Protect habitat ‘stepping stones’ to help species cope with climate change, scientists say

Peer-Reviewed Publication

UNIVERSITY OF LIVERPOOL

 

IMAGE: MAP SHOWING AN EXAMPLE SPATIAL OUTPUT FROM CONDATIS FOR CALCAREOUS GRASSLAND. EACH BLUE POINT IS AN AREA OF HABITAT, THE DARKER THE BLUE THE MORE IMPORTANT THAT PATCH IS TO CONNECTIVITY BETWEEN THE SOUTH COAST OF ENGLAND, AND ITS NORTHERN BORDER WITH SCOTLAND. view more 

CREDIT: THOMAS TRAVERS AND CONDATIS

Safe passages for species adapting to climate change aren’t always being protected, a new study by the University of Liverpool warns.

With rising temperatures altering where species can survive, many are moving to newly hospitable patches further north. Key to this journey is ensuring suitable connectivity between where species currently live and where they might do in the future.

“If patches of habitat vital to connectivity are lost because they aren’t protected, a major way species can adapt to climate change will be hindered. We therefore need methods to identify the most important ‘stepping stones’ and consider these when designating protected areas for conservation,” explains researcher Thomas Travers.

In a new paper published today in the Proceedings of the Royal Society B, researchers used a cutting-edge software tool called Condatis to explore how species might move northwards through 16 different habitat networks in England, quantifying the importance of different patches to this connectivity. They also explored how much connectivity could be improved by protecting some of the key areas. 

The study was carried out by researchers from the University of Liverpool, Natural England and the UK Centre for Ecology and Hydrology.

The team found that important connecting patches were often left out of the existing networks of protected area, meaning that less connectivity was protected than you might expect given the amount of habitat protection. Across 12 of the 16 habitat networks they studied, this shortfall averaged 13.6%.

However, they also found that if just a small amount of additional area was protected, it could have a major impact on helping to redress this imbalance and reduce vulnerability to climate change. By focusing on additional nature reserves to prioritise connectivity, the team estimates that an average of 41% more connectivity could be achieved with just a 10% increase in area protection.

Lead author Thomas Travers, a PhD student at the University of Liverpool, said: "The scientific community has been emphasising the importance of incorporating connectivity into the planning process for at least 30 years, and as global climates continue to change this importance will grow. Unfortunately, it appears the connectedness of habitats remains vulnerable to degradation and loss through lack of protection. We have shown that patches important to long-distance connectivity can be easily identified, allowing the proportion protected to be greatly increased with minimal additional resources.”

Co-author Dr Jamie Alison, from the UK Centre for Ecology and Hydrology, added: “We mustn’t forget to protect habitats that seem to be small and peripheral. They are valuable places for people to enjoy nature - but also for species to cope with climate change.”

Senior author Dr Jenny Hodgson, from the University of Liverpool, said “Securing the protection of our best habitats for wildlife is a fundamental first step towards making the natural world resilient in a changing climate. The Convention on Biological Diversity’s proposed target to protect 30% of the Earth’s land and seas for nature by 2030 (30x30 goal) provides an important and timely opportunity to shore up some of this connectivity protection deficit.”

Dr Humphrey Crick, from Natural England welcomed the study, and said: “The importance of connectivity has been emphasised in the Government’s approach to climate change adaptation and this study provides an excellent example of how we can use the latest science to help identify those areas that are potentially important”.

The software Condatis was developed by Dr Jenny Hodgson and has been used around the world to prioritise the best habitat to protect and restore.

Thomas Travers was funded by a NERC studentship through the ACCE (Adapting to the Challenges of a Changing Environment) Doctoral Training Partnership. The study also received financial and logistical support from Natural England.

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JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2021.1010 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Habitat patches providing south–north connectivity are under-protected in a fragmented landscape

ARTICLE PUBLICATION DATE

25-Aug-2021

COI STATEMENT

No competing interests.

 

History of human antibiotic use written in the oral bacteria of wild brown bears

Peer-Reviewed Publication

UPPSALA UNIVERSITY

 

IMAGE: RESEARCHERS USED HISTORICAL MUSEUM COLLECTIONS OF SWEDISH BROWN BEARS TO FOLLOW THE EFFECTS OF HUMAN-MADE ANTIBIOTICS. view more 

CREDIT: KATERINA GUSCHANSKI

An international team of researchers used historical museum collections to study the effects of human-made antibiotics over the entire history of their application. They found that the increased use of antibiotics in medicine and agriculture in the 1950-1990s led to increases in antibiotic resistance in wild Swedish brown bears. However, they also detected a clear downward trend in antibiotic resistance after national policies to control antibiotic use were implemented.

