It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Friday, November 17, 2023
Deep dive on sea level rise: new modelling gives better predictions on Antarctic ice sheet melt
Using historical records from around Australia, an international team of researchers have put forward the most accurate prediction to date of past Antarctic ice sheet melt, providing a more realistic forecast of future sea level rise.
The Antarctic ice sheet is the largest block of ice on earth, containing over 30 million cubic kilometers of water.
Hence, its melting could have a devasting impact on future sea levels. To find out just how big that impact might be, the research team, including Dr Mark Hoggard from The Australian National University, turned to the past.
“If we want to know what is going to happen in the next 100 years, we need to have an accurate model for how ice sheets respond to climate change,” Dr Hoggard said.
“Previous forecasts of the Antarctic contribution to global mean sea level rise were anywhere between 20 and 52cm by 2100. But by getting a better idea of sea levels during the Mid-Pliocene era, our study reduces this estimate to between 5 and 9cm.
“The Mid-Pliocene period 3 million years ago is considered the best equivalent to conditions expected this coming century in terms of CO2 levels and temperature.”
Dr Hoggard said accurately determining sea level during this period can help reveal how the Antarctic ice sheet behaved in the past and therefore how it might behave in the future.
To determine the historic sea level, researchers first looked at the geological record of Australia to find fossilised corals and other sea-level markers that indicate how high the shoreline used to be.
“This is not a perfect method as fossil markers are not only affected by the movement of the sea, but also the movement of the land,” Dr Hoggard said.
Over millions of years, Earth’s tectonic plates move up and down in a process called dynamic topography.
“If you stand on the shoreline of Australia today and see that our sea level is rising, it could be one of two things. It could be sea level genuinely rising, or it could be the land you’re standing on subsiding,” Dr Hoggard said.
“For the first time, we have corrected for these up and down movements across a whole continent, so we can see where the sea level markers really sit.”
Previous estimates had sea level during the Mid-Pliocene somewhere between six and 60 meters above current sea level in Australia. Now, it can be more accurately pinned at 16 meters, with the Antarctic ice sheet likely contributing 9.8 meters in height.
Dr Hoggard credited the accuracy of these predictions to significant advances in science over the past 10 years.
“Thanks to better models, improvements in computational power and a greater understanding of the geological processes, our ability to map the movement of tectonic plates over the mantle has been revolutionised,” he said.
“Right now, this is probably the best reconstruction we’ve got.”
Reducing this uncertainty will allow for more accurate modelling of future sea level rise.
While a lower estimated contribution by the Antarctic ice sheet is good news, the researchers point out there is still plenty of work to be done.
“If you live in a Pacific Island nation like Tuvalu where the highest point of elevation is only 4.6 meters, small changes in the baseline sea level can have devastating impacts when disaster events like cyclones or storm surges hit,” Dr Hoggard said.
“Ensuring we have more accurate models can help improve policy, especially when looking at coastal and low-lying communities which can be impacted by just centimeters of sea level change.”
Geodynamically corrected Pliocene shoreline elevations in Australia consistent with mid-range projections of Antarctic ice loss
ARTICLE PUBLICATION DATE
17-Nov-2023
MOZAMBIQUE
Idai vs. Impalas: New study shows in real-time what helps mammals survive a natural disaster
With a network of cameras and GPS collars, Gorongosa National Park researchers watched in real time as animals reacted to Cyclone Idai, the deadliest cyclone in the southern hemisphere in recorded history.
