SOS#SaveOurSharks

Overfishing is driving coral reef sharks toward extinction

Peer-Reviewed Publication

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)

Five of the most common shark species living in coral reefs have declined 60% to 73%, according to a massive global study by Colin Simpfendorfer and colleagues. Some individual shark species were not found at 34% to 47% of the reefs in the survey. The likely cause, say the authors, is overfishing, which has removed both the sharks themselves and the prey they depend on. As shark numbers decline, ray species are increasing on the reefs, suggesting a shift in the top elasmobranch species in the communities. Simpfendorfer et al. surveyed 391 coral reefs in 67 nations and territories using 22,756 remote underwater video stations. They show that shark-dominated reefs persist in wealthy, well-governed nations and in protected marine sanctuaries. In areas of poverty and limited governance, rays dominate the reef communities. The estimated declines of these resident reef shark species meet the IUCN Red List criteria for Endangered status, the researchers note. In a related Perspective, David Shiffman discusses how the authors, under the Global FinPrint project, analyzed almost three years’ worth of raw video. The study is “the latest in a long line of papers showing that global-scale problems require huge and multidisciplinary teams,” Shiffman writes.

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JOURNAL

Science

DOI

10.1126/science.ade4884 

ARTICLE TITLE

Widespread diversity deficits of coral reef sharks and rays

ARTICLE PUBLICATION DATE

16-Jun-2023

Wide-ranging report warns of shark extinction risk

BY JARED GANS 

THE HILL

- 06/16/23

A team of researchers analyzing almost 400 coral reefs found significantly declining numbers of certain shark species, warning that they face a risk of extinction because of overfishing.

The researchers released a report in the academic journal Science on Thursday after analyzing the presence of five common species of sharks that live by coral reefs. They surveyed 391 reefs across 67 countries and territories using almost 23,000 underwater video stations.

The report states that the researchers found global declines between 60 and 73 percent for the five species, and individual shark species were not detected in 34 to 47 percent of reefs.

The decline in shark species has also caused rays to increasingly dominate these reefs, having further implications for the ecosystem at large.

The researchers reviewed four key ray species — yellow and southern stingrays in the Atlantic, and blue spotted mask and blue spotted ribbontail rays in the Indo-Pacific region — and found that their populations only increased with the depletion of one or more shark species.

The report also states that the depletion levels of the shark species were closely tied to socioeconomic and management factors of their environment.

Reefs are more likely to be dominated by sharks in wealthy, well-governed countries and in marine protected areas or shark sanctuaries, where targeted shark fishing and trade is prohibited. However, countries struggling with poverty and poor governance were more likely to have reefs dominated by rays.

The report states that previous studies of reef sharks and rays have been geographically limited, only finding high abundances or local extinction among surveyed reefs. But this study evaluates the global extinction risk for the shark species.

The researchers concluded that reef shark species are at a much higher risk of extinction than previously thought. All major reef shark species have declined enough that they qualify as endangered under the standards set by the International Union for the Conservation of Nature, an international organization that works to promote sustainability and conservation efforts.

The report did state that the potential to rebuild the shark populations is high if protected areas or stronger fishing management are implemented in a region.

“This study builds the case that species-specific reef shark management provides the best way forward for conservation and rebuilding of reef sharks in places where they have declined, among nations with the desire and capacity to do so,” the report states.

Carbon mitigation payments can make bioenergy crops more appealing for farmers

Peer-Reviewed Publication

UNIVERSITY OF ILLINOIS COLLEGE OF AGRICULTURAL, CONSUMER AND ENVIRONMENTAL SCIENCES

 

IMAGE: FAHD MAJEED (PICTURED, WITH MISCANTHUS) AND MADHU KHANNA, UNIVERSITY OF ILLINOIS, STUDIED THE EFFECT OF CARBON MITIGATION PAYMENTS ON BIOENERGY CROP PROFITABILITY. view more 

CREDIT: UNIVERSITY OF ILLINOIS

URBANA, Ill. — Bioenergy crops such as miscanthus and switchgrass provide several environmental benefits, but low returns and profit risks are barriers for investment by farmers. A new study from the University of Illinois Urbana-Champaign shows that carbon mitigation payments could increase net returns and reduce income risk, potentially enticing more farmers to grow these crops.

