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, April 30, 2021
An OU-led study sheds new insight on forest loss and degradation in Brazilian Amazon
IMAGE: INTERANNUAL CHANGES OF FOREST AREA, ABOVEGROUND BIOMASS (AGB), ACTIVE FIRE AREA, BURNED AREA, AND ATMOSPHERIC CO2 CONCENTRATION IN THE BRAZILIAN AMAZON view more
CREDIT: XIANGMING XIAO
An international team led by Xiangming Xiao, George Lynn Cross Research Professor in the Department of Microbiology and Plant Biology, University of Oklahoma College of Arts and Sciences, published a paper in the April issue of the journal Nature Climate Change that has major implications on forest policies, conservation and management practices in the Brazilian Amazon. Xiao also is director of OU's Center for Earth Observation and Modeling. Yuanwei Qin, a research scientist at the Center for Earth Observation and Modeling, is the lead author of the study.
For the study described in the paper, "Carbon loss from forest degradation exceeds that from deforestation in the Brazilian Amazon," Xiao, Qin and a team of research scientists and faculty from institutes and universities in the United States, France, the United Kingdom, Denmark and China used satellite data to track spatial-temporal changes of forest area and aboveground biomass in the Brazilian Amazon from 2010 to 2019. They discovered that carbon loss from forest degradation was greater than that resulting from deforestation in the region, which indicates forest degradation should become a high priority in policies, conservation and management.
Tropical forests in the Amazon account, Qin notes, for approximately 50% of the rainforests in the world and are important for global biodiversity, hydrology, climate and the carbon cycle. Accurate and timely data on vegetation aboveground biomass and forest area in the region at various spatial and temporal scales are also essential for data-based policies and decision making. This international team harnessed diverse data for monitoring, reporting and verification of tropical forests. The paper published in Nature Climate Change is a follow-up of a previous study published in Nature Sustainability in 2019, which reported improved estimates of forest areas in the Brazilian Amazon.
IMAGE: THIS ILLUSTRATION OF THE NEWLY FORMING EXOPLANET PDS 70B SHOWS HOW MATERIAL MAY BE FALLING ONTO THE GIANT WORLD AS IT BUILDS UP MASS. BY EMPLOYING HUBBLE'S ULTRAVIOLET LIGHT (UV)... view more
CREDIT: CREDITS: NASA, ESA, STSCI, JOSEPH OLMSTED (STSCI)
NASA's Hubble Space Telescope is giving astronomers a rare look at a Jupiter-sized, still-forming planet that is feeding off material surrounding a young star.
"We just don't know very much about how giant planets grow," said Brendan Bowler of the University of Texas at Austin. "This planetary system gives us the first opportunity to witness material falling onto a planet. Our results open up a new area for this research."
Though over 4,000 exoplanets have been cataloged so far, only about 15 have been directly imaged to date by telescopes. And the planets are so far away and small, they are simply dots in the best photos. The team's fresh technique for using Hubble to directly image this planet paves a new route for further exoplanet research, especially during a planet's formative years.
This huge exoplanet, designated PDS 70b, orbits the orange dwarf star PDS 70, which is already known to have two actively forming planets inside a huge disk of dust and gas encircling the star. The system is located 370 light-years from Earth in the constellation Centaurus.
"This system is so exciting because we can witness the formation of a planet," said Yifan Zhou, also of the University of Texas at Austin. "This is the youngest bona fide planet Hubble has ever directly imaged." At a youthful five million years, the planet is still gathering material and building up mass.
Hubble's ultraviolet light (UV) sensitivity offers a unique look at radiation from extremely hot gas falling onto the planet. "Hubble's observations allowed us to estimate how fast the planet is gaining mass," added Zhou.
The UV observations, which add to the body of research about this planet, allowed the team to directly measure the planet's mass growth rate for the first time. The remote world has already bulked up to five times the mass of Jupiter over a period of about five million years. The present measured accretion rate has dwindled to the point where, if the rate remained steady for another million years, the planet would only increase by approximately an additional 1/100th of a Jupiter-mass.
Zhou and Bowler emphasize that these observations are a single snapshot in time - more data are required to determine if the rate at which the planet is adding mass is increasing or decreasing. "Our measurements suggest that the planet is in the tail end of its formation process."
