A Mars orbiter has detected a wide lake of liquid water hidden below the planet’s southern ice sheets. There have been much-debated hints of tiny, ephemeral amounts of water on Mars before. But if confirmed, this lake marks the first discovery of a long-lasting cache of the liquid.

“This is potentially a really big deal,” says planetary scientist Briony Horgan of Purdue University in West Lafayette, Ind. “It’s another type of habitat in which life could be living on Mars today.”
The lake is about 20 kilometers across, planetary scientist Roberto Orosei of the National Institute of Astrophysics in Bologna, Italy and his colleagues report online July 25 in Science — but the water is buried beneath 1.5 kilometers of solid ice.

Orosei and colleagues spotted the lake by combining more than three years of observations from the European Space Agency’s orbiting Mars Express spacecraft. The craft’s MARSIS instrument, which stands for Mars Advanced Radar for Subsurface and Ionosphere Sounding, aimed radar waves at the planet to probe beneath its surface.
As those waves passed through the ice, they bounced off different materials embedded in the glaciers. The brightness of the reflection tells scientists about the material doing the reflecting — liquid water makes a brighter echo than either ice or rock.

Combining 29 radar observations taken from May 2012 to December 2015, MARSIS revealed a bright spot in the ice layers near Mars’ south pole, surrounded by much less reflective areas. Orosei and colleagues considered other explanations for the bright spot, such as radar bouncing off a hypothetical layer of carbon dioxide ice at the top of the sheet, but decided those options either wouldn’t produce the same radar signal or were too contrived to be physically likely.

That left one option: A lake of liquid water. Similar lakes beneath the ice in Antarctica and Greenland have been discovered in the same way (SN: 9/7/13, p. 26).

“On Earth, nobody would have been surprised to conclude that this was water,” Orosei says. “But to demonstrate the same on Mars was much more complicated.”

The lake is probably not pure water — temperatures at the bottom of the ice sheet are around –68° Celsius, and pure water would freeze there, even under the pressure of so much ice. But a lot of salt dissolved in the water could lower the freezing point. Salts of sodium, magnesium and calcium have been found elsewhere on Mars, and may be helping to keep this lake liquid (SN: 4/11/09, p. 12). The pool could also be more mud than water, but that could still be a habitable environment, Horgan says.

Previously, scientists have discovered extensive solid water ice sheets under the Martian dirt (SN Online: 1/11/18). There were also hints that liquid water flowed down cliff walls (SN: 10/31/15, p. 17), but those may turn out to be tiny dry avalanches. The Phoenix lander saw what looked like frozen water droplets at its site near the north pole in 2008, but that water may have been melted by the lander itself (SN Online: 9/9/10).

“If this [lake] is confirmed, it’s a substantial change in our understanding of the present-day habitability of Mars,” says Lisa Pratt, NASA’s planetary protection officer.

Though the newly discovered lake’s depth is unclear, its volume still dwarfs any previous signs of liquid water on Mars, Orosei says. The lake has to be at least 10 centimeters deep for MARSIS to have noticed it. That means it could contain at least 10 billion liters of liquid water.

“That’s big,” Horgan says. “When we’ve talked about water in other places, it’s in dribs and drabs.”

Under-ice lakes on Mars were first suggested in 1987, and the MARSIS team has been searching since Mars Express began orbiting the Red Planet in 2003. It took the team more than a decade to collect enough data to convince themselves the lake was real.

For the first several years of observations, limitations in the spacecraft’s onboard computer forced the team to average hundreds of radar pulses together before sending the data back to Earth. That strategy sometimes cancelled out the lake’s reflections, Orosei says — on some orbits, the bright spot was visible, on others, it wasn’t.

In the early 2010s, the team switched to a new technique that let them store the data and send it back to Earth more slowly. Then in August 2015, months before the end of the observing campaign, the experiment’s principal investigator, Giovanni Picardi of the University of Rome Sapienza, died unexpectedly.

“It was incredibly sad,” Orosei says. “We had all the data, but we had no leadership. The team was in disarray.”

Finally discovering the lake is “a testament to perseverance and longevity,” says planetary scientist Isaac Smith of the Planetary Science Institute, who is based in Lakewood, Colo. “Long after everyone else gave up looking, this team kept looking.”

But there is still room for doubt, says Smith, who works on a different radar experiment on NASA’s Mars Reconnaissance Orbiter that has seen no sign of the lake, even in CT scan–like 3-D views of the poles. It could be that MRO’s radar is scattering off the ice in a different way, or that the wavelengths it uses don’t penetrate as deep into the ice. The MRO team will look again, and will also try to create a 3-D view from the MARSIS data. Having a specific spot to aim for is helpful, he says.

“I expect there will be debate,” Smith says. “They’ve done their homework. This paper is well earned. But we should do some more follow-up.”

Stonehenge attracted the dead from far beyond its location in southern England.

A new analysis of cremated human remains interred at the iconic site between around 5,000 and 4,400 years ago provides the first glimpse of who was buried there. Some were outsiders who probably spent the last decade or so of their lives in what’s now West Wales, more than 200 kilometers west of Stonehenge, researchers report August 2 in Scientific Reports.

