Study shows making cities greener doesn’t just capture carbon – it reduces it

Peer-Reviewed Publication

KTH, ROYAL INSTITUTE OF TECHNOLOGY

 

IMAGE: NOT JUST A COOL AND SHADY OASIS IN THE CITY, STOCKHOLM'S KARLAVÄGEN CONTRIBUTES TO CLIMATE-POSITIVE BEHAVIORS SUCH AS BICYCLING AND WALKING. view more 

CREDIT: DAVID CALLAHAN/KTH ROYAL INSTITUTE OF TECHNOLOGY

Dozens of European cities could reach net zero carbon emissions over the next 10 years by incorporating nature into their infrastructure, according to a new study.

Published recently in the journal, Nature Climate Change, the analysis shows the ways cities can orchestrate a wide range of green solutions like parks, streetscaping and roof gardens to not only capture carbon emissions, but help reduce them.

The study was undertaken by researchers from Sweden, the U.S. and China. It recommends the most effective approaches for natural carbon sequestration in 54 cities in the EU. And it shows how blending these steps with other climate actions can enable cities to reach net-zero carbon and actually reduce emissions by an average of 17.4 percent.

Zahra Kalantari, an associate professor in Water and Environmental Engineering at KTH Royal Institute of Technology, says the researchers focused on the indirect ways that so-called “nature-based solutions” can contribute to carbon neutrality.

“Nature-based solutions not only offset a proportion of a city’s emissions, but can contribute to reduction in emissions and resource consumption too,” Kalantari says.

The results are based on integrating data from previous studies on the effects of nature-based solutions. These include urban farming, permeable pavements which enable rainwater absorption into the ground, narrower roads with more greenery and trees, wildlife habitat preservation, and creating more agreeable environments for walking and bicycling.

For example, urban parks, greenspace and trees promote more walking, bicycling and other environmentally positive habits that replace automobile driving. Combined with other solutions like green infrastructure, these measures can further improve urban microclimates by absorbing heat and cold, and as a result reduce energy use in buildings.

It also provides guidance on which measures should be prioritized and where to locate them for the best effect, she says. For example, in Berlin the study recommends prioritizing green buildings and urban green spaces, which could result in an emissions reduction rate of 6 percent for residences, 13 percent in industry and 14 percent in transportation.

“There are many studies that examine the effects of individual nature-based solutions, but this merges all of them and analyzes the potential systemic effect,” she says. “That’s new.”

The study was a collaboration by researchers from KTH Royal Institute of Technology in Stockholm, MIT, Stockholm University, University of Gävle, Linköping University, Royal Swedish Academy of Sciences and Shanghai Jiao Tong University.

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JOURNAL

Nature Climate Change

DOI

10.1038/s41558-023-01737-x 

ARTICLE TITLE

Contribution of prioritized urban nature-based solutions allocation to carbon neutrality

 

Flowering for naught: 120 years with nothing to show

Peer-Reviewed Publication

HIROSHIMA UNIVERSITY

 

IMAGE: BAMBOO FLOWERING view more 

CREDIT: TOSHIHIRO YAMADA, HIROSHIMA UNIVERSITY

A long-lived monocarpic species of bamboo, Phyllostachys nigra var. henonis, only flowers once every 120 years before it dies. The upcoming flowering event for this species does not bode well for its continued long-term survival, as most flowers are not producing viable seeds.

Flowering for some plants is a yearly occurrence, for others, it is a once-in-a-lifetime event. A widespread species of bamboo in Japan, Phyllostachys nigra var. henonis, takes this one-time flowering event and pushes it to the extreme: they flower once every 120 years before dying to make way for the next generation. Researchers have realized there might be another issue at hand with this monocarpic species, which is the lack of germination of the seeds from a majority of the flowering specimens. Implications of a once dense field of bamboo, something that serves both as a food source and a source of material for crafts, turning to grassland for several years until the regeneration of bamboo begins to start somehow, can impact the ecology of the area in addition to the country’s economy.

Researchers published their results in PLOS ONE on June 12.

