Nine new snail species discovered in Papua New Guinea, a biodiversity hot spot at risk

Peer-Reviewed Publication

FLORIDA MUSEUM OF NATURAL HISTORY

 

IMAGE: 

JOHN SLAPCINSKY, MANAGER OF THE FLORIDA MUSEUM OF NATURAL HISTORY’S INVERTEBRATE ZOOLOGY COLLECTION, NAMED NINE NEW SPECIES OF CARNIVOROUS LAND SNAILS FOUND IN PAPUA NEW GUINEA.

view more 

CREDIT: FLORIDA MUSEUM PHOTO BY JEFF GAGE

Nine new species of carnivorous land snails have been found in the remote forests of Papua New Guinea, a biodiversity hot spot. A new study describes the species, which are so small that all nine could fit together on a U.S. nickel. They present a rare opportunity to study a group that in many other places is disappearing fast. Worldwide, mollusks account for more than 50% of all recorded extinctions since the year 1500, and many of these were land snails from Pacific islands.

The island of New Guinea accounts for less than 1% of Earth’s land area, but it contains roughly 5% of the planet’s biodiversity and the largest intact rainforests in Australasia. Wildlife thrives within this large swath of undeveloped land, but Papua New Guinea’s old-growth forests are also highly desirable to loggers and are likely to become a conservation battleground in the future.

“These new species of snails were found in areas that still have native vegetation and still appear to be doing well, but they could easily become endangered if things change,” said John Slapcinsky, lead author of the paper and manager of the Florida Museum’s invertebrate zoology collection.

To reach Papua New Guinea's isolated forests, researchers had to travel on foot over steep mountains, sometimes using fallen trees to cross crevices that were more than 100 feet deep. There are few roads in the country, which historically posed a challenge to scientists interested in researching the region but has also shielded native plants and animals from human disturbance and habitat destruction.

Slapcinsky took nine trips to Papua New Guinea between 2002 and 2012, each time staying for at least a month to comb through the soil and fallen leaves. He ultimately collected more than 19,000 snails from over 200 sites.

Only 31% of the snail species he surveyed had been previously documented, a sign of Papua New Guinea’s high biodiversity and low levels of sampling. But the snails are also exceptionally hard to find because of their small size, pickiness about their habitats and limited distribution. Nearly all of them are restricted to a single island or mountain.

The newly named snails have tightly coiled, Frisbee-shaped shells in various shades of brown and tan, some with attractive gold or brown flamelike bands.  One of the new species, Torresiropa paterivolans, was named for its resemblance to flying saucers (in Latin, “patera” means “saucer,” and “volans” means “flying”).

All nine species have dagger-shaped teeth on their radula, which is characteristic of predatory snails. Just what they’re eating, Slapcinsky said, is a mystery, since the snails did not eat anything under observation. Still, the shape of the teeth, combined with the fact that other species in the same family — Rhytididae — are predators, suggests that these newly discovered snails do eat meat.

There is not yet enough data to know the conservation status of the new species, but it is a promising sign that their habitat has not yet been dramatically altered by human activity.

Slapcinsky contrasted this with the Hawaiian Islands, where native snails are at imminent risk of extinction. He works with a team at the Bishop Museum in Honolulu that collaborates with the state and federal government on captive breeding programs for native snail colonies, many of which harbor the last members of their species. They also provide native snails for fenced-in areas, known as exclosures, where predators have been removed and the native forest has been replanted. These are expensive programs that Papua New Guinea still has the chance to avoid, Slapcinsky said, by slowing deforestation and preventing the introduction of non-native predators before it becomes a more serious problem.

Snails are highly vulnerable to habitat disturbances because they cannot easily travel long distances and are usually adapted only to the environment in their immediate vicinity. “When these habitats are threatened, snails are often out of luck, since they can’t go anywhere,” Slapcinsky said.

Many past discoveries of new snail species, especially on Pacific islands, have come after it was too late to save them. Scientists did not know that many snails lived on Easter Island, which was completely deforested centuries ago, until examining fossil deposits. But species on the island of New Guinea can still be saved if the forest is saved. The newly named snails provide a rare glimpse at an ecosystem that remains largely intact, and there are surely many similar discoveries yet to be made.