West Wales was the source of rocks known as bluestones used in early stages of constructing Stonehenge. Bluestones are smaller than the ancient monument’s massive sandstone boulders.
The new investigation “adds detail to a previously rather shaky framework” of archaeological finds suggesting that links existed among ancient societies across southern England and Wales, says archaeologist Timothy Darvill of Bournemouth University in Poole, England, who was not involved in the research.

Geographic origins of cremated remains at the site had previously eluded scientists. In the new study, bioarchaeologist Christophe Snoeck of Vrije Universiteit Brussel in Belgium and colleagues analyzed two forms of the element strontium in human skull fragments that were previously found among cremated remains at Stonehenge to narrow down individuals’ origins. Signature levels of these strontium types characterize rock formations and soil in different regions. Humans and other animals incorporate strontium into their bones and teeth by eating plants.
Snoeck demonstrated several years ago that, rather than absorbing strontium from surrounding soil like unburned bone, pieces of cremated bone retain a strontium signal from around the last 10 years of a person’s life. Of 25 cremated people whose bones were studied, 10 individuals spent their last decade in West Wales or near there, the researchers found. The rest were locals.
“Our results show that it was not just bluestones but people, or in some cases perhaps just their cremated remains, that came to Stonehenge in its early phases,” says coauthor Rick Schulting, an archaeologist at the University of Oxford.

Stonehenge served as a cemetery for at least 500 years, beginning around 5,000 years ago (SN: 6/21/08, p. 13). Excavations at Stonehenge between 1919 and 1926 recovered cremated remains of up to 58 individuals that had been placed in 56 pits. Researchers reburied these finds in 1935. Archaeologist and study coauthor Mike Parker Pearson of University College London led a team that in 2008 re-excavated remnants of the 25 individuals analyzed in the new study.
Nonlocal people buried at Stonehenge were cremated before being transported to the ancient site, Snoeck’s group suspects. Levels of two forms of carbon absorbed into the bones during cremation indicate that funeral pyres consisted of trees from dense woods such as those in Wales. A different carbon makeup characterizes trees from relatively open landscapes, as in southern England. The extent of contacts between communities in the two regions is unknown. One reason: Cremation destroys tooth enamel, which preserves a strontium record of childhood diet. As a result, investigators can’t determine whether nonlocal people buried at Stonehenge grew up in West Wales or elsewhere.

For now, the best bet is that nonlocal people buried at Stonehenge around 5,000 years ago spent their final years in western Britain, possibly West Wales, says archaeologist Alasdair Whittle of Cardiff University in Wales. Archaeological finds from that time link inhabitants of the Orkney Islands off Scotland’s northeast coast to communities in mainland Britain and probably continental Europe, boosting the plausibility of long-distance contacts between western Britain and Stonehenge, Whittle adds.

Archaeologists also have discovered cultural ties between southern England and France’s northwestern Brittany region dating to as early as around 5,000 years ago, Darvill says. That means outsiders could have come from other places. Snoeck’s group should compare strontium signatures typical of Brittany folk to those of people buried at Stonehenge, he suggests.

The extinction event that wiped out all nonbird dinosaurs about 66 million years ago also shook up shark evolution.

Fossilized shark teeth show that the extinction marked a shift in the relative fates of two groups of sharks. Apex predators called lamniformes, which include modern great white sharks, dominated the oceans before the event, which took place at the end of the Cretaceous Period. But afterward, midlevel predator sharks called carcharhiniformes came to dominate the waters — as they still do today, researchers report August 2 in Current Biology.
Paleontologist Mohamad Bazzi of Uppsala University in Sweden and colleagues examined the shapes of nearly 600 shark teeth dating from 72 million to 56 million years ago. Unlike their cartilaginous skeletons, sharks’ teeth, which the fish shed throughout their lives, are well preserved in the fossil record, Bazzi says. By looking at patterns in tooth shape variation — the height of the crown or the breadth of the tooth — scientists can measure trends in shark diversity. After the extinction event, lamniform sharks that had a particular tooth shape — low-crowned and triangular — appeared to decline, while carcharhiniform sharks with the same low-crowned tooth shape proliferated.

The extinction “is one of the more transformative events in shark evolution,” Bazzi says. Today, there are only 15 known species of lamniformes, but hundreds of carcharhiniformes, including hammerheads and lemon sharks.

It’s difficult to know how the event caused the shift, but one possibility is that the extinction affected the sharks’ preferred food sources. Modern great whites, for example, eat everything from cephalopods to seals; ancient lamniformes may have had a similarly varied diet and experienced a loss of primary food sources such as marine reptiles following the extinction. But the rapid increase in small bony fish after the event may have given a boost to the smaller carchariniform predators, such as houndsharks.

The first new treatment in 60 years for a particularly stubborn kind of malaria is raising hopes that it might help eradicate the disease, even though the treatment can cause a dangerous side effect.

Called tafenoquine, the drug targets the parasite that causes relapsing malaria. Plasmodium vivax infects an estimated 8.5 million people, mainly in Asia and Latin America. Each time infected people have a malaria relapse, the parasite returns to their bloodstream, allowing them to transmit the infection if a mosquito bites them again. Tafenoquine was approved as a treatment in July by the U.S. Food and Drug Administration and is under consideration as a preventative medication, too.
“This is a game changer because we’ve really been struggling with eliminating [P.] vivax,” says malaria physician Ric Price from the Menzies School of Health Research in Darwin, Australia.

