Air from Greenland snow shows industrialization's impact on atmospheric methane

Reconstruction based on clumped isotopes

Utrecht University, Faculty of Science

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Researchers obtained up to 40-year-old air from compacted snow, called firn, on Greenland

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Credit: Thomas Röckmann

[Lead]

An international team of researchers, including scientists from Utrecht University and the University of Maryland, has reconstructed the concentration of clumped isotopes of methane in air from the past for the first time. This provides new insights into how atmospheric methane concentrations have changed since the start of the industrial era, around 1850. For the study, the scientists used air roughly forty years old, preserved in compacted snow (firn) in Greenland. The results were published in Science Advances.

 

[Intro]

Methane is the second most important greenhouse gas after CO2, responsible for around thirty percent of global warming to date. Atmospheric methane concentrations are rising, but it is not yet fully understood why that happens.

 

Human fingerprint

The researchers' measurements and analyses showed that the concentration of clumped methane isotopes, rare methane molecules with two heavy atoms clustered together, has changed significantly over the past decades. At first, the researchers couldn't fully explain this shift, but after running model simulations of the atmosphere spanning the last thousand years, they were able to pinpoint a cause. "Since the start of industrialisation, humans have disrupted the balance between methane emissions and breakdown so profoundly that it's visible in our measurements," explains Malavika Sivan, first author of the study.

 

Malavika Sivan, former researcher at IMAU and first author of the study: “Since the start of industrialisation, humans have disrupted the balance between methane emissions and breakdown so much that it's visible in our measurements.”

 

Methane balance

The clumped isotope signal reflects the balance between how much methane is emitted and how much is removed from the atmosphere. That balance determines whether atmospheric methane concentrations keep rising or start to fall. With this information, researchers can reconstruct the methane balance over time, and going forward, allowing them to check whether measures taken to reduce methane emissions are working.

That matters, says Thomas Röckmann, professor of Atmospheric Physics and Chemistry. "Reducing methane concentrations is one of the fastest ways to slow global warming in the short term." Continued human emissions and possible climate feedback from natural sources could drive further increases. "Policy initiatives like the Global Methane Pledge, which aims for a thirty percent cut in methane emissions by 2030 compared to 2020, might help slow or reverse that trend," Röckmann explains.

 

Thomas Röckmann, professor of Atmospheric Physics and Chemistry: “Reducing methane concentrations is one of the fastest ways to slow global warming in the short term.”

 

A surprising measurement

The research was prompted by an unexpected finding: the researchers measured clumped methane isotopes in the current atmosphere. The occurrence of these molecules was far higher than in methane from known sources such as wetlands, agriculture, and fossil fuels. Those sources couldn't account for such a strong signal.

The team concluded that the clumped isotope signal must originate from methane removal: when methane breaks down in the atmosphere through reactions with other substances. These clumped molecules react slower than normal methane molecules. “Following this, we wondered if we could use these clumped methane signatures to learn how the removal reactions changed in the atmosphere over time”, Röckmann explains.

 

Forty-year-old air

Methane is mainly released from biological and fossil sources. It forms naturally in wetlands, rice paddies, landfills, and agricultural systems, and is also released from fossil fuels such as coal, oil, and natural gas. To understand how methane sources and removal have changed over time, the researchers needed access to air from the past. And not just a little: analysing clumped methane isotopes requires as much as a thousand liters of air.

That old air can be found in firn: a layer of dense snow between the surface and the underlying glacial ice, where air remains trapped that is sometimes up to seventy years old. At the EastGRIP research station in Greenland, Röckmann collected the necessary air samples by drilling deep into the snow and essentially pumping the air out with specialised equipment. “We collected 500 to 700 litre air samples that were up to forty years old,” Röckmann says. “Analysing that air tells you a lot about the composition of the atmosphere in the past.”

 

An international collaboration

The amount of air was still on the low end for reaching the best precision with the instrument that is used in Utrecht. But a research group at the University of Maryland had a different instrument that could do the same measurements using less air. Sivan travelled to the University of Maryland for two months to analyse the air samples, together with her colleague Jiayang Sun. "There was a lot of trial and error, but in the end, we were excited to see such a strong temporal change in the clumped isotope signal.”

The results were unexpected, and it took a lot of discussion and modelling to understand the signal measured. “But it was worth it: we really understand how the clumped isotope signal records the influence of humans on the atmosphere in the industrial period" Sivan says.

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Journal

Science Advances

DOI

10.1126/sciadv.aeb2203 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Anthropogenic perturbations to atmospheric methane reflected in Greenland firn air clumped isotope measurements

Article Publication Date

15-Jul-2026

 

Researchers obtained up to 40-year-old air from compacted snow, called firn, on Greenland

Researchers obtained up to 40-year-old air from compacted snow, called firn, on Greenland. In this image you see Thomas Röckmann holding two barrels of compressed air.