The study is published in the scientific journal Current Biology.

Antibiotic resistance is a major global health threat and hundreds of thousands of people die each year because of infections with resistant bacteria. Antibiotics and resistant bacteria, e.g., from hospitals, can escape into the environment through wastewater treatment plants and spread by water and wind over large distances. From there, they can be picked up by wild animals, which in turn can transmit resistant bacteria to humans during recreational activities or hunting. However, studying how antibiotic resistance has changed in wildlife since the start of antibiotic mass-production in the 1940s has not been possible until recently. Now, scientists have used specimens from museum collections to analyse changes in the bacterial communities that live in the mouth of wild animals and preserve as solid calculus deposits on teeth. This dental calculus can remain unchanged for millennia, which allowed the study of historical bacterial communities, the microbiomes, from Swedish brown bears as old as 180 years.

“We specifically looked for bacterial genes that provide resistance to antibiotics,” says Jaelle Brealey, a postdoctoral researcher at NTNU in Norway and lead author of the study. “Their abundance closely follows human antibiotic use in Sweden, increasing in the 20th century and then decreasing in the last 20 years. We also find a greater diversity of antibiotic resistance genes in the recent past, likely as a result of different kinds of antibiotics being used by humans.”

Scandinavian brown bears usually live far away from humans but sometimes approach villages and cities. The researchers expected to find more antibiotic resistance genes in bears that lived in more densely populated regions of Sweden. However, to their surprise, no such relationship was observed.

CAPTION

Researchers used historical museum collections of Swedish brown bears to follow the effects of human-made antibiotics.

CREDIT

Katerina Guschanski

“We found similar levels of antibiotic resistance in bears from remote areas and those found near human habitation. This suggests that the contamination of the environment with resistant bacteria and antibiotics is really widespread,” says Katerina Guschanski, lead senior author of the study with joint appointments at Uppsala University and the University of Edinburgh.

Sweden was one of the first countries to implement strict control measures for the use of antibiotics, introducing a ban on antibiotics in agriculture in the mid 1980s and a national strategic program against antibiotic resistance in medicine in 1995. These measures seem to have taken effect. Oral bacteria of bears that were born after 1995 show low antibiotic resistance, albeit not as low as in bears that lived before humans started antibiotic mass-production. Only the comparison of microbiomes through time could uncover these changes.

“Our study highlights once again the value of historical museum collections, like the one at the Swedish Museum of Natural History, as a unique resource for understanding the effect of recent human actions on the environment,” says Daniela Kalthoff, curator of the museum and a co-author on the study.

Historical microbiomes could be used to not only investigate the past but also to monitor environmental changes in response to new strategies for reduction of contamination and pollution. This study provides an encouraging example for how governmental policies can be effective in mitigating a major health threat on a national level. It showcases that human actions, both negative and positive, have a profound effect on the environment.

CAPTION

Researchers used historical museum collections of Swedish brown bears to follow the effects of human-made antibiotics.

CREDIT

Mats Björklund

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JOURNAL

Current Biology

DOI

10.1016/j.cub.2021.08.010 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

The oral microbiota of wild bears in Sweden reflects the history of antibiotic use by humans

ARTICLE PUBLICATION DATE

24-Aug-2021

 

Dams ineffective for cold-water conservation

Study of California Streams Reveals Fish Give Dams the Cold Shoulder

Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - DAVIS

 

IMAGE: ANN WILLIS, A RESEARCHER WITH THE UC DAVIS CENTER FOR WATERSHED SCIENCES, TAKES MEASUREMENTS ON THE LITTLE SHASTA RIVER WITH COLLEAGUE ROB LUSARDI IN 2017. view more 

CREDIT: JOE PROUDMAN/UC DAVIS

Dams poorly mimic the temperature patterns California streams require to support the state’s native salmon and trout — more than three-quarters of which risk extinction. Bold actions are needed to reverse extinction trends and protect cold-water streams that are resilient to climate warming, according to a study published in the journal PLOS ONE by the University of California, Davis. 