The FDA’s action is expected to spur other countries where relapsing malaria is more prevalent to approve the drug as well. Companies are also working to develop speedy, low-cost tests that can identify people with a genetic deficiency who may risk getting a kind of anemia from the new drug. This test is essential for putting the drug to use in rural areas where rates of both P. vivax and this deficiency can be high.

Like its deadlier cousin P. falciparum, P. vivax is spread by the Anopheles mosquito and causes chills, a cyclical fever and joint aches (SN: 3/18/17, p. 10). Unlike P. falciparum, once inside the body, P. vivax can stay dormant in the liver for weeks or months before flaring up again and again.

Tafenoquine (which will be marketed in the United States as Krintafel) is designed to prevent these relapses. It is similar to an older drug called primaquine, but it is taken in two 150-milligram doses a few hours apart, instead of daily for two weeks. In clinical trials, that dosage, paired with acute malaria medication chloroquine, prevented 70 percent of malaria relapses.
With its compressed dosing schedule, patients prescribed tafenoquine are more likely than those on primaquine to complete the treatment, preventing more relapses and problems with drug resistance.

But tafenoquine’s biggest selling point is also a weakness. Both primaquine and tafenoquine can cause a dangerous side effect in people with glucose-6-phosphate dehydrogenase, or G6PD, deficiency, an abnormality on the X chromosome that affects 400 million people worldwide. When people who have G6PD deficiency take these medications, they are at a higher risk for hemolytic anemia, the destruction of red blood cells.

Tafenoquine’s long-lasting formula makes it harder for the body to clear it out, which could potentially lead to life-threatening damage to red blood cells and severe anemia. “Once it’s in your body, it stays in your body,” says Nick White, a physician and malaria expert at the Mahidol Oxford Tropical Medicine Research Unit at the University of Oxford in Bangkok.

Tests to determine which patients have G6PD deficiency are not widely available, particularly in developing countries such as those in Asia and South America where relapsing malaria is endemic. “The test exists,” says Gonzalo Domingo, a scientific director at PATH, a nonprofit global health organization in Seattle, “but it is quite complicated, and it requires quite complicated laboratory facilities.”

PATH funds companies that are developing a new version of the test for use in rural areas. Field trials of a prototype test that can be performed in two minutes with just a finger prick are under way in Ethiopia, Brazil and India. People with relapsing malaria who test positive for G6PD deficiency instead take a low-dose, eight-week treatment of primaquine that’s less likely to cause side effects.

“It’s a great tool,” Domingo says of the new G6PD deficiency test. “It provides people access to the drug safely.”

A gene that helps mammals break down certain toxic chemicals appears to be faulty in marine mammals — potentially leaving manatees, dolphins and other warm-blooded water dwellers more sensitive to dangerous pesticides.

The gene, PON1, carries instructions for making a protein that interacts with fatty acids ingested with food. But that protein has taken on another role in recent decades: breaking down toxic chemicals found in a popular class of pesticides called organophosphates. As the chemicals drain from agricultural fields, they can poison waterways and coastal areas and harm wildlife, says Wynn Meyer, an evolutionary geneticist at the University of Pittsburgh.
An inspection of the genetic instructions of 53 land mammal species found the gene intact. But in five marine mammal species, PON1 was riddled with mutations that made it useless, Meyer and colleagues report in the Aug. 10 Science. The gene became defunct about 64 million to 21 million years ago, possibly due to dietary or behavioral changes related to marine mammal ancestors’ move from land to sea, the researchers say.

The team also gauged the rate at which two organophosphate chemicals — chlorpyrifos oxon and diazoxon — broke down in blood samples from five land mammal species and six marine or semiaquatic mammal species. While blood from the terrestrial species, including sheep, goats and ferrets, showed a decrease in toxic molecules over time, the marine species’ blood showed almost no change. Mice genetically engineered to lack the gene couldn’t break down the chemicals either.
A nonfunctional PON1 doesn’t necessarily mean marine mammals are helpless against organophosphates, says environmental toxicologist Andrew Whitehead at the University of California, Davis who was not involved in the work. The animals may have other defense mechanisms, but in this study, “they aren’t stepping up to the plate to metabolize these organophosphates,” he says.
It’s unclear if organophosphates build up in marine mammals’ bodies in a way similar to DDT, a type of pesticide that doesn’t break down easily in the environment. DDT, which is banned in dozens of countries, can accumulate in marine mammals’ tissues and cause nervous system damage and birth defects (SN Online: 1/19/16).

What’s more, “even though organophosphates don’t stick around as long in the environment as DDT, there’s persistent input,” Whitehead says. The chemicals are often used on crops and to kill mosquitoes and other pests.

The researchers plan to collect blood samples from dolphins and manatees in coastal areas suffused with agricultural runoff, says study coauthor Nathan Clark, an evolutionary biologist also at the University of Pittsburgh. That could help scientists monitor if the animals have been exposed to the pesticides and if that corresponds with levels of the chemicals in the environment, he says.

Rogue nations that want to hide nuclear weapons tests may one day be thwarted by antineutrinos.

