Scientists pin down the origins of the moon's tenuous atmosphere

While the moon lacks any breathable air, it does host a barely-there atmosphere. Since the 1980s, astronomers have observed a very thin layer of atoms bouncing over the moon's surface. This delicate atmosphere -- technically known as an "exosphere" -- is likely a product of some kind of space weathering. But exactly what those processes might be has been difficult to pin down with any certainty.

Now, scientists at MIT and the University of Chicago say they have identified the main process that formed the moon's atmosphere and continues to sustain it today. In a study appearing in Science Advances, the team reports that the lunar atmosphere is primarily a product of "impact vaporization."

In their study, the researchers analyzed samples of lunar soil collected by astronauts during NASA's Apollo missions. Their analysis suggests that over the moon's 4.5-billion-year history its surface has been continuously bombarded, first by massive meteorites, then more recently, by smaller, dust-sized "micrometeoroids." These constant impacts have kicked up the lunar soil, vaporizing certain atoms on contact and lofting the particles into the air. Some atoms are ejected into space, while others remain suspended over the moon, forming a tenuous atmosphere that is constantly replenished as meteorites continue to pelt the surface.

The researchers found that impact vaporization is the main process by which the moon has generated and sustained its extremely thin atmosphere over billions of years.

"We give a definitive answer that meteorite impact vaporization is the dominant process that creates the lunar atmosphere," says the study's lead author, Nicole Nie, an assistant professor in MIT's Department of Earth, Atmospheric, and Planetary Sciences. "The moon is close to 4.5 billion years old, and through that time the surface has been continuously bombarded by meteorites. We show that eventually, a thin atmosphere reaches a steady state because it's being continuously replenished by small impacts all over the moon."

Nie's co-authors are Nicolas Dauphas, Zhe Zhang, and Timo Hopp at the University of Chicago, and Menelaos Sarantos at NASA Goddard Space Flight Center.

Weathering's roles

In 2013, NASA sent an orbiter around the moon to do some detailed atmospheric reconnaissance. The Lunar Atmosphere and Dust Environment Explorer (LADEE, pronounced "laddie") was tasked with remotely gathering information about the moon's thin atmosphere, surface conditions, and any environmental influences on the lunar dust.

LADEE's mission was designed to determine the origins of the moon's atmosphere. Scientists hoped that the probe's remote measurements of soil and atmospheric composition might correlate with certain space weathering processes that could then explain how the moon's atmosphere came to be.

Researchers suspect that two space weathering processes play a role in shaping the lunar atmosphere: impact vaporization and "ion sputtering" -- a phenomenon involving solar wind, which carries energetic charged particles from the sun through space. When these particles hit the moon's surface, they can transfer their energy to the atoms in the soil and send those atoms sputtering and flying into the air.

"Based on LADEE's data, it seemed both processes are playing a role," Nie says. "For instance, it showed that during meteorite showers, you see more atoms in the atmosphere, meaning impacts have an effect. But it also showed that when the moon is shielded from the sun, such as during an eclipse, there are also changes in the atmosphere's atoms, meaning the sun also has an impact. So, the results were not clear or quantitative."

Answers in the soil

To more precisely pin down the lunar atmosphere's origins, Nie looked to samples of lunar soil collected by astronauts throughout NASA's Apollo missions. She and her colleagues at the University of Chicago acquired 10 samples of lunar soil, each measuring about 100 milligrams -- a tiny amount that she estimates would fit into a single raindrop.

Nie sought to first isolate two elements from each sample: potassium and rubidium. Both elements are "volatile," meaning that they are easily vaporized by impacts and ion sputtering. Each element exists in the form of several isotopes. An isotope is a variation of the same element, that consists of the same number of protons but a slightly different number of neutrons. For instance, potassium can exist as one of three isotopes, each one having one more neutron, and there being slightly heavier than the last. Similarly, there are two isotopes of rubidium.

The team reasoned that if the moon's atmosphere consists of atoms that have been vaporized and suspended in the air, lighter isotopes of those atoms should be more easily lofted, while heavier isotopes would be more likely to settle back in the soil. Furthermore, scientists predict that impact vaporization, and ion sputtering, should result in very different isotopic proportions in the soil. The specific ratio of light to heavy isotopes that remain in the soil, for both potassium and rubidium, should then reveal the main process contributing to the lunar atmosphere's origins.

With all that in mind, Nie analyzed the Apollo samples by first crushing the soils into a fine powder, then dissolving the powders in acids to purify and isolate solutions containing potassium and rubidium. She then passed these solutions through a mass spectrometer to measure the various isotopes of both potassium and rubidium in each sample.

In the end, the team found that the soils contained mostly heavy isotopes of both potassium and rubidium. The researchers were able to quantify the ratio of heavy to light isotopes of both potassium and rubidium, and by comparing both elements, they found that impact vaporization was most likely the dominant process by which atoms are vaporized and lofted to form the moon's atmosphere.

"With impact vaporization, most of the atoms would stay in the lunar atmosphere, whereas with ion sputtering, a lot of atoms would be ejected into space," Nie says. "From our study, we now can quantify the role of both processes, to say that the relative contribution of impact vaporization versus ion sputtering is about 70:30 or larger." In other words, 70 percent or more of the moon's atmosphere is a product of meteorite impacts, whereas the remaining 30 percent is a consequence of the solar wind.

"The discovery of such a subtle effect is remarkable, thanks to the innovative idea of combining potassium and rubidium isotope measurements along with careful, quantitative modeling," says Justin Hu, a postdoc who studies lunar soils at Cambridge University, who was not involved in the study. "This discovery goes beyond understanding the moon's history, as such processes could occur and might be more significant on other moons and asteroids, which are the focus of many planned return missions."

"Without these Apollo samples, we would not be able to get precise data and measure quantitatively to understand things in more detail," Nie says. "It's important for us to bring samples back from the moon and other planetary bodies, so we can draw clearer pictures of the solar system's formation and evolution."

Read more at Science Daily

Land under water: What causes extreme flooding?

If rivers overflow their banks, the consequences can be devastating -- just like the catastrophic floods in North Rhine-Westphalia and Rhineland-Palatinate of 2021 showed. In order to limit flood damage and optimise flood risk assessment, we need to better understand what factors can lead to extreme forms of flooding and to what extent. Using methods of explainable machine learning, researchers at the Helmholtz Centre for Environmental Research (UFZ) have shown that floods are more extreme when several factors are involved in their development. The research was published in Science Advances.

There are several factors that play an important role in the development of floods: air temperature, soil moisture, snow depth, and the daily precipitation in the days before a flood. In order to better understand how individual factors contribute to flooding, UFZ researchers examined more than 3,500 river basins worldwide and analysed flood events between 1981 and 2020 for each of them. The result: precipitation was the sole determining factor in only around 25% of the almost 125,000 flood events. Soil moisture was the decisive factor in just over 10% of cases, and snow melt and air temperature were the sole factors in only around 3% of cases. In contrast, 51.6% of cases were caused by at least two factors. At around 23%, the combination of precipitation and soil moisture occurs most frequently.

However, when analysing the data, the UFZ researchers discovered that three -- or even all four -- factors can be jointly responsible for a flood event. For example, temperature, soil moisture, and snow depth were decisive factors in around 5,000 floods whilst all four factors were decisive in around 1,000 flood events. And not only that: "We also showed that flood events become more extreme when more factors are involved," says Dr Jakob Zscheischler, Head of the UFZ Department "Compound Environmental Risks" and senior author of the article. In the case of one-year floods, 51.6% can be attributed to several factors; in the case of five- and ten-year floods, 70.1% and 71.3% respectively can be attributed to several factors. The more extreme a flood is, the more driving factors there are and the more likely they are to interact in the event generation. This correlation often also applies to individual river basins and is referred to as flood complexity.

According to the researchers, river basins in the northern regions of Europe and America as well as in the Alpine region have a low flood complexity. This is because snow melt is the dominant factor for most floods regardless of the flood magnitude. The same applies to the Amazon basin, where the high soil moisture resulting from the rainy season is often a major cause of floods of varying severity. In Germany, the Havel and the Zusam, a tributary of the Danube in Bavaria, are river basins that have a low flood complexity. Regions with river basins that have a high flood complexity primarily include eastern Brazil, the Andes, eastern Australia, the Rocky Mountains up to the US west coast, and the western and central European plains. In Germany, this includes the Moselle and the upper reaches of the Elbe. "River basins in these regions generally have several flooding mechanisms," says Jakob Zscheischler. For example, river basins in the European plains can be affected by flooding caused by the combination of heavy precipitation, active snow melt, and high soil moisture.