The study helps identify where high-quality, cold-water habitat remains to help managers prioritize conservation efforts.

“It is no longer a good investment to put all our cold-water conservation eggs in a dam-regulated basket,” said lead author Ann Willis, a senior staff researcher at the UC Davis Center for Watershed Sciences and a fellow for the John Muir Institute of the Environment. “We need to consider places where the natural processes can occur again.”

The uncommon cold

Understanding where cold water is likely to stay cold is critical for conservation. But “cold” is more than just a number on a thermometer. The term represents the many factors that combine to create cold water capable of supporting aquatic ecosystems.

Water managers deliver cold water from reservoirs to streams to support aquatic life. But Willis said this assumes that all cold water is the same — akin to giving blood to another person without understanding their blood type and health status. 

While previous studies have suggested that dams can be operated to achieve ideal temperatures, few tested that hypothesis against the temperature patterns aquatic ecosystems need.

The UC Davis study assessed stream temperature data from 77 sites in California to model and classify their “thermal regimes,” or annual temperature patterns. It found the state’s reservoirs do not adequately replicate natural thermal patterns, making them incapable of supporting cold-water species effectively.  

“I’m an engineer; I thought we could operate ourselves into success, but the science doesn’t support that,” Willis said. “It’s not a question of whether we remove a dam, but which dam, and how we need to restructure how we manage water. Or we need to be willing to take responsibility to be the generation that says, ‘OK, we’re letting this ecosystem go extinct.’” 

What about the drought? 

Drought often tempts people to double-down on hard-infrastructure solutions for water storage. 

“We falsely equate dams with water security,” Willis said. “More storage does not mean more water. A giant, empty refrigerator doesn’t help you if you’re starving. The same is true for water.” 

Of California’s 1,400 dams, only one very large and highly-engineered dam — Shasta — stood out in the study as replicating natural cold-water patterns. 

The study does not suggest removing all dams. However, considering removing “deadbeat dams” where there are critical ecosystems could help restore natural processes and support fish, people and biodiversity amid climate warming.

Cold comfort

Key cold-water conservation candidates include streams highly influenced by groundwater, such as in the Cascade Range, and places where water easily infiltrates the soil, such as Northern California’s Feather River. 

“Classifying these streams and understanding their thermal regimes is an effective way to focus our time and money on the places most likely to make a difference,” Willis said. 

The study’s co-authors include Ryan Peek and Andrew Rypel of the UC Davis Center for Watershed Sciences. 

Funding for this research was provided by internal support from the UC Davis Center for Watershed Sciences and the John Muir Institute of the Environment.

CAPTION

Mill Creek, a spring-fed creek that flows from the base of Mt. Lassen to the Sacramento Valley, is an important cold-water stream.

CREDIT

Ann Willis/UC Davis

JOURNAL

PLoS ONE

DOI

doi.org/10.1371/journal.pone.0256286 

METHOD OF RESEARCH

Meta-analysis

ARTICLE TITLE

Classifying California’s stream thermal regimes for cold-water conservation

ARTICLE PUBLICATION DATE

20-Aug-2021

How firefighters deal with heat stress and fatigue

New research draws on sport performance strategies to help firefighters

Peer-Reviewed Publication

UNIVERSITY OF TECHNOLOGY SYDNEY

 

IMAGE: NEW RESEARCH DRAWS ON SPORT PERFORMANCE STRATEGIES TO HELP FIREFIGHTERS view more 

CREDIT: IMAGE BY ELG21 FROM PIXABAY

Searing heat, fireballs and walls of embers. Australian firefighters faced extreme conditions during the 2020 summer bushfires, which claimed the lives of nine firefighters across the country. Now research is drawing on sport performance strategies to better help them combat heat stress and fatigue. 
 
A new study asked more than 470 firefighters how they recover in the field, especially in situations of greatest heat stress. Air and helmet temperatures at residential fires can reach 750C and 190C respectively, while flame temperatures during bushfires can be as high as 1100C.
 
The study found firefighters generally rely on simple strategies to lower their core body temperature, such as finding shade, drinking water and removing helmets and jackets. However, the research suggests there is potential for better cooling and recovery protocols.
 