Credit

Thomas Röckmann

The air was analysed by Malavika Sivan and Jaiyang Sun in a lab at the University of Maryland.

 

Malavika Sivan working on the analysis of the obtained air at the University of Maryland.

Credit

Malavika Sivan

 

Roadless rule helps protect clean drinking water for 25 million Americans, new study shows

University of Washington

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Approximately 90% of the U.S. population relies on public water systems. A significant portion of the water supplying those systems comes from forested lands, which means that policies impacting forests also impact our water access. 

In 2001, the Clinton administration passed the Roadless Area Conservation Rule, blocking 60 million acres of national forest land from development to limit industrial timber harvest and preserve forest ecosystems. Although popular with the public, the roadless rule drew immediate criticism from timber and related industries. Last summer, the federal government announced plans to rescind it. 

A new study from the University of Washington and Conservation Science Partners, published July 15 in PLOS, highlights the potential consequences of losing those protections by mapping how the roadless rule protects rivers. 

“The roadless rule supports the drinking water supply for 25 million Americans and offers critical protection of wildlife habitat and recreational assets. In short, rivers in roadless areas are essential for both people and nature,” said lead author Julian Olden, a UW professor of aquatic and fishery science.

To show how forests impact freshwater, the researchers looked at nearly 110,000 square miles of national forest representing 2,488 officially designated “roadless areas.” They cross-referenced the roadless areas map with a recent study assessing river protections nationwide to see where rivers and roadless areas overlap, and therefore which rivers were vulnerable to losing protection. 

The researchers found that more than 80,000 miles of rivers in the continental U.S. receive some protection from the roadless rule. Of those protected segments, nearly 62,000 miles of river are protected by only the roadless rule. That water reaches 25 million people across the country, often at downstream distances far from roadless areas.

Research shows that forested lands provide higher quality water because soil microbes and plant roots filter contaminants before water arrives at treatment facilities. Cleaner water requires less processing, reducing potential treatment costs for public utilities. Some water utilities are investing in watershed protection as a way to save money and limit chemical use as demand for water rises.

“Forest cover is well recognized for generating economic benefits by avoiding the large capital costs of water treatment plants needed to ensure clean, safe drinking water for people,” said Olden. 

Roadless areas are also vital strongholds for sensitive aquatic species, Olden added. At-risk species such as the bull trout use protected habitat for spawning and raising young. Hunters and anglers also value roadless areas because they support such productive fish and wildlife habitat and offer unparalleled opportunities for outdoor recreation. 

After the U.S. Agriculture Secretary Brooke Rollins announced the plan to rescind the roadless rule last year, more than half a million people submitted comments during the public comment period, which ended in September. According to the Center for Western Priorities, more than 99% of those comments expressed opposition to the plan.

Earlier this year, Republican lawmakers attempted to push the measure through by attaching it to the Wildfire Prevention Act, which supports prescribed burns and forest thinning to fight megafires. Their initial argument to justify clawing back protections claimed that rescinding the roadless rule would allow for better forest management, but most scientists disagree. Research shows that roadbuilding in formerly roadless areas is more likely to increase fire risk.

“To be clear, the rule does not block any management action that supports forest health, wildfire mitigation or recreation,” Olden said. “In fact, energy projects, transmission lines and mining development remain permitted within roadless areas.”

Roadbuilding and logging can cause sediment build up in lakes and rivers, which must be filtered out. Chemicals from construction can also end up in the water supply. Reductions in forest cover resulting from rescinding the roadless rule may compromise water quality in the U.S., among other negative consequences for animals and ecosystems. 

The U.S. Forest Service says it is reviewing public comments and plans to publish a proposed rule and draft statement of environmental impact this year.

“Any decision to rescind or downgrade the roadless rule that may put forested lands at risk requires careful consideration of the numerous benefits they offer to people and nature,” said Olden. “Our study offers data to inform such decisions.”

This study was funded by the University of Washington and from a contract from American Rivers to Conservation Science Partners.

For more information, contact Olden at olden@uw.edu.

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Journal

PLOS Water

Method of Research

Data/statistical analysis

Article Title

Assessing the value of the U.S. Roadless Rule for people and nature

Article Publication Date

15-Jul-2026

The Trump administration's 2025 repeal of the U.S. "Roadless Rule" prohibiting logging and road construction in national parks and wilderness areas may impact the 25 million Americans whose drinking water comes from previously roadless watersheds

PLOS

 

Article URL: https://plos.io/4eYT2bn 

Article Title: Assessing the value of the U.S. Roadless Rule for people and nature

Author Countries: United States

Funding: This work was supported by funding from the University of Washington (JO) and from a contract from American Rivers to Conservation Science Partners (LC, PF, and HK). No funding sources are reported for SP and MD. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Journal

PLOS Water

DOI

10.1371/journal.pwat.0000538 

Article Publication Date

15-Jul-2026

 

Bone ‘fingerprints’ unlock hidden stories of underwater caves

Griffith University

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Griffith University PhD Candidate Meg Walker examines retrived megafauna fossils from Engelbrechts cave in Mount Gambier, South Australia.