“We don’t know everything that’s out there,” Slapcinsky said. “Most people may not realize how poorly known most of the invertebrates are, even though 95 to 99% of all animals are invertebrates. You can go to a place, look around for a few months and find all sorts of things that haven’t been described before.”

Detailed photos of the snails, while beautiful, also serve a scientific purpose by providing documentation of the species.

CREDIT

Florida Museum photo by Jeff Gage

The country of Papua New Guinea includes the eastern half of the island of New Guinea and several offshore islands.

CREDIT

Florida Museum photo by John Slapcinsky

---

JOURNAL

Archiv für Molluskenkunde

DOI

10.1127/arch.moll/152/135-152 

ARTICLE TITLE

Overlooked predatory snails from Papua New Guinea: nine new Torresiropa Solem, 1959 (Gastropoda: Stylommatophora: Rhytididae)

 

How fruit bats got a sweet tooth without sour health

Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - SAN FRANCISCO

Levi Gadye,
Levi.Gadye@ucsf.edu | @UCSF

Video: https://ucsf.app.box.com/s/i3atd54ye4m1z1spi0qf59axq7tq7640

A high-sugar diet is bad news for humans, leading to diabetes, obesity and even cancer. Yet fruit bats survive and even thrive by eating up to twice their body weight in sugary fruit every day. 
 
Now, UC San Francisco scientists have discovered how fruit bats may have evolved to consume so much sugar, with potential implications for the 37 million Americans with diabetes. The findings, published on Tuesday, Jan. 9, 2024 in Nature Communications, point to adaptations in the fruit bat body that prevent their sugar-rich diet from becoming harmful. 
 
Diabetes is the eighth leading cause of death in the United States, according to the Centers for Disease Control and Prevention, and it’s responsible for $237 billion in direct medical costs each year. 
 
“With diabetes, the human body can’t produce or detect insulin, leading to problems controlling blood sugar,” said Nadav Ahituv, PhD, director of the UCSF Institute for Human Genetics and co-senior author of the paper. “But fruit bats have a genetic system that controls blood sugar without fail. We’d like to learn from that system to make better insulin- or sugar-sensing therapies for people.”  
 
Ahituv’s team focused on evolution in the bat pancreas, which controls blood sugar, and the kidneys. They found that the fruit bat pancreas, compared to the pancreas of an insect-eating bat, had extra insulin-producing cells as well as genetic changes to help it process an immense amount of sugar. And fruit bat kidneys had adapted to ensure that vital electrolytes would be retained from their watery meals.  
 
“Even small changes, to single letters of DNA, make this diet viable for fruit bats,” said Wei Gordon, PhD, co-first author of the paper, a recent graduate of UCSF’s TETRAD program, and assistant professor of biology at Menlo College. “We need to understand high-sugar metabolism like this to make progress helping the one in three Americans who are prediabetic.” 
 
A sweet tooth without consequences 
 
Each day, after 20 hours of sleep, fruit bats wake up for four hours to gorge on fruit. Then it’s back to the roost.  
 
To understand how a fruit bat pulls off this feat of sugar consumption, Ahituv and Gordon collaborated with scientists from a variety of institutions, ranging from Yonsei University in Korea to the American Museum of Natural History in New York City, to compare the Jamaican fruit bat to the big brown bat, which only eats insects.  
 
The researchers analyzed gene expression (which genes were on or off) and regulatory DNA (the parts of DNA that control gene expression) using a method for measuring both in individual cells. 
 
“This newer single-cell technology can explain not only which types of cells are in which organs, but also how those cells regulate gene expression to manage each diet,” Ahituv said. 
 
In fruit bats, the compositions of the pancreas and kidneys evolved to accommodate their diet. The pancreas had more cells to produce insulin, which tells the body to lower blood sugar, as well as more cells to produce glucagon, the other major sugar-regulating hormone. The fruit bat kidneys, meanwhile, had more cells to trap scarce salts as they filter blood.  
 
