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When did geology open a road for species to move between the Americas?

We recently covered a study indicating that the Isthmus of Panama docked with South America earlier than we once thought, connecting North and South America and separating the Pacific from Caribbean waters. Instead of linking up just 3 million to 4 million years ago, those researchers found evidence that a connection was present by 14 million years ago.

One of the loose ends created by the new result was that the exchange of North and South American species had also been pinned at about 3.5 million years ago. That raised the question of why species waited to migrate. One possible explanation is that migrations were triggered by a climatic cooling around 3 million years ago.

Well, a new study led by Smithsonian Tropical Research Institute and University of Gothenburg researcher Christine Bacon re-examines the evidence for the exchange of species, dubbed the Great American Biotic Interchange, and suggests that there might not be much of a delay to explain.

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Oldest fossils might just be mineral look-alikes

Researchers trying to study the earliest signs of life on Earth have a tall task—it would be easier to find a needle in a haystack. Not much of the rock that formed at the surface of the Earth over three billion years ago is around for us to examine today, and what’s left has taken a tectonic beating over the eons. But it’s in these rocks that we hope to find recognizable remains of single-celled organisms.

Indirect evidence for life has been claimed to be present in roughly 3.7-3.8 billion-year-old rocks in Greenland, where carbon isotopes could reflect the activity of living organisms. This is not definitive, however, and actual fossils would be much less ambiguous evidence for the existence of life.

The title for oldest fossils had been pinned on the 3.46-billion-year-old Apex chert in Western Australia. Those rocks contain microscopic structures interpreted by some geologists as similar to cyanobacteria (also called blue-green algae). But the interpretation of those structures is not without debate. In a newly published study highlighting the potential for new technology to aid in the ancient life “needle search," a team led by Oxford’s Martin Brasier (who passed away in December) turned a critical eye on those purported fossil microbes in the Apex chert.

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Magma beneath the Cascade volcanoes might be special blend

If we were to draw a schematic cartoon diagram of a subduction zone, it would include a diving oceanic plate, represented by a uniform slab. As the plate dove deeper, water driven off by the increasing heat might be shown with a blue arrow. And, of course, that water will create some blobs of red magma in the mantle between the two tectonic plates, as adding water lowers the melting point of the rock.

But in reality, the subducting plate is not a uniform slab. An oceanic plate can be divided into a number of layers. On the top, there’s the ocean mud that slowly accumulated as the plate traveled from the mid-ocean ridge toward the subduction zone. Beneath that, you’ve got the basalt (and basalt’s larger-crystalled sibling, gabbro) that makes up the oceanic crust. At the bottom, there’s a layer of mantle rock that stuck to the plate as it slowly cooled over the course its long life beneath an ocean of water. Water is everywhere in this process; it soaks into the sediment, and fills cracks in the rock, and it also works its way into the minerals themselves, becoming a part of them chemically.

When an oceanic plate is subducting, the gradual warming as it sinks deeper into the hot Earth can drive off the water within the sediments and fractures, but the minerals can transform and give up their store of water as well.

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Maybe climate science news makes a difference?

One thing we've learned about publicly controversial topics like climate change and evolution: the controversy won’t be solved by simply providing more information about the science. Cultural divides underlie these issues, and battle lines have been drawn for reasons that have little to do with facts. Information is often just fodder for selective hearing and motivated reasoning—biased analysis that twists incoming information to favor our pre-existing opinions.

This is made apparent in many studies and experiments, and it’s normally assumed that science news (like you’re reading right now) is really no different from other kinds of information in this regard (meaning it's interpreted through cultural biases). Michigan’s Sol Hart, Ohio State’s Erik Nisbet, and George Mason’s Teresa Myers wondered if, when it comes to the news, there might be some normal information processing—as one does with uncontroversial topics—going on at the same time as all this motivated reasoning. To find out, they looked for people who read more science news and determined what they think about climate science.

The researchers surveyed a random sample of almost 1,700 people. Subjects were asked basic demographic questions, how conservative or liberal they identified as, and whether they considered themselves evangelical Christians or environmentalists. They were also asked to rate how much attention they pay to political news, science and technology news, and news about environmental issues.

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Science by robot: Outfitting the world’s “smartest” lake

BOLTON LANDING, New York—Arriving at Rensselaer Polytechnic Institute's field research station on the shores of lovely Lake George, the offices appeared deserted. The station's staff didn't hide from us; they had all relocated to another building for a training session on a new piece of technology. They've been doing a lot of that lately.

The scene in their meeting room was mostly pretty standard—tables, chairs, coffee, and snacks—but not many field stations have a shiny new nine-panel computer display on the wall. And no field stations have what that display will soon be showing.

Nestled along the eastern edge of New York’s stout and beautiful Adirondack Mountains, south of sprawling Lake Champlain, Lake George is a long, glacially sculpted basin filled by clear waters. The lake is 51 kilometers long, doesn’t get much more than three kilometers wide, and has long been a natural attraction. Thomas Jefferson once called it “the most beautiful water I ever saw." But today, a partnership between IBM, the Rensselaer Polytechnic Institute, and the local FUND for Lake George has a different descriptor in mind—“smartest” lake in the world. It's an effort dubbed the “Jefferson Project.”