Upon the observation of some early flowering specimens, researchers decided to take advantage of this event to take a deeper look at the regeneration ecology since there is no recorded data since the last flowering of this species took place around 1908. It was found that more than 80% of the sampled culms flowered but all the flowering culms did not produce seeds, indicating this variation of P. nigra does not reliably undergo sexual regeneration via the germination of seeds.

“The bamboo did not produce any viable seeds that can germinate. Bamboo shoot production was stopped after flowering. There was no sign of regeneration of this bamboo after flowering for the initial three years” said Toshihiro Yamada, lead researcher and first author of the study.

Around .17 million hectares of Japan are occupied by three species of bamboo, one of them being P. nigra var. henonis. Given that this variety of bamboo isn’t producing viable seeds, it’s likely once this flowering event occurs, there will be wide open areas of grasslands, changing the ecology of the area in addition to reducing the availability of bamboo as a resource.

The environmental impacts of a rapidly shifting ecological area extend past the insects and animals that rely on the food or shelter of the bamboo stand but also can impact the area for years to come considering the potential for soil erosion. Bamboo can help keep soil in place thanks to its strong and widespread rhizomes, so a sudden loss of a large area of this plant can lead to changing topography of the area.

“So, a bamboo stand will turn into a grassland after bamboo flowering for at least several years. We may need to manage this drastic change after bamboo flowering” Yamada said.

There are measures that can be taken to protect the ecological habitat during the time it takes for the bamboo stands to regenerate, such as fertilizer applications or replanting the same bamboo species from non-flowering stands. However, management of the rapidly spreading rhizomatous bamboo can become an issue that would then need to be addressed regularly and somewhat aggressively.

More information to be gained includes addressing why this variety of bamboo doesn’t produce many viable seeds, and from there, considerations made on the longevity of this species as a whole have to be made, too. Furthermore, due to its aggressive spread and intense management required to keep it from overtaking forests and other agricultural areas, the best time to make widespread changes might be after the flowering event when the bamboo is at its weakest.

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Toshihiro Yamada, Hitoshi Aoyagi and Miyabi Nakabayashi of the Graduate School of Integrated Sciences for Life at Hiroshima University and Karin Imada of the Department of Integrated Global Studies, School of Integrated Arts and Sciences at Hiroshima University contributed to this research.

The Japan Society for the Promotion of Sciences made this research possible.

About Hiroshima University

Since its foundation in 1949, Hiroshima University has striven to become one of the most prominent and comprehensive universities in Japan for the promotion and development of scholarship and education. Consisting of 12 schools for undergraduate level and 4 graduate schools, ranging from natural sciences to humanities and social sciences, the university has grown into one of the most distinguished comprehensive research universities in Japan. English website: https://www.hiroshima-u.ac.jp/en

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JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0287114 

ARTICLE TITLE

Does monocarpic Phyllostachys nigra var. henonis regenerate after flowering in Japan? Insights from 3 years of observation after flowering

 

Researchers find Antarctic ice shelves thinner than previously thought

New effort aims to better tally Antarctic ice shelf loss

Peer-Reviewed Publication

OHIO STATE UNIVERSITY

COLUMBUS, Ohio – As global ice dams begin to weaken due to warming temperatures, a new study suggests that prior attempts to evaluate the mass of the huge floating ice shelves that line the Antarctic ice sheet may have overestimated their thickness.

The research, recently published in the Journal of Glaciology, is the first large-scale study of its kind to compare ice shelf thickness data from ice-penetrating radar measurements to thickness data estimated from contemporary surface elevation measurements.

By juxtaposing vast datasets of 20 of the 300 total separate ice shelf systems that surround about 75% of the Antarctic ice sheet, researchers from The Ohio State University found that on average, the Antarctic ice shelves are nearly 6% thinner than previous studies had assumed, a difference of about 17 meters. This may seem like a small shift in scale, but typical ice shelves can be anywhere from 50 to 600 meters thick. 

The study concludes that while prior assumptions about the ice shelves’ thickness were correct on a large scale, their accuracy varied greatly on a small scale, such as for individual structures like valleys or crevasses that are either too narrow or too small to be measured accurately. 