“We were interested in looking at the returns to farmers and the risks to farm income of adopting bioenergy crops compared to conventional corn and soybean crops. We also wanted to look at the effects of paying farmers for the carbon mitigation services from these crops and how that would impact returns and risks,” said Madhu Khanna, Alvin H. Baum Family Chair and director of the Institute for Sustainability, Energy, and Environment (iSEE). She is also the ACES Distinguished Professor of Environmental Economics in the Department of Agricultural and Consumer Economics (ACE) and co-director of the Center for the Economics of Sustainability (CEOS), part of the College of Agricultural, Consumer and Environmental Sciences (ACES) at the U. of I. 

“There are two main carbon mitigation benefits from bioenergy crops: First, bioenergy crops have deep roots that sequester more soil carbon than conventional crops. And second, the harvested biomass can be used to produce cellulosic biofuel to replace fossil fuels,” explained Fahd Majeed, a postdoctoral research associate at iSEE and the U.S. Department of Energy’s Center for Advanced Bioenergy and BioProducts Innovation (CABBI) at the U. of I. Majeed conducted the research as a doctoral student in CEOS.  

Potential biomass profitability and return riskiness, along with the subsequent carbon mitigation potential of these crops, varies spatially due to weather-related yield risk and relative returns from conventional crops. Policies aimed at incentivizing farmers to convert cropland to bioenergy crops will need to address return riskiness along with high upfront costs and long establishment periods.

“Some farmers may be risk-averse and prefer lower but more stable profits, while others may be risk-neutral and prefer higher profits regardless of risk; however, this information may not be known to a policymaker,” Majeed noted. “Our analysis allows us to compare and rank risky returns from bioenergy crops and conventional crops when farmer risk preferences are unknown.” 

The study, funded by the USDA National Institute of Food and Agriculture and CABBI, employed a biogeochemical model to simulate yields of bioenergy crops (miscanthus and switchgrass) and conventional crops (corn and soybean) under 30 years of randomized weather conditions. The researchers performed the analysis for 2,122 counties in the rainfed region of the United States, on or east of the 100th meridian. For conventional crops, they included corn-corn or corn-soybean rotation and till versus no-till practices.

They combined the yield analysis with an economic model estimating crop prices and carbon mitigation payments to gauge the appeal to different types of farmers across locations.

As both bioenergy and conventional crops vary in returns and riskiness across biomass and carbon prices, the researchers examined bioenergy crop profitability at biomass prices of $40 and $60 per metric ton and carbon payments of $0, $40, and $80 per metric ton of carbon dioxide (CO2). They found that bioenergy crops would not be profitable without carbon payments at lower prices. With carbon mitigation payments, these crops would appeal to risk-averse farmers; that is, farmers who are willing to accept slightly lower but less variable returns relative to conventional crops. At the higher biomass price of $60 per metric ton, carbon mitigation payments increase returns and reduce riskiness such that growing bioenergy crops would appeal to farmers regardless of risk preference.

Further, comparing the two bioenergy crops, the researchers found that miscanthus would be preferred over switchgrass by farmers in the Midwest, while switchgrass would be preferred over miscanthus by farmers in the southern states. This is due to spatial differences in the expected yield, carbon mitigation potential, and costs across bioenergy crops, the researchers said. 

Overall, carbon mitigation payments can make bioenergy crops more appealing to farmers, but payments should be adapted to the varying potential yield, carbon mitigation, and riskiness of returns across regions.

“One policy implication from this study is that if you want to reduce risk, carbon credits are a good policy. But the incentives need to be tailored spatially; a uniform payment per acre of land across the whole region is not going to be the most effective. Carbon credits that vary across the region based on carbon mitigated will create differentiated incentives across the region compared to a uniform policy. The former will also be cost-effective in achieving an aggregate target for carbon mitigation,” Khanna said.