HEAVY RAINS FALL ON THREE IMPALA IN GORONGOSA NATIONAL PARK IN CENTRAL MOZAMBIQUE. WHEN CYCLONE IDAI SLAMMED GORONGOSA WITH 105 MPH WINDS AND POUNDING RAINS ON MARCH 15, 2019, THE RESULTING FLOODWATERS TRANSFORMED THE ECOSYSTEM OF THE PARK, KILLING HALF OF THE ORIBI AND REEDBUCK (TWO SMALL ANTELOPE SPECIES) AND DAMAGING MANY OTHER HERBIVORE POPULATIONS. SOME DIED DURING THE STORM, UNABLE TO OUTRUN THE RISING WATERS, AND OTHERS DIED OF STARVATION OR MALNUTRITION IN THE AFTERMATH, AS NUTRIENT-DENSE GRASSES DROWNED, LEAVING ANIMALS TO FORAGE ON NUTRIENT-POOR SUBSTITUTES.
When Cyclone Idai swept through Mozambique’s Gorongosa National Park in May 2019, one of nature‘s deadliest forces encountered one of the most technologically sophisticated wildlife parks on the planet. Princeton researchers and colleagues from around the world documented the effects using trail cameras and animal-tracking devices that had been in use before the storm.
Thanks to the extensive network of cameras, GPS collars and other instruments, park staff and wildlife ecologists had an “unprecedented opportunity” to assemble a minute-by-minute view of how the storm affected the park and how the animals responded, said Hallie Brown, a postdoctoral research associate in Princeton’s Department of Ecology and Environmental Biology and the first author of a new paper in Nature about the hurricane’s impact.
“This is the first study that has ever been able to track the real-time responses of a large-mammal community to a natural disaster,” said Robert Pringle, an EEB professor who has worked with Gorongosa National Park since its inception.
Brown, now a postdoctoral research associate in Pringle’s lab, was a graduate student at the time with Ryan Long, an associate professor of wildlife sciences at the University of Idaho and a former Princeton postdoc. Long and Pringle shared senior author credits on the new Nature paper.
“We watched the waters rise,” Brown recalled. “We watched the animals’ reactions in the hours, days, weeks after the cyclone: how some of them escaped the floodwaters, and some of them didn’t. We used the data we had from before, during and after the storm to create, not just a description of this one event, but a broader set of expectations, so managers can better anticipate the effects of increasingly severe weather events.”
The research team found that the best predictor of survival was size. The tiny oribi, about the size of a greyhound, saw its population plummet by 50%. About half of the slightly larger reedbucks died as well. The bushbucks, which are the smallest species that can wear a GPS collar, saw three of its eight collared animals die — the smallest male and the two smallest females — but only lost 4% of their population overall.
GPS data revealed that the bushbucks looked for hills to climb, including termite mound hillocks that reach up to 16 feet tall (5 meters) and 65 feet long (20 meters), which became islands in the flood. The researchers saw that one survivor hopscotched from mound to mound, passing quickly through the floodwaters in between, before finding safety in the woods at higher elevations. The four largest herbivores wearing GPS collars — nyala, kudu, sable and elephant — had no fatalities.
Body size also offered a secondary protection, the researchers found.
“Not only could the smaller-sized animals not outpace the waters, they were also not able to buffer the nutritional limitation afterwards,” said Brown. “Because the flood was so high for so long, it killed a lot of the grasses and low-lying vegetation. Smaller animals can’t withstand those nutritionally limited periods like larger animals, who have more fat to rely on.”
The only previous study of hurricane effects on island populations looked at lizards and spiders in the Bahamas and found very similar patterns. “It’s incredible how the patterns we found cross taxonomic and geographic lines,” said Brown. “They seem to play out the same ways in our terrestrial ecosystem, with the largest mammals on earth, and with these tiny little invertebrates and reptiles in the Bahamas.”
The researchers have two primary recommendations for other wildlife managers: evacuate the smallest and most ecologically vulnerable creatures to safer areas before storms come, and provide supplementary feed after the storm. Once all of the grasses have drowned, animals will turn to foraging on less-nutritious shrubs and bark, and many small creatures can’t survive that dietary shift.
The few carnivores in the park weathered the storm just fine, Brown said. The wild dogs and leopards benefited from having their prey animals concentrated in the upland areas, and the lions’ primary food source — warthogs — stayed in the uplands for several months but were otherwise largely unaffected by the cyclone.