The youthful PDS 70 system is filled with a primordial gas-and-dust disk that provides fuel to feed the growth of planets throughout the entire system. The planet PDS 70b is encircled by its own gas-and-dust disk that's siphoning material from the vastly larger circumstellar disk. The researchers hypothesize that magnetic field lines extend from its circumplanetary disk down to the exoplanet's atmosphere and are funneling material onto the planet's surface.
"If this material follows columns from the disk onto the planet, it would cause local hot spots," Zhou explained. "These hot spots could be at least 10 times hotter than the temperature of the planet." These hot patches were found to glow fiercely in UV light.
These observations offer insights into how gas giant planets formed around our Sun 4.6 billion years ago. Jupiter may have bulked up on a surrounding disk of infalling material. Its major moons would have also formed from leftovers in that disk.
A challenge to the team was overcoming the glare of the parent star. PDS 70b orbits at approximately the same distance as Uranus does from the Sun, but its star is more than 3,000 times brighter than the planet at UV wavelengths. As Zhou processed the images, he very carefully removed the star's glare to leave behind only light emitted by the planet. In doing so, he improved the limit of how close a planet can be to its star in Hubble observations by a factor of five.
"Thirty-one years after launch, we're still finding new ways to use Hubble," Bowler added. "Yifan's observing strategy and post-processing technique will open new windows into studying similar systems, or even the same system, repeatedly with Hubble. With future observations, we could potentially discover when the majority of the gas and dust falls onto their planets and if it does so at a constant rate."
The researchers' results were published in April 2021 in The Astronomical Journal.
CAPTION
The European Southern Observatory's Very Large Telescope caught the first clear image of a forming planet, PDS 70b, around a dwarf star in 2018. The planet stands out as a bright point to the right of the center of the image, which is blacked out by the coronagraph mask used to block the light of the central star.
CREDIT
Credits: ESO, VLT, André B. Müller (ESO
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C
CAPTION
Hubble observations pinpoint planet PDS 70b. A coronagraph on Hubble's camera blocks out the glare of the central star for the planet to be directly observed. Though over 4,000 exoplanets have been cataloged so far, only about 15 have been directly imaged to date by telescopes. The team's fresh technique for using Hubble to directly image this planet paves a new route for further exoplanet research, especially during a planet's formative years.
CREDIT
Credits: Joseph DePasquale (STScI)
Combining solar panels and lamb grazing increases land productivity, study finds
IMAGE: SHEEP GRAZING UNDERNEATH SOLAR PANELS AT OREGON STATE UNIVERSITY. view more
CREDIT: SEAN NEALON, OREGON STATE UNIVERSITY
CORVALLIS, Ore. - Land productivity could be greatly increased by combining sheep grazing and solar energy production on the same land, according to new research by Oregon State University scientists.
This is believed to be the first study to investigate livestock production under agrivoltaic systems, where solar energy production is combined with agricultural production, such as planting agricultural crops or grazing animals.
The researchers compared lamb growth and pasture production in pastures with solar panels and traditional open pastures. They found less overall but higher quality forage in the solar pastures and that lambs raised in each pasture type gained similar amounts of weight. The solar panels, of course, provide value in terms of energy production, which increases the overall productivity of the land.
Solar panels also benefit the welfare of the lambs by providing shade, which allows the animals to preserve energy. Also lamb grazing alleviates the need to manage plant growth under the solar panels through herbicides or regular mowing, which require extra labor and costs.
"The results from the study support the benefits of agrivoltaics as a sustainable agricultural system," said Alyssa Andrew, a master's student at Oregon State who is the lead author of the paper published in Frontier in Sustainable Food Systems.
Solar photovoltaic installation in the U.S. has increased by an average of 48% per year over the past decade, and current capacity is expected to double again over the next five years, the researchers say.
Past research has found that grasslands and croplands in temperate regions are the best places to install solar panels for maximum energy production. However, energy production in photovoltaic systems requires large areas of land, potentially causing a competition between agricultural uses.
Agrivoltaics looks to diffuse that competition by measuring the economic value of energy production and agricultural use of the same land. Past research has focused on crops and solar panels and found that some crops, particularly types that like shade, can be more productive in combination with solar panels.
Another recent Oregon State study found that shade provided by solar panels increased the abundance of flowers under the panels and delayed the timing of their bloom, both findings that could aid the agricultural community.
The just-published study with lambs and solar panels was carried out in 2019 and 2020 at Oregon State's campus in Corvallis. Findings included:
The lambs gained almost the same amount of weight in the two pasture types in both years.
