The snow is made of tiny particles of iron — much heavier than any snowflake on Earth’s surface — that fall from the molten outer core and pile on top of the inner core, creating piles up to 200 miles thick that cover the inner core.

The image may sound like an alien winter wonderland. But the scientists who led the research said it is akin to how rocks form inside volcanoes.

“The Earth’s metallic core works like a magma chamber that we know better of in the crust,” said Jung-Fu Lin, a professor in the Jackson School of Geosciences at The University of Texas at Austin and a co-author of the study.

The study is available online and will be published in the print edition of the journal JGR Solid Earth on December 23.

Youjun Zhang, an associate professor at Sichuan University in China, led the study. The other co-authors include Jackson School graduate student Peter Nelson; and Nick Dygert, an assistant professor at the University of Tennessee who conducted the research during a postdoctoral fellowship at the Jackson School.

The Earth’s core can’t be sampled, so scientists study it by recording and analyzing signals from seismic waves (a type of energy wave) as they pass through the Earth.

However, aberrations between recent seismic wave data and the values that would be expected based on the current model of the Earth’s core have raised questions. The waves move more slowly than expected as they passed through the base of the outer core, and they move faster than expected when moving through the eastern hemisphere of the top inner core.

The study proposes the iron snow-capped core as an explanation for these aberrations. The scientist S.I. Braginkskii proposed in the early 1960s that a slurry layer exists between the inner and outer core, but prevailing knowledge about heat and pressure conditions in the core environment quashed that theory. However, new data from experiments on core-like materials conducted by Zhang and pulled from more recent scientific literature found that crystallization was possible and that about 15% of the lowermost outer core could be made of iron-based crystals that eventually fall down the liquid outer core and settle on top of the solid inner core.

“It’s sort of a bizarre thing to think about,” Dygert said. “You have crystals within the outer core snowing down onto the inner core over a distance of several hundred kilometers.”

The researchers point to the accumulated snow pack as the cause of the seismic aberrations. The slurry-like composition slows the seismic waves. The variation in snow pile size — thinner in the eastern hemisphere and thicker in the western — explains the change in speed.

“The inner-core boundary is not a simple and smooth surface, which may affect the thermal conduction and the convections of the core,” Zhang said.

The paper compares the snowing of iron particles with a process that happens inside magma chambers closer to the Earth’s surface, which involves minerals crystalizing out of the melt and glomming together. In magma chambers, the compaction of the minerals creates what’s known as “cumulate rock.” In the Earth’s core, the compaction of the iron contributes to the growth of the inner core and shrinking of the outer core.

And given the core’s influence over phenomena that affects the entire planet, from generating its magnetic field to radiating the heat that drives the movement of tectonic plates, understanding more about its composition and behavior could help in understanding how these larger processes work.

Bruce Buffet, a geosciences professor at the University of California, Berkley who studies planet interiors and who was not involved in the study, said that the research confronts longstanding questions about the Earth’s interior and could even help reveal more about how the Earth’s core came to be.

“Relating the model predictions to the anomalous observations allows us to draw inferences about the possible compositions of the liquid core and maybe connect this information to the conditions that prevailed at the time the planet was formed,” he said. “The starting condition is an important factor in Earth becoming the planet we know.”

The research was funded by the National Natural Science Foundation of China, Fundamental Research Funds for the Central Universities, the Jackson School of Geosciences, the National Science Foundation and the Sloan Foundation.

“Those sweeping conservation efforts in returning cropland to vegetated land might have done so with an until-now hidden consequence: it increased the wildlife damage to remaining cropland and thus caused unintended cost that whittled away at the program’s compensation for farmers,” said Hongbo Yang, lead author in a recent paper in the Ecological Economics journal.

Yang, who recently earned a PhD at from Michigan State University (MSU) and is currently a research associate at the Smithsonian Conservation Biology Institute and his colleagues analyzed the reforestation achieved via programs that encourage, and compensate, farmers to convert their cropland to forests via China’s enormous Grain-to-Green Program (GTGP).

The research found that even as newly regrown forests are sucking up greenhouse gases, they’re also sheltering critters bent on destroying crops. And while farmers were compensated, they ultimately took a financial beating. Not only did they find that converting a portion of their fields brought wildlife that much closer to their remaining crops, but they were also now farming smaller areas and thus recognizing lower yields.