However, the complexity of flood processes in a river basin also depends on the climate and land surface conditions in the respective river basin. This is because every river basin has its own special features. Among other things, the researchers looked at the climate moisture index, the soil texture, the forest cover, the size of the river basin, and the river gradient. "In drier regions, the mechanisms that lead to flooding tend to be more heterogeneous. For moderate floods, just a few days of heavy rainfall is usually enough. For extreme floods, it needs to rain longer on already moist soils," says lead author Dr Shijie Jiang, who now works at the Max Planck Institute for Biogeochemistry in Jena.

The scientists used explainable machine learning for the analysis. "First, we use the potential flood drivers air temperature, soil moisture, and snow depth as well as the weekly precipitation -- each day is considered as an individual driving factor -- to predict the run-off magnitude and thus the size of the flood," explains Zscheischler. The researchers then quantified which variables and combinations of variables contributed to the run-off of a particular flood and to which extent. This approach is referred to as explainable machine learning because it uncovers the predictive relationship between flood drivers and run-off during a flood in the trained model. "With this new methodology, we can quantify how many driving factors and combinations thereof are relevant for the occurrence and intensity of floods," adds Jiang.

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Climate change will see Australia's soil emit CO2 and add to global warming

New Curtin University research has shown the warming climate will turn Australia's soil into a net emitter of carbon dioxide (CO2), unless action is taken.

Soil helps to keep the planet cool by absorbing carbon, however as the climate gets warmer its ability to retain carbon decreases -- and in some instances can start to release some carbon back into the air.

A global research team -- led by Professor Raphael Viscarra Rossel from Curtin's School of Molecular and Life Sciences -- predicted the changes in the amount of carbon in Australia's soil between now and the year 2100.

To do so, the team ran simulations using three different paths for society: an eco-focused 'sustainable' scenario, a 'middle-of-the-road' scenario and another which predicted a continued reliance on 'fossil-fuelled development'.

It found Australian soil will be a net emitter and could account for 8.3 per cent of Australia's total current emissions under the 'sustainable' scenario and more than 14 per cent by 2045 under the 'middle-of-the-road' and 'fossil-fuelled' scenarios.

By 2100, soil emissions under both scenarios are predicted to account for an even higher proportion of total emissions, but the predictions are more uncertain.

While some areas with arable farmland could continue to store carbon, the study found it would not be enough to offset the amounts of carbon lost from the soil in areas which are more sensitive to warmer weather, such as coastal regions and Australia's vast rangelands.

Australian soil holds an estimated 28 gigatons of carbon, 70 per cent of which is stored in these rangelands.

"Unless farming methods are further improved so farmland soils can continue to store carbon, any gains and benefit will likely decrease by 2045 and worsen in time, if the Earth continues to warm at its current rate," Professor Viscarra Rossel said.

"This means Australia's soil could release even more carbon into the air instead of storing it, which will in turn make climate change worse.

"If emissions continue at the current rate, the Earth's temperature is expected to reach 2 degrees above pre-industrial temperatures sometime this century, which is predicted to have dire consequences and

potentially catastrophic impacts for the planet."

Professor Viscarra Rossel said more sustainable pathways and improved management and conservation of soils were essential for Australia to meet its emissions reduction goals.

"Ensuring Australia's rangeland soils can maintain their carbon stocks is imperative: capturing and storing additional carbon will require interdisciplinary science, innovation, cultural awareness and effective policies" Professor Viscarra Rossel said.

"It will be challenging, given the rangelands' drier and more variable climate, its relatively sparse vegetation and other factors such as bushfires -- however, only a slight change over such large areas will make a positive difference.

Read more at Science Daily

Scientists uncover evidence that microplastics are contaminating archaeological remains

Researchers have for the first time discovered evidence of microplastic contamination in archaeological soil samples.

The team discovered tiny microplastic particles in deposits located more than seven metres deep, in samples dating back to the first or early second century and excavated in the late 1980s.

Preserving archaeology in situ has been the preferred approach to managing historical sites for a generation.

However, the research team say the findings could prompt a rethink, with the tiny particles potentially compromising the preserved remains.

Microplastics are small plastic particles, ranging from 1μm (one thousandth of a millimetre) to 5mm.

They come from a wide range of sources, from larger plastic pieces that have broken apart, or resin pellets used in plastic manufacturing which were frequently used in beauty products up until around 2020.

The study, published in the journal Science of the Total Environment, was carried out by the universities of York and Hull and supported by the educational charity York Archaeology.

Professor John Schofield from the University of York's Department of Archaeology, said: "This feels like an important moment, confirming what we should have expected: that what were previously thought to be pristine archaeological deposits, ripe for investigation, are in fact contaminated with plastics, and that this includes deposits sampled and stored in the late 1980s.

"We are familiar with plastics in the oceans and in rivers. But here we see our historic heritage incorporating toxic elements. To what extent this contamination compromises the evidential value of these deposits, and their national importance is what we'll try to find out next."

David Jennings, chief executive of York Archaeology, added: "We think of microplastics as a very modern phenomenon, as we have only really been hearing about them for the last 20 years, when Professor Richard Thompson revealed in 2004 that they have been prevalent in our seas since the 1960s with the post-war boom in plastic production,"

"This new study shows that the particles have infiltrated archaeological deposits, and like the oceans, this is likely to have been happening for a similar period, with particles found in soil samples taken and archived in 1988 at Wellington Row in York."

The study identified 16 different microplastic polymer types across both contemporary and archived samples.

"Where this becomes a concern for archaeology is how microplastics may compromise the scientific value of archaeological deposits. Our best-preserved remains -- for example, the Viking finds at Coppergate -- were in a consistent anaerobic waterlogged environment for over 1000 years, which preserved organic materials incredibly well. The presence of microplastics can and will change the chemistry of the soil, potentially introducing elements which will cause the organic remains to decay. If that is the case, preserving archaeology in situ may no longer be appropriate," added David Jennings.

Read more at Science Daily

Say hello to biodegradable microplastics

Microplastics are tiny, nearly indestructible fragments shed from everyday plastic products. As we learn more about microplastics, the news keeps getting worse. Already well-documented in our oceans and soil, we're now discovering them in the unlikeliest of places: our arteries, lungs and even placentas. Microplastics can take anywhere from 100 to 1,000 years to break down and, in the meantime, our planet and bodies are becoming more polluted with these materials every day.

Finding viable alternatives to traditional petroleum-based plastics and microplastics has never been more important. New research from scientists at the University of California San Diego and materials-science company Algenesis shows that their plant-based polymers biodegrade -- even at the microplastic level -- in under seven months. The paper, whose authors are all UC San Diego professors, alumni or former research scientists, appears in Nature Scientific Reports.

"We're just starting to understand the implications of microplastics. We've only scratched the surface of knowing the environmental and health impacts," stated Professor of Chemistry and Biochemistry Michael Burkart, one of the paper's authors and an Algenesis co-founder. "We're trying to find replacements for materials that already exist, and make sure these replacements will biodegrade at the end of their useful life instead of collecting in the environment. That's not easy."

"When we first created these algae-based polymers about six years ago, our intention was always that it be completely biodegradable," said another of the paper's authors, Robert Pomeroy, who is also a professor of chemistry and biochemistry and an Algenesis co-founder. "We had plenty of data to suggest that our material was disappearing in the compost, but this is the first time we've measured it at the microparticle level."

Putting it to the test

To test its biodegradability, the team ground their product into fine microparticles, and used three different measurement tools to confirm that, when placed in a compost, the material was being digested by microbes.

The first tool was a respirometer. When the microbes break down compost material, they release carbon dioxide (CO2), which the respirometer measures. These results were compared to the breakdown of cellulose, which is considered the industry standard of 100% biodegradability. The plant-based polymer matched the cellulose at almost one hundred percent.

Next the team used water flotation. Since plastics are not water soluble and they float, they can easily be scooped off the surface of water. At intervals of 90 and 200 days, almost 100% of the petroleum-based microplastics were recovered, meaning none of it had biodegraded. On the other hand, after 90 days, only 32% of the algae-based microplastics were recovered, showing that more than two thirds of it had biodegraded. After 200 days, only 3% was recovered indicating that 97% of it had disappeared.

The last measurement involved chemical analysis via gas chromatography/mass spectrometry (GCMS), which detected the presence of the monomers used to make the plastic, indicating that the polymer was being broken to its starting plant materials. Scanning-electron microscopy further showed how microorganisms colonize the biodegradable microplastics during composting.

"This material is the first plastic demonstrated to not create microplastics as we use it," said Stephen Mayfield, a paper coauthor, School of Biological Sciences professor and co-founder of Algenesis. "This is more than just a sustainable solution for the end-of-product life cycle and our crowded landfills. This is actually plastic that is not going to make us sick."