Atomic blasts emit immense numbers of the lightweight subatomic particles, which can travel long distances through the Earth. In general, the particles — the antimatter twins of neutrinos — are notoriously difficult to spot. But a large antineutrino detector located within a few hundred kilometers of a powerful nuclear explosion could glimpse a handful of the particles, scientists report in the August Physical Review Applied.
An antineutrino detector wouldn’t spot an explosion solely on its own, but would use seismic activity picked up by existing sensors to trigger a search for particles arriving from a suspected blast. It’s “a very smart and clever idea,” says physicist Patrick Huber of Virginia Tech in Blacksburg.

A global network of sensors already gathers detailed information about nuclear explosions by monitoring for telltale seismic activity and radioactive isotopes. In recent years, those sensors have revealed details of North Korean nuclear tests performed underground (SN: 8/5/17, p. 18).

But if those sensors were unable to confirm that a nuclear explosion occurred, spotting antineutrinos would eliminate doubt, says study coauthor and physicist Adam Bernstein of Lawrence Livermore National Laboratory in California. “If you see a burst of antineutrinos, there’s really no other way you could have gotten that,” he says, aside from an exploding star in the Milky Way (SN: 2/18/17, p. 24). Those stellar bursts are rare events unlikely to coincide with a seismic signature.

And while stealthy bomb makers might be able to contain an explosion’s radioactive isotopes or mask some of its seismic signals, there’s no way to stop antineutrinos from escaping. Neutrinos could also provide information about how powerful the explosion was and what type of nuclear weapon was used.
None of the existing antineutrino detectors, however, are big enough and in the right location to monitor North Korea. One of the biggest is the Super-Kamiokande detector, located in a mine in Hida, Japan. It’s filled with 50,000 tons of water and lined with sensors that detect light produced when antineutrinos interact in the water. If located within about 100 kilometers of a nuclear test site, a detector of this size could likely spot a 250-kiloton nuclear fission explosion.

A detector about 10 times bigger could spot such an explosion several hundred kilometers away. But building such large detectors wouldn’t be easy. “It’s not the kind of thing that’s going to be the go-to method for monitoring nuclear testing,” says physicist Kate Scholberg of Duke University.

Scientists are planning a beefed-up antineutrino experiment of that size called Hyper-Kamiokande, which would consist of two detectors, one in Japan and the other in South Korea. Hyper-Kamiokande’s main purpose is to study the physics of neutrinos. But, says study coauthor Rachel Carr, a physicist at MIT, the proposed South Korean detector is “actually big enough that it would possibly detect a few antineutrinos from a North Korean test.”

The boardwalk at Pa-hay-okee Overlook is a brief, winding path into a dreamworld in Everglades National Park. Beyond the wooden slats, an expanse of gently waving saw grass stretches to the horizon, where it meets an iron-gray sky. Hardwood tree islands — patches of higher, drier ground called hammocks — rise up from the prairie like surfacing swimmers. The rhythmic singing of cricket frogs is occasionally punctuated by the sharp call of an anhinga or a great egret.

And through this ecosystem, a vast sheet of water flows slowly southward toward the ocean.

The Everglades, nicknamed the river of grass, has endured its share of threats. Decades of human tinkering to make South Florida an oasis for residents and a profitable place for farmers and businesses has redirected water away from the wetlands. Runoff from agricultural fields bordering the national park causes perennial toxic algal blooms in Florida’s coastal estuaries.

But now, the Everglades — home to alligators and crocodiles, deer, bobcats and the Florida panther, plus a dizzying array of more than 300 bird species — is facing a far more relentless foe: rising seas.

South Florida is ground zero when it comes to sea level rise in the United States. By 2100, waters near Key West are projected to be as much as two meters above current mean sea level. Daily high tides are expected to flood many of Miami’s streets. The steady encroachment of saltwater is already changing the landscape, killing off saw grass and exposing the land to erosion.

Against this looming threat, Everglades ecologists and hydrogeologists are racing to find ways to mitigate the damage before the land is reclaimed by the ocean, irrevocably lost.

Sea level rise is a global problem, but coastal water management in South Florida faces some particular challenges, as a 2014 National Climate Assessment report noted. Growing urban centers need access to freshwater, flat topography encourages ponds of water to linger, and porous limestone aquifers are particularly vulnerable to encroaching saltwater. Storm surges occasionally drive seawater far inland, compounding the problem.

“We can’t ignore it anymore,” says Shimelis Dessu, a hydrogeologist at Florida International University in Miami. When it comes to water management needs in South Florida, ecological conservation has tended to be low on the list, compared with human and agricultural needs, Dessu says. Now, sea level rise is forcing people to think differently. “The ocean is no longer an external thing,” he says. “It’s already in the house.”
Draining the swamp
Florida’s tug-of-war over water has a long history.

In the 1800s, settlers first began draining the land to make way for agriculture and communities. Water management in the state began in earnest in 1948, when the U.S. Congress authorized the Central and Southern Florida Project for Flood Control and Other Purposes.

That project was meant to control flooding along the Kissimmee River and Lake Okeechobee, in the south-central part of the state. During the rainy months in summer and fall, the river and the broad, shallow lake often overflowed, flooding surrounding areas. The spillage would travel slowly southward across southern Florida in a broad sheet and eventually drain into Florida Bay, an open water body between the mainland and the Florida Keys. During the journey, some of the water would seep into the ground, replenishing the Biscayne Aquifer, a limestone layer that underlies much of the southeastern part of the state.