Bottom line: The costs of conservation were being borne by poor people and those impacts have been slow to be revealed.

“Conservation policies only can endure, and be declared successful, when both nature and humans thrive,” said Jianguo “Jack” Liu, senior author and Rachel Carson Chair in Sustainability at MSU’S Center for Systems Integration and Sustainability. “Many of these trade-offs and inequities are difficult to spot unless you take a very broad, deep look at the situation, yet these balances are crucial to success.”

As a first attempt to quantify this previously hidden cost, the authors estimated the impact of converting cropland to forest under the GTGP, which is one of the world’s largest conservation programs, on crop raiding in a demonstration site.

They found that GTGP afforestation was responsible for 64% of the crop damage by wildlife on remaining cropland, and that cost was worth 27% of GTGP’s total payment to local farmers. That loss was not anticipated as the policy was designed and was in addition to the known loss of income from farming smaller plots, Yang said.

“The ignorance of this hidden cost might leave local communities under-compensated under the program and exacerbate poverty,” Yang said. “Such problems may ultimately compromise the sustainability of conservation. As losses due to human-wildlife conflicts increase, farmers may increasingly resent conservation efforts.”

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The work may represent preliminary progress toward deciphering just how enzymes, honed by evolution, so efficiently produce natural compounds. More immediately, the new method could help researchers synthesize drugs that have large ring backbones, such as those for hepatitis. The research is published Dec. 19 in the journal Science.

Nature prefers the disorder of a long, flexible molecule to the order of a rigid ring, which makes it notoriously difficult for chemists to coax large rings to form in the lab. “If the linear molecules get long enough, it’s as if the ends don’t know anymore that they’re connected, and they’re just as likely to bond with other molecules as they are to come together,” says UW-Madison Professor of Chemistry Sam Gellman, the senior author of the report.

Yet biological enzymes can easily bring these ends together and form rings of all sizes. They accomplish this feat thanks to their complex, three-dimensional shapes that act as a specialized lock — the linear molecule fits into place like a key in just the right way for an organized reaction to take place.

To both study how enzymes work and mimic their abilities, Gellman’s team turned to much smaller, three-dimensional protein-like molecules called foldamers that their lab has helped develop.

Because the foldamer has a three-dimensional shape that can grab on to the ends of the flexible precursor molecule, it greatly increases the odds that the ends find one another. At the same time, the foldamer catalyzes the right reaction that links the ends into a closed ring. The upshot is straightforward and predictable synthesis of a challenging, and useful, molecular shape.

“As chemists, we see how extraordinarily effective enzymes are at doing reactions that are hard to accomplish in a flask, but we don’t truly understand how they work,” says Gellman. “If we learn how these small foldamer catalysts work, we may be able to build catalysts that are effective for many different reactions. Ultimately, perhaps we can bootstrap our way toward foldamers that have truly enzyme-like activity.”

Graduate student and lead author Zebediah Girvin began the research by testing the abilities of a short, spiral-shaped foldamer. Girvin tried to use the foldamer to bend a linear molecule containing nine carbon atoms so it would form a ring. But instead of a ring of the expected size, Girvin got one twice as large — the result of two precursor molecules first joining and then closing the circle.

“This is a common situation in science. You try something and it doesn’t work out the way you expected,” says Gellman. “The challenge is to recognize when the surprising result is as interesting as the original goal, or even more interesting.”

Guided by this serendipity, Girvin began testing how well the foldamer could produce the larger rings it seemed to prefer creating. He found that he could readily manufacture rings made up of 12 to 22 carbon atoms when the foldamer’s reactive sites, where the ring closure occurs, were lined up with one another on one side. This orientation brought the two ends of diverse linear molecules close enough to fuse.

As a proof-of-concept for the new technique, Girvin synthesized the natural product robustol from scratch. Derived from the leaves of the Australian silky oak tree, robustol weighs in with a hefty 22-atom ring.

Gellman’s team is most excited about the potential for foldamers to catalyze other useful reactions and possibly help unravel longstanding mysteries about how enzymes, nature’s chemical virtuosos, produce the molecules required for life simply by arranging amino acid building blocks in the right shape. While those answers are years away, the ring-closing technique they’ve discovered could have more immediate use synthesizing drug candidates. The hepatitis C drug vaniprevir, which is used in Japan and in late-stage trials in the U.S., contains just this kind of large ring.