Zooming in, the regulatory DNA in those cells had evolved to turn the appropriate genes for fruit metabolism on or off. The big brown bat, on the other hand, had more cells for breaking down protein and conserving water. And the gene expression in those cells was tuned to handle a diet of bugs. 
 
“The organization of the DNA around the insulin and glucagon genes was very clearly different between the two bat species,” Gordon said. “The DNA around genes used to be considered ‘junk,’ but our data shows that this regulatory DNA likely helps fruit bats react to sudden increases or decreases in blood sugar.” 
 
While some of the biology of the fruit bat resembled what’s found in humans with diabetes, the fruit bat appeared to evolve something that humans with a sweet tooth could only dream of: a sweet tooth without consequences. 
 
“It’s remarkable to step back from model organisms, like the laboratory mouse, and discover possible solutions for human health crises out in nature,” Gordon said. “Bats have figured it out, and it’s all in their DNA, the result of natural selection.” 
 
Superheroes of evolution 
 
The study benefited from a recent groundswell of interest in studying bats to better human health. Gordon and Ahituv traveled to Belize to participate in an annual Bat-a-Thon with nearly 50 other bat researchers, taking a census of wild bats as well as field samples for science. One of the Jamaican fruit bats captured at this event was used in the sugar metabolism study.  
 
As one of the most diverse families of mammals, bats include many examples of evolutionary triumph, from their immune systems to their peculiar diets and beyond. 
 
“For me, bats are like superheroes, each one with an amazing super power, whether it is echolocation, flying, blood sucking without coagulation, or eating fruit and not getting diabetes,” Ahituv said. “This kind of work is just the beginning.” 
 
Key collaborators included co-first author Seungbyn Baek, PhD, from Yonsei University (South Korea); co-senior author Martin Hemberg, PhD, from Harvard Medical School; Tony Schountz, PhD, from Colorado State University; Lisa Noelle Cooper, PhD, from Northeast Ohio Medical University; Melissa R. Ingala, PhD, Fairleigh Dickinson University; and Nancy B. Simmons, PhD, American Museum of Natural History. Other UCSF authors are Hai P. Nguyen, PhD, Yien-Ming Kuo, PhD, Rachael Bradley, and Sarah L. Fong, PhD. For all authors see the paper. 

 

About UCSF: The University of California, San Francisco (UCSF) is exclusively focused on the health sciences and is dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. UCSF Health, which serves as UCSF's primary academic medical center, includes top-ranked specialty hospitals and other clinical programs, and has affiliations throughout the Bay Area. UCSF School of Medicine also has a regional campus in Fresno. Learn more at https://ucsf.edu, or see our Fact Sheet.

###

 

Follow UCSF
ucsf.edu | Facebook.com/ucsf | YouTube.com/ucsf

 

---

JOURNAL

Nature Communications

 

Orbitally-induced strong monsoons facilitated early human dispersal to East Asia

Peer-Reviewed Publication

CHINESE ACADEMY OF SCIENCES HEADQUARTERS

 

IMAGE: 

FIELD PHOTOGRAPH OF THE HUANXIAN LOESS-PALEOSOL SEQUENCE ON THE CENTRAL CHINESE LOESS PLATEAU

view more 

CREDIT: AO HONG

In a study published in PNAS, researchers have shown that orbitally induced strengthening of the Asian summer monsoon played a key role in the dispersal of Homo sapiens from Africa to East Asia during the last interglacial period 125,000 to 70,000 years ago.

Led by Prof. AO Hong from the Institute of Earth Environment of the Chinese Academy of Sciences (CAS), the researchers integrated a comprehensive compilation of paleoanthropological site data with new high-resolution reconstructions of the Asian summer monsoon based on Chinese loess data, continuous modeling of the East Asian hydroclimate, and a novel human habitat simulation—all covering the past 280,000 years.