Dr Hugh Fullagar from the Human Performance Research Centre at the University of Technology Sydney (UTS) led the study, which was conducted in partnership with Fire and Rescue NSW – the fourth largest urban fire service in the world.

“NSW’s 7000 firefighters are tasked with protecting the homes and lives of 8 million people from the perils of fire. They have to perform physical tasks in extreme heat while wearing heavily insulated protective clothing, which results in acute physical and psychological fatigue.

“We know from data overseas that more than 75 per cent of firefighters experience heat-related illness symptoms such as headache, sudden muscle cramps, dizziness, nausea, and fainting, and that sudden cardiac death accounts for almost half of all firefighter duty-related fatalities.

"Heat stress also results in poorer cognitive functioning and decision making, which in turn likely increases the risk of fatalities,” Dr Fullagar said.

Despite these risks, there has been limited understanding of how firefighters perceive the challenging tasks they perform, the conditions they face, or the fatigue and recovery strategies required to optimise performance and health during active duty.

“Given the predicted increased prevalence of bushfires in Australia due to climate change, along with the unique conditions, terrains and duties our firefighters face - which pose risks to operational safety - it is important to identify more effective, yet practical cooling strategies to recover from physically and mentally demanding tasks in the heat,” Dr Fullagar said.

“We need to understand how firefighters are feeling, what they like or dislike and what is available to them to help optimise cooling and safety, if we want to improve best-practice.” 

While the firefighters surveyed generally used simple cooling strategies such as sitting in the shade, drinking water or removing protective clothing, it is thought this is mainly due to what is available.

They expressed a desire for improved access to similar methods being applied to promote safety and performance in sport such as cold consumables (eg. slushies), external cooling aids (eg. ice packs/vests), as well as other recovery equipment (eg. cooling fans, portable shade cover).

This study was the first part of a two-part study. With a better understanding of the available and relevant cooling and recovery strategies preferred by firefighters, the next step is to determine the optimum combination, timing and selection of these strategies.

This will be assessed in a controlled, laboratory environment to help establish ‘best practice’ recovery protocols following fire-fighting activity. The identification of these protocols will help firefighters recover, as well as enhance the safety of the workforce.

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The study: Australian firefighters perceptions of heat stress, fatigue and recovery practices during fire-fighting tasks in extreme environments, was recently published in the journal Applied Ergonomics.

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JOURNAL

Applied Ergonomics

DOI

10.1016/j.apergo.2021.103449 

METHOD OF RESEARCH

Survey

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Australian firefighters perceptions of heat stress, fatigue and recovery practices during fire-fighting tasks in extreme environments

ARTICLE PUBLICATION DATE

31-Aug-2021

COI STATEMENT

N/A

In hot weather, outdoor laborers work less - when economy is growing

Peer-Reviewed Publication

PLOS

A new analysis suggests that U.S. workers in industries that expose them to weather conditions work fewer hours per day when temperatures surpass 90 degrees Fahrenheit—but only during periods of economic growth. Matthew Neidell of Columbia University, New York, and colleagues present these findings in the open-access journal PLOS ONE on August 25, 2021.

Earlier research conducted by Neidell and co-author Joshua Graff Zivin of the University of California, San Diego, revealed an association between extreme heat and fewer hours worked by people in weather-exposed conditions in the U.S. However, that analysis was conducted during a four-year period of economic growth, so it was unclear whether the same relationship would hold up over time or under different economic conditions.

To clarify, Neidell, Graff Zivin, and colleagues used historical weather records and data from the American Time Use Survey to analyze the relationship between time worked per day and daily temperatures for the period spanning 2003 through 2018. They focused on high-risk laborers, meaning workers in industries that expose them to weather conditions, such as agriculture, construction, and manufacturing.

The analysis showed that, when the U.S. economy was in a period of growth, such as from 2003 to 2007 and from 2015 to 2018, high-risk laborers worked fewer hours on high-heat days. Specifically, on days above 90 degrees, a high-risk laborer worked 2.6 minutes less on average for every degree above 90 than they worked on a 90-degree day.

However, during the Great Recession, from 2008 to 2014, there was no association between high-heat days and daily hours worked—perhaps, the authors suggest, because workers faced higher competition for employment and employers were less flexible.