The real potential of foldamers stems from their diversity. Chemists can make a nearly infinite variety of foldamers in the lab because they have access to more building blocks than are found in natural proteins. This could allow chemists to build more useful catalysts, which led Gellman to patent certain foldamers and found the company Longevity Biotech to explore their therapeutic uses.

Going forward, that wealth of options will allow researchers to arrange these catalysts in shapes likely to be useful in unexpected ways. Only more research will tell.

“We don’t really know what these catalysts are capable of yet,” says Girvin. “It will take years to figure out their potential, and it’s important that we cast a broad net and keep open minds about what we can accomplish with these new tools.”

“The Devonian Period represents a time in which the first forest appeared on planet Earth,” says first author William Stein, an emeritus professor of biological science at Binghamton University, New York. “The effects were of first order magnitude, in terms of changes in ecosystems, what happens on the Earth’s surface and oceans, in global atmosphere, CO2 concentration in the atmosphere, and global climate. So many dramatic changes occurred at that time as a result of those original forests that basically, the world has never been the same since.”

Stein, along with collaborators, including Christopher Berry and Jennifer Morris of Cardiff University and Jonathan Leake of the University of Sheffield,have been working in the Catskill region in New York, where in 2012 they uncovered “footprint evidence” of a different fossil forest at Gilboa, which, for many years has been termed the Earth’s oldest forest. The discovery at Cairo, about a 40-minute drive from the original site, now reveals an even older forest with dramatically different composition.

The Cairo site presents three unique root systems, leading Stein and his team to hypothesize that much like today, the forests of the Devonian Period were composed of different trees occupying different places depending on local conditions.

First, Stein and his team identified a rooting system that they believe belonged to a palm tree-like plant called Eospermatopteris. This tree, which was first identified at the Gilboa site, had relatively rudimentary roots. Like a weed, Eospermatopteris likely occupied many environments, explaining its presence at both sites. But its roots had relatively limited range and probably lived only a year or two before dying and being replaced by other roots that would occupy the same space. The researchers also found evidence of a tree called Archaeopteris, which shares a number of characteristics with modern seed plants.

“Archaeopteris seems to reveal the beginning of the future of what forests will ultimately become,” says Stein. “Based on what we know from the body fossil evidence of Archaeopteris prior to this, and now from the rooting evidence that we’ve added at Cairo, these plants are very modern compared to other Devonian plants. Although still dramatically different than modern trees, yet Archaeopteris nevertheless seems to point the way toward the future of forests elements.”

Stein and his team were also surprised to find a third root system in the fossilized soil at Cairo belonging to a tree thought to only exist during the Carboniferous Period and beyond: “scale trees” belonging to the class Lycopsida.

“What we have at Cairo is a rooting structure that appears identical to great trees of the Carboniferous coal swamps with fascinating elongate roots. But no one has yet found body fossil evidence of this group this early in the Devonian.” Stein says. “Our findings are perhaps suggestive that these plants were already in the forest, but perhaps in a different environment, earlier than generally believed. Yet we only have a footprint, and we await additional fossil evidence for confirmation.”

Moving forward, Stein and his team hope to continue investigating the Catskill region and compare their findings with fossil forests around the world.

“It seems to me, worldwide, many of these kinds of environments are preserved in fossil soils. And I’d like to know what happened historically, not just in the Catskills, but everywhere,” Says Stein. “Understanding evolutionary and ecological history — that’s what I find most satisfying.”

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Recent research has now shown that grasshoppers, crickets and locusts, comprising orthopterans, and also dragonflies and amphibians have severely declined since the 1970s. This provides evidence of substantial deterioration of the Camargue ecosystem.

Many of the biodiversity changes had previously gone unnoticed, because there has been no systematic biodiversity monitoring for many of the species under study. Researchers now used a new and innovative method based on expert knowledge to identify changes in biodiversity in the study area.

During a period of seven months, the researchers managed to gather information on population trends and population abundance for almost 1400 species, and also presence and absence data for more than 1500 species for a total of eight different taxonomic groups.

“These include amphibians, reptiles, breeding birds, fish, mammals, dragonflies, orthopterans such as crickets and locusts, and vascular plants. This information has allowed us to detect some interesting patterns of change within a period of only 40 years,” says post-doctoral researcher Sara Fraixedas, from the Helsinki Institute of Sustainability Science (HELSUS), University of Helsinki.