Yet as ice shelves play a large role in stabilizing the Antarctic ice sheet as well as Earth’s complex climate system, getting an accurate estimation of their size is essential for calculating how their melt could contribute to sea level rise, said Allison Chartrand, lead author of the study and recent doctoral graduate of the Byrd Polar and Climate Research Center. 

“Because the Antarctic ice sheet is so big, a 1% misestimation in how fast it’s melting could mean inches or feet of sea level rise that we’re not accounting for,” she said. “So it’s really important to be as accurate as we can.”

Even the most minute changes to Antarctica’s ice shelves could pose a significant threat to coastal communities, Chartrand said, as a few inches of significantly displaced ice shelf could cause thicker ice to flow into the ocean and potentially cause some coastlines to retreat several feet.  

According to Chartrand, she and her co-author, Ian Howat, a glaciologist and a Distinguished University Scholar in earth sciences at Ohio State, first began to investigate ice shelf thickness when examining basal channels – channels in which warmer ocean water melts grooves into the bottom of the ice shelf, accelerating mass loss – during a previous study.

One of the largest discrepancies the study found was that the assumptions used to estimate ice shelf thickness in previous research sometimes exaggerated ice shelf thickness in some areas, and at other times understated it. 

While many of these inconsistencies don’t take away much from the big picture, individually, these snapshots are vastly out of focus, said Chartrand. “In comparing the thickness estimate with the radar estimate, we saw that the numbers we had on basal channels and other features like them could be different by up to hundreds of meters, which meant that we could potentially be underestimating or overestimating rates of change,” she said. 

Overall, the study concludes that more abundant and accurate data is needed to enable better predictions of ice shelf loss in Antarctica, as the ultimate goal of their work is to improve observations of the processes that contribute to sea level rise, said Chartrand. 

“What this research really shows is that we need to be a lot more careful about the assumptions we make to estimate the ice shelf thickness, and about how we account for uncertainties and what they mean for the final result,” she said. 

While their work also seeks to inspire others to probe into older datasets, Chartrand hopes that using the past to study the future changes in our environment spurs the development of more advanced technologies, ones that might be able to offer greater aid in the task of assessing the ups and downs of Antarctica’s ever-shifting landscape.

“There’s potential for new discoveries even with data collected anywhere from two to 15 years ago, so we know that a lot still hasn’t been fully explored,” said Chartrand. 

This study was supported by NASA and the National Science Foundation.

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JOURNAL

Journal of Glaciology

DOI

10.1017/jog.2023.49 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

A comparison of contemporaneous airborne altimetry and ice-thickness measurements of Antarctic ice shelves

Two out of three volcanoes are little-known. How to predict their eruptions?

A UNIGE team reveals how three easily measurable parameters provide valuable information about the structure of volcanoes. A step forward in risk assessment and preventive measures.

Peer-Reviewed Publication

UNIVERSITÉ DE GENÈVE

 

IMAGE: MT LIAMUIGA ON THE ISLAND STATE OF ST KITTS AND NEVIS. IT IS ONE OF THE MAIN VOLCANOES STUDIED BY LUCA CARICCHI AND HIS TEAM. © OLIVER HIGGINS view more 

CREDIT: OLIVER HIGGINS

What is the risk of a volcano erupting? To answer this question, scientists need information about its underlying internal structure. However, gathering this data can take several years of fieldwork, analyses and monitoring, which explains why only 30% of active volcanoes are currently well documented. A team from the University of Geneva (UNIGE) has developed a method for rapidly obtaining valuable information. It is based on three parameters: the height of the volcano, the thickness of the layer of rock separating the volcano’s reservoir from the surface, and the average chemical composition of the magma. These results open new prospects for identifying volcanoes that present the greatest risk and are published in the journal Geology.