But the recurrent flooding made the land uninhabitable and farming impossible. So with Congress’ 1948 authorization, the U.S. Army Corps of Engineers built a complex system of levees, canals and reservoirs to control the floods and channel water away from farmlands south of Lake Okeechobee and from growing population centers. Three large “water conservation areas” were constructed to collect and store water during high rainfall events and release it in times of drought. The remaining wetlands — encompassing about half of their original area — were enclosed into two protected areas, Everglades National Park and Big Cypress National Preserve.

Such an intensive overhaul of South Florida’s water cycle led, perhaps inevitably, to new problems. Reducing the amount of freshwater that naturally heads south into the Everglades proved destructive to the habitats of plants and animals. Wading bird populations, for example, shrank by 90 percent over the last century. Diverting the water away from its natural overland course also meant less water was available to replenish the Biscayne Aquifer, which provides drinking water to 3 million people.

Agriculture is big business in Florida; the state’s exports total more than $4 billion each year. But fertilizer from the agricultural regions pollutes waterways feeding into Lake Okeechobee, causing algal blooms in the lake. Regulated discharges from the lake to control flooding shunt polluted water to the east, west and south, causing periodic algal blooms on the coasts and in Florida Bay.

Hoping to undo some of the damage, Congress approved a 35-year, $10.5 billion project in 2000 to send more freshwater south into the river of grass. That project, the Comprehensive Everglades Restoration Plan, or CERP, remains the largest hydrologic restoration project ever undertaken in the United States.

CERP has shown signs of success. The National Academies of Sciences, Engineering and Medicine, which evaluates the progress of Everglades restoration every two years, reported in 2016 that freshwater flow through the Everglades has indeed increased since the project began. And in some areas, groundwater levels and vegetation are beginning to return to how they looked before the extensive water management began.

But the academy’s 2016 report also pointed to a glaring problem. Researchers know a lot more about the effects of climate change now than they did in 2000. Without accounting for these effects, particularly rising sea levels, the restoration plan will not be able to meet its intended goals: restoring the wetlands and buffering inhabited areas against Florida’s intensely fluctuating hydrologic cycle.

Managed water
Water flow in the Everglades begins with the Kissimmee River and other rivers, which pour into Lake Okeechobee. Left to its natural course (left), the water periodically spilled over the lake’s banks and flowed southward in a broad, shallow sheet (dark blue). But decades of heavy management (center) have channeled the water away from the wetlands to make way for South Florida’s cities and agriculture. The Comprehensive Everglades Restoration Plan (right) aims to restore some of the natural flow while still managing the water.
Source: U.S. Army Corps of Engineers, Jacksonville District

Losing ground
Over the last half-century, the freshwater-saltwater transition zone in the Everglades has moved inland by at least a kilometer, due both to rising sea levels and to the reduction of freshwater flow through the Everglades. Some scientists call this inland shift of saltwater the Anthropocene Marine Transgression, a nod to the fact that humans are ultimately responsible for the rising seas and freshwater management.

In part, it’s a simple problem of water pressure. Freshwater flowing down off the land, or in belowground aquifers, pushes toward the sea. If that tap is slowed to a trickle and freshwater pressure is reduced, the seawater meets less resistance and can drive farther inland. It’s a problem many coastal communities around the world have faced when overdrawing from coastal aquifer wells: Removing too much freshwater at once allowed seawater to sneak in and poison the well. Add rising sea levels to the mix, and the low-lying Everglades face a double hit of saltwater intrusion above ground and below.

Because it is underground, the saltwater intrusion zone is not visible on a map. “But you can see the legacy effect … above ground,” says wetland ecologist Stephen Davis of the Everglades Foundation, a nonprofit group based in Palmetto Bay, Fla. “The salinity periodically knocks back the plant community.”

Hardest hit is the ubiquitous saw grass. Saw grass is hardy stuff; it is resistant to wildfires and thrives even in nutrient-poor soil. But saltwater is another matter. In 2000, a team of scientists surveyed the southernmost portion of the Everglades from the air. The researchers noted odd pockmarks dotting the land — bare patches where the saw grass had died. “Some of these landscapes look like Swiss cheese,” Davis says.
Thick, organic peat soil is the building block of many wetlands, including the Everglades, says Fred Sklar, director of the South Florida Water Management District’s Everglades division, based in West Palm Beach. But peat soil is fragile: Too little freshwater and it dries up. And worse, the combination of dwindling freshwater and increasing saltwater inundation is a one-two punch, “a kind of turbo boost, allowing the soil to break down,” Davis says. Chemical or biological changes within the peat soil — scientists aren’t sure exactly what — then trigger a sudden collapse. Soil elevation drops rapidly, exposing the roots of the saw grass, which eventually die.

The bare patches of ground are the most visible scars of saltwater intrusion, but the extent of the damage is probably much greater than is visually apparent, Davis says. Storm surges from hurricanes such as 2017’s Irma, along with king tide events, the highest high tides of the year, can push saltwater several kilometers inland. As a result, many regions that look fine to the eye are destabilizing beneath the surface, on the verge of collapse, he says.

Widespread peat collapse could be devastating to the Everglades on two fronts. Maintaining the elevation of the soil is a bulkhead against seawater intrusion; the collapsed areas become zones of open water. And peat-filled wetlands represent a vast carbon sink — a region where far more carbon dioxide is absorbed through photosynthesis than is released through respiration. Losing the soil effectively changes the region from a place that stores carbon to one that adds carbon dioxide to the atmosphere, fueling climate change.