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Credit: Steve Trewavas

Bones preserved in underwater caves offer a rare and powerful window into the past – but until now, researchers have had limited tools to understand how the remains of extinct megafauna and other animals came to be found in their underwater graveyards.  

New research led by Griffith University changes that.  

“By analysing animal bones from two underwater cave systems in South Australia, we have revealed how different cave environments leave distinct preservation ‘fingerprints’ on skeletal remains,” said Meg Walker, a PhD Candidate supervised by Australian Research Centre for Human Evolution Director Professor Julien Louys.  

“Backed by radiocarbon-dated bones, we tracked how skeletons accumulated and were modified over decades and centuries in underwater caves, then compared them to those buried in dry caves. 

“Using a range of methods, from the macro to the micro, we looked at features associated with wet and dry caves. 

“Things like spatial distributions of the bones and their surfaces, down to elemental compositions and proteins trapped in ancient cells.”  

The results were clear: underwater caves often preserved bones remarkably well, maintaining their structure and surfaces in exquisite detail.  

Yet these same environments also left unique chemical and biological traces, shaped by light levels and aquatic life.  

Different types of algae and plants grew in cave waters near bright entrances, often on bone surfaces where they left unique signatures.  

But in the midnight regions of the caves, where light never reaches and no plants grow, bones stayed pristine.  

Bones left in dry caves, by contrast, did not show these signatures, and were instead eaten by land-based bacteria, and marked by plant roots in the form of long grooves. 

Ms Walker and the team, including specialist cave divers from the Cave Divers Association of Australia, collected historical animal bones from two underwater caves, Green Waterhole and Gouldens Sinkhole, near Mount Gambier, South Australia. 

Native and non-native animals included cows, kangaroos, emus, sheep, pigs, dingoes, rabbits, possums, quolls and swamp rats – some of which may date to the very first European arrival and establishment of the city in the 1840s.  

By studying these bones, the researchers hoped to better understand how the fossil remains of extinct megafauna also ended up in these underwater caves, and under what sort of environmental conditions. 

“This study has delivered the first framework for interpreting how megafauna fossils formed, survived, and changed in underwater caves,” Miss Walker said. 

“It will provide archaeologists and palaeontologists worldwide with a powerful new tool for reconstructing past environments and histories in these challenging conditions.” 

The study ‘Neotaphonomic characteristics of vertebrate site formation in underwater caves’ has been published in PLOS One.

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Journal

PLOS One

DOI

10.1371/journal.pone.0343896 

 

Study reveals a winter version of the biological clock

Washington State University

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PULLMAN, Wash. – Researchers at Washington State University have discovered a molecular “winter lock” that keeps animals in a less active winter state until favorable conditions return, a discovery that could improve pest control and lead to a better understanding of seasonal health conditions in humans.

Using fruit flies as a model, researchers found the "winter lock" is driven by seasonal changes in a key gene found in the circadian clock, which regulates daily biological rhythms. Through a process called alternative splicing, the gene, known as timeless, produces a winter-specific protein that alters activity patterns and suppresses reproduction. The findings, published in Science Advances, suggest animals may rely on multiple versions of their biological clock, with different molecular arrangements helping them adapt to seasonal environmental changes.

“We've known for a long time that animals use environmental cues to prepare for seasonal changes, but we haven't understood exactly how that information is integrated by the biological clock,” said Sergio Hidalgo, an assistant professor in the WSU College of Veterinary Medicine's Department of Integrative Physiology and Neuroscience and corresponding author on the study. “What we found is that the clock itself can be rearranged into a winter state that helps animals stay there until conditions are favorable enough to switch back to summer mode.”

Animals, plants and even bacteria use environmental cues to anticipate seasonal change and adjust their behavior and physiology accordingly. These adaptations can include migration, hibernation, reproductive changes and periods of dormancy that help organisms survive harsh conditions and food shortages.

While scientists know changes in day length and temperature help trigger these seasonal responses, exactly how organisms integrate those signals to coordinate seasonal behavior was largely unknown. The circadian clock was suspected to play a role in that process, but exactly how it influenced seasonal timing was unclear.

The new study found that alternative splicing – a process that allows the gene to produce different proteins – of the timeless gene plays a critical role in helping fruit flies enter and maintain a winter state, which includes shifted daily activity patterns and reproductive dormancy. The produced protein alters the function of the circadian clock, creating a molecular "winter lock" that remains in place until environmental cues signal it is time to return to a summer state.