Currently, carbon mitigation payments are primarily facilitated through voluntary markets where companies and other organizations can purchase credits to meet their carbon reduction goals. Such markets can be supplemented with government programs to incentivize bioenergy crop production, the researchers noted.

Editor’s Notes:

The paper, “Carbon mitigation payments can reduce the riskiness of bioenergy crop production,” is published in the Journal of the Agricultural and Applied Economics Association [DOI: 10.1002/jaa2.52]. Authors include Fahd Majeed, Madhu Khanna, Ruiqing Miao, Elena Blanc-Betes, Tare Hudiburg, and Evan DeLucia.

Funding was provided by the National Institute of Food and Agriculture, Grant/Award Number: 2017‐67019‐26283; Hatch Project Number, Grant/Award Number: ALA011‐1‐ 17002; and the U.S. Department of Energy,Grant/Award Number: DE‐SC0018420

The College of Agricultural, Consumer and Environmental Sciences (ACES) at the University of Illinois has top-ranked programs, dedicated students, and world-renowned faculty and alumni who are developing solutions to the world’s most critical challenges to provide abundant food and energy, a healthy environment, and successful families and communities. 

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JOURNAL

Journal of the Agricultural and Applied Economics Association

DOI

10.1002/jaa2.52 

METHOD OF RESEARCH

Data/statistical analysis

ARTICLE TITLE

Carbon mitigation payments can reduce the riskiness of bioenergy crop production

Holistic management is key to increase

carbon sequestration in soils

Increased carbon sequestration in soil to help mitigate climate change can only be achieved by a more holistic management

Peer-Reviewed Publication

UNIVERSITY OF COPENHAGEN - FACULTY OF SCIENCE

 

IMAGE: MICROSCALE VIEW ON PARTICULATE ORGANIC MATTER (POM), WITH NICELY VISIBLE PLANT CELL STRUCTURES WHICH REPRESENT THE CARBON STORED IN THE SOILS. view more 

CREDIT: CARSTEN W. MÜELLER

Increased carbon sequestration in soil to help mitigate climate change can only be achieved by a more holistic management. This is the conclusion from an opinion paper conceptualized by a team led by researchers from the German Centre for Integrative Biodiversity Research (iDiv), Leipzig University, the Czech Academy of Sciences, and the University of Copenhagen. The authors developed a novel framework that can guide informed and effective management of soils as carbon sinks. The study has recently been published in Nature Communications.

A key question for land management is how to sustain and increase the vast amounts of carbon stored in soil to help mitigate climate change. In this respect, carbon associated with minerals that can persist for centuries to millennia has received specific attention as a potential management target.

Undifferentiated focus on this “mineral-associated” carbon, however, falls short of establishing soils as carbon sinks because various environmental factors, such as related to land use or specific soil types, render management of this carbon inefficient.

“We were puzzled by the overwhelming emphasis on mineral-associated carbon in the literature, whose context-independent valuation certainly hampers informed and targeted management of soils as carbon sinks,” says Dr Gerrit Angst, lead author of the article from iDiv, Leipzig University, and the Czech Academy of Sciences.

The international author team, comprised of researchers from Germany, the Czech Republic, the United States, and Denmark thus developed a framework for the contextualization of management strategies that considers the diversity and complexity of soils.

Synergies with soil health and biodiversity

The framework specifically highlights the relevance of “labile” carbon, which typically remains in the soil for days to a few years, as a management target in various environmental contexts. For example, the capacity of some soils to accumulate rather stable, mineral-associated carbon is very low; some soils also feature conditions that hamper the formation of stabilized carbon but favor the accumulation of labile carbon.

Management that is aimed at increasing and perpetuating labile carbon in such soils will be more effective in increasing carbon sequestration than that focused on stabilized carbon.