The researchers also used climate and economic projections to predict the future effects of this relationship between heat and work time. They estimated that, in a “business-as-usual” scenario where greenhouse-gas emissions remain high, lost wages due to high-heat days could add up to $80 billion per year by 2090.

Further research will be needed to confirm and clarify these findings and predictions, which could help inform policies and adaptations to address high-heat labor conditions.

The authors add: “Our findings support previous results that the amount of time people work is affected by temperature, but the magnitude of this relationship depends on where we are in the business cycle. During hard economic times, work time is less sensitive to temperature changes, suggesting the relative bargaining power of employers and employees seems to influence who bears the costs of extreme heat.”

 

#####

Citation: Neidell M, Graff Zivin J, Sheahan M, Willwerth J, Fant C, Sarofim M, et al. (2021) Temperature and work: Time allocated to work under varying climate and labor market conditions. PLoS ONE 16(8): e0254224. https://doi.org/10.1371/journal.pone.0254224

Funding: This research was funded by the U.S. Environmental Protection Agency’s (EPA) Office of Air and Radiation (Contract EP-D-14-031). The views expressed in this document are solely those of the authors, and do not necessarily reflect those of the Agency. Industrial Economics provided support in the form of salaries for authors MS, JW, and CF and EPA provided support in the form of salaries for authors MS and JM. The authors had sole responsibility for study design, data collection and analysis, decision to publish, and preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.

Competing Interests: The authors have declared that no competing interests exist.

In your coverage please use this URL to provide access to the freely available article in PLOS ONE:  https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0254224

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JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0254224 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Temperature and work: Time allocated to work under varying climate and labor market conditions

ARTICLE PUBLICATION DATE

25-Aug-2021

COI STATEMENT

The authors have declared that no competing interests exist.

QUANTUM ALCHEMY

In a first, scientists capture a ‘quantum tug’ between neighboring water molecules

The work sheds light on the web of hydrogen bonds that gives water its strange properties, which play a vital role in many chemical and biological processes.

Peer-Reviewed Publication

DOE/SLAC NATIONAL ACCELERATOR LABORATORY

 

IMAGE: RESEARCHERS HAVE MADE THE FIRST DIRECT OBSERVATION OF ATOMIC MOTION IN LIQUID WATER MOLECULES THAT HAVE BEEN EXCITED WITH LASER LIGHT. THEIR RESULTS REVEAL EFFECTS THAT COULD UNDERPIN THE MICROSCOPIC ORIGIN OF WATER’S STRANGE PROPERTIES. view more 

CREDIT: GREG STEWART/SLAC NATIONAL ACCELERATOR LABORATORY

Water is the most abundant yet least understood liquid in nature. It exhibits many strange behaviors that scientists still struggle to explain. While most liquids get denser as they get colder, water is most dense at 39 degrees Fahrenheit, just above its freezing point. This is why ice floats to the top of a drinking glass and lakes freeze from the surface down, allowing marine life to survive cold winters. Water also has an unusually high surface tension, allowing insects to walk on its surface, and a large capacity to store heat, keeping ocean temperatures stable.

Now, a team that includes researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and Stockholm University in Sweden have made the first direct observation of how hydrogen atoms in water molecules tug and push neighboring water molecules when they are excited with laser light. Their results, published in Nature today, reveal effects that could underpin key aspects of the microscopic origin of water’s strange properties and could lead to a better understanding of how water helps proteins function in living organisms.

“Although this so-called nuclear quantum effect has been hypothesized to be at the heart of many of water’s strange properties, this experiment marks the first time it was ever observed directly,” said study collaborator Anders Nilsson, a professor of chemical physics at Stockholm University. “The question is if this quantum effect could be the missing link in theoretical models describing the anomalous properties of water.”

Each water molecule contains one oxygen atom and two hydrogen atoms, and a web of hydrogen bonds between positively charged hydrogen atoms in one molecule and negatively charged oxygen atoms in neighboring molecules holds them all together. This intricate network is the driving force behind many of water’s inexplicable properties, but until recently, researchers were unable to directly observe how a water molecule interacts with its neighbors.

“The low mass of the hydrogen atoms accentuates their quantum wave-like behavior,” said collaborator Kelly Gaffney, a scientist at the Stanford Pulse Institute at SLAC. “This study is the first to directly demonstrate that the response of the hydrogen bond network to an impulse of energy depends critically on the quantum mechanical nature of how the hydrogen atoms are spaced out, which has long been suggested to be responsible for the unique attributes of water and its hydrogen bond network.”