Researchers don’t yet know how quickly land is subsiding in the Everglades. But research suggests that even slightly salty waters could cause the soil to sink at a “potentially staggering” rate, Davis says, dramatically increasing how quickly rising seas will be able to reclaim land. Biologist Sean Charles of Florida International University infused plots of saw grass–bearing peat soil with brackish water (still much less salty than seawater). In just one year, soil elevation in the salty plots sank by almost three centimeters, while the soil in the freshwater plots held its elevation or increased slightly.

A tale of two field sites
There’s a second boardwalk at Pa-hay-okee, which gets its name from a Native American word for “grassy waters.” Unlike the visitors’ overlook, getting to this platform requires a short, gutsy slog across a few meters of open wetland, possibly under the watchful gaze of an alligator.

That expanse is an intentional deterrent, says Benjamin Wilson, a wetland ecologist at Florida International University. This boardwalk isn’t meant for visitors; it’s for scientists, who built it as part of a long-term research study to try to understand what, exactly, causes peat soil collapse.

About a 20-minute drive to the south, a sister field site near West Lake is hidden behind a forest screen of salt-tolerant mangroves, their roots entangled and exposed, their branches creaking eerily. The two sites sit on either side of the saltwater intrusion zone: Pa-hay-okee is still largely fresh, but West Lake is brackish.

The first phase of the project, led by wetland ecologist Tiffany Troxler of Florida International University, was to figure out where the peat is most vulnerable to sea level rise, now and in the future, using existing well data, geologic maps and computer simulations of sea level rise. The second step — and the reason for studying the paired sites — examined how salinity changes might affect the peat soil and saw grass. “And then we should have a better idea of where saw grass is going to be, and where peat collapse may occur in the future,” Troxler says.

Alongside the boardwalk, the team embedded a dozen Plexiglas tubes right into the marsh. The chambers, each about half a meter in diameter, are open at the bottom and top, but can be twisted open or closed to allow the water to flow freely through them, or to temporarily sequester the chambers from the rest of the wetland.
Many factors can alter soil chemistry. Reduced freshwater flow can dry out the soil briefly, exposing it to oxygen. And seawater seeping up from the phosphorus-rich limestone aquifer below the wetlands brings in an extra supply of the nutrient, which is otherwise in short supply in the Everglades.

Once a month for four years — during wet and dry seasons — team members visited the chambers at both sites, closing them and dosing them with cocktails composed of different amounts of saltwater and nutrients.

“It was fun,” Wilson says cheerfully. Despite the muddy slog, team members chose not to wear full-body waders. “We’re lucky to be in South Florida, where the water never really gets cold.” Then, he pauses. “Well, it can get really miserable,” he acknowledges after a few seconds. Although they didn’t wear waders, the researchers covered up in long-sleeved shirts and pants, even in the summertime, and shielded their faces, despite the stifling heat. “Do you want 100 mosquitoes in your face, or do you want to be sitting in 95-degree humidity, not being able to breathe with these masks on?” he asks rhetorically.

This sometimes grueling work yielded results, as the team tracked how different factors might affect the saw grass ecosystem and peat collapse. Specifically, the researchers assessed changes in how much carbon dioxide the soil released into the atmosphere as a result of added salt and phosphorus, and also tracked changes in saw grass root growth.

A change in microbe activity was another possible culprit in soil collapse. So microbial biologist Shelby Servais of Florida International University examined whether the saltwater increased microbial growth, which could in turn speed breakdown of organic material. It didn’t happen. “What we found is that, in general, salt exposure suppresses activity of the microbial community.”

Even saltwater inundation — by itself — may not be causing the soil breakdown, Wilson says. What really seemed to matter was how dry the soil was to begin with, before saltwater was added. When the soil was already wet, adding more salt had no effect on how much carbon dioxide the soil released to the atmosphere, the team found. But when the researchers added salt to dry soil, carbon dioxide spiked. The team also noticed that saw grass plants grew fewer roots.

A third phase of the peat soil project is now getting underway. The researchers will precisely track where soil elevation has dropped, and by how much. The team will plunge a rod into the ground all the way to the bedrock and use pins attached to the rod to measure elevation changes over time. From that, Troxler says, “you can get an idea of whether [soil creation in] the wetlands is keeping up with sea level rise.”
Race against the rise
What should planners do if, as some simulations suggest, sea level rise is already outpacing the efforts by state and federal authorities to restore freshwater flow through the Everglades?

Dessu and colleagues took a close look at freshwater management efforts side by side with projections of sea level rise. “We have some control over the freshwater management. The other side, the sea level rise, we don’t have any control over,” he says.

The researchers had about 16 years’ worth of data on changing ecology in the wetlands, including information about the transitions of freshwater saw grass to salt-tolerant mangroves, loss of tree islands and proliferations of water- and nutrient-loving cattail plants. The team analyzed these changes, as well as changes in salinity and nutrients measured in wells in the region, to observe which areas had become saltier over time.
Then, Dessu says, the researchers examined freshwater management practices. Since 1985, South Florida water managers have been gauging how much freshwater to release from the water conservation areas based on the amount of rainfall that fell 10 weeks earlier. In the dry season, that delay is a problem, the team reported in April in the Journal of Environmental Management.