The Earth is home to some 1,500 active volcanoes, yet we only have accurate data for 30% of them. This is due to the difficulty of observing their "fuel", the famous magma, which is rich in information. This molten rock is first generated at a depth of between 60 km and 150 km in the Earth’s mantle, whereas the deepest human boreholes generally only reach a depth of around ten kilometres, preventing direct observation. The production rate of magma in the Earth’s deep crust beneath a volcano determines the size and frequency of future eruptions.

This lack of data is a danger as more than 800 million people live close to active volcanoes. Therefore, in many regions, there is no basis on which to assess the risk a given volcano poses and the extent of the protective measures to be taken - the evacuation perimeter, for example - in the event of a suspected eruption.

Three key parameters

Geochemical and geophysical analysis methods are regularly used by scientists to monitor volcanoes, but it can take decades to gain an in-depth understanding of how a specific volcano works. Thanks to recent work by the team of Luca Caricchi, full professor at the Department of Earth Sciences of the UNIGE Faculty of Science, it is now possible to obtain valuable information more rapidly.

This method uses three easy-to-measure parameters: the height of the volcano, the thickness of the rocks separating the volcano’s "reservoir" from the surface, and the chemical composition of the magma released over its eruptive history. The first can be determined by satellite, the second by geophysics and/or chemical analysis of minerals (crystals) in the volcanic rocks, and the third by direct sampling in the field.

A "snapshot"

By analysing existing data on the volcanic arc of the Lesser Antilles, a well-studied archipelago of volcanic islands, the UNIGE team has highlighted a correlation between the height of volcanoes and the rate at which magma is produced. "The highest volcanoes produce the biggest eruptions on average during their life. In other words, they can erupt a greater quantity of magma in a single event", explains Oliver Higgins, a former doctoral student in Luca Caricchi’s group and first author of the study.

Scientists have also found that the thinner the Earth’s crust beneath the volcano, the closer its magma reservoir is to the surface, and the more thermally mature the volcano is. "When the magma rises from depth, it tends to cool and solidify, which halts its ascent. But when the supply of magma is large, magma retains its temperature, accumulates in the reservoir that will fuel a future eruption, and ‘eats away’ at the Earth’s crust", explains Luca Caricchi, the second and last author of the study.

Identifying the volcanoes most at risk

Finally, the researchers observed that the average chemical composition of magma that has already erupted is an indicator of its explosiveness. "High levels of silica, for example, indicate that the volcano is fed by a large quantities of magma. In this case, there is a greater risk of a large, explosive eruption from that volcano", explains the researcher.

Together, the three parameters identified by the UNIGE team produce a "snapshot" of a volcano’s internal structure. They enable an initial assessment of the hazard associated with poorly studied volcanoes, without the need for major technical and financial resources. This method can be used to identify the active volcanoes that are most likely to produce a large-scale eruption, and that require increased surveillance.

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JOURNAL

Geology

DOI

10.1130/G51355.1 

METHOD OF RESEARCH

News article

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Eruptive dynamics reflect crustal structure and mantle productivity beneath volcanoes

 

Coastal fisheries show surprising resilience to marine heat waves

Rutgers-led study finds that in the years following marine heat waves, effects on fish communities were often minimal

Peer-Reviewed Publication

RUTGERS UNIVERSITY

Rutgers-led research found that marine heat waves – prolonged periods of unusually warm ocean temperatures – haven’t had a lasting effect on the fish communities that feed most of the world.

The finding is in stark contrast to the devastating effects seen on other marine ecosystems cataloged by scientists after similar periods of warming, including widespread coral bleaching and harmful algal blooms.

“There is an emerging sense that the oceans do have some resilience, and while they are changing in response to climate change, we don’t see evidence that marine heat waves are wiping out fisheries,” said Alexa Fredston, the lead author of the study who conducted the research as a postdoctoral associate in the Global Change Research Group, part of the Department of Ecology, Evolution and Natural Resources in the Rutgers School of Environmental and Biological Sciences (SEBS.)

The study, published in Nature, assessed effects on commercially important fish such as flounder, pollock and rockfish based on data extracted from long-running scientific trawl surveys – conducted by towing a net along the seafloor – of continental shelf ecosystems in North America and Europe between 1993 and 2019. The analysis included 248 marine heat waves with extreme sea bottom temperatures during this period. The researchers were surprised to find that marine heat waves in general don’t show major adverse effects on regional fish communities.