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Understanding Greenland’s wild climate swings

If we polled climate scientists for the weirdest thing we learned by drilling into Greenland’s ice, Dansgaard-Oeschger cycles would be strong contenders. During the colder parts of Greenland’s ice age history, it has frequently experienced a wicked case of climate whiplash. Parts of Greenland could endure a warming of 10 degrees Celsius in the space of a couple of decades. That would be followed by centuries of cooling and, eventually, another abrupt warming.

Look at ocean sediment cores in the Atlantic and you’ll see something else happening at the same time: sand and stones appearing in the seafloor mud, carried there by dirty, slowly melting icebergs. (In fact, some icebergs may have made it as far as Florida.) These impressive launches of iceberg armadas are called Heinrich events—and there’s clearly some connection between Heinrich and Dansgaard-Oeschger.

We’re pretty sure these wild events relate to the downward flow of salty, dense surface water in the North Atlantic, which completes the conveyor belt that turns northward-flowing surface water into southward-flowing deep water. If the salty surface water loses its greater density, the conveyor belt—and the warmth it carries northward—seizes up. Conversely, switching the conveyor belt back on can rapidly deliver warmth northward, which may explain some of the sudden warmings.

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Wisconsin cutting environmental science, limiting talk of climate change

Since taking office in 2010, Wisconsin Gov. Scott Walker has reshaped the state’s Department of Natural Resources (DNR). He appointed a former state senator and critic of the agency to be its secretary, and hired an outside “deer czar” in response to hunters’ complaints about the state’s management of the deer herd. Gov. Walker also re-wrote state mining regulations to clear the way for an ill-fated iron mine proposal that was finally abandoned last month. Several days ago, the Milwaukee Journal Sentinel reported that the mining company’s lobbyist and spokesman had been considered for appointment as the DNR’s deputy secretary—until officials realized there was a federal law specifically preventing that kind of thing. (He was, instead, hired for a job in another agency.)

Now, the DNR has come under the budget knife. Among other changes and position cuts, the agency’s science bureau faces a 30 percent reduction in staff. Now, Wisconsin Watch reports that the DNR is considering eliminating the science bureau altogether, shuffling remaining staff into other divisions.

The bureau performs the local, applied ecological research and monitoring that informs state regulations. Timothy Van Deelen, a University of Wisconsin ecologist, told Wisconsin Watch he was concerned about losing that work. “Long-term data sets are so incredibly rare,” he said. “And now a lot of that monitoring, such as with the deer herd, is up in the air.”

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When did Panama link North and South America?

Over a hundred years ago, laborers rectified an inconvenience imposed by geology some millions of years before by digging the Panama Canal. The less-than-one-hundred-kilometer-wide Isthmus of Panama was all that blocked the way of ships wishing to travel between the Atlantic and Pacific Oceans without an outrageous detour.

The waters of those oceans could lodge the same complaint. Before Panama was there, currents would have connected the two oceans near the equator, producing a profoundly different pattern of ocean circulation from what we see today. At the same time the thin land bridge connected the long-separated organisms of North and South America, releasing terror birds into North America and horses into South America, for example.

So when did all this happen? That’s not an easy question to answer. Our best guess was that it had occurred 3 to 4 million years ago, coinciding with fossil evidence of species migrations, changes in the salinity of the Caribbean Sea, and a transition from the warm Pliocene climate toward a Pleistocene defined by ice sheets.

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Epic 2013 Colorado rainstorm accomplished centuries’ worth of erosion

In early September, 2013, the rain started in Colorado. It didn’t relent for an incredible five days, until it had dropped about a year’s worth of water. Washed out roads dominated the news images, but there were also more than 1,100 landslides in the rugged Colorado Front Range terrain. It was unlike anything seen in 150 years of recorded history there.

University of Colorado Boulder’s Scott Anderson, Suzanne Anderson, and Robert Anderson (Suzanne and Robert are a married science duo, but Suzanne told Ars that “Scott is unrelated to us as far as we know”) saw an opportunity to learn something interesting from those landslides. Part of the area had been mapped two years prior by airborne LiDAR, which measures surface elevation very precisely. The researchers wanted to get a repeat survey funded right away to measure the changes, but Suzanne Anderson said their efforts were complicated by the sixteen day shutdown of the federal government in early October.

In the end, the Federal Emergency Management Agency undertook its own LiDAR flights in November, though the data was slightly lower resolution. By calculating the differences in the 100 square kilometer overlap between the two LiDAR datasets, they could work out the volume of sediment that slid downslope and was washed downstream.

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How human land use is changing the number of species in ecosystems

When we think about good wildlife habitat, we generally picture lands undisturbed by human construction or agriculture. Given that humans use roughly half the planet’s land area for such purposes, Earth’s “good habitat” ain’t what it used to be.

But what effect, exactly, has the loss of habitat had on all the species not named Homo sapiens? That’s a big, and therefore difficult, question to answer precisely. Plenty of effort has gone into estimating the number of species we’ve driven to extinction—we’ll eventually become the Sixth Mass Extinction event if we keep up at our current clip—but that can obscure the local details that tell us how the ecosystems around us are functioning.

A huge group of researchers led by Tim Newbold of the UNEP World Conservation Monitoring Centre and Lawrence Hudson of London’s Natural History Museum have now focused in on those local details. The researchers compiled the results of 378 published ecology studies of over 11,000 sites around the world, including observations of almost 27,000 species—vertebrates, invertebrates, and plants. The goal? To find ecological communities living on lands with varying human impact and see how they're doing.

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