“By the time the flow is delivered, it’s two months too late,” Dessu says. The study concluded that the state’s water managers should consider not just how much water to send down into the Everglades, but when, exactly, would be the best time to do it. “That actually was kind of a surprise,” says Florida International University hydrogeologist René Price, a study coauthor.

Managers can use the difference between measured freshwater level and seawater level to decide when best to deliver a plug of freshwater to maintain enough water pressure to help push seawater back, Dessu says. It’s a kind of Band-Aid fix — one that won’t solve the long-term problem of saltwater encroachment into the wetlands, but may at least ameliorate its immediate effects, he adds.

The future of the Everglades
Such fixes are, perhaps, the story of Everglades restoration. In fact, restoration is a misnomer, Sklar notes. “It’s not really possible to bring back the past.”

Rehabilitation is more to the point. In March, Sklar and other South Florida water managers proposed an ambitious plan that could increase the overall flow of freshwater to the Everglades. The plan centers around the construction of a vast new water reservoir that would collect much of the fertilizer-polluted water from Lake Okeechobee to keep it from running to the coasts where it stimulates algal blooms. Within the reservoir, the water would be scrubbed, then sent to the wetlands. If the U.S. Army Corps of Engineers approves the project, it will become part of legislation headed to Congress in the fall for approval, Sklar says.

The Everglades water managers are walking a tightrope, juggling the needs of residents, farmers and business leaders who want a say about where the water goes. Conservationists in Florida understand this all too well. “If we made it all about climate change and sea level rise, there are those that wouldn’t be receptive,” Davis says. “So we talk about … issues like water supply and making the system more drought resilient.”

“Let’s face it,” he adds. “Science is incredibly important in shaping Everglades restoration projects, but it’s politics that gets the projects authorized and ultimately built.” But he notes that researchers still have many questions about how best to save the Everglades. For example, Davis says, scientists are just beginning to examine whether increasing freshwater flow can even save the saw grass.

Too much freshwater might, in fact, be a cure that’s worse than the disease. “There are models out there that show if we continue to release more freshwater to stem the tide of saltwater, it will end up just flooding the Everglades,” Price says, pointing to the push and pull. “We want to save the freshwater system, but how much flooding can it stand?”

In fact, the best hope for Everglades rehabilitation may be the mangroves. The gnarled, salt-tolerant trees are a visible sign of how the ecosystem is already changing, as they steadily march into regions vacated by freshwater saw grass.

Mangroves colonize new areas as their seeds wash inland. When the seeds settle into a spot, the plants can begin to grow, rapidly producing an abundance of fine roots — the primary component of peat soil. The trees can’t prevent all inundation or save the freshwater plants, but they may, at least, be able to keep the soil in place.

But as with so much in the Everglades, it’s a question of timing, Price says. Mangroves can’t move in if the soil is already completely gone. The trees need enough sediment to establish a foothold. Once established, however, mangroves can build up soil quickly, perhaps even at a pace that matches sea level rise.

“If they don’t, the peat collapse will take over,” Price says. “And it’ll just turn to open water.”
This story appears in the August 18, 2018 issue of Science News with the headline, “Everglades on the Edge: Scientists wrestle with how to fight the effects of sea level rise.”

Scientists have the power to genetically engineer many types of animals. Most Americans think it’s OK to alter or insert genes in animals and insects — provided it’s done in the interest of human health, according to a poll released August 16 from the Pew Research Center. The findings are similar to those from an earlier Pew survey, which found that a majority of Americans are fine with tweaking a baby’s genes, but only if it is to prevent disease.

In the new survey, a majority of respondents support engineering animals for the benefit of human health. For instance, 70 percent approve of preventing the spread of disease by reducing mosquitoes’ fertility (SN Online: 8/5/16), and 57 percent are on board with engineering animals to be organ donors for humans (SN: 11/2/17, p. 15). But people are not as comfortable with genetically manipulating animals for cosmetic or convenience reasons. A majority of respondents — 55 percent — object to genetically tweaking animal to produce more nutritious meat, saying that crosses a line.
The results, based on a survey of 2,537 U.S. adults from April 23 to May 6, reveal the mixed feelings people have about this emerging biotechnology.

Harvesting organs
Of the 41 percent opposed to genetically engineering animals to grow organs or tissue for human transplant, 21 percent said they worried about harm to the animals. Only 16 percent said they were worried about potential human health risks.

Extinct means extinct
Bringing species back from extinction didn’t sit well with 67 percent of respondents, who balked at the idea of altering a living species to revive one no longer in existence (SN: 10/28/17, p. 28). Of that group,18 percent said species are extinct for a reason; 23 percent said it messes with nature or God’s plan; and 14 percent said it’s a waste of resources. Only 4 percent said they were afraid it would create a “Jurassic Park scenario,” in which the de-extinct animals would run amok and kill people.

No to the glow
Engineering aquarium fish to make them glow got the thumbs down from 77 percent of respondents, who gave a variety of reasons: 48 percent of that group said it was a waste of resources, including 23 percent who said it offered no benefit to people or the fish and 13 percent who called it “frivolous.” Only 2 percent worried about how the fish could affect ecosystems if they were released into the wild.