The daily water consumption of the lambs in the two pasture types in spring 2019 were similar during early spring, but lambs in open pastures consumed more water than those grazed under solar panels in the late spring period. There was no difference observed in water intake of the lambs in spring 2020.
Over the two years, solar pastures produced 38% less forage than open pastures.
Overall, the return from grazing was $1,046 per hectare (one hectare equals 2.47 acres) per year in open pastures and $1,029 per hectare per year in pastures with solar panels.
"The overall return is about the same, and that doesn't take into account the energy the solar
Lightning and subvisible discharges produce molecules that clean the atmosphere
IMAGE: NITROGEN, OXYGEN AND WATER VAPOR MOLECULES ARE BROKEN APART BY LIGHTNING AND ASSOCIATED WEAKER ELECTRICAL DISCHARGES, GENERATING THE REACTIVE GASES NO, O3, HO2, AND THE ATMOSPHERE'S CLEANSER, OH. view more
CREDIT: JENA JENKINS, PENN STATE
Lightning bolts break apart nitrogen and oxygen molecules in the atmosphere and create reactive chemicals that affect greenhouse gases. Now, a team of atmospheric chemists and lightning scientists have found that lightning bolts and, surprisingly, subvisible discharges that cannot be seen by cameras or the naked eye produce extreme amounts of the hydroxyl radical -- OH -- and hydroperoxyl radical -- HO2.
The hydroxyl radical is important in the atmosphere because it initiates chemical reactions and breaks down molecules like the greenhouse gas methane. OH is the main driver of many compositional changes in the atmosphere.
"Initially, we looked at these huge OH and HO2 signals found in the clouds and asked, what is wrong with our instrument?" said William H. Brune, distinguished professor of meteorology at Penn State. "We assumed there was noise in the instrument, so we removed the huge signals from the dataset and shelved them for later study."
The data was from an instrument on a plane flown above Colorado and Oklahoma in 2012 looking at the chemical changes that thunderstorms and lightning make to the atmosphere.
But a few years ago, Brune took the data off the shelf, saw that the signals were really hydroxyl and hydroperoxyl, and then worked with a graduate student and research associate to see if these signals could be produced by sparks and subvisible discharges in the laboratory. Then they did a reanalysis of the thunderstrom and lightning dataset.
"With the help of a great undergraduate intern," said Brune, "we were able to link the huge signals seen by our instrument flying through the thunderstorm clouds to the lightning measurements made from the ground."
The researchers report their results online today (April 29) in Science First Release and the Journal of Geophysical Research -- Atmospheres.
Brune notes that airplanes avoid flying through the rapidly rising cores of thunderstorms because it is dangerous, but can sample the anvil, the top portion of the cloud that spreads outward in the direction of the wind. Visible lightning happens in the part of the anvil near the thunderstorm core.
"Through history, people were only interested in lightning bolts because of what they could do on the ground," said Brune. "Now there is increasing interest in the weaker electrical discharges in thunderstorms that lead to lightning bolts."
Most lightning never strikes the ground, and the lightning that stays in the clouds is particularly important for affecting ozone, and important greenhouse gas, in the upper atmosphere. It was known that lightning can split water to form hydroxyl and hydroperoxyl, but this process had never been observed before in thunderstorms.
What confused Brune's team initially was that their instrument recorded high levels of hydroxyl and hydroperoxyl in areas of the cloud where there was no lightning visible from the aircraft or the ground. Experiments in the lab showed that weak electrical current, much less energetic than that of visible lightning, could produce these same components.
While the researchers found hydroxyl and hydroperoxyl in areas with subvisible lightning, they found little evidence of ozone and no evidence of nitric oxide, which requires visible lightning to form. If subvisible lightning occurs routinely, then the hydroxyl and hydroperoxyl these electrical events create need to be included in atmospheric models. Currently, they are not.
According to the researchers, "Lightning-generated OH (hydroxyl) in all storms happening globally can be responsible for a highly uncertain but substantial 2% to 16% of global atmospheric OH oxidation."
"These results are highly uncertain, partly because we do not know how these measurements apply to the rest of the globe," said Brune. "We only flew over Colorado and Oklahoma. Most thunderstorms are in the tropics. The whole structure of high plains storms is different than those in the tropics. Clearly we need more aircraft measurements to reduce this uncertainty."