Creating an eco-friendly alternative to petroleum-based plastics is only one part of the long road to viability. The ongoing challenge is to be able to use the new material on pre-existing manufacturing equipment that was originally built for traditional plastic, and here Algenesis is making progress. They have partnered with several companies to make products that use the plant-based polymers developed at UC San Diego, including Trelleborg for use in coated fabrics and RhinoShield for use in the production of cell phone cases.

"When we started this work, we were told it was impossible," stated Burkart. "Now we see a different reality. There's a lot of work to be done, but we want to give people hope. It is possible."

Read more at Science Daily

Drought, soil desiccation cracking, and carbon dioxide emissions: an overlooked feedback loop exacerbating climate change

The accuracy of climate models depends on many factors -- greenhouse gas emissions from industrial and transportation activity, farm animal "emissions," urban growth and loss of forests, and solar reflections off snow and ground cover. Natural phenomena like volcanic eruptions also contribute and are incorporated into models.

However, some other natural processes have been overlooked. Farshid Vahedifard, professor and Louis Berger Chair in civil and environmental engineering, points to an important one that lies directly beneath our feet and covers most of our planet above water.

In a study published in Environmental Research Letters, Vahedifard notes that soil stores 80 percent of carbon on Earth, and with increasing cycles and severity of droughts in several regions, that crucial reservoir is cracking and breaking down, releasing even more carbon dioxide and other greenhouse gases into the atmosphere.

In fact, it may be creating an amplified feedback loop that could accelerate climate change well beyond current predictions.

"This process has not been sufficiently evaluated in the existing literature or incorporated into models," said Vahedifard.

"If we don't consider the interplay of drought, soil desiccation cracking, and CO2 emissions, that could result in significant inaccuracies when modeling and predicting climate change. There are other repercussions as well. Poorer soil health can lead to reduced photosynthesis and lower carbon dioxide uptake, and it can compromise the structural integrity of earthen dams that protect against floods."

There are also other amplifying feedback loops that may not have been fully accounted for in climate change models, he said.

These include melting of sea ice and exposure of darker ocean surfaces that absorb more heat from the sun.

The increase of wildfires due to warm, dry conditions releases a lot of carbon dioxide into the atmosphere, which in turn creates hotter, drier weather more conducive to fires.

Another amplified feedback loop is the thawing of Arctic and sub-Arctic permafrost, which also releases carbon dioxide into the atmosphere and raises climate temperature, leading to more melted permafrost.

But soil changes caused by drought could be as significant, if not more significant, than any of those factors.

Drought, manifested by long periods of low soil moisture content and high temperature, leads to cracking in fine-grained soils, sometimes extending meters below the surface.

The cracks result in more exposure to the air, increased microbial activity and breakdown of organic matter, released carbon dioxide, and loss of nutrients and ability to support plant growth, reducing carbon dioxide sequestering.

The deep cracks expose much older reserves of carbon that had previously been stable and protected.

The permeation of air into the soil accelerates the release of not only carbon dioxide from organic matter but also other greenhouse gases like nitrous oxide.

Small animals like earthworms and millipedes that help turn the soil over are also affected by the reduced moisture and increased air exposure, being less able to play active roles in nutrient cycling and soil structure maintenance.

That, in turn, increases the likelihood of soil cracking and aeration.

"The amplifying effect of soil carbon feedback loops and its interactions with other loops could carry us across tipping points and lead to even more severe and permanent shifts in climate," said Vahedifard.

Read more at Science Daily

Understanding how soil traps carbon

When carbon molecules from plants enter the soil, they hit a definitive fork in the road.

Either the carbon gets trapped in the soil for days or even years, where it is effectively sequestered from immediately entering the atmosphere. Or it feeds microbes, which then respire carbon dioxide (CO2) into the ever-warming environment.

In a new study, Northwestern University researchers determined the factors that could tip plant-based organic matter in one direction or the other.

By combining laboratory experiments and molecular modeling, researchers examined interactions between organic carbon biomolecules and a type of clay minerals known for trapping organic matter in soil. They found that electrostatic charges, structural features of carbon molecules, surrounding metal nutrients in soil and competition among molecules all play major roles in soil's ability (or inability) to trap carbon.

The new findings could help researchers predict which soil chemistries are most favorable for trapping carbon -- potentially leading to soil-based solutions for slowing human-caused climate change.

The research will be published on Feb. 9 in the Proceedings of the National Academy of Sciences.

"The amount of organic carbon stored in soil is about ten times the amount of carbon in the atmosphere," said Northwestern's Ludmilla Aristilde, the study's senior author. "If this enormous reservoir is perturbed, it would have substantial ripple effects. There are many efforts to keep carbon trapped to prevent it from entering the atmosphere. If we want to do that, then we first must understand the mechanisms at play."

An expert in the dynamics of organics in environmental processes, Aristilde is an associate professor of civil and environmental engineering at Northwestern's McCormick School of Engineering. Jiaxing Wang, a Ph.D. student in Aristilde's laboratory, is the paper's first author. Rebecca Wilson, an undergraduate student at Northwestern, is the paper's second author.

Common clay

Holding 2,500 billion tons of sequestered carbon, soil is one of Earth's largest carbon sinks -- second only to the ocean. But even though soil is all around us, researchers are only just beginning to understand how it locks in carbon to sequester it from the carbon cycle.

To investigate this process, Aristilde and her team looked to smectite clay, a type of clay mineral known to sequester carbon in natural soils. Then, they examined how the clay mineral's surface bonded to ten different biomolecules -- including amino acids, sugars related cellulose and phenolic acids related to lignin -- with varying chemistry and structures.

"We decided to study this clay mineral because it's everywhere," Aristilde said. "Nearly all soils have clay minerals. Also, clays are prevalent in semi-arid and temperate climates -- regions that we know will be affected by climate change."

Opposites attract

Aristilde and her team first looked at interactions between clay minerals and individual biomolecules. Because clay minerals are negatively charged, biomolecules with positively charged components (lysine, histidine and threonine) experienced the strongest binding. But, interestingly, this binding was not solely determined by electrostatic charges. Using 3D computational modeling, the researchers found that the structure of the biomolecules also played a role.

"There are instances where two molecules are both positively charged, yet one has a better interaction with the clay than the other," Aristilde said. "It's because the structural features of the binding are also important. A molecule has to be flexible enough to adopt a structural arrangement that can position itself in a way that aligns its positively charged components with the clay. The lysine, for example, has a long arm with a positive charge that it can use to anchor itself."

A little help from friends

Following this logic, one might assume that negatively charged biomolecules were unable to bind to the clay. But Aristilde and her team discovered that surrounding, natural metal nutrients could intervene. Positively charged metals, such as magnesium and calcium, formed a bridge between the negatively charged biomolecules and clay minerals to create a bond.

"Even with a biomolecule that wouldn't normally bind to the clay, we saw a significant increase in binding when magnesium was there," Aristilde said. "So, natural metal constituents in the soil can facilitate carbon trapping. Although this is a widely reported phenomenon, we shed light on the structures and mechanisms."

Mix and mingle

When studying interactions between individual biomolecules and clay minerals, the researchers found binding was predictable and straightforward. To attain information more closely aligned with real-world environments, Aristilde and her team mixed the different biomolecules together.

"We know different types of biomolecules in the environment exists together," Aristilde said. "So, we also performed experiments with a mixture of biomolecules."

Although the researchers initially thought the biomolecules would compete with one another to interact with the clay, they instead discovered unexpected behaviors. In a surprising twist, even positively charged biomolecules with flexible structures were inhibited from binding to the clay minerals. While they easily bonded to the clay when alone, the biomolecules' urges to bond with one another appears to supersede their attractions to the clay.

"This has not been shown before," Aristilde said. "The energy of attraction between two biomolecules was actually higher than the energy of attraction of a biomolecule to the clay. That led to a decrease in adsorption. It changes the way we think about how molecules compete on the surface. They aren't just competing for binding sites on the surface. They can actually attract each other."

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Rising sea levels could lead to more methane emitted from wetlands

As sea levels rise due to global warming, ecosystems are being altered. One small silver lining, scientists believed, was that the tidal wetlands found in estuaries might produce less methane -- a potent greenhouse gas -- as the increasing influx of seawater makes these habitats less hospitable to methane-producing microbes.

However, research from biologists at Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley indicates that these assumptions aren't always true. After examining the microbial, chemical, and geological features of 11 wetland zones, the team found that a wetland region exposed to a slight amount of seawater was emitting surprisingly high levels of methane -- far more than any of the freshwater sites.

Their results, now published in mSystems, indicate that the factors governing how much greenhouse gas is stored or emitted in natural landscapes are more complex and difficult to predict than we thought.