Although declines in biomass did occur after some marine heat waves, the researchers said these cases were the exception, not the rule. Overall, they found that the effects of marine heat waves aren’t distinguishable from the natural variability in these ecosystems.

“The oceans are highly variable, and fish populations vary quite a lot,” said Fredston, now an assistant professor of ocean sciences at University of California, Santa Cruz. “Marine heat waves can drive local change, but there have been hundreds of marine heat waves with no lasting impacts.”

In addition to assessing the impact on the total quantity of organisms in a given area, known as biomass, the researchers examined whether marine heat waves were causing changes in the variety of fish species composing fish communities. For example, evidence might show the loss of species associated with cold water and an increase in species associated with warm water, a phenomenon known as tropicalization.

The findings suggest fish may be able to find safe havens by moving to areas with cooler water during marine heat waves, which the researchers defined as periods of more than five days with extreme sea bottom temperatures for that region and season.

The data included some notable examples of marine heat waves that did have profound impacts, such as the 2014-2016 marine heat wave in the Northeast Pacific known as “the Blob,” one of the largest on record.

While “the Blob” led to a 22 percent loss of biomass in the Gulf of Alaska, a 2012 marine heat wave in the Northwest Atlantic led to a 70 percent biomass gain. The authors also noted that these weren’t large changes compared to natural variability in biomass, and similar effects weren’t seen after most other marine heat waves.

“We found that these negative impacts are unpredictable and that other heat waves had no strong impacts,” said Malin Pinsky, an associate professor in the Department of Ecology, Evolution and Natural Resources and director of the Global Change Research Group at SEBS and a co-author of the study. “This means that each heat wave that hits is like rolling the dice: Will it be a bad one or not? We don't know until it happens.”

Other Rutgers researchers who participated in the study include Zoë Kitchel, a doctoral student, and Aurore Maureaud, a postdoctoral associate, both with the Department of Ecology, Evolution and Natural Resources at SEBS.

Researchers from other institutions participated in the study, including the University of British Columbia, the University of Bern in Switzerland, the National Oceanic and Atmospheric Administration, the French Research Institute for Exploitation of the Sea, the University of Montpellier in France, the University of Tromsø in Norway and Fisheries and Oceans Canada.

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JOURNAL

Nature

DOI

10.1038/s41586-023-06449-y 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Marine heatwaves are not a dominant driver of change in demersal fishes

ARTICLE PUBLICATION DATE

31-Aug-2023

 

The scent of the afterlife unbottled in new study of ancient Egyptian mummification balms

Peer-Reviewed Publication

MAX PLANCK INSTITUTE OF GEOANTHROPOLOGY

 

IMAGE: LIMESTONE CANOPIC JAR OF THE EGYPTIAN LADY SENETNAY (C. 1450 BCE); MUSEUM AUGUST KESTNER, HANNOVER (INV.-NO. 1935.200.1018) view more 

CREDIT: MUSEUM AUGUST KESTNER, HANNOVER; PHOTO: CHRISTIAN TEPPER (MUSEUM PHOTOGRAPHER)

In an innovative endeavor to create a sensory bridge to the ancient past, a team of researchers led by Barbara Huber of the MPI of Geoanthropology has recreated one of the scents used in the mummification of an important Egyptian woman more than 3500 years ago.

Coined 'the scent of the eternity’, the ancient aroma will be presented at the Moesgaard Museum in Denmark in an upcoming exhibition, offering visitors a unique sensory experience: to encounter firsthand an ambient smell from antiquity - and catch a whiff of the ancient Egyptian process of mummification.

The team’s research centered on the mummification substances used to embalm the noble lady Senetnay in the 18th dynasty, circa 1450 BCE. The researchers utilized advanced analytical techniques – including Gas Chromatography-Mass Spectrometry, High-Temperature Gas Chromatography-Mass Spectrometry, and Liquid Chromatography-Tandem Mass Spectrometry – to reconstruct the substances that helped to preserve and scent Senetnay for eternity.