The research team included institutions from five countries: Princeton University; the University of Idaho-Moscow; the University of California-Merced; Montana State University-Bozeman;Yale University; Archbold Biological Station in Venus, Florida; the University of British Columbia-Vancouver; Gorongosa National Park; the University of Kent; the University of the Witwatersrand-Johannesburg; Associação Azul Moçambique in Maputo, Mozambique.
Other Princeton authors on the paper are then-graduate students Matt Hutchinson, Ph.D. 2021; Justine Atkins Becker, Ph.D. 2020; Arjun Potter, Ph.D. 2022; and then-NSF postdoctoral fellow Meredith Palmer.
“For me, the most exciting thing about this paper is the incredible collaboration between so many groups of researchers, from hydrology to large animal ecology, to create this really integrated piece of science,” Brown said. “The best work happens in collaborative projects.”
“Trait-based sensitivity of large mammals to a catastrophic tropical cyclone,” by Reena H. Walker, Matthew C. Hutchinson, Justine A. Becker, Joshua H. Daskin, Kaitlyn M. Gaynor, Meredith S. Palmer, Dominique D. Gonçalves, Marc E. Stalmans, Jason Denlinger, Paola Bouley, Mercia Angela, Antonio Paulo, Arjun B. Potter, Nikhail Arumoogum, Francesca Parrini, Jason P. Marshal, Robert M. Pringle and Ryan A. Long, was published in Nature on Nov. 15 (DOI: 10.1038/s41586-023-06722-0). The research was supported by the U.S. National Science Foundation (IOS-1656527, DEB-2225088, IOS-1656642 and PRFB-1810586); the National Research Foundation of South Africa (116304); the Greg Carr and Cameron Schrier Foundations;; the Howard Hughes Medical Initiative BioInteractive; the Yale Institute for Biospheric Studies; the Grand Challenges Program of the High Meadows Environmental Institute at Princeton University; and the National Geographic Society (000039685).
Mammals in Gorongosa National Park range in size from the tiny oribi, which lost half of its population to Cyclone Idai, to the massive elephants that saw no fatalities from the storm or its aftermath. When Cyclone Idai slammed Gorongosa with 105 mph winds and pounding rains on March 15, 2019, the resulting floodwaters transformed the ecosystem of the park, the smallest animals were hardest hit. Half of the oribi and reedbuck (two small antelope species) died, but the largest mammals saw few if any fatalities. Some of the small herbivores died during the storm, unable to outrun the rising waters, while others died of starvation or malnutrition in the aftermath, as nutrient-dense grasses drowned, leaving animals to forage on nutrient-poor substitutes.
Geochemist Alexandra Phillips has sulfur on her mind. The yellow element is a vital macronutrient, and she’s trying to understand how it cycles through the environment. Specifically, she’s curious about the sulfur cycle in Earth’s ancient ocean, some 3 billion years ago.
Fortunately, the nutrient-poor waters of Lake Superior offer a welcome glimpse into the past. “It’s really hard to look back billions of years,” said Phillips, a former postdoctoral researcher at UC Santa Barbara and University of Minnesota, Duluth. “So this is a great window.” She and her co-authors discovered a new type of sulfur cycle in the lake. Their findings, published in Limnology and Oceanography, focus attention on the role organic sulfur compounds play in this biogeochemical cycle.
The sulfate ion (SO4) is the most common form of sulfur in the environment, and a major component of seawater. In the bottoms of oceans and lakes, where oxygen becomes unavailable, some microbes make their living by turning sulfate into hydrogen sulfide (H2S). The fate of this hydrogen sulfide is complex; it can be consumed quickly by microorganisms during respiration, or it can be retained in sediments for millions of years. Converting sulfate into hydrogen sulfide is a time-honored profession; genomic evidence suggests microbes have been doing it for at least 3 billion years.