"We looked at how many methanogens, the organisms that make methane, are present in soils at these sites and it wasn't really well correlated with the amount of methane observed," said senior author Susannah Tringe, director of Berkeley Lab's Environmental Genomics & Systems Biology Division. "And even if you look at the amount of methanotrophs, organisms that eat methane, in combination with methanogens, that doesn't seem to fully explain it."

Tringe and her colleagues took soil samples from the 11 sites and used high-throughput sequencing to analyze DNA from organisms found in the samples, including bacteria, viruses, and fungi. They examined what genes were present in the sequences and mapped them to known functions -- for example, identifying genes known to be involved in metabolizing nitrogen or genes from bacteria that use sulfate during respiration. Then they worked to model how the genetic information they found, combined with chemical factors in the soil and water, could result in the methane emissions they observed.

Across most of the sites, which ranged from freshwater to full seawater salinities, the amount of methane emitted was inversely related to the amount of salt water that was flowing in and mingling with the river water. But at one site, which had been restored in 2010 from a seasonal grassy pasture for livestock grazing back to its original wetland habitat, the team saw high methane emissions despite the moderate amount of salt water.

Seawater contains more sulfate (an ion with sulfur and oxygen) than freshwater, leading to the assumption that increased influx of seawater in these environments would lead to less methane production as the methanogens that use CO2 to make cellular energy are outcompeted by the bacteria that use sulfate instead.

"Ultimately, we found that there were significant influences from other bacterial groups like the ones that break down carbon and even organisms that are better known as nitrogen cyclers, and we couldn't readily explain the methane emissions by something as simple as, for example, how much sulfate is available or how many methanogens are there," said Tringe.

Another concept in ecology is that restoring habitats to their native state can boost carbon storage, improve water quality, and increase wildlife populations. In recent decades, wetlands have been increasingly recognized as critical ecosystems for these environmental services, leading to widespread efforts to restore ecosystems by removing barriers, pollution, and non-native organisms.

Modeling work by co-author Dennis D. Baldocchi, Executive Associate Dean and professor of Biometeorology at UC Berkeley, suggests that although the restored wetland is adding greenhouse gas to the atmosphere currently, the ecosystem will stabilize and begin to serve as a net carbon sink within 100 to 150 years. This may not be the timeline that stakeholders were hoping for when they restored the area with the goal of carbon sequestration.

"We want to know if these systems will act as long-term carbon sinks," said Baldocchi. "And these microbiological investigations can help refine our models and predictions."

Tringe noted that other labs have observed increased methane production from wetland soils with increased salinity. Scientists from Duke University took soil core samples from a coastal freshwater wetland and exposed them to artificial seawater, and artificial seawater lacking sulfate. In both cases, methane production went up. Tringe's lab recently collaborated with Marcelo Ardón of North Carolina State University to analyze the microbial communities in those soils.

"There was this expectation that sulfate would be the most important thing. And in those studies, not only did salt water stimulate methane production, which again is kind of counter to the dogma that sulfate is important, it happened whether you had sulfate there or not; in fact the sulfate didn't have a big effect on the methane emissions," said Tringe. "So I think these experimental manipulations are reconfirming the story that there's more nuanced effects of seawater intrusion than just a sulfate addition, and also more nuanced factors behind ecosystem restoration."

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Bottled water can contain hundreds of thousands of previously uncounted tiny plastic bits

In recent years, there has been rising concern that tiny particles known as microplastics are showing up basically everywhere on Earth, from polar ice to soil, drinking water and food. Formed when plastics break down into progressively smaller bits, these particles are being consumed by humans and other creatures, with unknown potential health and ecosystem effects. One big focus of research: bottled water, which has been shown to contain tens of thousands of identifiable fragments in each container.

Now, using newly refined technology, researchers have entered a whole new plastic world: the poorly known realm of nanoplastics, the spawn of microplastics that have broken down even further. For the first time, they counted and identified these minute particles in bottled water. They found that on average, a liter contained some 240,000 detectable plastic fragments -- 10 to 100 times greater than previous estimates, which were based mainly on larger sizes.

The study was just published in the journal Proceedings of the National Academy of Sciences.

Nanoplastics are so tiny that, unlike microplastics, they can pass through intestines and lungs directly into the bloodstream and travel from there to organs including the heart and brain. They can invade individual cells, and cross through the placenta to the bodies of unborn babies. Medical scientists are racing to study the possible effects on a wide variety of biological systems.

"Previously this was just a dark area, uncharted. Toxicity studies were just guessing what's in there," said study coauthor Beizhan Yan, an environmental chemist at Columbia University's Lamont-Doherty Earth Observatory. "This opens a window where we can look into a world that was not exposed to us before."

Worldwide plastic production is approaching 400 million metric tons a year. More than 30 million tons are dumped yearly in water or on land, and many products made with plastics including synthetic textiles shed particles while still in use. Unlike natural organic matter, most plastics do not break down into relatively benign substances; they simply divide and redivide into smaller and smaller particles of the same chemical composition. Beyond single molecules, there is no theoretical limit to how small they can get.

Microplastics are defined as fragments ranging from 5 millimeters (less than a quarter inch) down to 1 micrometer, which is 1 millionth of a meter, or 1/25,000th of an inch. (A human hair is about 70 micrometers across.) Nanoplastics, which are particles below 1 micrometer, are measured in billionths of a meter.

Plastics in bottled water became a public issue largely after a 2018 study detected an average of 325 particles per liter; later studies multiplied that number many times over. Scientists suspected there were even more than they had yet counted, but good estimates stopped at sizes below 1 micrometer -- the boundary of the nano world.

"People developed methods to see nano particles, but they didn't know what they were looking at," said the new study's lead author, Naixin Qian, a Columbia graduate student in chemistry. She noted that previous studies could provide bulk estimates of nano mass, but for the most part could not count individual particles, nor identify which were plastics or something else.

The new study uses a technique called stimulated Raman scattering microscopy, which was co-invented by study coauthor Wei Min, a Columbia biophysicist. This involves probing samples with two simultaneous lasers that are tuned to make specific molecules resonate. Targeting seven common plastics, the researchers created a data-driven algorithm to interpret the results. "It is one thing to detect, but another to know what you are detecting," said Min.

The researchers tested three popular brands of bottled water sold in the United States (they declined to name which ones), analyzing plastic particles down to just 100 nanometers in size. They spotted 110,000 to 370,000 particles in each liter, 90% of which were nanoplastics; the rest were microplastics. They also determined which of the seven specific plastics they were, and charted their shapes -- qualities that could be valuable in biomedical research.

One common one was polyethylene terephthalate or PET. This was not surprising, since that is what many water bottles are made of. (It is also used for bottled sodas, sports drinks and products such as ketchup and mayonnaise.) It probably gets into the water as bits slough off when the bottle is squeezed or gets exposed to heat. One recent study suggests that many particles enter the water when you repeatedly open or close the cap, and tiny bits abrade.

However, PET was outnumbered by polyamide, a type of nylon. Ironically, said Beizhan Yan, that probably comes from plastic filters used to supposedly purify the water before it is bottled. Other common plastics the researchers found: polystyrene, polyvinyl chloride and polymethyl methacrylate, all used in various industrial processes.

A somewhat disturbing thought: the seven plastic types the researchers searched for accounted for only about 10% of all the nanoparticles they found in samples; they have no idea what the rest are. If they are all nanoplastics, that means they could number in the tens of millions per liter. But they could be almost anything, "indicating the complicated particle composition inside the seemingly simple water sample," the authors write. "The common existence of natural organic matter certainly requires prudent distinguishment."

The researchers are now reaching beyond bottled water. "There is a huge world of nanoplastics to be studied," said Min. He noted that by mass, nanoplastics comprise far less than microplastics, but "it's not size that matters. It's the numbers, because the smaller things are, the more easily they can get inside us."

Among other things, the team plans to look at tap water, which also has been shown to contain microplastics, though far less than bottled water. Beizhan Yan is running a project to study microplastics and nanoplastics that end up in wastewater when people do laundry -- by his count so far, millions per 10-pound load, coming off synthetic materials that comprise many items. (He and colleagues are designing filters to reduce the pollution from commercial and residential washing machines.) The team will soon identify particles in snow that British collaborators trekking by foot across western Antarctica are currently collecting. They also are collaborating with environmental health experts to measure nanoplastics in various human tissues and examine their developmental and neurologic effects.

"It is not totally unexpected to find so much of this stuff," said Qian. "The idea is that the smaller things get, the more of them there are."