“For years, we've been studying what is essentially the summer version of the clock,” Hidalgo said. “This work shows that the clock can be remodeled in winter, creating a system that functions differently and helps animals maintain a winter program.”

Hidalgo suspects similar mechanisms exist in agricultural pests and disease-carrying insects such as mosquitoes. Understanding how insects determine seasonal timing could provide new ways to disrupt populations by interfering with the biological processes that help them survive changing seasons.

The findings may also help scientists better understand seasonal influences on human health. Conditions such as seasonal affective disorder and some neurological and psychiatric disorders have been linked to seasonal patterns, though the biological processes driving those changes remain poorly understood.

The study included researchers from WSU and the University of California, Davis. Co-authors included Audrey Berry, a WSU alumna and research intern in Hidalgo's lab, along with collaborators from both institutions.

The research was supported by the National Institutes of Health and the Pew Charitable Trusts.

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Journal

Science Advances

DOI

10.1126/sciadv.aed4249 

Article Title

Splicing of a core circadian clock gene regulates seasonal adaptations by a winter gating mechanism

Article Publication Date

15-Jul-2026

 

Connection between forests and rivers strengthens amphibians’ microbiome and protects them against a lethal fungus

A study involving a FAPESP-funded center concludes that conserving landscapes means more than just protecting isolated fragments

Fundação de Amparo à Pesquisa do Estado de São Paulo

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A study published in the Proceedings of the National Academy of Sciences indicates that a frog’s resistance to a fungus that has decimated hundreds of amphibian species worldwide is due not only to its genes, but also to the beneficial bacteria living on its skin and to the organization of its surrounding landscape.

Scientists have demonstrated that a disconnect between forests and bodies of water impairs amphibians’ ability to recruit defensive microbes, making them more susceptible to Batrachochytrium dendrobatidis (Bd), a fungus that is one of the most devastating pathogens for this class of animals.

This phenomenon is called “habitat split” – the spatial separation of the terrestrial and aquatic environments required by many amphibian species to complete their life cycle (reproduction in water and adulthood in the forest).

Led by Daniel Medina, a professor at the School for Field Studies in the United States, and Renato A. Martins, the team collected skin samples from 586 frogs of four species in the Atlantic Forest of the state of São Paulo, Brazil. The team also included Guilherme Becker from Penn State University in the United States and Célio Haddad from São Paulo State University (UNESP) in Rio Claro, who is the scientific coordinator of the Center for Research on Biodiversity Dynamics and Climate Change (CBioClima). Using high-resolution genetic sequencing, the researchers identified the present bacteria and cross-referenced this information with the AmphiBac database, which contains over 7,800 bacterial isolates tested in a laboratory for their ability to inhibit Bd growth.

CBioClima is one of FAPESP’s Research, Innovation, and Dissemination Centers (RIDCs).

The team then quantified the fungal infection load in each animal, as well as landscape metrics such as the percentage of forest cover, edge density within the fragments, and most importantly, the distance between forest fragments and bodies of water. Advanced statistical models (GLMMs and joint species distribution models) isolated the effect of habitat split from other variables, such as collection date and surrounding landscapes.

The results were striking. In areas with high habitat split, the proportion of genetic reads corresponding to bacteria capable of inhibiting Bd dropped sharply. Two migratory species, Ischnocnema henselii and Rhinella ornata, exhibited higher fungal loads precisely where habitat split was greatest. In contrast, species able to use tank bromeliads (such as Boana faber) were less affected. The data suggest that moist microhabitats within the forest itself can mitigate the effects of fragmentation.

According to the authors, the study provides the first robust field evidence for the “adaptive microbiome principle”: repeated, low-level exposure to the pathogen – which occurs naturally in connected landscapes – selects for microbial communities that are better prepared to cope with future infections. When connectivity is disrupted, amphibians lose access to beneficial microbes in the environment and the opportunity to “train” their microbial defenses.

“The significance of this study lies in the evidence that preserved and connected habitats are the cradle of healthy populations – a reality that dissipates under the impact of human-caused fragmentation. More than just a diagnosis, the research provides insights for forest reconnection strategies that focus on combating the aftermath of the illegal deforestation plaguing the country. It’s crucial to acknowledge that human survival is inextricably linked to environmental health. In this context, amphibians emerge as sentinels of environmental quality, reminding us that functional ecosystems are the foundation of our own health and longevity,” says Haddad.

About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe

 

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DOI

10.1073/pnas.2520745123 

Article Title

Connecting habitats, boosting disease resistance: Spatial connectivity enhances amphibian microbiome defenses against fungal pathogen