But scientists believe sulfate didn’t become abundant until around 2.7 to 2.4 billion years ago, when photosynthetic activity of newly evolved cyanobacteria began pumping massive amounts of oxygen into the ocean and atmosphere. So where were these ancient microbes getting their sulfate?
Alexandra Phillips is a marine and climate scientist with expertise in oceanography, geochemistry, and geobiology. Her research focuses on organic sulfur in oceans and lakes as well as how social media can display diverse role models for women in STEM. Phillips also serves as a science communicator and policy officer.
Mulling over this quandary, Phillips turned her attention toward organic sulfur, molecules in which sulfur is bound to a carbon compound. These include sulfo-lipids, and sulfur amino acids. In the modern ocean, sulfate is almost a million times more abundant than organic sulfur. “But in a system where there’s not very much sulfate, all of a sudden organic sulfur matters a lot more,” she said.
“For a long time, our thinking was dominated by what we could learn from modern oceans, which are sulfate-rich,” said senior author Sergei Katsev, a professor at University of Minnesota’s Large Lakes Observatory. Katsev served as the senior scientist of the National Science Foundation-funded project. “Understanding early Earth, however, requires looking at processes that emerge when sulfate is scarce, and this is where organic sulfur can change the whole paradigm.”
It just so happens that Lake Superior has very little sulfate, nearly a thousand times less than the modern ocean. “In terms of sulfate, Lake Superior looks a lot closer to the ocean billions of years ago and may help us understand processes we can’t go back in time to observe directly,” Phillips said. The early oceans had very little sulfate because there was much less free oxygen available to form SO4.
The great lake serves as an analog for the ancient ocean, enabling Phillips to see how the sulfur cycle may have been playing out back then under similar chemistries. She had three questions in mind:
If sulfate reduction is happening, which microbes are responsible?
If organic sulfur is fueling this process, what types of compounds do microbes prefer?
And, what happens to the hydrogen sulfide that’s produced?
Phillips and her collaborators headed out to Lake Superior to trace organic sulfur from source to sink. The team took water and sediment samples back to the lab for analysis from two sites: one with plentiful oxygen in the sediment and one without. Sulfate reduction usually occurs in anoxic parts of the environment. Oxygen is a great resource, so organisms prefer to use oxygen instead of sulfate when they can. The team used shotgun metagenomics to look for microbes with genes involved in sulfate reduction. And they found plenty, precisely in the layer where sulfate levels peaked in the sediment. In all, they identified eight sulfate-reducing taxa.
The researchers then set off to determine what variety of organic sulfur the microbes preferred. They gave different forms of organic sulfur to separate microbial communities and observed the results. The authors found the microbes produced most of their sulfate from sulfo-lipids, rather than the sulfur amino acids. Although this process takes some energy, it’s much less than the microbes can get from the subsequent reduction of sulfate to hydrogen sulfide.
Not only were the sulfo-lipids preferred for this process, they were also more abundant in the sediment. Sulfo-lipids are produced by other microbial communities, and drift to the lake bottom when they die.
With the “who” and the “how” answered, Phillips turned her attention to the fate of the hydrogen sulfide. In the modern ocean, hydrogen sulfide can react with iron to form pyrite. But it can also react with organic molecules, producing organic sulfur compounds. “And we found that there is a ton of organic matter sulfurization in the lake, which is really surprising to us,” she said. “Not only is organic sulfur fueling the sulfur cycle as a source, but it’s also an eventual sink for the hydrogen sulfide.”
This cycle — from organic sulfur to sulfate to hydrogen sulfide and back — is completely new to researchers. “Scientists studying aquatic systems need to start thinking about organic sulfur as a central player,” Phillips said. These compounds can drive the sulfur cycle in nutrient-poor environments like Lake Superior, or even the ancient ocean.