Read more at Science Daily

Humans are disrupting natural 'salt cycle' on a global scale, new study shows

The planet's demand for salt comes at a cost to the environment and human health, according to a new scientific review led by University of Maryland Geology Professor Sujay Kaushal. Published in the journal Nature Reviews Earth & Environment, the paper revealed that human activities are making Earth's air, soil and freshwater saltier, which could pose an "existential threat" if current trends continue.

Geologic and hydrologic processes bring salts to Earth's surface over time, but human activities such as mining and land development are rapidly accelerating the natural "salt cycle." Agriculture, construction, water and road treatment, and other industrial activities can also intensify salinization, which harms biodiversity and makes drinking water unsafe in extreme cases.

"If you think of the planet as a living organism, when you accumulate so much salt it could affect the functioning of vital organs or ecosystems," said Kaushal, who holds a joint appointment in UMD's Earth System Science Interdisciplinary Center. "Removing salt from water is energy intensive and expensive, and the brine byproduct you end up with is saltier than ocean water and can't be easily disposed of."

Kaushal and his co-authors described these disturbances as an "anthropogenic salt cycle," establishing for the first time that humans affect the concentration and cycling of salt on a global, interconnected scale.

"Twenty years ago, all we had were case studies. We could say surface waters were salty here in New York or in Baltimore's drinking water supply," said study co-author Gene Likens, an ecologist at the University of Connecticut and the Cary Institute of Ecosystem Studies. "We now show that it's a cycle -- from the deep Earth to the atmosphere -- that's been significantly perturbed by human activities."

The new study considered a variety of salt ions that are found underground and in surface water. Salts are compounds with positively charged cations and negatively charged anions, with some of the most abundant ones being calcium, magnesium, potassium and sulfate ions.

"When people think of salt, they tend to think of sodium chloride, but our work over the years has shown that we've disturbed other types of salts, including ones related to limestone, gypsum and calcium sulfate," Kaushal said.

When dislodged in higher doses, these ions can cause environmental problems. Kaushal and his co-authors showed that human-caused salinization affected approximately 2.5 billion acres of soil around the world -- an area about the size of the United States. Salt ions also increased in streams and rivers over the last 50 years, coinciding with an increase in the global use and production of salts.

Salt has even infiltrated the air. In some regions, lakes are drying up and sending plumes of saline dust into the atmosphere. In areas that experience snow, road salts can become aerosolized, creating sodium and chloride particulate matter.

Salinization is also associated with "cascading" effects. For example, saline dust can accelerate the melting of snow and harm communities -- particularly in the western United States -- that rely on snow for their water supply. Because of their structure, salt ions can bind to contaminants in soils and sediments, forming "chemical cocktails" that circulate in the environment and have detrimental effects.

"Salt has a small ionic radius and can wedge itself between soil particles very easily," Kaushal said. "In fact, that's how road salts prevent ice crystals from forming."

Road salts have an outsized impact in the U.S., which churns out 44 billion pounds of the deicing agent each year. Road salts represented 44% of U.S. salt consumption between 2013 and 2017, and they account for 13.9% of the total dissolved solids that enter streams across the country. This can cause a "substantial" concentration of salt in watersheds, according to Kaushal and his co-authors.

To prevent U.S. waterways from being inundated with salt in the coming years, Kaushal recommended policies that limit road salts or encourage alternatives. Washington, D.C., and several other U.S. cities have started treating frigid roads with beet juice, which has the same effect but contains significantly less salt.

Kaushal said it is becoming increasingly important to weigh the short- and long-term risks of road salts, which play an important role in public safety but can also diminish water quality.

"There's the short-term risk of injury, which is serious and something we certainly need to think about, but there's also the long-term risk of health issues associated with too much salt in our water," Kaushal said. "It's about finding the right balance."

The study's authors also called for the creation of a "planetary boundary for safe and sustainable salt use" in much the same way that carbon dioxide levels are associated with a planetary boundary to limit climate change. Kaushal said that while it's theoretically possible to regulate and control salt levels, it comes with unique challenges.

Read more at Science Daily

Protein root discovery seals future of climate-proof plants

Researchers have discovered a protein that seals plant roots to regulate the uptake of nutrients and water from the soil, the discovery could help develop climate proof crops that require less water and chemical fertilizers.

Researchers from the University of Nottingham identified new components of the lignin barrier in plant roots and the specific function of dirigent proteins (DPs), located in the root endodermis that control water and nutrient uptake. Their findings have been published today in Science Direct.

Plant roots function by absorbing mineral nutrients and water from the soil and also controlling their proper balance in the plant. This control is exerted by a specialised layer of root tissue called the endodermis.

The endodermis contains a barrier to the movement of solutes and water that is made of lignin, the same material present in wood. This impermeable barrier blocks the uncontrolled movement of material into the root, by forming a tight seal between cells. This seal ensures the only pathway for nutrients and water to be taken up by roots is through the cells of the endodermis. This allows full cellular control over what enters and leaves the plant via the roots.

This research has identified new components of the lignin deposition machinery that focus on the function of dirigent proteins (DPs), located in the root endodermis. These proteins act in coordination with other described root regulatory components to direct and organize the correct deposition of lignin in the endodermis allowing the plant to ensure it receives the optimum balance of nutrients from the soil.

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Enhanced chemical weathering: A solution to the climate crisis?

The Earth is getting hotter and consequences have been made manifest this summer around the world. Looking back in geological history, global warming events are not uncommon: Around 56 million years ago, during the period known as the Paleocene-Eocene Thermal Maximum (PETM), the temperatures rose by an average of 5 to 8 degrees Celsius. This development was most likely linked to increased volcanism and the associated release of masses of carbon dioxide into the atmosphere. The higher temperatures persisted for about 200,000 years. Back in 2021, Professor Philip Pogge von Strandmann of Johannes Gutenberg University Mainz (JGU) had already investigated the effect that eventually led to global cooling and climatic recovery after the PETM warming.

In short: Rainwater combined with the atmospheric carbon dioxide, resulting in carbonic acid that caused enhanced weathering of rock, thus releasing calcium and magnesium. Rivers then transported the calcium, magnesium, and carbonic acid into the oceans where the calcium, magnesium -- and also the carbon dioxide -- came together to form insoluble limestone. "In other words, there is a feedback effect that helps control the climate. High temperatures accelerate the chemical rock weathering process, reducing the levels of carbon dioxide in the atmosphere, allowing the climate to recover," said Pogge von Strandmann.

Climate required twice as long to regenerate 40 million years ago

Climate warming occurred again 16 million years after the PETM during the Middle Eocene Climatic Optimum or MECO. Although volcanic activity resulted in the discharge of roughly the same amounts of carbon dioxide into the atmosphere as during the PETM, it took far longer for the climate to restabilize. The warming effect lasted for an immense 400,000 years, twice as long as in the PETM. Why was recovery so slow during that period?

In searching for an answer, Pogge von Strandmann and co-authors, including first author Alex Krause, began analyzing 40-million-year-old oceanic carbonates and clay minerals to compare the results with those for similar 56-million-year-old examples. "Just as during the PETM, there was also intensified weathering and erosion in the MECO. However, there was far less exposed rock on the Earth's surface 40 million years ago. Instead, the Earth was extensively covered by a global rainforest the soil of which largely consisted of clay minerals," explained the researcher. In contrast with rock, clay does not weather; in fact, it is actually the product of weathering. "So despite the high temperatures, the widespread clay soil prevented rocks from being effectively weathered, a process known as soil shielding," the geoscientist pointed out.

Enhanced weathering for climate protection

How can we use this knowledge in today's world? "We study paleoclimates to determine whether and how we can positively influence our present climate. One option might be to boost the chemical weathering of rock. To help achieve this, we could plough finely crushed rock into our fields," said Pogge von Strandmann. The fine-grained particles of rock would erode rapidly, resulting in the binding of atmospheric carbon dioxide, thus enabling the climate to recuperate. Negative emissions technologies (NETs) such as this involving the absorption of carbon dioxide are the subjects of intense research across the globe. At the same time, however, if the weathering results in the formation of clay, the effects of the process would be significantly less efficient, as Pogge von Strandmann has discovered. Clay retains the calcium and magnesium that would otherwise be delivered to the ocean. The carbon dioxide would continue to flow into the oceans, but it would not be bound there and would be able to escape back into the atmosphere. In this case, the weathering effect would have next to no influence on the climate.

If the rock particles fully dissolve as a result of weathering, the enhanced weathering concept would turn out to be 100 percent efficient. However, if all the weathered materials were turned into clay, this would in its turn completely nullify the effect. In reality, the actual outcome would probably be somewhere between the two extremes: While there was enhanced erosion of rock in the PETM so that the climate normalized more rapidly, clay formation was predominant during the MECO. The extent to which the crushed rock dissolves and how much of it is preserved as clay depends on a range of local factors, such as the globally pre-existing levels of clay and rock. So in order to establish whether the process of enhanced weathering is a viable approach, it would first be necessary to find out how much clay is formed during the weathering process at each potential location.