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Other researchers at Penn State include Patrick J. McFarland, undergraduate; David O. Miller, doctoral recipient; and Jena M. Jenkins, doctoral candidate, all in meteorology and atmospheric science.
Also working on the project were Eric Bruning, associate professor of atmospheric science, Texas Tech University; Sean Waugh, research meteorologist, and Donald MacGorman, senior research scientist, both at NOAA National Severe Storm Laboratory; Xinrong Ren, physical scientist, NOAA Air Resources Laboratory; Jingqiu Mao, assistant professor of atmospheric chemistry, Univeristy of Alaska; and Jeff Peischl, senior professional research assistant, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder.
The National Science Foundation, NASA, and the National Oceanic and Atmospheric Administration supported this work.
IMAGE: THE KOREAN ICEBREAKER ARAON, WHICH UNEXPECTEDLY FOUND ITSELF IN AN ARCTIC CYCLONE IN 2016, UNLOCKED THE KEY TO HOW THESE STORMS WREAK HAVOC ON SEA ICE IN THE ARCTIC OCEAN. view more
CREDIT: PHOTO BY JOO-HONG KIM, KOREA POLAR RESEARCH INSTITUTE
In August 2016 a massive storm on par with a Category 2 hurricane churned in the Arctic Ocean. The cyclone led to the third-lowest sea ice extent ever recorded. But what made the Great Arctic Cyclone of 2016 particularly appealing to scientists was the proximity of the Korean icebreaker Araon.
For the and their international colleagues recently published a new study showing that sea ice declined 5.7 times faster than normal during the storm. They werefirst t me ever, scientists were able to see exactly what happens to the ocean and sea ice when a cyclone hits. University of Alaska Fairbanks researchers also ab and their international colleagues recently published a new study showing that sea ice declined 5.7 times faster than normal during the storm. They were e to prove that the rapid decline was driven by cyclone-triggered processes within the ocean.
"Generally, when storms come in, they decrease sea ice, but scientists didn't understand what really caused it," said lead author Xiangdong Zhang from the UAF International Arctic Research Center.
There was general speculation that sea ice declined solely from atmospheric processes melting ice from above. Zhang and his team proved this theory incomplete using "in-situ" observations from directly inside the cyclone. The measurements reflected things like air and ocean temperature, radiation, wind and ocean currents.
It was a stroke of good luck for science, and perhaps a bit nerve-racking for those onboard, that the icebreaker was in position to capture data from the cyclone. Usually ships try to avoid such storms, but Araon had just sailed into the middle of an ice-covered zone and was locked in an ice floe.
Thanks to the ship's position so close to the storm, Xiangdong and his team were able to explain that cyclone-related sea ice loss is primarily due to two physical ocean processes.
First, strong spinning winds force the surface water to move away from the cyclone. This draws deeper warm water to the surface. Despite this warm water upwelling, a small layer of cool water remains directly beneath the sea ice.
That's where a second process comes into play. The strong cyclone winds act like a blender, mixing the surface water.
Together, the warm water upwelling and the surface turbulence warm the entire upper ocean water column and melt the sea ice from below.
Although the August storm raged for only 10 days, there were lasting effects.
"It's not just the storm itself," explained Zhang. "It has lingering effects because of the enhanced ice-albedo feedback."
The enlarged patches of open water from the storm absorb more heat, which melts more sea ice, causing even more open water. From Aug. 13-22, the amount of sea ice in the entire Arctic Ocean declined by 230,000 square miles, an area more than twice the size of the state of Arizona.
Xiangdong is now working with a new computer model for the Department of Energy to evaluate whether climate change will lead to more Arctic cyclones. Previous research shows that over the past half-century, the number and intensity of cyclones in the Arctic have increased. Some of those storms, like the biggest Arctic cyclone on record in 2012, also led to record low sea ice extent.
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Additional co-authors for this paper include two University of Alaska Fairbanks graduate students, Liran Peng and Han Tang, along with Korean researchers Joo-Hong Kim, Kyoung-Ho Cho and Baek-Min Kim, and Zhaomin Wang from China.