CAPTION

An animation shows how a water molecule responds after being hit with laser light.. As the excited water molecule starts to vibrate, its hydrogen atom (white) tugs oxygen atoms (red) from neighboring water molecules closer, before pushing them away, expanding the space between the molecules. This new view of an effect that’s thought to be behind many of water’s strange properties was created with SLAC’s MeV-UED “electron camera,” which blasts samples with short pulses of high-energy electrons to look inside.

CREDIT

Greg Stewart/SLAC National Accelerator Laboratory

Love thy neighbor

Until now, making this observation has been challenging because the motions of the hydrogen bonds are so tiny and fast. This experiment overcame that problem by using SLAC’s MeV-UED, a high-speed “electron camera” that detects subtle molecular movements by scattering a powerful beam of electrons off samples.

The research team created 100-nanometer-thick jets of liquid water ­– about 1,000 times thinner than the width of a human hair – and set the water molecules vibrating with infrared laser light. Then they blasted the molecules with short pulses of high-energy electrons from MeV-UED.

This generated high-resolution snapshots of the molecules’ shifting atomic structure that they strung together into a stop-motion movie of how the network of water molecules responded to the light.

The snapshots, which focused on groups of three water molecules, revealed that as an excited water molecule starts to vibrate, its hydrogen atom tugs oxygen atoms from neighboring water molecules closer before pushing them away with its newfound strength, expanding the space between the molecules.

“For a long time, researchers have been trying to understand the hydrogen bond network using spectroscopy techniques,” said Jie Yang, a former SLAC scientist and now a professor at Tsinghua University in China, who led the study. “The beauty of this experiment is that for the first time we were able to directly observe how these molecules move.”

A window on water

The researchers hope to use this method to gain more insight into the quantum nature of hydrogen bonds and the role they play in water’s strange properties, as well as the key role these properties play in many chemical and biological processes.

“This has really opened a new window to study water,” said Xijie Wang, a SLAC distinguished staff scientist and study collaborator. “Now that we can finally see the hydrogen bonds moving, we’d like to connect those movements with the broader picture, which could shed light on how water led to the origin and survival of life on Earth and inform the development of renewable energy methods.”

MeV-UED is an instrument of the LCLS user facility, operated by SLAC on behalf of the DOE Office of Science, which funded this research.

Citation: Yang et al., Nature, 25 August 2021 (10.1038/s41586-021-03793-9)

SLAC is a vibrant multiprogram laboratory that explores how the universe works at the biggest, smallest and fastest scales and invents powerful tools used by scientists around the globe. With research spanning particle physics, astrophysics and cosmology, materials, chemistry, bio- and energy sciences and scientific computing, we help solve real-world problems and advance the interests of the nation.

SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.

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JOURNAL

Nature

DOI

10.1038/s41586-021-03793-9 

 

European welfare states: not taking from the rich and giving to the poor, but taking from the working-aged and giving to the old and young

Peer-Reviewed Publication

PLOS

European welfare states: not taking from the rich and giving to the poor, but taking from the working-aged and giving to the old and young.

Article Title: Welfare states as lifecycle redistribution machines: Decomposing the roles of age and socio-economic status shows that European tax-and-benefit systems primarily redistribute across age groups

 

Funding: This study received support from the European Commission, FP7 framework (grant agreement 613247). No additional external funding was received for this study.

 

Competing Interests: The authors have declared that no competing interests exist.

Article URL:  https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0255760

Degradable coatings for compostable paper food packaging block grease and oil

Reports and Proceedings

AMERICAN CHEMICAL SOCIETY

ATLANTA, Aug. 26, 2021 — Cups, cartons and food wrappers made of paper might seem like they would be biodegradable, but many contain a plastic coating that can’t be composted. Although plastic-free, sustainable paper products are available, they often let grease and oil pass through, weakening the paper and creating a mess. Today, scientists report they have developed a degradable polymer coating that can block this seepage and could lead to new biodegradable, paper-based materials.

The researchers will present their results at the fall meeting of the American Chemical Society (ACS). ACS Fall 2021 is a hybrid meeting being held virtually and in-person Aug. 22-26, and on-demand content will be available Aug. 30-Sept. 30. The meeting features more than 7,000 presentations on a wide range of science topics.