This process may also be important in systems with high sulfate. “Organic sulfur cycling, like what we see in Lake Superior, is probably ubiquitous in marine and freshwater sediments. But in the ocean sulfate is so abundant that its behavior swamps out most of our signals,” said senior author Morgan Raven, a biogeochemist at UC Santa Barbara. “Working in low-sulfate Lake Superior lets us see how dynamic the sedimentary organic sulfur cycle really is.” Organic sulfur seems to serve as an energy source for microbial communities as well as preserve organic carbon and molecular fossils. Combined, these factors could help scientists understand the evolution of early sulfur-cycling microorganisms and their impact on Earth’s chemistry.
Some of the earliest biochemical reactions likely involved sulfur, Phillips added. “We’re pretty sure that sulfur played an important role in really early metabolisms.” A better understanding of the sulfur cycle could provide insights on how early lifeforms harnessed this type of redox chemistry.
JOURNAL
Limnology and Oceanography
2023 Canadian wildfires impacted air quality as far away as Europe, China
The whole of the northern hemisphere suffered deterioration of air quality as a result of 2023’s record-setting Canadian wildfires, while Canada’s own ten-year greenhouse gas reduction plan has essentially been erased as a result of emissions from this
Numerical air quality models have described the extent of severe negative impacts on air quality resulting from the record 2023 Canadian wildfires, demonstrating that almost the whole of the Northern Hemisphere, not just Canada and the northern United States, were affected.
Canadian record-setting wildfires in 2023 made headlines around the world not just for their extent—the largest area burnt in the country’s history—but also for how severely they impacted air quality across this very large country, and even deep into the United States. Smoke from the fires produced repeated severe air quality alerts and even evacuations in many locations.
But it was not known how far beyond Canada and the northern US such dangerous air pollution had reached, and even within North America, the understanding of the dispersal of the most harmful pollutants was limited.
“There were photographs from New York City in July in news outlets around the world that showed the city trapped in an almost unbreathable orange haze like something out of a dystopian movie,” said Zhe Wang, lead author of the study and a researcher with the State Key Laboratory of Atmospheric Boundary Layer Physics at Institute of Atmospheric Physics (IAP) of Chinese Academy of Sciences. “But what we know about long-range transport of particulate matter means that the fires likely impacted Europe and Asia as well. We just didn't know to what extent.”
So Dr. Wang and other researchers from IAP set out to calculate the full global reach of this threat to public health by using numerical air quality model models. Similar to climate models, air quality models use mathematical techniques to simulate how weather and chemical reactions impact the dispersal of air pollutants.
For this work, the IAP scientists used the Aerosol and Atmospheric Chemistry Model of the Institute of Atmospheric Physics (IAP-AACM), a computer model developed in house as a module within the broader Chinese Academy of Sciences Earth System Model (CAS-ESM).
The researchers found that while Canada was most severely affected, almost the whole of the northern hemisphere was subject to marked significant declines in air quality due to long-range wind transport of pollutants.
There were six main widespread air pollution episodes over the course of Canada’s wildfire ‘season’: May 15-22, June 5-9, June 24-July 1, July 12-19, August 17-15, and August 17-22. In addition to Canada itself, the first such episode affected air quality in the central northern parts of the US. The second episode impacted the northeastern US, and particularly badly.
The model results here match real-world observations. The concentration of fine particles with diameters of 2.5 microns or less (termed ‘PM2.5’—the particulate matter that is most dangerous, as compared to larger but less harmful particles with a diameter of 10 microns, or PM10) on June 7 was found by 11 monitoring sites in New York City to have reached the worst air quality level for more than 50 years.
During the third main episode of severe air pollution, the model suggested that PM2.5 pollutants were transported to Europe, while the fourth such episode concentrated its severest presence in western Canada and the central northern US once again. The fifth episode mainly affected northern Canada, while the sixth episode affected both western and eastern coast regions of the USA. Due to the northward movement of the wildfires, high concentrations of PM2.5 were transported to the Arctic region over the course of the mid and late summer.