How human ancestors responded to past climate change remains a key question in research on human evolution. Climate variability was a key driver of human evolution and dispersal within Africa during the Pleistocene. However, our understanding of the orbital hydroclimatic influence on the early dispersal of our species, Homo sapiens, from Africa to East Asia, is hampered by the lack of integrated paleoclimatic and paleoanthropological studies from Asia. 

To reconstruct orbitally resolved Asian summer monsoon variability over the past 280,000 years, the researchers collected 2,066 samples in the field from the rapidly accumulating Huanxian loess–paleosol section on the central Chinese Loess Plateau for measurements in the laboratory. 

The resulting unprecedented centennial-resolution reconstructions suggest that the orbital-scale variability of the Asian summer monsoon responds to the combined action of changes in insolation (a so-called external forcing, i.e., one coming from outside Earth), and ice volume and greenhouse gas concentration (examples of what we call internal forcings, i.e., those coming from the Earth system), rather than to their individual actions. This argument is strongly supported by AO et al.'s model-based reconstructions of the East Asian hydroclimate over the past 280,000 years.

"When we integrated proxy- and model-based spatiotemporal paleoclimatic reconstructions with paleoanthropological data compilations from Asia across time and space, we found, to our surprise, that H. sapiens dispersed to East Asia at the same time as the Asian summer monsoon was intensified. This suggests an important influence of the paleo-monsoon on the early dispersal of H. sapiens from Africa to East Asia," said Prof. AO, lead author of the study.

"In contrast to the strengthening of the Asian summer monsoon, the climate in much of southeast Africa worsened during the last interglacial. It is possible that these Asian and Southeast African hydroclimate changes acting together spurred the early dispersal of H. sapiens from Africa to East Asia," said Dr. Thibaut Caley, an author of the study and paleoclimatologist from Université de Bordeaux, France. In contrast, the lush vegetation in East Asia at the time would have attracted H. sapiens habitation.

To provide further quantitative evidence of climate effects on H. sapiens dispersal, Dr. RUAN Jiaoyang, corresponding author of the study and assistant researcher at the IBS Center for Climate Physics, South Korea, performed computer simulations of H. sapiens habitats and found that the H. sapiens occupation of East Asia was consistent with a transcontinental increase in simulated habitat suitability.

This study was funded by the Strategic Priority Research Program of CAS, the Second Tibetan Plateau Scientific Expedition and Research Program, and the National Natural Science Foundation of China.

---

JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2308994121 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Concurrent Asian monsoon strengthening and early modern human dispersal to East Asia during the last interglacial

ARTICLE PUBLICATION DATE

8-Jan-2024

Red deer populations in Europe: more influenced by humans than by wolves and other predators

Peer-Reviewed Publication

UNIVERSITY OF FREIBURG

Alongside the occasional bison and elk, red deer are Europe's largest native wild animal. An international study led by wildlife ecologists from the University of Freiburg has now investigated the factors that affect the red deer population in a particular area. The researchers were able to show that the population density of the animals in Europe is primarily influenced by human hunting and land use and not by large predators such as wolves, lynx and brown bears. “While large carnivores are often considered key factors in controlling prey populations in undisturbed ecosystems, this is less visible in human-dominated landscapes. Our study illustrates that these interactions are context-dependent,” says Dr. Suzanne T. S. van Beeck Calkoen, former PhD student at the Chair of Wildlife Ecology and Management at the University of Freiburg and first author of the study.

The researchers collected data on the population density of red deer at over 492 study sites in 28 European countries and analysed the influence of various factors such as habitat productivity, the presence of large carnivores, human activities, climatic variables and the protection status of the area. The evaluation of the data showed that human hunting reduced red deer density more than the presence of all large carnivores. Human land use, on the other hand, led to an increase in red deer density. In most cases, the presence of large carnivores had no statistically significant effect on the red deer population. Only when the three predators wolf, lynx and bear occurred together in one area did the number of red deer decrease. However, the study published in the Journal of Applied Ecology did not investigate how the presence of predators affects the behavior of red deer.