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What causes mudslides and floods after wildfires? Hint: It's not what scientists thought

In 2020, one of the largest wildfires in Los Angeles County raged across the San Gabriel Mountains, scorching more than 115,000 acres, damaging or destroying over 150 structures and raining ash and smoke down on pandemic-weary Angelenos.

But even after exhausted firefighters had finally snuffed out the flames, the Bobcat Fire -- like other so-called "mega-fires" that have become more common due to climate change -- carried the potential to wreak more havoc in its wake. As rainstorms deluge burnt areas, flooding, mudslides and debris flow can compound the fire's damage.

Understanding how water accumulates and monitoring the movement of runoff and streamflow in burn areas helps authorities predict when and where these post-wildfire events might occur so they can provide affected residents with early warning of flash flooding and debris movement.

A slippery slope

Common knowledge has long held that loss of vegetation during a fire leaves soil vulnerable to erosion because the plant roots that hold the soil in place wither and die. Scientists, however, have long held a different view, that as leaves burn, their waxy coating forms an organic, oily substance on the soil's surface. This waxy coating creates a water-repellant layer at or near the surface. Scientists believed this layer prevented the ground from absorbing water, resulting in rapid water runoff akin to a Slip 'N Slide that carries mud and debris.

New research published in Nature Communications has called that scientific theory into question.

A watershed finding

Images of the 2020 Bobcat Fire area indicate soil burn severity and the locations the researchers studied. (Image Source: a- USDA Forest Service; b- A.J. West; d- Pléiades ©CNES, Distribution AIRBUSDS, sourced via SkyWatch Space Applications Inc., and USGS 3D Elevation Program.)

Scientists at the USC Dornsife College of Letters, Arts and Science, in collaboration with researchers from the University of Michigan, the U.S. Geological Survey and Rutgers University, monitored two wet seasons following the Bobcat Fire, from December 2020 to March 2022. The team concluded that water was, in fact, being absorbed by the burnt ground that contained this waxy coating.

Specifically, the team studied three watersheds -- areas of land that drain rainfall and snowmelt into streams and rivers -- in Southern California's San Gabriel Mountains. Two of the watersheds burned during the 2020 Bobcat Fire and the other was mainly untouched.

The researchers found that post-wildfire, a significant portion of the water flow in all three watersheds came from water that had been absorbed in the ground.

Joshua West, professor of Earth sciences who led the study at USC Dornsife, said it was no surprise that the flow of water and debris in the burned area's stream was four to 10 times greater than the flow in the unburnt area's stream. What he didn't expect was that stormwater had permeated the ground in both of the burnt watersheds.

This finding contradicted scientists' previous beliefs that little water would be absorbed in the burnt watershed due to the presence of waxy soils.

In the unburnt watershed, however, the researchers found that trees absorbed the water as anticipated, preventing it from reaching streams.

West and PhD candidate Abra Atwood surmised that, in keeping with the popular notion, increased water in rivers originated from the burnt areas because burned trees and vegetation could not retain water in their roots as they normally would, but not from the inability of the soil to absorb water.

The research team's finding that the water-repellant layer does not prevent water from being absorbed into the soil strengthened their hypothesis that the water in streams comes from both rainfall and groundwater, leading to increased flooding in burnt areas versus unburnt.

Water build-up poses enduring threat

Identifying areas that are at high-risk for debris flow and mudslides and accurately predicting the amount of debris flow following rainfall in burn areas depends on understanding how water infiltrates the soil in different areas and how it contributes to the flow of streams.

Also, the dynamics of water flow and how water accumulates below the surface can significantly impact how quickly landscapes recover after a wildfire. This recovery affects the stability of hill slopes and helps buffer forests against severe drought.

On the flip side, water accumulation can contribute to landslides for up to four years after a fire as pressure builds up in the soil.

"The underground water accumulation suggests that the potential for landslides extends far beyond the two years following the fire, posing an enduring problem," West said. "The abundance of water stored in areas affected by the Bobcat Fire, for example, could serve as a harbinger of future flooding concerns in the years to come."

Read more at Science Daily

Preserving forests to protect deep soil from warming

A recent study led by scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of Zurich has revealed that the organic compounds proposed for carbon sequestration in deep soil are highly vulnerable to decomposition under global warming.

The finding has implications for a key strategy in carbon management that relies on soil and forests -- natural carbon "sinks" -- to mitigate global warming.

About 25 percent of global carbon emissions are captured by forests, grasslands, and rangelands. During photosynthesis, plants store carbon in their cell walls and in the soil. Because of rich carbon stores from decades past, soils contain twice as much carbon as the atmosphere does, and deeper subsoils (more than 8 inches or 20 centimeters) account for roughly half of the soil carbon. But as global populations rise, so do our demands for new croplands and timber. Research shows that disturbing the natural world for commerce has a price: the United Nations' Intergovernmental Panel on Climate Change has warned that emissions from deforestation and agriculture account for around a fifth of global greenhouse gases.

"Our study shows that climate change will affect all aspects of soil carbon and nutrient cycling. It also shows that in terms of carbon sequestration, there's no silver bullet. If we want soil to sustain carbon sequestration in a warming world, we will need better soil management practices, which can mean minimal disturbance of soils during forest management and agriculture," said Margaret Torn, a senior scientist in Berkeley Lab's Earth & Environmental Sciences Area and a senior author of the study.

In 2021, Torn and her research team provided the first physical evidence that warmer temperatures lead to a significant drop in the carbon stocks stored in deep forest soils -- a loss of 33% over five years.

In the new study, Torn and first author Cyrill Zosso of the University of Zurich unveil a clearer picture of soil in a warming world. This time, the research team is the first to show that warmer temperatures lead to a significant drop in the soil organic carbon compounds that are created by plants during photosynthesis.

During an experiment at the University of California's Blodgett Forest Research Station in the foothills of California's Sierra Nevada mountains, the researchers used vertical heating rods to continuously warm 1-meter-deep (three-foot-deep) plots of soil by 4 degrees Celsius (7 degrees Fahrenheit). That is the amount of warming projected by the end of the 21st century if greenhouse gas emissions remain high.

They found that just 4.5 years of warming at this temperature led to large changes in carbon stocks at a depth of more than 30 centimeters (or approximately 12 inches) below the soil surface.

During spectroscopic experiments at the University of Zurich, Zosso identified the organic compounds that were affected by the warming.

The results were shocking: a 17% loss in lignin -- the compounds that give plants rigidity -- and a nearly 30% loss in cutin and suberin, the waxy compounds in leaves, stems, and roots that protect plants from pathogens.

Torn and Zosso were also surprised to find a significant difference in the amount of "pyrogenic carbon" in the soil samples that were artificially heated versus the ones that were not. Pyrogenic carbon is a type of soil organic carbon derived from charred vegetation and other organic matter remnants left in the wake of a wildfire.

Many researchers assume that pyrogenic carbon has the most potential to serve as a very stable form of sequestered carbon. "We found much less pyrogenic carbon in the deep soils when they were heated," Torn said.

"Pyrogenic carbon can stay in the soil for decades or even centuries, but we need to understand its vulnerability to warming or to changes in land management. Our study suggests that this material decomposed just as fast as anything else would when the soil was warmed," Torn explained. "This shows that when you put material deep into soil where it's in contact with minerals and microbes, those natural systems will decompose the material over time."

The researchers next plan to resample soil from the study to determine how nine years of warming impact soil composition and health. A new grassland warming experiment at the Point Reyes National Seashore in Northern California is also on the horizon. "We are also organizing all the world's deep-soil warming (or whole-soil warming) experiments to share data and know-how and conducting synthesis of the data to see what we can learn," Torn said.

Read more at Science Daily

Ecosystem evolution in Africa

Ohio University's Nancy J. Stevens Ph.D., distinguished professor in the Department of Biomedical Sciences in the Heritage College of Osteopathic Medicine, is coauthor on a paper published in the journal Science and funded by the National Science Foundation that documents the evolution of grassland ecosystems on continental Africa.

Collaborating with an extensive team of geologists and paleoanthropologists from universities around the world, led by researchers from Baylor University and the University of Minnesota, the team synthesized data from nine Early Miocene fossil localities in the East African Rift of Kenya and Uganda to determine that the expansion of grassy biomes dominated by grasses with the C4 photosynthetic pathway in Eastern Africa occurred more than 10 million years earlier.