Northern forest fires could accelerate climate change
BU researchers used NASA satellite imaging data to analyze 30 years of Earth's northern forests and found that fires are increasingly hampering forests' ability to capture and store atmospheric carbon
IMAGE: THE STUDY FOCUSED ON WOODED PEATLAND AND FORESTS LIKE THE LANDSCAPE PICTURED HERE NEAR THE TOWN OF WRIGLEY IN CANADA'S NORTHWEST TERRITORIES. THIS DRONE IMAGERY WAS TAKEN BY THEN-BU PHD... view more
CREDIT: COURTESY OF JONATHAN WANG
New research indicates that the computer-based models currently used to simulate how Earth's climate will change in the future underestimate the impact that forest fires and drying climate are having on the world's northernmost forests, which make up the largest forest biome on the planet. It's an important understanding because these northern forests absorb a significant amount of Earth's carbon dioxide.
The finding, reached by studying 30 years of the world's forests using NASA satellite imaging data, suggests that forests won't be able to sequester as much carbon as previously expected, making efforts to reduce carbon emissions all the more urgent.
"Fires are intensifying, and when forests burn, carbon is released into the atmosphere," says Boston University environmental earth scientist Mark Friedl, senior author on the study published in Nature Climate Change. "But we're also seeing longer growing seasons, warmer temperatures, which draws carbon out of the atmosphere [and into plants]. More CO2 in the atmosphere acts as a fertilizer, increasing growth of trees and plants—so, scientifically, there's been this big question out there: What is happening on a global scale to Earth's forests? Will they continue to absorb as much carbon as they do now?"
Today's forests capture about 30 percent of all human-related CO2 emissions, which Friedl calls a "huge buffer on anthropogenic climate change." The new study, however, reveals that scientists have so far been underestimating the impact that fires and other disturbances—like timber harvests—are having on Earth's northern forests and, at the same time, have been overestimating the growth-enhancing effect of climate warming and rising atmospheric CO2 levels.
"Current Earth systems models appear to be misrepresenting a big chunk of the global biosphere. These models simulate the atmosphere, oceans, and biosphere, and our results suggest [the model-based simulation of northern forests] has been way off," says Friedl, a BU College of Arts & Sciences professor of earth and environment and interim director of BU's Center for Remote Sensing. He is an expert in utilizing satellite imaging data to monitor Earth's ecosystems on a global scale.
"It is not enough for a forest to absorb and store carbon in its wood and soils. For that to be a real benefit, the forest has to remain intact—an increasing challenge in a warming, more fire-prone climate," says Jonathan Wang, the paper's lead author. "The far north is home to vast, dense stores of carbon that are very sensitive to climate change, and it will take a lot of monitoring and effort to make sure these forests and their carbon stores remain intact."
Working on his PhD in Friedl's lab, Wang researched new ways to leverage the record of data collected from the long-standing Landsat program, a joint NASA/US Geological Survey mission that has been extensively imaging Earth's surface from satellites for decades, to understand how Earth's forests are changing. Wang says new computational and machine learning techniques for combining large remote sensing datasets have become much more advanced, "enabling the monitoring of even the most remote ecosystems with unprecedented detail."
He developed a method to gain richer information from 30 years of Landsat data by comparing it with more recent measurements from NASA's ICESat mission, a satellite carrying laser-based imaging technology, called LiDAR, that can detect the height of vegetation within a forest. Landsat, on the other hand, primarily detects forest cover but not how tall the trees are.
Comparing the newer LiDAR measurements with imaging data gathered from Landsat during the same time period, the team then worked backwards to calculate how tall and dense the vegetation was over the last three decades. They could then determine how the biomass in Earth's northern forests has changed over time—revealing that the forests have been losing more biomass than expected due to increasingly frequent and extensive forest fires.
Specifically, Friedl says, the forests are losing conifers, trees that are emblematic of Earth's northern forests, and for good reason. "Fires come in and burn, and then the most opportunistic types of species grow back first—like hardwoods—which then get replaced by conifers such as black spruce," he says. "But over the last 30 years, which isn't a long time frame in the context of climate change, we see fires taking out more forests, and we see hardwoods sticking around longer rather than being replaced by conifers."
Conifers are better adapted to cold climates than hardwoods, which could potentially be contributing to the dwindling overall biomass of the forests.
"An often-stated argument against climate action is the supposed benefits that far northern ecosystems and communities will enjoy from increased warmth," Wang says. He hopes the study's discovery will help people understand that the global climate crisis has serious issues for the far north, as well. "It may be greening, in some sense," he says, "but in reality the climate-driven increase in wildfires is undoing much of the potential benefits of a warming, greening north."