“We analyzed balm residues found in two canopic jars from the mummification equipment of Senetnay that were excavated over a century ago by Howard Carter from Tomb KV42 in the Valley of the Kings,” says Huber. Today, the jars are housed in the Museum August Kestner in Hannover, Germany. The team found that the balms contained a blend of beeswax, plant oil, fats, bitumen, Pinaceae resins (most likely larch resin), a balsamic substance, and dammar or Pistacia tree resin.

“These complex and diverse ingredients, unique to this early time period, offer a novel understanding of the sophisticated mummification practices and Egypt’s far-reaching trade-routes,” says Christian E. Loeben, Egyptologist and curator at the Museum August Kestner.

“Our methods were also able to provide crucial insights into balm ingredients for which there is limited information in contemporary ancient Egyptian textual sources,” observes Huber.

The work also highlights the trade connections of the Egyptians in the 2nd millennium BCE. “The ingredients in the balm make it clear that the ancient Egyptians were sourcing materials from beyond their realm from an early date,” says Prof. Nicole Boivin, senior researcher on the project. “The number of imported ingredients in her balm also highlights Senetnay’s importance as a key member of the pharaoh’s inner circle.”

Among those imported ingredients were larch tree resin, which likely came from the northern Mediterranean, and possibly dammars, which come exclusively from trees in Southeast Asian tropical forests. If the presence of dammar resin is confirmed, as in balms recently identified from Saqqara dating to the 1st millennium BCE, it would suggest that the ancient Egyptians had access to this Southeast Asian resin via long-distant trade almost a millennium earlier than previously known.

Working closely with the French perfumer Carole Calvez and the sensory museologist Sofia Collette Ehrich, the team meticulously recreated the scent based on their analytical findings.

“'The scent of eternity’ represents more than just the aroma of the mummification process,” notes Huber. “It embodies the rich cultural, historical, and spiritual significance of Ancient Egyptian mortuary practices.”

In creating this smell for museum display, the team hopes to help provide an immersive, multisensory experience to visitors, allowing them to connect with the past in a uniquely olfactory way, while bringing the mystique of Ancient Egyptian mummification to the modern day. Their groundbreaking approach not only bridges a deep temporal divide, but also enables visually impaired individuals to participate more fully in the exhibition of Egypt’s past, making new research results on ancient mummification accessible to a broader audience.

Perfume (IMAGE)

MAX PLANCK INSTITUTE OF GEOANTHROPOLOGY

Dammar resin, an ingredient in embalming, next to a bottle of the ancient scent recreated by perfumer Carole Calvez based on scientific analyses

CREDIT

Barbara Huber

CAPTION

Perfumer Carole Calvez in the process of recreating the scent of eternity

CREDIT

Carole Calvez

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JOURNAL

Scientific Reports

DOI

10.1038/s41598-023-39393-y 

ARTICLE TITLE

Biomolecular characterization of 3500-year-old ancient Egyptian mummification balms from the Valley of the Kings

ARTICLE PUBLICATION DATE

31-Aug-2023

 

Acting fast when an epidemic hits

Using machine learning to predict short-term disease progression

Peer-Reviewed Publication

UNIVERSITY OF WATERLOO

A team of researchers at the University of Waterloo and Dalhousie University have developed a method for forecasting the short-term progression of an epidemic using extremely limited amounts of data. 

Their model, the Sparsity and Delay Embedding-based Forecasting model, or SPADE4, uses machine learning to predict the progression of an epidemic using only limited infection data. SPADE4 was tested on both simulated epidemics and real data from the fifth wave of the Covid-19 pandemic in Canada and successfully predicted the epidemics’ progressions with 95 per cent confidence. 

“Covid taught us that we really need to come up with methods that can predict with the least amount of information,” said applied mathematics PhD candidate Esha Saha, the lead author of the study. “If we have a new virus emerge and testing has just started, we have to know what to do in the short-term.” 

When a disease breakout occurs – whether for new infections like Covid-19 or existing ones like Ebola – being able to predict the development of the disease is essential for making public policy decisions.