The return of the wolf
The study also sheds new light on the ongoing debate about the return of the wolf to Central Europe, notes Prof. Dr. Marco Heurich, Professor of Wildlife Ecology and Conservation Biology at the Faculty of Environment and Natural Resources at the University of Freiburg and initiator of the study. “Our research shows that the return of a large carnivore such as the wolf alone does not have a major impact on the occurrence of red deer. This is because in Central Europe, human influences predominate both indirectly through interventions in the red deer’s habitat and directly through the killing of the animals.” In addition, the mortality rate of wolves in Central European landscapes is very high, mainly due to road traffic, which further limits their influence on prey populations. “However, we also found a high variability in red deer densities, which indicates that there may be specific situations in which large carnivores do have an impact. Investigating this will be the task of future studies,” states Heurich.

• Original publication: Suzanne T. S. van Beeck Calkoen, Dries P. J. Kuijper, Marco Apollonio, Lena Blondel, Carsten F. Dormann, Ilse Storch, Marco Heurich: “Numerical top-down effects on red deer (Cervus elaphus) are mainly shaped by humans rather than large carnivores across Europe.” In: Journal of Applied Ecology (2023). DOI: 10.1111/1365-2664.14526
• Prof. Dr. Marco Heurich is Professor of Wildlife Ecology and Conservation Biology at the University of Freiburg
• Dr. Suzanne T. S. van Beeck Calkoen completed her doctorate at the Chair of Wildlife Ecology and Management at the University of Freiburg. She is a research associate at the University of Göttingen and the Technical University of Dresden.

Contact:
Office of University and Science Communications
University of Freiburg
Tel.: 0761/203-4302
e-mail: kommunikation@zv.uni-freiburg.de

---

JOURNAL

Journal of Applied Ecology

DOI

10.1111/1365-2664.14526 

 

'Carbon vault' peat suffers greatly from drought

Peer-Reviewed Publication

RADBOUD UNIVERSITY NIJMEGEN

 

IMAGE: 

PEAT BEING TESTED AT RADBOUD UNIVERSITY.

view more 

CREDIT: BJORN ROBROEK, RADBOUD UNIVERSITY

Peatlands are affected more by drought than expected. This is concerning, as these ecosystems are an important ally in the fight against climate change. Following long periods of drought, peat is able to absorb little to no extra carbon (CO2). Increasing biodiversity also does little to make peat more drought-resilient. These are the conclusions drawn by researchers from Radboud University in a publication appearing today in Proceedings of the Royal Society B.

Peat is a vast carbon sink: per square metre it is able to store more CO2 than any other ecosystem in the world. The peatlands of the Netherlands, but also those in places such as Scandinavia and the Baltic states, therefore play an important role in the fight against climate change. However, peat is coming under increasing pressure and is extremely sensitive to the dry summers we are experiencing as a result of climate change. This is what researchers from the Radboud Institute for Biological and Environmental Sciences have concluded.

‘In our lab, under controlled conditions, we first ensured that large blocks of peat were well moistened over a long period of time’, explains lead author Bjorn Robroek. ‘We then slowly dried the peat out. One half was exposed to mild drought, with the water level roughly five centimetres lower than the peat itself. The other half was subjected to extreme drought conditions; in this case the water was twenty centimetres below the peat. This is comparable to a period of three weeks without rain – something that has also become increasingly common in the Netherlands in recent years.’

These experiments revealed that peat exposed to mild drought still absorbs a reasonable amount of carbon. Robroek: ‘Under extreme drought conditions, however, the peat can hardly take on any more carbon. In the event of an extended period of drought it even releases the carbon again.’

Biodiversity

Drought not only affects peatlands, of course. Dry summers have made other ecosystems more fragile too. However, in the case of grasslands, for example, we now have methods to combat problems caused by drought. Increasing the biodiversity in this kind of ecosystem (by incorporating a greater number of different plants), as in the case of the Future Dikes project, keeps the ecosystem healthy and resilient.

Nevertheless, according to Robroek, when it comes to peatlands, improving biodiversity in this way is of little use in terms of tackling drought. ‘The different mosses that we tested in our peat experiments do little to nothing to combat drought. That does not mean that biodiversity is not important for peat: it helps with carbon storage, for example. But in the battle against drought a different approach is needed.’