According to the paper, previous reconstructions of early Miocene ecosystems, 15-20 million years ago, have suggested that equatorial Africa was covered by a semi-continuous forest, with open habitats dominated by warm-season, or C4, grasses that were uncommon until 8-10 million years ago. C4 refers to the different pathways that plants use to capture carbon dioxide during photosynthesis. C4 plants produce a four-carbon molecule and are more adapted to warm or hot season condition under moist or dry environments.

As the researchers gathered expertise about geological features, isotopes and fossils found at the sites, the paradigm of a continuous forest blanketing equatorial Africa during the early Miocene shifted to a more complex mosaic of habitats that already included open environments with C4 grasses.

The result of this research pushes back the oldest evidence of C4 grass-dominated habitats in Africa -- and globally -- by more than 10 million years, with important implications for primate evolution and the origins of tropical C4 grasslands and savanna ecosystems across the African continent and around the world.

"We suspected that we would find C4 plants at some sites, but we didn't expect to find them at as many sites as we did, and in such high abundance," Daniel Peppe, lead author and associate professor at Baylor University, said.

A critical aspect of this work was that the team combined many different lines of evidence together: geology, fossil soils, isotopes and phytoliths (plant silica microfossils) to reach their conclusions.

Read more at Science Daily

Increased droughts are disrupting carbon-capturing soil microbes, concerning ecologists

Soil stores more carbon than plants and the atmosphere combined, and soil microbes are largely responsible for putting it there. However, the increasing frequency and severity of drought, such as those that have been impacting California, could disrupt this delicate ecosystem. In a perspective publishing in the journal Trends in Microbiology on April 12, microbial ecologist Steven Allison warns that soil health and future greenhouse gas levels could be impacted if soil microbes adapt to drought faster than plants do. He argues that we need to better understand how microbes respond to drought so that we can manage the situation in both agricultural and natural settings.

"Soil microbes are beneficial, and we couldn't live without their cycling of carbon and nutrients, but climate change and drought can tweak that balance, and we have to be aware of how it's changing," says Allison of the University of California, Irvine.

Some soil microbes take carbon from decomposing plants and store it in the soil, while others release plant carbon back into the atmosphere. The carbon that ends up in the soil is beneficial in multiple ways. "The carbon in the soil has these reverberating effects out to the rest of the world in terms of the infrastructure in our natural and managed ecosystems," says Allison. "Carbon-rich soils hold more nutrients, so plants growing in those soils tend to be more productive, and the carbon changes the physical properties of the soil, which prevents erosion."

"In California now, we have this system where the droughts are more intense, and then the rainfall is more intense," he says. "So, if you're losing your soil carbon, when it rains really hard it could carry away your soil and cause erosion, landslides, mudslides, sediments, and all kinds of problems that we're actually seeing right now."

The carbon that is released back into the atmosphere is another story. "From a climate mitigation standpoint, what we want is for more carbon to be in plants and soils and less carbon to be in the atmosphere, so the more carbon we can absorb into plants through photosynthesis and the more we can transfer and keep in the soil, the better off we're going to be in terms of climate change," says Allison. "That's why it's really important to know how the balance of incoming versus outflowing carbon changes with drought, or warming, or any other climate factor."

Plants and microbes will both be impacted by the increasing frequency of drought, but Allison suspects that microbes will be able to bounce back faster. "Microbes are really adaptable -- they can change their physiology, they can change their abundances so that more drought-adapted microbes take over, and they can potentially evolve -- so we expect that they are going to resist or bounce back from drought," says Allison. "All those different processes can happen pretty quickly with microbes, and much more quickly than with plants."

If more carbon-releasing microbes survive than carbon-sequestering microbes, we could end up with carbon-depleted soils, which would have serious negative implications for plant productivity and future greenhouse gas levels.

We may be able to nudge the balance in the right direction, Allison says, but more research is needed first. "There's still a lot to be done. Right now, we have data that suggests that when we have drought, something changes that results in carbon loss, but we don't understand exactly how or why that's happening, whether drought's changing the abundance of beneficial plant associated microbes versus the carbon releasing microbes, or if it's causing the evolution of one of the microbe groups, or if it's more determined by changes to their immediate physiology," says Allison.

Some microbes could actually help plants cope with drought. If we knew which microbes were most beneficial to plants, and most likely to retain carbon in soil, we could try to tip the balance in their favor.

"There's a lot of potential for us to manage or engineer soil microbes," says Allison. "In agricultural systems, we can look into manipulating the soil or adding beneficial microbes back in. In more natural systems, management would probably be on the plant side: soil microbes are often closely intertwined with plants, so managing the plants can also benefit the microbial part of the ecosystem."

Read more at Science Daily

How evolution works

With its powerful digging shovels, the European mole can burrow through the soil with ease. The same applies to the Australian marsupial mole. Although the two animal species live far apart, they have developed similar organs in the course of evolution -- in their case, extremities ideally adapted for digging in the soil.

Science speaks of "convergent evolution" in such cases, when animal, but also plant species independently develop features that have the same shape and function. There are many examples of this: Fish, for example, have fins, as do whales, although they are mammals. Birds and bats have wings, and when it comes to using poisonous substances to defend themselves against attackers, many creatures, from jellyfish to scorpions to insects, have all evolved the same instrument: the venomous sting.

Identical characteristics despite lack of relationship

It is clear that scientists around the world are interested in finding out which changes in the genetic material of the respective species are responsible for the fact that identical characteristics have evolved in them, even though there is no relationship between them.

The search for this is proving difficult: "Such traits -- we speak of phenotypes -- are of course always encoded in genome sequences," says plant physiologist Dr. Kenji Fukushima of the Julius-Maximilians-Universität (JMU) Würzburg. Mutations -- changes in the genetic material -- can be the triggers for the development of new traits.

However, genetic changes rarely lead to phenotypic evolution because the underlying mutations are largely random and neutral. Thus, a tremendous amount of mutations accumulate over the extreme time scale at which evolutionary processes occur, making the detection of phenotypically important changes extremely difficult.

Novel metric of molecular evolution.

Now, Fukushima and his colleague David D. Pollock of the University of Colorado (USA) have succeeded in developing a method that achieves significantly better results than previously used methods in the search for the genetic basis of phenotypic traits. They present their approach in the current issue of the journal Nature Ecology & Evolution.

"We have developed a novel metric of molecular evolution that can accurately represent the rate of convergent evolution in protein-coding DNA sequences," says Fukushima, describing the main result of the now-published work. This new method, he says, can reveal which genetic changes are associated with the phenotypes of organisms on an evolutionary time scale of hundreds of millions of years. It thus offers the possibility of expanding our understanding of how changes in DNA lead to phenotypic innovations that give rise to a great diversity of species.

Tremendous treasure trove of data as a basis

A key development in the life sciences forms the basis of Fukushima's and Pollock's work: the fact that in recent years more and more genome sequences of many living organisms across the diversity of species have been decoded and thus made accessible for analysis. "This has made it possible to study the interrelationships of genotypes and phenotypes on a large scale at a macroevolutionary level," Fukushima says.

However, because many molecular changes are nearly neutral and do not affect any traits, there is often a risk of "false-positive convergence" when interpreting the data -- that is, the result predicts a correlation between a mutation and a particular trait that does not actually exist. In addition, methodological biases could also be responsible for such false-positive convergences.

Correlations over millions of years

"To overcome this problem, we expanded the framework and developed a new metric that measures the error-adjusted convergence rate of protein evolution," Fukushima explains. This, he says, makes it possible to distinguish natural selection from genetic noise and phylogenetic errors in simulations and real-world examples. Enhanced with a heuristic algorithm, the approach enables bidirectional searches for genotype-phenotype associations, even in lineages that have diverged over hundreds of millions of years, he says.

The two scientists analyzed more than 20 million branch combinations in vertebrate genes to examine how well the metric they developed works. In a next step, they plan to apply this method to carnivorous plants. The goal is to decipher the genetic basis that is partly responsible for these plants' ability to attract, capture and digest prey.

Read more at Science Daily

Less intensively managed grasslands have higher plant diversity and better soil health

Researchers have shown -- for the first time -- that less intensively managed British grazed grasslands have on average 50% more plant species and better soil health than intensively managed grassland. The new study could help farmers increase both biodiversity and soil health, including the amount of carbon in the soil of the British countryside.

Grazed grassland makes up a large proportion of the British countryside and is vital to farming and rural communities. This land can be perceived as only being about food production, but this study gives more evidence that it could be key to increasing biodiversity and soil health.

Researchers at the UK Centre for Ecology & Hydrology (UKCEH) studied 940 plots of grassland, comparing randomly selected plots which sampled the range of grassland management across Great Britain; from intensively- managed land with a few sown grassland species and high levels of soil phosphorus (indicating ploughing/reseeding and fertiliser and slurry application), to grassland with higher levels of species and lower levels of soil phosphorus. The plots were sampled as part of the UKCEH Countryside Survey, a nationally representative long-term dataset.