“That’s what policymakers need right at the beginning,” Saha said. “What should we do in the next seven days? How should I allocate resources?” 

Traditionally, epidemiologists prefer to build and use complex models to understand the progression of epidemics. These models, however, have several drawbacks, Saha said. 

They require complex demographic information that is frequently unavailable at the beginning of an outbreak. Even if that detailed information is available, the models may not accurately reflect the complexity of the population or dynamics of the disease.  

The Waterloo research team’s new model addresses these drawbacks. 

“By the time we’re working on vaccines and cures, we’re looking at longer-term data,” Saha said. “But when a new disease arrives, this method can help give us insight into how to behave.” 

The study, “Spade4: Sparsity and Delay Embedding Based Forecasting of Epidemics,” appears in the Bulletin of Mathematical Biology. 

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JOURNAL

Bulletin of Mathematical Biology

US Rule allowing rail shipments of LNG will be put on hold to allow more study of safety concerns




OMAHA, Neb. (AP) — A Trump-era rule allowing railroads to haul highly flammable liquefied natural gas will now be formally put on hold to allow more time to study the safety concerns related to transporting that fuel and other substances like hydrogen that must be kept at extremely low temperatures when they are shipped, regulators announced Thursday.

Right after it was announced in the summer of 2020, the rule was challenged in court by a number of environmental groups and 14 states. The uncertainty about the rule on transporting the fuel known as LNG kept railroads from shipping it. The Pipelines and Hazardous Materials Safety Administration says no one has ever even ordered one of the specially fortified rail cars that would have been required to ship LNG, and several hundred of those cars that would each take at least 18 months to build would likely be needed to make the idea viable.

“We need to do more safety investigative work,” said Tristan Brown, the deputy administrator who is leading the agency. “Until we do that work, we don't want someone to, you know, make investments and deploy something where we haven't fully done the process we normally do need to do.”

Brown acknowledged that the rule was rushed under a directive from former President Donald Trump, so it needs to be refined.

This latest action ensures the rule that was backed by the freight rail and natural gas industries will remain on hold at least until regulators finalize changes to the rule the Biden administration wants to make or the end of June 2025 — whichever comes first.

One of the big railroads that said it may have been interested in hauling the fuel, CSX, abandoned any plans to build the infrastructure needed to load and unload LNG from railcars after the agency first announced this proposal to suspend the rule in 2021.

Current federal rules do allow trucks to haul LNG but not rail. But Brown said there's only a tiny amount of natural gas that isn't delivered by pipelines, so there was never much demand for rail shipments of LNG. After pipelines deliver gas to ports, ships haul the LNG that is exported.

The rail industry maintains that it is the safest option to transport hazardous materials across land. The Association of American Railroads trade group touts railroads' record of delivering more than 99% of all toxic shipments without incident.

But rail safety has been in the spotlight this year ever since a Norfolk Southern train derailed in eastern Ohio in February and spilled several chemicals that caught fire. That railroad is still cleaning the mess that prompted calls for reforms and fears of possible health problems for people who live in and around East Palestine.

Brown said he thinks the East Palestine derailment highlighted the importance of some of his agency's previous rules because the tougher tank cars recommended in 2015 performed better in the wreck. But that derailment highlights the need for railroad regulations.

“I think that has that has underscored the need to address rail safety — generally hazmat transportation by rail,” Brown said.

U.S. natural gas production has continued to surge in recent years amid strong global demand for the fuel. Natural gas exports have grown steadily over the past two decades, and the U.S. has become the world's largest exporter of liquefied natural gas.

Russia's invasion of Ukraine only added to global demand. That's particularly the case in Europe, where many nations were accustomed to relying on Russian energy before the war prompted them to sever those ties.

The states that challenged the LNG rule in court alongside groups like the Sierra Club, the Center for Biological Diversity and the Clean Air Council included California, Delaware, Illinois, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington. Washington D.C. and the Puyallup Tribe of Indians are also part of the lawsuit.

Josh Funk, The Associated Press