Politics

There are little things that consumers can do to protect peat. ‘Buy peat-free potting substrate and compost, for example’, cautions Robroek. ‘In the end, however, this is mainly a problem that will have to be solved at political level. In the past the buffer zones alongside rivers often consisted of peatland, but today much of this is grassland intended for agricultural use. These areas are constantly mowed and ploughed and therefore hardly retain any water. As a result, water from these floodplains drains more quickly into the rivers, causing flooding.’

‘Switching over to natural management methods costs time and money, but will have huge benefits in the future. Peatlands, even lowland peat areas, will then retain considerably more water and therefore offer much better protection. You could compare this to a sponge that gradually releases water back to the landscape. In such places peat is also the most effective option when it comes to storing carbon.’

---

JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2023.2622 

ARTICLE TITLE

More is not always better: peat moss mixtures slightly enhance peatland stability

ARTICLE PUBLICATION DATE

10-Jan-2024

 

Climate change behind sharp drop in snowpack since 1980s

Study finds steepest drops in areas of Northern Hemisphere reliant on snow for water

Peer-Reviewed Publication

DARTMOUTH COLLEGE

 

IMAGE: 

EFFECT OF HUMAN-DRIVEN GLOBAL WARMING ON SPRING SNOWPACKS IN NORTHERN HEMISPHERE WATERSHEDS FROM 1981-2020 BY PERCENTAGE OF CHANGE PER DECADE. RED INDICATES A DECREASE AND BLUE INDICATES AN INCREASE. SNOWPACKS IN MANY FAR-NORTH WATERSHEDS INCREASED AS CLIMATE CHANGE LED TO MORE PRECIPITATION THAT FELL AS SNOW. BUT THE LOWER-LATITUDE WATERSHEDS THAT PROVIDE WATER AND ECONOMIC BENEFITS TO NORTHERN POPULATION CENTERS EXPERIENCED THE GREATEST LOSSES.

view more 

CREDIT: JUSTIN MANKIN AND ALEX GOTTLIEB/DARTMOUTH

Snow is one of the most contradictory cues we have for understanding climate change. As in many recent winters, the lack of snowfall in December seemed to preview our global warming future, with peaks from Oregon to New Hampshire more brown than white and the American Southwest facing a severe snow drought.

On the other hand, record blizzards like those in early 2023 that buried California mountain communities, replenished parched reservoirs, and dropped 11 feet of snow on northern Arizona defy our conceptions of life on a warming planet.

Similarly, scientific data from ground observations, satellites, and climate models do not agree on whether global warming is consistently chipping away at the snowpacks that accumulate in high-elevation mountains, complicating efforts to manage the water scarcity that would result for many population centers.

Now, a new Dartmouth study cuts through the uncertainty in these observations and provides evidence that seasonal snowpacks throughout most of the Northern Hemisphere have indeed shrunk significantly over the past 40 years due to human-driven climate change. The sharpest global warming-related reductions in snowpack—between 10% to 20% per decade—are in the Southwestern and Northeastern United States, as well as in Central and Eastern Europe.

The researchers report in the journal Nature that the extent and speed of this loss potentially puts the hundreds of millions of people in North America, Europe, and Asia who depend on snow for their water on the precipice of a crisis that continued warming will amplify.

"We were most concerned with how warming is affecting the amount of water stored in snow. The loss of that reservoir is the most immediate and potent risk that climate change poses to society in terms of diminishing snowfall and accumulation," said first author Alexander Gottlieb, a PhD student in the Ecology, Evolution, Environment and Society graduate program at Dartmouth.

"Our work identifies the watersheds that have experienced historical snow loss and those that will be most vulnerable to rapid snowpack declines with further warming," Gottlieb said. "The train has left the station for regions such as the Southwestern and Northeastern United States. By the end of the 21st century, we expect these places to be close to snow-free by the end of March. We're on that path and not particularly well adapted when it comes to water scarcity."