PM2.5 concentrations higher than the World Health Organization air-quality guidelines of 15 micrograms per cubic meter mainly occurred over North America, with an excess of 40 pollution days exceeding this limit over western and eastern Canada, as well as more than 10 such days over the northeastern USA.
But due to the wildfire plumes being transported by prevailing westerly winds across the Atlantic Ocean, vast swathes of Europe and western, central and east Asia suffered from increases in such concentrations. This meant that maximum PM2.5 concentrations exceeded 1 microgram per cubic meter over most areas of the Northern Hemisphere—lower than the WHO guideline but not without impact. PM2.5 concentration in the northwest region of China increased to roughly two micrograms per cubic meter.
Western and eastern Canada were most severely impacted, suffering PM2.5 concentration over 150 PM2.5, some ten times the WHO maximum.
While focussing on air quality, the researchers also used computer modelling to investigate the global distribution of greenhouse gases (GHGs) produced by the Canadian fires. They found that the conflagration had resulted in an increase in carbon dioxide levels mainly over North America in May, and also over Europe and northwestern Asia in June. The wildfire-related CO2 concentrations exceeded 0.1 part per million (ppm) over most Northern Hemisphere areas except southeast Asia, India and southern China in July, and increased to more than 0.2 ppm in August.
This increase in GHGs due to the fires has two major consequences. First, its production of enhanced warming in these regions atop existing global warming increases the likelihood of the sort of conditions that exacerbated wildfires. In other words, more wildfires means even more wildfires.
Second, the level of wildfire-related greenhouse gas emissions in Canada in 2023 were more than twice the country’s legislated plan for cumulative reductions in human-caused GHGs over the next ten years.
“Canada's 2030 Emissions Reduction Plan has been wiped out by a single year of wildfires,” said Zifa Wang, corresponding author of the study.
Severe global environmental issues caused by Canada's record-breaking wildfires in 2023
ARTICLE PUBLICATION DATE
17-Nov-2023
Epidemic-economic model provides answers to key pandemic policy questions
Is lockdown an effective response to a pandemic, or would it be better to let individuals spontaneously reduce their risk of infection? These two highly-debated options lead to similar outcomes
Is lockdown an effective response to a pandemic, or would it be better to let individuals spontaneously reduce their risk of infection? Research published today suggests these two highly-debated options lead to similar outcomes.
A ground-breaking economic-pandemic model, created by an international team of researchers, addresses some of the key policy debates of the Covid-19 pandemic but it will, in future, enable governments and policymakers to take tough decisions - and assess effective actions.
The modelling, designed by the team, including Oxford experts, has been tested using data from New York city responses to Covid-19 - and it accurately predicted both death rates and the impact on the city's economy of the first wave of the pandemic.
Professor Doyne Farmer, Director of the Complexity Economics Programme at INET Oxford, says the research paper is timely, given the Covid-19 inquiries across the world, 'We are seeing governments across the globe begin their 'moments of reckoning', reviewing the effectiveness of a great variety of policies brought in during Covid-19.
‘According to some, lockdowns were not imposing any trade-off between health and the economy because, if the virus got out of control, the economy would be equally damaged. According to others, letting at-risk individuals spontaneously reduce their risk of infection would have led to the best epidemic and economic outcomes, with no trade-off. These debates have remained contested and unresolved.’
Professor Farmer continues, 'Our quantitative research helps provide evidence-based answers to these questions, suggesting that both lockdowns and spontaneous behaviour change lead to similar trade-offs between health and the economy. Those that claimed that there was no trade-off between health and the economy were not basing their belief in a quantitative model. '
The health-economy trade-off modelling, in the journal Nature Human Behaviour, is the culmination of years of work from an interdisciplinary team of researchers with backgrounds in economics and epidemiology, as well as physics, computer science, and applied mathematics, all united by a shared expertise in complexity science.
The research paper makes a number of conclusions on the effectiveness of government interventions, including:
Both stricter lockdown and strong behaviour change lead to more unemployment and fewer Covid-19 deaths.