“We cannot overemphasize the need to consider context-dependent environmental conditions for an effective management of soils as carbon sinks, which constrain whether management should target labile or stabilized carbon, or both,” explains Angst.

Contextualization of management strategies within the novel framework can be expected to maximize carbon sequestration in soil and generate synergies with related management targets, such as related to soil health, biodiversity, or crop performance. Senior author of the study, Prof Carsten W. Mueller from the University of Copenhagen concludes:

“Only if we see soils as a complex, holistic system with its specific chemical, physical, and biological features, will we be able to successfully manage them in a rapidly changing environment.”

 

Original publication:
(Scientists with iDiv affiliation in bold)

Angst, G., Mueller, K.E., Castellano, M.J., Vogel, C., Wiesmeier, M., Mueller, C.W. (2023):  Unlocking complex soil systems as carbon sinks: multi-pool management as the key. Nature Communications. DOI: https://doi.org/10.1038/s41467-023-38700-5

Contact:

Dr Gerrit Angst
Experimental Interaction Ecology
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Leipzig University

Institute of Soil Biology and Biogeochemistry

Biology Centre of the Czech Academy of Sciences
Phone: +49 341 9739179
Email: gerrit.angst@idiv.de
Web: www.idiv.de/en/profile/1575.html

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JOURNAL

Nature Communications

DOI

10.1038/s41467-023-38700-5 

ARTICLE TITLE

Unlocking complex soil systems as carbon sinks: multi-pool management as the key

ARTICLE PUBLICATION DATE

15-Jun-2023

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?

Peer-Reviewed Publication

CARNEGIE INSTITUTION FOR SCIENCE

 

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.

 

__________________

 

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.

 

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JOURNAL

Nature Ecology & Evolution

DOI

10.1038/s41559-023-02093-x 

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

Peer-Reviewed Publication

SCIENTIFIC REPORTS

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.

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JOURNAL

Communications Earth & Environment

DOI

10.1038/s43247-023-00833-2 

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

Grant and Award Announcement

INDIANA UNIVERSITY

 

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.”

We’ve pumped so much groundwater that we’ve nudged the Earth’s spin

The shifting of mass and consequent sea level rise due to groundwater withdrawal has caused the Earth’s rotational pole to wander nearly a meter in two decades

Peer-Reviewed Publication

AMERICAN GEOPHYSICAL UNION

 

IMAGE: HERE, THE RESEARCHERS COMPARE THE OBSERVED POLAR MOTION (RED ARROW, “OBS”) TO THE MODELING RESULTS WITHOUT (DASHED BLUE ARROW) AND WITH (SOLID BLUE ARROW) GROUNDWATER MASS REDISTRIBUTION. THE MODEL WITH GROUNDWATER MASS REDISTRIBUTION IS A MUCH BETTER MATCH FOR THE OBSERVED POLAR MOTION, TELLING THE RESEARCHERS THE MAGNITUDE AND DIRECTION OF GROUNDWATER’S INFLUENCE ON THE EARTH’S SPIN. view more 

CREDIT: SEO ET AL. (2023), GEOPHYSICAL RESEARCH LETTERS

American Geophysical Union
15 June 2023
Release No. 23-25
For Immediate Release

This press release is available online at: https://news.agu.org/press-release/weve-pumped-so-much-groundwater-that-weve-nudged-the-earths-spin

AGU press contact:
Rebecca Dzombak, news@agu.org (UTC-4 hours)

Contact information for the researchers:
Ki-Weon Seo, Seoul National University, seokiweon@snu.ac.kr (UTC+9 hours)

WASHINGTON — By pumping water out of the ground and moving it elsewhere, humans have shifted such a large mass of water that the Earth tilted nearly 80 centimeters (31.5 inches) east between 1993 and 2010 alone, according to a new study published in Geophysical Research Letters, AGU’s journal for short-format, high-impact research with implications spanning the Earth and space sciences.

Based on climate models, scientists previously estimated humans pumped 2,150 gigatons of groundwater, equivalent to more than 6 millimeters (0.24 inches) of sea level rise, from 1993 to 2010. But validating that estimate is difficult.