Wang and Friedl's findings shed light on a question that would have been difficult to answer without the help of NASA's "eyes in the sky."
"Fire regimens are changing because of climate, and many areas of the world's forests are in uninhabited areas where the effects of intense fires may not be easily noticed," Friedl says. "When big chunks of real estate in places like California go up in flames, that gets our attention. But northern forests, which hold some of the largest stocks of carbon in the world, are being impacted by fires more than we realized until now."
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Additional authors on the study include James Randerson, faculty member of UC Irvine Earth System Science; BU alum Mary Farina, now a PhD candidate at Montana State University; and Alessandro Baccini, research professor in BU's Center for Remote Sensing.
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news rele
Could the makeup of medical teams help explain why Black patients are more likely than white patients to die after heart surgery in the same hospitals?
IMAGE: COULD THE MAKEUP OF MEDICAL TEAMS HELP EXPLAIN WHY BLACK PATIENTS ARE MORE LIKELY THAN WHITE PATIENTS TO DIE AFTER HEART BYPASS SURGERY IN THE SAME HOSPITALS? view more
CREDIT: JACOB DWYER/ MICHIGAN MEDICINE
A new study finds Black patients are more likely to die after their heart bypass surgery if they're at a hospital where some care teams see mostly white patients and others see mostly Black patients. On the other hand, mortality rates are comparable between Black and white patients after heart bypass surgery when the teams of health care providers at their hospitals all care for patients of all races.
Some level of care team segregation within hospitals was very common, and the findings bring up another angle to better understand racial inequities in surgical outcomes, says co-first author John Hollingsworth, M.D., M.Sc., a professor of urology at Michigan Medicine and of health management and policy at the University of Michigan School of Public Health.
Previous studies have already shown that mortality after heart bypass surgery is higher overall in Black patients than white patients, but known factors such as access to care and use of lower resourced hospitals don't fully explain the disparities.
Hollingsworth and colleagues' new paper reviewed Medicare claims from more than 12,000 heart bypass procedures between 2008 and 2014. The data included claims from 72 hospitals across the country where at least 10 Black patients and at least 10 white patients underwent heart bypass surgery over the study interval.
Researchers used social network analysis to see where provider overlap happened--or didn't happen--between Black and white heart bypass patients and create a provider care team segregation score for each hospital.
"In the Medicare population, there is a lack of overlap in the composition of the provider care teams that treat Black and white patients undergoing heart bypass surgery in the same hospital," Hollingsworth says. "Such provider care team segregation is associated with higher operative mortality for this procedure among Black patients."
Researchers say the reasons for this segregation may include patient preference, in which people prefer to have a care provider who looks like them; admission priority, in which Black patients are more likely to come from the emergency room for their heart bypass than schedule it in advance as an elective surgery; and effects of structural racism on the process of assigning patients to provider care teams, which includes a variety of decisions that don't always get shared or explained.
Co-senior author Brahmajee Nallamothu, M.D., M.P.H., a professor of internal medicine and an interventional cardiologist at the Michigan Medicine Frankel Cardiovascular Center, says the findings point to the need for in-depth study of provider care team segregation as part of the effort to reduce health care inequities.
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Hollingsworth and Nallamothu are both members of U-M's Institute for Healthcare Policy & Innovation.
Fish have been swallowing microplastics since the 1950s
Museum collections reveal the history of microplastics
IMAGE: A THIN, THREAD-LIKE STRAND OF MICROPLASTIC FROM A FISH'S DIGESTIVE TRACT. view more
CREDIT: LOREN HOU
Forget diamonds--plastic is forever. It takes decades, or even centuries, for plastic to break down, and nearly every piece of plastic ever made still exists in some form today. We've known for a while that big pieces of plastic can harm wildlife--think of seabirds stuck in plastic six-pack rings--but in more recent years, scientists have discovered microscopic bits of plastic in the water, soil, and even the atmosphere. To learn how these microplastics have built up over the past century, researchers examined the guts of freshwater fish preserved in museum collections; they found that fish have been swallowing microplastics since the 1950s and that the concentration of microplastics in their guts has increased over time.
"For the last 10 or 15 years it's kind of been in the public consciousness that there's a problem with plastic in the water. But really, organisms have probably been exposed to plastic litter since plastic was invented, and we don't know what that historical context looks like," says Tim Hoellein, an associate professor of biology at Loyola University Chicago and the corresponding author of a new study in Ecological Applications. "Looking at museum specimens is essentially a way we can go back in time."