The new methodology has made possible the detection of declines in certain taxa that are associated with land-use changes in the area.

“Temporary ponds and grasslands reduced in surface area by around 60% between 1942 and 1984. These two habitats have declined the most in the Camargue, and they have been converted into farmland or industrial areas. Amphibians and dragonflies are closely linked to freshwater wetlands, whereas many orthopteran species are associated with grasslands. Therefore, it is likely that the severe degradation of the conservation status of these three groups is related to the loss of those habitats,” adds Thomas Galewski, leader of the Biodiversity Monitoring and Assessment project at the Tour du Valat.

The study also shows that breeding birds and vascular plants have increased in abundance. Authors attribute the increase in bird populations to conservation and management actions related to the implementation of the EU Birds and Habitats Directives, as well as to the arrival of new bird species to the ecosystem.

However, many bird species have disappeared from the Camargue between the 1970s and the 2010s. Especially farmland birds are showing a steep decline since the 1950s. The increase in vascular plants is linked to the introduction of new species, some of the them highly invasive, into the study area.

Results suggest that the current protection measures in the Camargue area have failed to protect certain taxa. On the other hand, the observed increase in novel and invasive species and the patterns of increases and declines in different groups reveal important changes in the community structure of the studied taxonomic groups.

“This may be an indication that the Camargue has undergone significant changes with important implications for local ecosystem functioning,” Sara Fraixedas says.

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But a new study published in the journal Conservation Letters reveals a different picture of how and when bears eat salmon. Most of these bears, also known as grizzlies, are dipping into small streams to capture their iconic prey.

Using a foraging model based on the Wood River basin in southwest Alaska, a study team led by Oregon State University determined that while small-stream habitats have only about 20% of the available salmon in the watershed, they provide 50% of bear consumption of salmon.

“This tells us that populations of sockeye salmon that spawn in little streams are disproportionately important to bears,” said study lead author Jonny Armstrong, an ecologist at Oregon State University. “Bears profit from these small streams because they offer salmon at unique times of the season. To capitalize on plentiful salmon runs, bears need them to be spread across time.”

Small streams typically have cold water, which leads to populations of salmon that spawn much earlier in the season when no other populations are available to predators such as bears.

These results have potential consequences for how environmental impact assessments are conducted and evaluated for large projects such as the proposed Pebble Mine in Alaska’s Bristol Bay.

These reports typically focus on how the project will affect the abundance of salmon in lakes and rivers, but they usually overlook smaller habitats, Armstrong said.

“When people want to build a large mine, they think these streams don’t matter because they represent a small fraction a watershed, in terms of area or salmon abundance. In conservation and management, we generally place value on the largest runs of salmon at the expense of the smallest ones,” Armstrong said. “If we pose a different question and ask which habitats are important for the ecosystem, then small streams become particularly relevant.”

The researchers developed a mathematical model that explores how watershed development and commercial fisheries affect how many sockeye salmon are available to grizzlies. The model simulated different patterns of development and explored how they affected the number of salmon bears consumed.

Protecting large salmon runs at the expense of smaller ones turned out to be bad for bears.

“This causes the bears’ total salmon consumption to drop off faster compared to strategies that protected small salmon runs and the early feeding opportunities they offer to bears,” Armstrong said. “If you impair these areas, you may only reduce the total number of salmon by a little, but the number of salmon that end up in bear’s stomachs — you could reduce that a lot.”

According to the study authors, there are two significant reasons why the largest bears in the world are drawn to small streams to eat salmon.

First, the fish in these streams are easy to catch for adult and juvenile grizzlies. And second, because the water is colder than in lakes and rivers, salmon spawn in them earlier — probably to give their eggs more time to incubate, the authors said. So, the fish are plentiful by the first week of July — making them the first places bears fish after they emerge from hibernation.

“When they come out of hibernation, the bears are just scraping by and barely making it,” Armstrong said. “Having these streams means they can start eating salmon in early July, which is about six weeks before the river- and lake-salmon populations start spawning and become available to bears. It’s an incredible foraging opportunity for bears.”

Armstrong added, “I’m sure that native Alaskans who subsisted on salmon were keenly aware of this, too.”

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