Water security is only one dimension of snow loss, said Justin Mankin, an associate professor of geography and the paper's senior author.

The Hudson, Susquehanna, Delaware, Connecticut, and Merrimack watersheds in the Northeastern U.S., where water scarcity is not as dire, experienced among the steepest declines in snowpack. But these heavy losses threaten economies in states such as Vermont, New York, and New Hampshire that depend on winter recreation, Mankin said—even machine-made snow has a temperature threshold many areas are fast approaching.

"The recreational implications are emblematic of the ways in which global warming disproportionately affects the most vulnerable communities," Mankin said. "Ski resorts at lower elevations and latitudes have already been contending with year-on-year snow loss. This will just accelerate, making the business model inviable."

"We'll likely see further consolidation of skiing into large, well-resourced resorts at the expense of small and medium-sized ski areas that have such crucial local economic and cultural values. It will be a loss that will ripple through communities," he said.

In the study, Gottlieb and Mankin focused on how global warming's influence on temperature and precipitation drove changes in snowpack in 169 river basins across the Northern Hemisphere from 1981 through 2020. The loss of snowpacks potentially means less meltwater in spring for rivers, streams, and soils downstream when ecosystems and people demand water.

Gottlieb and Mankin programmed a machine learning model to examine thousands of observations and climate-model experiments that captured snowpack, temperature, precipitation, and runoff data for Northern Hemisphere watersheds.

This not only let them identify where snowpack losses occurred due to warming, it also gave them the ability to examine the counteracting influence of climate-driven changes in temperature and precipitation, which decrease and increase snowpack thickness, respectively.

The researchers identified the uncertainties that the models and observations shared so they could home in on what scientists had previously missed when gauging the effect of climate change on snow. A 2021 study by Gottlieb and Mankin similarly leveraged uncertainties in how scientists measure snow depth and define snow drought to improve predictions of water availability.

Snow comes with uncertainties that have masked the effects of global warming, Mankin said. "People assume that snow is easy to measure, that it simply declines with warming, and that its loss implies the same impacts everywhere. None of these are the case," Mankin said.

"Snow observations are tricky at the regional scales most relevant for assessing water security," Mankin said. "Snow is very sensitive to within-winter variations in temperature and precipitation, and the risks from snow loss are not the same in New England as in the Southwest, or for a village in the Alps as in high-mountain Asia."

Gottlieb and Mankin in fact found that 80% of the Northern Hemisphere's snowpacks—which are in its far-northern and high-elevation reaches—experienced minimal losses. Snowpacks actually expanded in vast swaths of Alaska, Canada, and Central Asia as climate change increased the precipitation that falls as snow in these frigid regions.

But it is the remaining 20% of the snowpack that exists around—and provides water for—many of the hemisphere's major population centers that has diminished. Since 1981, documented declines in snowpack for these regions have been largely inconsistent due to the uncertainty in observations and naturally occurring variations in climate.

But Gottlieb and Mankin found that a steady pattern of annual declines in snow accumulation emerge quickly—and leave population centers suddenly and chronically short on new supplies of water from snowmelt.

Many snow-dependent watersheds now find themselves dangerously near a temperature threshold Gottlieb and Mankin call a "snow-loss cliff." This means that as average winter temperatures in a watershed increase beyond 17 degrees Fahrenheit (minus 8 degrees Celsius), snow loss accelerates even with only modest increases in local average temperatures.

Many highly populated watersheds that rely on snow for water supply are going to see accelerating losses over the next few decades, Mankin said.

"It means that water managers who rely on snowmelt can't wait for all the observations to agree on snow loss before they prepare for permanent changes to water supplies. By then, it's too late," he said. "Once a basin has fallen off that cliff, it's no longer about managing a short-term emergency until the next big snow. Instead, they will be adapting to permanent changes to water availability."

###

---

JOURNAL

Nature

DOI

10.1038/s41586-023-06794-y 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Evidence of human influence on Northern Hemisphere snow loss

ARTICLE PUBLICATION DATE

11-Jan-2024