The study counted the number of plant species in sample areas and analysed co-located soil samples for numbers of soil invertebrates and carbon, nitrogen and phosphorus levels.

Researchers found that less intensively managed grassland had greater diversity of plant species and, strikingly, this correlated with better soil health, such as increased nitrogen and carbon levels and increased numbers of soil invertebrates such as springtails and mites.

In the same study, the researchers used the same methods to examine the plant diversity and soil from grasslands on 56 mostly beef farms from the Pasture Fed Livestock Association (PFLA) -- a farmer group that has developed standards to manage and improve soil and pasture health.

The researchers found that plots of land from PFLA farms had greater plant diversity -- on average an additional six plant species, including different types of grasses and herbaceous flowering plants, compared to intensively farmed plots from the Countryside Survey. In addition, grassland plants on these farms were often taller, a quality which is proven to be beneficial to butterflies and bees.

Pasture Fed Livestock Association grasslands did not yet show increased soil health, but the research indicated that this may be due to a time lag between increasing numbers of plant species and changes in soil health, particularly on farms which have been intensively managed in the past.

Lead author Dr Lisa Norton, Senior Scientist at UKCEH, says: "We've shown for the first time, on land managed by farmers for production, that a higher diversity of plants in grasslands is correlated with better soil health. This work also tells us that the Pasture Fed Livestock Association members are on the right track to increase biodiversity, though it may take longer to see improvements in soil health.

"Grassland with different types of plants able to grow tall and flower is associated with improved soil health measures, and is beneficial for creepy crawlies below and above ground. Having this abundance of life in our grasslands can in turn support small mammals and birds of prey, and farmers have told us that they are seeing voles and mice in their fields for the first time."

Dr Norton adds: "My hope for the future is that our grasslands can be managed less intensively -- with all the improvements in plant and animal biodiversity and soil health that brings -- but still remain productive for farmers."

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Botany: From the soil to the sky

Every day, about one quadrillion gallons of water are silently pumped from the ground to the treetops. Earth's plant life accomplishes this staggering feat using only sunlight. It takes energy to lift all this liquid, but just how much was an open question until this year.

Researchers at UC Santa Barbara have calculated the tremendous amount of power used by plants to move water through their xylem from the soil to their leaves. They found that, on average, it was an additional 14% of the energy the plants harvested through photosynthesis. On a global scale, this is comparable to the production of all of humanity's hydropower. Their study, published in the Journal of Geophysical Research: Biogeosciences, is the first to estimate how much energy goes into lifting water up to plant canopies, both for individual plants and worldwide.

"It takes power to move water up through the xylem of the tree. It takes energy. We're quantifying how much energy that is," said first author Gregory Quetin, a postdoctoral researcher in the Department of Geography. This energy is in addition to what a plant produces via photosynthesis. "It's energy that's being harvested passively from the environment, just through the tree's structure."

Photosynthesis requires carbon dioxide, light and water. CO2 is widely available in the air, but the other two ingredients pose a challenge: Light comes from above, and water from below. So, plants need to bring the water up (sometimes a considerable distance) to where the light is.

More complex plants accomplish this with a vascular system, in which tubes called xylem bring water from the roots to the leaves, while other tubes called phloem move sugar produced in the leaves down to the rest of the plant. "Vascular plants evolving xylem is a huge deal that allowed for trees to exist," Quetin said.

Many animals also have a vascular system. We evolved a closed circulatory system with a heart that pumps blood through arteries, capillaries and veins to deliver oxygen and nutrients around our bodies. "This is a function that many organisms pay a lot for," said co-author Anna Trugman, an assistant professor in the Department of Geography. "We pay for it because we have to keep our hearts beating, and that's probably a lot of our metabolic energy."

Plants could have evolved hearts, too. But they didn't. And it saves them a lot of metabolic energy.

In contrast to animals, plant circulatory systems are open and powered passively. Sunlight evaporates water, which escapes from pores in the leaves. This creates a negative pressure that pulls up the water beneath it. Scientists call this process "transpiration."

In essence, transpiration is merely another way that plants harvest energy from sunlight. It's just that, unlike in photosynthesis, this energy doesn't need to be processed before it can be put to use.

Scientists understand this process fairly well, but no one had ever estimated how much energy it consumes. "I've only seen it mentioned specifically as energy in one paper," co-author Leander Anderegg said, "and it was to say that 'this is a really large number. If plants had to pay for it with their metabolism, they wouldn't work.'"

This particular study grew out of basic curiosity. "When Greg [Quetin]and I were both graduate students, we were reading a lot about plant transpiration," recalled Anderegg, now an assistant professor in the Department of Ecology, Evolution, and Marine Biology. "At some point Greg asked, 'How much work do plants do just lifting water against gravity?'

"I said, 'I have no idea. I wonder if anyone knows?' And Greg said, 'surely we can calculate that.'"

About a decade later, they circled back and did just that. The team combined a global database of plant conductance with mathematical models of sap ascent to estimate how much power the world's plant life devotes to pumping water. They found that the Earth's forests consume around 9.4 petawatt-hours per year. That's on par with global hydropower production, they quickly point out.

This is about 14.2% of the energy that plants take in through photosynthesis. So it's a significant chunk of energy that plants benefit from but don't have to actively process. This free energy passes to the animals and fungi that consume plants, and the animals that consume them, and so on.

Surprisingly, the researchers discovered that fighting gravity accounts for only a tiny fraction of this total. Most of the energy goes into simply overcoming the resistance of a plant's own stem.

These findings may not have many immediate applications, but they help us better understand life on Earth. "The fact that there's a global energy stream of this magnitude that we didn't have quantified, is mildly jarring," Quetin said. "It does seem like a concept that slipped through the cracks."

The energies involved in transpiration seem to fall in between the scales that different scientists examine. It's too big for plant physiologists to consider and too small for scientists who study Earth systems to bother with, so it was forgotten. And it's only within the past decade that scientists have collected enough data on water use and xylem resistance to begin addressing the energy of transpiration at global scales, the authors explained.

Within that time, scientists have been able to refine the significance of transpiration in Earth systems using new observations and models. It affects temperatures, air currents and rainfall, and helps shape a region's ecology and biodiversity. Sap ascent power is a small component of transpiration overall, but the authors suspect it may turn out to be noteworthy given the significant energy involved.

It's still early days, and the team admits there's a lot of work to do in tightening their estimates. Plants vary widely in how conductive their stems are to water flow. Compare a hardy desert juniper with a riverside cottonwood, for instance. "A juniper tree that is very drought adapted has a very high resistance," Anderegg said, "while cottonwoods just live to pump water."

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Lunar soil has the potential to generate oxygen and fuel

Soil on the moon contains active compounds that can convert carbon dioxide into oxygen and fuels, scientists in China report May 5 in the journal Joule. They are now exploring whether lunar resources can be used to facilitate human exploration on the moon or beyond.

Nanjing University material scientists Yingfang Yao and Zhigang Zou hope to design a system that takes advantage of lunar soil and solar radiation, the two most abundant resources on the moon. After analyzing the lunar soil brought back by China's Chang'e 5 spacecraft, their team found the sample contains compounds -- including iron-rich and titanium-rich substances -- that could work as a catalyst to make desired products such as oxygen using sunlight and carbon dioxide.

Based on the observation, the team proposed an "extraterrestrial photosynthesis" strategy. Mainly, the system uses lunar soil to electrolyze water extracted from the moon and in astronauts' breathing exhaust into oxygen and hydrogen powered by sunlight. The carbon dioxide exhaled by moon inhabitants is also collected and combined with hydrogen from water electrolysis during a hydrogenation process catalyzed by lunar soil.

The process yields hydrocarbons such as methane, which could be used as fuel. The strategy uses no external energy but sunlight to produce a variety of desirable products such as water, oxygen, and fuel that could support life on a moonbase, the researchers say. The team is looking for an opportunity to test the system in space, likely with China's future crewed lunar missions.

"We use in-situ environmental resources to minimize rocket payload, and our strategy provides a scenario for a sustainable and affordable extraterrestrial living environment," Yao says.

While the catalytic efficiency of lunar soil is less than catalysts available on Earth, Yao says the team is testing different approaches to improve the design, such as melting the lunar soil into a nanostructured high-entropy material, which is a better catalyst.

Previously, scientists have proposed many strategies for extraterrestrial survival. But most designs require energy sources from Earth. For example, NASA's Perseverance Mars rover brought an instrument that can use carbon dioxide in the planet's atmosphere to make oxygen, but it's powered by a nuclear battery onboard.

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