Caleb McMahan, an ichthyologist at the Field Museum, cares for some two million fish specimens, most of which are preserved in alcohol and stored in jars in the museum's underground Collections Resource Center. These specimens are more than just dead fish, though--they're a snapshot of life on Earth. "We can never go back to that time period, in that place," says McMahan, a co-author of the paper.
Hoellein and his graduate student Loren Hou were interested in examining the buildup of microplastics in freshwater fish from the Chicagoland region. They reached out to McMahan, who helped identify four common fish species that the museum had chronological records of dating back to 1900: largemouth bass, channel catfish, sand shiners, and round gobies. Specimens from the Illinois Natural History Survey and University of Tennessee also filled in sampling gaps.
"We would take these jars full of fish and find specimens that were sort of average, not the biggest or the smallest, and then we used scalpels and tweezers to dissect out the digestive tracts," says Hou, the paper's lead author. "We tried to get at least five specimens per decade."
To actually find the plastic in the fishes' guts, Hou treated the digestive tracts with hydrogen peroxide. "It bubbles and fizzes and breaks up all the organic matter, but plastic is resistant to the process," she explains.
The plastic left behind is too tiny to see with the naked eye, though: "It just looks like a yellow stain, you don't see it until you put it under the microscope," says Hou. Under the magnification, though, it's easier to identify. "We look at the shape of these little pieces. If the edges are frayed, it's often organic material, but if it's really smooth, then it's most likely microplastic." To confirm the identity of these microplastics and determine where they came from, Hou and Hoellein worked with collaborators at the University of Toronto to examine the samples using Raman spectroscopy, a technique that uses light to analyze the chemical signature of a sample.
The researchers found that the amount of microplastics present in the fishes' guts rose dramatically over time as more plastic was manufactured and built up in the ecosystem. There were no plastic particles before mid-century, but when plastic manufacturing was industrialized in the 1950s, the concentrations skyrocketed.
"We found that the load of microplastics in the guts of these fishes have basically gone up with the levels of plastic production," says McMahan. "It's the same pattern of what they're finding in marine sediments, it follows the general trend that plastic is everywhere."
The analysis of the microplastics revealed an insidious form of pollution: fabrics. "Microplastics can come from larger objects being fragmented, but they're often from clothing," says Hou--whenever you wash a pair of leggings or a polyester shirt, tiny little threads break off and get flushed into the water supply.
"It's plastic on your back, and that's just not the way that we've been thinking about it," says Hoellein. "So even just thinking about it is a step forward in addressing our purchases and our responsibility."
It's not clear how ingesting these microplastics affected the fish in this study, but it's probably not great. "When you look at the effects of microplastic ingestion, especially long term effects, for organisms such as fish, it causes digestive tract changes, and it also causes increased stress in these organisms," says Hou.
While the findings are stark--McMahan described one of the paper's graphs showing the sharp rise in microplastics as "alarming"--the researchers hope it will serve as a wake-up call. "The entire purpose of our work is to contribute to solutions," says Hoellein. "We have some evidence that public education and policies can change our relationship to plastic. It's not just bad news, there's an application that I think should give everyone a collective reason for hope."
The researchers say the study also highlights the importance of natural history collections in museums. "Loren and I both love the Field Museum but don't always think about it in terms of its day-to-day scientific operations," says Hoellein. "It's an incredible resource of the natural world, not just as it exists now but as it existed in the past. It's fun for me to think of the museum collection sort of like the voice of those long dead organisms that are still telling us something about the state of the world today."
"You can't do this kind of work without these collections," says McMahan. "We need older specimens, we need the recent ones, and we're going to need what we collect in the next 100 years."
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Stalagmites Embody Clock-Like Chronicles of Time Over Thousands of Years
Stalagmites in Carlsbad Caverns, New Mexico. (Cabezonication/Getty Images)
Deep underground, in mysterious caverns that seem almost measureless to humans, caves have devised their own strange ways of keeping time as the eternities pass by.
Over millennia, a ponderous exchange takes place so slowly, it makes the growing of grass look action-packed in comparison. Hanging from cave ceilings, downward-growing stalactites drip water containing chemicals onto the cave floor, which slowly aggregates into an upward-growing stalagmite.