They lead to more jobs lost and to more lives saved among low-income workers, while they make less of a difference to high-income workers.
Closing non-customer-facing industries such as manufacturing has little impact on infections but significantly increases unemployment;
Delaying the start of protective measures does little to help the economy and worsens epidemic outcomes in all scenarios;
Dr François Lafond, Deputy Director of INET Oxford's Complexity Economics Programme at the Oxford Martin School, says the model is a big step forward in helping governments prepare for future pandemics, 'Thanks to the level of detail of the model, we could show that low-income workers were affected more by policy decisions, on either side of the health-economy trade-off. Of course, the trade-offs might be different for future crises, but to evaluate these we will need the same kind of interdisciplinary collaboration, building computational models of behaviour to simulate realistic synthetic populations in real time.
Led by Marco Pangallo of CENTAI Institute, the international research group combined economic modelling with epidemic data, to create a holistic tool that can predict health-economy outcomes from pandemic policy decisions. The model's accuracy has been proven in predicting death rates and impact on the economy in the first wave of the pandemic in New York City.
Air filtration systems do not reduce the risk of picking up viral infections, according to new research from the University of East Anglia.
A new study published today reveals that technologies designed to make social interactions safer in indoor spaces are not effective in the real world.
The team studied technologies including air filtration, germicidal lights and ionisers.
They looked at all the available evidence but found little to support hopes that these technologies can make air safe from respiratory or gastrointestinal infections.
Prof Paul Hunter, from UEA’s Norwich Medical School, said: “Air cleaners are designed to filter pollutants or contaminants out of the air that passes through them.
“When the Covid pandemic hit, many large companies and governments - including the NHS, the British military, and New York City and regional German governments - investigated installing this type of technology in a bid to reduce airborne virus particles in buildings and small spaces.
“But air treatment technologies can be expensive. So it’s reasonable to weigh up the benefits against costs, and to understand the current capabilities of such technologies.”
The research team studied evidence about whether air cleaning technologies make people safe from catching airborne respiratory or gastrointestinal infections.
They analysed evidence about microbial infections or symptoms in people exposed or not to air treatment technologies in 32 studies, all conducted in real world settings like schools or care homes. So far none of the studies of air treatment started during the Covid era have been published.
Lead researcher Dr Julii Brainard, also from UEA’s Norwich Medical School, said: “The kinds of technologies that we considered included filtration, germicidal lights, ionisers and any other way of safely removing viruses or deactivating them in breathable air.
“In short, we found no strong evidence that air treatment technologies are likely to protect people in real world settings.
“There is a lot of existing evidence that environmental and surface contamination can be reduced by several air treatment strategies, especially germicidal lights and high efficiency particulate air filtration (HEPA). But the combined evidence was that these technologies don’t stop or reduce illness.
“There was some weak evidence that the air treatment methods reduced likelihood of infection, but this evidence seems biased and imbalanced.
“We strongly suspect that there were some relevant studies with very minor or no effect but these were never published.
“Our findings are disappointing - but it is vital that public health decision makers have a full picture.
“Hopefully those studies that have been done during Covid will be published soon and we can make a more informed judgement about what the value of air treatment may have been during the pandemic.”
This research was led by the University of East Anglia with collaborators at University College London, the University of Essex, the Norfolk and Norwich University Hospital Trust, and the University of Surrey.
It was funded by the National Institute for Health and Care Research Health Protection Unit in Emergency Preparedness and Response, led by Kings College London and UEA in collaboration with the UK Health Security Agency.
‘Effectiveness of filtering or decontaminating air to reduce or prevent respiratory infections: A systematic review’ is published in Preventive Medicine.