One approach lies with the Earth’s rotational pole, which is the point around which the planet rotates. It moves during a process called polar motion, which is when the position of the Earth’s rotational pole varies relative to the crust. The distribution of water on the planet affects how mass is distributed. Like adding a tiny bit of weight to a spinning top, the Earth spins a little differently as water is moved around.

“Earth’s rotational pole actually changes a lot,” said Ki-Weon Seo, a geophysicist at Seoul National University who led the study. “Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole.”

Water’s ability to change the Earth’s rotation was discovered in 2016, and until now, the specific contribution of groundwater to these rotational changes was unexplored. In the new study, researchers modeled the observed changes in the drift of Earth’s rotational pole and the movement of water — first, with only ice sheets and glaciers considered, and then adding in different scenarios of groundwater redistribution.

The model only matched the observed polar drift once the researchers included 2150 gigatons of groundwater redistribution. Without it, the model was off by 78.5 centimeters (31 inches), or 4.3 centimeters (1.7 inches) of drift per year.

“I’m very glad to find the unexplained cause of the rotation pole drift,” Seo said. “On the other hand, as a resident of Earth and a father, I’m concerned and surprised to see that pumping groundwater is another source of sea-level rise.”

“This is a nice contribution and an important documentation for sure,” said Surendra Adhikari, a research scientist at the Jet Propulsion Laboratory who was not involved in this study. Adhikari published the 2016 paper on water redistribution impacting rotational drift. “They’ve quantified the role of groundwater pumping on polar motion, and it’s pretty significant.”

The location of the groundwater matters for how much it could change polar drift; redistributing water from the midlatitudes has a larger impact on the rotational pole. During the study period, the most water was redistributed in western North America and northwestern India, both at midlatitudes.

Countries’ attempts to slow groundwater depletion rates, especially in those sensitive regions, could theoretically alter the change in drift, but only if such conservation approaches are sustained for decades, Seo said.

The rotational pole normally changes by several meters within about a year, so changes due to groundwater pumping don’t run the risk of shifting seasons. But on geologic time scales, polar drift can have an impact on climate, Adhikari said.

The next step for this research could be looking to the past.

“Observing changes in Earth’s rotational pole is useful for understanding continent-scale water storage variations,” Seo said. “Polar motion data are available from as early as the late 19th century. So, we can potentially use those data to understand continental water storage variations during the last 100 years. Were there any hydrological regime changes resulting from the warming climate? Polar motion could hold the answer.”

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Notes for journalists:

This study is published in Geophysical Research Letters, a fully open-access journal. View and download a pdf of the study here.

Paper title:

“Drift of the Earth’s pole confirms groundwater depletion as a significant contributor to global sea level rise 1993-2010”

Authors:

• Ki-Weon Seo (corresponding author), Center for Educational Research and Department of Earth Science Education, Seoul National University, Seoul, Republic of Korea
• Jae-Seung Kim, Kookhyoun Youm, Department of Earth Science Education, Seoul National University, Seoul, Republic of Korea
• Dongryeol Ryu, Department of Infrastructure Engineering, The University of Melbourne, Parkville, Australia
• Jooyoung Eom, Department of Earth Science Education, Kyungpook National University, Daegu, Republic of Korea
• Taewhan Jeon, Center for Educational Research, Seoul National University, Seoul, Republic of Korea
• Jianli Chen, Department of Land Surveying and Geo-informatics, and Research Institute for Land and Space, Hong Kong Polytechnic University, Hong Kong
• Clark Wilson, Department of Geological Sciences, and Center for Space Research, University of Texas at Austin, Austin, TX, USA

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JOURNAL

Geophysical Research Letters

DOI

10.1029/2023GL103509 

ARTICLE TITLE

“Drift of the Earth’s pole confirms groundwater depletion as a significant contributor to global sea level rise 1993-2010”

ARTICLE PUBLICATION DATE

15-Jun-2023