Scientists have understood the basics of this speleothem relationship for a long time, but we're still discovering just how much of the ancient past is inscribed in these underground formations: echoes of ancient wildfires, sagas of societal collapse, and even grim predictions of our own destiny.
In a new study led by geochemist Andy Baker from UNSW in Australia, researchers have now found that stalagmites don't just record these dramatic instances of sudden and extreme climate events – they also act as natural timekeepers, chronicling the steady passage of time into the layers of rocks they become.
"Our new global analysis shows that we can consider stalagmite growth as being like a metronome and very constant over hundreds and thousands of years," Baker explains.
"In general, stalagmite growth is predictable and it is this unique property that makes them so valuable to researchers – you can tell the time in the past by using the very regular growth rings that are widely present across the globe."
In their research, Baker and his team analyzed stalagmites from 23 caves across 6 continents, looking for any common mechanisms that might explain their development.
They found that stalagmite growth rates increased in line with warmer temperatures, and that the formations only seem to grow in regions with seasonal precipitation.
While many kinds of climate disturbances can affect the ways stalagmites develop, once you average out these extreme episodes, the growth rate over time is relatively common and consistent across the globe – not to mention mind-bogglingly slow.
"The 'global average stalagmite' increased in height by about one meter over the last 11,000 years," Baker says.
Over such epic timeframes, stalagmites generally grow in an ordered fashion, much like tree rings, except for when long-lasting, multi-year disturbances – such as prolonged wet or dry years associated with things like El Niño or La Niña events – stand out in the record.
When those disturbances pass, though, the stalagmite growth layers (laminae) return to their regular rhythm, informed by the consistency of moisture descending onto them from above.
"Stalagmite accumulation rate is relatively unchanging over time," the researchers write in their paper.
"This is because their drip water source has enough volume and a stable chemical composition to be a buffer to rapid changes. Year‐to‐year, we see a 'flickering', where accumulation rate returns toward the long‐term average, also due to this buffering effect."
For these reasons, the researchers say stalagmites have much to teach us about the chronology of the ancient past – a vast archive of climate‐related proxy data we've only just begun to explore.
The spectacle of space has our jaws constantly dropping, and the picture that was just released to celebrate 31 years of the Hubble Space Telescope is another incredibly powerful shot that we could gaze at for hours.
It shows the giant, ultra-bright star AG Carinae, 20,000 light-years away from Earth, in a phase that makes it a Luminous Blue Variable (LBV) – where massive stars such as this one go through thousands of years of instability and varying luminosity.
Some 70 times bigger and around 1 million times brighter than our own Sun, AG Carinae is battling itself as it tries to avoid complete annihilation. With gravity pushing inwards and radiation pushing outwards at almost unimaginable levels, the star reaches pressure points where its outer layers blast off in an explosion – as shown in this image.
(NASA, ESA, STScI)
What you can see around AG Carinae is a gigantic nebula, an expanding shell of gas and dust, around five light-years wide – that's the same distance from our planet to Alpha Centauri, our next nearest star, to give you a sense of scale.
This particular eruption happened several thousand years ago. You can see both red material, which is glowing hydrogen gas laced with nitrogen gas, and blue material, which is dust clumps pushed out from the star.
Stellar winds are traveling away from the star at around 1 million kilometers (621,371 miles) per hour, eventually catching up to the circling material and pushing it out into space. To the top left of the photo you can see a more diffuse area of red, where the stellar winds have burst through.
The tadpole-like shapes in blue are clumps of dust that the winds have specifically sculpted. It's thanks to Hubble, and the way it can capture both visible and ultraviolet light from above Earth's atmosphere, that we can see all this in so much detail.
Outbursts like this one will happen a few times during the lifetime of an LBV, and in this case it's estimated that AG Carinae has pushed out a volume of material that's equivalent to 10 times the mass of our Sun.
These spectacular shows happen when a star is about to come apart: by shedding all of these outer layers, the LBV can shrink again and become stable... at least for a while. These stars only live for a few million years (rather than the 10-billion-year lifetime of our Sun).
"I like studying these kinds of stars because I am fascinated by their instability," says astronomer Kerstin Weis, from Ruhr University in Germany. "They are doing something weird."
Happy birthday Hubble, and thanks for all the fantasticimages. Since 24 April 1990, the telescope has made over 1.5 million observations of around 48,000 celestial objects.