Messing with mosquitoes
Though a majority supported engineering mosquitoes to improve public health, 29 percent disapproved. Of those, 23 percent worried about potential effects on other species, 23 percent were concerned about upsetting nature’s balance and 18 percent mentioned unintended consequences. Only 2 percent expressed worry about making mosquitoes extinct.

The Puerto Rican government has officially updated its tally of lives lost to Hurricane Maria to an estimated 2,975. That number, reported August 28 in a government-commissioned study by George Washington University in Washington D.C., dwarfs the island’s previous count of 64, which officials later acknowledged was far too low.

The study covers September 2017 through February 2018 — two months longer than other recent estimates for the post-hurricane death toll (SN Online: 8/2/18). An absence of clear guidelines for how to certify deaths during a disaster, the researchers found, meant many death certificates didn’t reflect the role of the Category 5 storm, which hit the island on September 20, 2017.
Based on mortality data including death certificates, the new 2,975 estimate falls between two other recent counts. One study in May estimated 4,645 deaths from the hurricane through December 2017 by surveying nearly 3,300 randomly selected households in January and February (SN Online: 5/29/18). Another study in August counted 1,139 excess deaths during the same period, by analyzing and comparing monthly death counts from January 2010 through December 2017.

In a report to Congress, a draft of which was published in July, Puerto Rican officials unofficially acknowledged that the death toll was likely far higher than 64, based on its counting roughly 1,427 more deaths in the four months after the storm than in the same period in the previous four years.

While different methodologies have resulted in different death estimates, the new report “highlights that the humanitarian crisis in Puerto Rico continued until February 2018,” says Alexis Santos, a demographer at Penn State University who was not involved in the new report but was a coauthor of the August study. “All we can do is try to help those still suffering in Puerto Rico.”

A new artificial intelligence is turning its big brain to mapping earthquake aftershocks.

Scientists trained an artificial neural network to study the spatial relationships between more than 130,000 main earthquakes and their aftershocks. In tests, the AI was much better at predicting the locations of aftershocks than traditional methods that many seismologists use, the team reports in the Aug. 30 Nature.

Although it’s not possible to predict where and when an earthquake will happen, seismologists do know a few things about aftershocks. “We’ve known for a long time that they will cluster spatially and decay over time,” says geophysicist Susan Hough of the U.S. Geological Survey in Pasadena, Calif., who was not an author on the new study.
Then, in 1992, a series of temblors prompted a flurry of interest in trying to map out where exactly an aftershock might occur, based on how a mainshock might shift stresses on other faults. First, a magnitude 7.3 earthquake shook the Southern California town of Landers and other nearby desert communities. Three hours later, a magnitude 6.5 aftershock struck the more populous area of Big Bear, about 35 kilometers away. The next day, a magnitude 5.7 aftershock struck near Yucca Mountain, Nev., nearly 300 kilometers away.

“After 1992, people were looking to understand [aftershock] patterns in more detail,” Hough says. Researchers began trying to distill the complicated stress change patterns using different criteria. The most used criterion, the “Coulomb failure stress change,” depends on fault orientations.

But fault orientations in the subsurface can be as complicated as a three-dimensional crazy quilt, and stresses can push on the faults from many different directions at once. Imagine a book sitting on a table: Shear stress pushes the book sideways, and might cause it to slide to the left or right. Normal stress pushes downward on the book, perpendicular to the table, so that it wouldn’t budge. Such a thorny computational problem may be tailor-made for a neural network, Hough says.
Earthquake scientist Phoebe DeVries of Harvard University and colleagues, including a Cambridge, Mass.–based team from Google AI, fed data on more than 130,000 mainshock-aftershock pairs into an AI. Those data included not only locations and magnitudes, but also different measures of changes in stress on the faults from the quakes. The AI learned from the data to determine how likely an aftershock was to occur in a given place, and then the team tested how well the system could actually pinpoint aftershock locations using data from another 30,000 mainshock-aftershock pairs.

The artificial intelligence system consistently predicted aftershock locations much better than the Coulomb failure criterion, the researchers found. That’s because the AI’s results were strongly correlated with other measures of stress change, such as the maximum amount of change in shear stress on a fault, the scientists say.

“It’s a cool study and might pave the way for future work to improve forecasting,” Hough says. But the study focuses just on static stresses, which are permanent shifts in stress due to a quake. Aftershocks may also be triggered by a more ephemeral source of stress known as dynamic stress, produced by a quake’s rumbling through the ground, she says.

Another question is whether a forecast system that used such an AI could leap into action quickly enough after a quake for its aftershock predictions to be helpful. The predictions in the new study benefited from a lot of information about which faults slipped and by how much. In the immediate aftermath of a big quake, such data wouldn’t be available for at least a day.

Using a neural network to study the aftershock problem “is a really nice, efficient approach,” says seismologist Lucy Jones of Caltech and the founder of the Dr. Lucy Jones Center for Science and Society, based in Los Angeles (SN: 3/31/18, p. 26).

But she agrees with Hough that, to help with risk management, the system would need to be able to respond more rapidly. The rule of thumb is that “whatever number of aftershocks you have on the first day, you get half of that on the second day, and so on,” says Jones, who was not involved in the new study. “A week after the earthquake, the majority of aftershocks have already happened.”