“Consumers are driving a push to more sustainable products,” Matthew Carter, Ph.D., principal investigator on the project. “But making a fully degradable paper product for single-use applications — like the sandwich wrappers, bowls and trays you get at a cafeteria — is a big challenge,” adds Carter, who is presenting the work at the meeting.

Current oil- and grease-resistant coatings for disposable paper products often include fluorocarbons or polyolefins, but those polymers are environmentally persistent and can’t be composted. “One of the things that makes conventional polymers useful is their durability,” says his fellow principal investigator, Andrew Hejl, Ph.D., who works with Carter at Dow. That toughness, which originates in the stable carbon-carbon bonds that form during polymerization, is desirable in, say, a latex-based house paint that must last for years but problematic in a paper bowl destined for composting. 

One way to make polymers less durable is to insert degradable linkages to disrupt their carbon-carbon backbones, Carter says. To do so, the researchers turned to a free radical polymerization technique that had been around for years but hadn’t been widely adopted. Noticing a recent resurgence of interest in academia for using this technique with cyclic ketene acetal and vinyl monomers, the Dow team began exploring how to translate this chemistry to an industrial setting. In academia, the reaction was typically carried out in organic solvents, but Dow wanted to switch to water as a “greener” substitute. That was difficult because cyclic ketene acetal monomers are unstable in water, but the researchers addressed that problem by tweaking reaction conditions, including pH, temperature and monomer concentration.

Their reaction mixed the cyclic ketene acetal 2-methylene-1,3-dioxepane and vinyl acetate to form a polymer with ester linkages in the backbone. The team then coated paper with a water-based emulsion of this polymer — a synthetic “latex” unrelated to natural latex rubber, and therefore unlikely to trigger an allergic reaction — and let it dry. They recently reported that the coating provided an effective barrier against oil and grease, and that its ester linkages could break apart in water, quite slowly at neutral pH but faster at higher pH under lab conditions. Now, the researchers are beginning to assess the coating’s degradability under industrially relevant conditions. So far they have shown that microorganisms that are used in industrial composters can help biodegrade the polymer in simulated wastewater. “The concept is to have a long polymer that breaks down into smaller pieces that will ultimately get broken down by microbes into CO2,” Hejl says.

Other researchers and companies have developed biodegradable food service products with coatings based on natural materials such as whey or chitosan. “Those are great options, but they have limitations in terms of getting the performance you want at an appropriate price point,” Hejl says. And some coatings have to be applied as a very dilute solution, so a lot of water has to be evaporated to dry them, he adds. “So there are a lot of potential materials, and I don't think that anything yet has checked off every box.” But the Dow researchers believe their coating might just fill the bill.

“More broadly, if you look at the concept of interrupting a stable carbon-carbon backbone with degradable linkages, that really opens up a lot of opportunities beyond just paper coatings,” Carter says. “Other applications include personal care or home care formulations, like shampoo and floor polish. Many of these materials currently contain synthetic carbon-carbon bond polymers. So this approach could be a powerful way to introduce degradability to new classes of materials in the future.”

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The researchers acknowledge support and funding from Dow.

The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.

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Title
Backbone-degradable vinyl acetate emulsion polymers: Coatings for single-use paper products

Abstract
Research in our labs has focused broadly on the development of sustainable paper coatings for the food service industry. Paper trays, bowls, and wrappers are often coated with synthetic polymers to improve oil and grease resistance, but these films are generally non-degradable and environmentally-persistent. Here, we report an approach to waterborne and degradable latex polymers based on the emulsion polymerization of vinyl acetate (VA) with the cyclic ketene acetal 2-methylene-1,3-dioxepane (MDO). These polymer particles and latex-based films are hydrolytically degradable due to the presence of MDO-based backbone ester groups. Control over the in-process conditions is critical: mildly basic pH and low temperature promote MDO ring-opening copolymerization, but when the pH is too acidic or the temperature too high, MDO is lost to hydrolysis. When coated onto commercial paper, VA-MDO films display excellent oil and grease resistance as compared to non-degradable, VA-only compositions. This new class of latex polymer is therefore well-suited for the design of next-generation biodegradable and compostable single-use food service products, as well as for other applications where erosion or degradation of films and coatings are required.