JOURNAL
Preventive Medicine
METHOD OF RESEARCH
Systematic review
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Effectiveness of filtering or decontaminating air to reduce or prevent respiratory infections: A systematic review
ARTICLE PUBLICATION DATE
17-Nov-2023
Plants that survived dinosaur extinction pulled nitrogen from air
Nitrogen fixing bacteria may have helped some cycads survive to the present day
DURHAM, N.C. -- Once a favored food of grazing dinosaurs, an ancient lineage of plants called cycads helped sustain these and other prehistoric animals during the Mesozoic Era, starting 252 million years ago, by being plentiful in the forest understory. Today, just a few species of the palm-like plants survive in tropical and subtropical habitats.
Like their lumbering grazers, most cycads have gone extinct. Their disappearance from their prior habitats began during the late Mesozoic and continued into the early Cenozoic Era, punctuated by the cataclysmic asteroid impact and volcanic activity that mark the K-Pg boundary 66 million years ago. However, unlike the dinosaurs, somehow a few groups of cycads survived to the present.
A new study appearing Nov. 16 in the journal Nature Ecology & Evolution has concluded that the cycad species that survived relied on symbiotic bacteria in their roots, which provide them with nitrogen to grow. Just like modern legumes and other plants that use nitrogen fixation, these cycads trade their sugars with bacteria in their roots in exchange for nitrogen plucked from the atmosphere.
What originally interested lead author Michael Kipp is that the tissues of nitrogen-fixing plants can provide a record of the composition of the atmosphere they grew up in. He combines geochemistry with the fossil record to try to understand the Earth’s climate history.
Knowing already that modern cycads are nitrogen-fixers, Kipp began analyzing some very old plant fossils during his Ph.D. work at the University of Washington to see if he could get a different look at ancient atmospheres. Most of the old cycads revealed that they weren’t nitrogen-fixers, but these also turned out to be the extinct lineages.
“Instead of being a story about the atmosphere, we realized this was a story about the ecology of these plants that changed through time,” said Kipp, who spent nearly a decade on this finding, first at UW and then as a postdoctoral researcher at CalTech.
Kipp is joining the Duke faculty this year as an assistant professor of Earth and Climate Sciences in the Nicholas School of the Environment to continue using the fossil record to understand Earth’s climate history so that we can understand its possible future.
Much of what we know about ancient atmospheres comes from chemical studies of ancient sea life and sediments, Kipp said. Applying some of those methods to terrestrial plants is a new wrinkle.
“Going into the project, there were no published nitrogen isotope data from fossilized plant foliage,” Kipp said. It took a while for him to fine-tune the method and to secure samples of precious plant fossils that museum curators were reluctant to see vaporized to get the data.
“In the few fossil samples that are of surviving (cycad) lineages, and that are not so old -- 20, 30 million years -- we see the same nitrogen signature as we see today,” Kipp said. That means their nitrogen came from symbiotic bacteria. But in the older and extinct cycad fossils, that nitrogen signature was absent.
What is less clear is how nitrogen fixation helped the surviving cycads. It may have helped them weather the dramatic shift in climate or it may have allowed them to compete better with the faster-growing angiosperm plants that flourished after the extinction, “or it could be both.”
“This is a new technique that we can do a lot more with,” Kipp said.
A fossil of a veined leaf from the same strata as an extinct cycad was used for comparison of nitrogen isotopes.
CREDIT
Michael Kipp – Duke University
Funding for this study came from: The Paleontological Society, the University of Washington Royalty Research Fund, and NASA Exobiology grant NNX16AI37G.
CITATION: “Nitrogen Isotopes Reveal Independent Origins of N2-Fixing Symbiosis in Extant Cycad Lineages,” Michael A. Kipp, Eva E. Stüeken, Caroline A. E. Strömberg, William H. Brightly, Victoria M. Arbour, Boglárka Erdei, Robert S. Hill, Kirk R. Johnson, Jiří Kvaček, Jennifer C. McElwain, Ian M. Miller, Miriam Slodownik, Vivi Vajda, & Roger Buick. Nature Ecology & Evolution, Nov. 16, 2023. DOI: 10.1038/s41559-023-02251-1
