentrations. These measurements were taken by a network of dozens of monitoring stations across North America.
The team revealed that atmospheric observations suggest lower temperature sensitivities of respiration than represented in most state-of-the-art models. They also found that this sensitivity differs between forests and croplands. Temperature sensitivities of respiration have not been constrained using observational data at this scale until now, as previous work has focused on sensitivities for much smaller plots of land.
“The beauty of our approach is that measurements of atmospheric carbon dioxide concentrations from a few dozen well-placed stations can inform carbon fluxes at the scale of entire biomes over North America,” Sun explained. “This enables a more comprehensive understanding of respiration at the continental scale, which will help us assess how future warming affects the biosphere’s ability to retain carbon,” Sun emphasized.
To their surprise, the researchers found that respiration is less sensitive to warming than previously thought, when viewed at the biome or continental scale. But they caution that this temperature sensitivity is just one piece of a complex puzzle.
“Although our work indicates that North American ecosystems may be more resilient to warming than plot-scale studies had implied, hitting the brakes on climate change ultimately depends on us ceasing to inject more and more carbon into the atmosphere as quickly as possible. We cannot rely on the natural components of the global carbon cycle to do the heavy lifting for us,” Michalak cautioned. “It is up to us to stop the runaway train.”
Other members of the research team include: Xiangzhong Luo, Yao Zhang, and Trevor Keenan of University of California Berkeley and Lawrence Berkeley National Laboratory; Yuanyuan Fang of the Bay Area Air Quality Management District; Yoichi P. Shiga of the Universities Space Research Association; and Joshua Fisher of Chapman University.
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This study was funded by the NASA Terrestrial Ecology Interdisciplinary Science and Carbon Monitoring System, the Carnegie Institution for Science’s endowment, Singapore’s Ministry of Education, the RUBISCO SFA, which is sponsored by the Regional and Global Model Analysis Program in the Climate and Environmental Sciences Division of the Office of Biological and Environmental Research in the U.S. Department of Energy Office of Science, and NASA.
The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with three research divisions on both coasts. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in the life and environmental sciences, Earth and planetary science, and astronomy and astrophysics.
JOURNAL
Nature Ecology & Evolution
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Biome-scale temperature sensitivity of ecosystem respiration revealed by atmospheric CO2 observations
ARTICLE PUBLICATION DATE
15-Jun-2023
Climate change: Challenges of capturing
sufficient carbon through large-scale
seaweed farming
The potential of global seaweed farming to help capture sufficient carbon may not be feasible given the large ocean areas needed to remove between 2.5 and 13 gigatonnes of atmospheric carbon per year to meet climate goals, according to a study published in Communications Earth & Environment. Modelling suggests that around one million square kilometres of the most productive ocean regions in exclusive economic zones (EEZs) is needed to grow enough seaweed to remove a single gigatonne of carbon from the atmosphere per year.
Seaweed can remove carbon dioxide from the atmosphere by converting it to organic biomass via photosynthesis. This biomass can subsequently sink into the deep ocean, removing it from surface waters. However, most global estimates of the efficacy of using seaweed to capture carbon are based on extrapolating observations from a few specific sites to a global scale.
Isabella Arzeno-Soltero and colleagues analysed predictions from Global Macroalgae Cultivation Modeling System to project potential seaweed productivity and harvestable biomass under different levels of nutrient availability and ocean conditions across the global ocean. They estimated that to harvest one gigatonne of seaweed-captured carbon each year, over one million square kilometres of the most productive EEZs waters, found in the equatorial Pacific, would need to be farmed. Outside of these productive equatorial waters, cultivation areas would need to be tripled to harvest the same amount of seaweed carbon due to the geographical variability in seaweed productivity and growth. In addition, the authors suggest that nutrients would need to be supplemented to maintain seaweed productivity — possibly though ‘depth cycling’ the seaweed by physically moving between deep and shallow water, or by upswelling nutrients from deeper water.
The authors suggest that to meaningfully assess the carbon removal potential of seaweed cultivation, the global variation in seaweed growth potential must be understood and future research into the refinement of seaweed farming is needed.
JOURNAL
Communications Earth & Environment
ARTICLE TITLE
Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints
ARTICLE PUBLICATION DATE
15-Jun-2023
IU researcher receives NSF award to study carbon-trapping mineral systems
IMAGE: CHEN ZHU view more
CREDIT: INDIANA UNIVERSITY
An Indiana University researcher is investigating critical geochemical processes that trap carbon dioxide in rock to better predict the potential for atmospheric carbon removal and storage at scale.
Chen Zhu, a globally recognized geologist and professor of Earth and Atmospheric Sciences within the College of Arts and Sciences at Indiana University Bloomington, has been awarded $736,000 from the National Science Foundation to solve long-standing gaps in scientists’ understanding of CO2-water-rock interactions that naturally remove carbon dioxide from the atmosphere.
According to the latest Intergovernmental Panel on Climate Change report, limiting global warming to 1.5°C or 2°C requires the storage of hundreds of gigatons of CO2 in aquifers, soils, and oceans in the next few decades. As the US and other countries accelerate efforts to decarbonize the global economy and avoid the worst impacts of climate change, strategies to remove carbon from the atmosphere are increasingly viewed as an essential part of the solution.
“It’s become clear that we must do more than just reduce global emissions,” said Zhu, an affiliate of the IU Environmental Resilience Institute. “No current technologies, however, have demonstrated the ability to capture and store CO2 at the necessary gigaton scale, though several show promise. New insight into the chemical processes that dictate CO2 mineralization could help accelerate the development of these technologies to meet society’s urgent need.”
Zhu’s team is particularly interested in investigating basalt-CO2-water interactions, which have shown potential for rapid, long-term carbon storage. Basalts, dark volcanic rocks commonly found around the world, have long piqued the interest of climate researchers. Their high concentrations of ionized calcium and magnesium act as CO2 magnets, binding with the gas to form calcite, dolomite, and magnesite. In one experiment conducted at a geothermal power plant in Iceland, 90% of carbon dioxide—dissolved in water and injected underground—transformed into minerals in just 2 years.
To better understand the ideal conditions and rate of reaction in basalt-CO2-water systems, Zhu’s team will employ the isotope tracer method, a technique in which a rare isotope is introduced to the mineral system. Researchers then monitor the isotope using mass spectrometry to gain insight into the system’s geochemical kinetics, which describe how natural materials react under a given set of conditions.
In past experiments, Zhu has successfully applied isotopes to study single mineral reactions. This time, the method will be applied to multi-mineral reactions, presenting new challenges.
“The basalt-CO2-water system is so complex, with many mineral phases and chemical components; it is difficult to define precisely which minerals are dissolving and which are precipitating into new compounds,” Zhu said. “However, this knowledge is critical. For example, clay minerals will also precipitate, competing with CO2 for available calcium and magnesium ions. Using multiple isotopic tracers, these experiments will yield unprecedented data that can be leveraged by the scientific community.”
Data gleaned from the experiments will be used to inform models that can be simulated on IU’s high performance computers to test a wide range of mineral systems relevant to carbon capture and storage. The data will also be made available to the scientific community through a public interactive data portal called a science gateway. The gateway will give other researchers the opportunity to download the data, conduct their own analysis, update existing models, or run entirely new models.
“There is a large community of climate scientists, geochemists, soil scientists, oceanographers, and others who are working on scaling up carbon capture and storage,” said Sudhakar Pamidighantam, a senior scientist with the IU Pervasive Technology Institute and a co-PI of the project. “Our science gateway will make it easier for researchers to build on this work and maximize its impact for society.”
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