Mathematics predicts a sixth mass extinction

In the past 540 million years, the Earth has endured five mass extinction events, each involving processes that upended the normal cycling of carbon through the atmosphere and oceans. These globally fatal perturbations in carbon each unfolded over thousands to millions of years, and are coincident with the widespread extermination of marine species around the world.

Scientists have analyzed significant changes in the carbon cycle over the last 540 million years, including the five mass 
extinction events. They have identified 'thresholds of catastrophe' in the carbon cycle that, if exceeded, would lead
 to an unstable environment, and ultimately, mass extinction [Credit: MIT]

The question for many scientists is whether the carbon cycle is now experiencing a significant jolt that could tip the planet toward a sixth mass extinction. In the modern era, carbon dioxide emissions have risen steadily since the 19th century, but deciphering whether this recent spike in carbon could lead to mass extinction has been challenging. That's mainly because it's difficult to relate ancient carbon anomalies, occurring over thousands to millions of years, to today's disruptions, which have taken place over just a little more than a century.

Now Daniel Rothman, professor of geophysics in the MIT Department of Earth, Atmospheric and Planetary Sciences and co-director of MIT's Lorenz Center, has analyzed significant changes in the carbon cycle over the last 540 million years, including the five mass extinction events. He has identified "thresholds of catastrophe" in the carbon cycle that, if exceeded, would lead to an unstable environment, and ultimately, mass extinction.

In a paper published in Science Advances, he proposes that mass extinction occurs if one of two thresholds are crossed: For changes in the carbon cycle that occur over long timescales, extinctions will follow if those changes occur at rates faster than global ecosystems can adapt. For carbon perturbations that take place over shorter timescales, the pace of carbon-cycle changes will not matter; instead, the size or magnitude of the change will determine the likelihood of an extinction event.

Taking this reasoning forward in time, Rothman predicts that, given the recent rise in carbon dioxide emissions over a relatively short timescale, a sixth extinction will depend on whether a critical amount of carbon is added to the oceans. That amount, he calculates, is about 310 gigatons, which he estimates to be roughly equivalent to the amount of carbon that human activities will have added to the world's oceans by the year 2100.

Does this mean that mass extinction will soon follow at the turn of the century? Rothman says it would take some time -- about 10,000 years -- for such ecological disasters to play out. However, he says that by 2100 the world may have tipped into "unknown territory."

"This is not saying that disaster occurs the next day," Rothman says. "It's saying that, if left unchecked, the carbon cycle would move into a realm which would be no longer stable, and would behave in a way that would be difficult to predict. In the geologic past, this type of behavior is associated with mass extinction."

History follows theory

Rothman had previously done work on the end-Permian extinction, the most severe extinction in Earth's history, in which a massive pulse of carbon through the Earth's system was involved in wiping out more than 95 percent of marine species worldwide. Since then, conversations with colleagues spurred him to consider the likelihood of a sixth extinction, raising an essential question:

"How can you really compare these great events in the geologic past, which occur over such vast timescales, to what's going on today, which is centuries at the longest?" Rothman says. "So I sat down one summer day and tried to think about how one might go about this systematically."

He eventually derived a simple mathematical formula based on basic physical principles that relates the critical rate and magnitude of change in the carbon cycle to the timescale that separates fast from slow change. He hypothesized that this formula should predict whether mass extinction, or some other sort of global catastrophe, should occur.

Rothman then asked whether history followed his hypothesis. By searching through hundreds of published geochemistry papers, he identified 31 events in the last 542 million years in which a significant change occurred in Earth's carbon cycle. For each event, including the five mass extinctions, Rothman noted the change in carbon, expressed in the geochemical record as a change in the relative abundance of two isotopes, carbon-12 and carbon-13. He also noted the duration of time over which the changes occurred.

He then devised a mathematical transformation to convert these quantities into the total mass of carbon that was added to the oceans during each event. Finally, he plotted both the mass and timescale of each event.

"It became evident that there was a characteristic rate of change that the system basically didn't like to go past," Rothman says.

In other words, he observed a common threshold that most of the 31 events appeared to stay under. While these events involved significant changes in carbon, they were relatively benign -- not enough to destabilize the system toward catastrophe. In contrast, four of the five mass extinction events lay over the threshold, with the most severe end-Permian extinction being the farthest over the line.

"Then it became a question of figuring out what it meant," Rothman says.

A hidden leak

Upon further analysis, Rothman found that the critical rate for catastrophe is related to a hidden process within the Earth's natural carbon cycle. The cycle is essentially a loop between photosynthesis and respiration. Normally, there is a "leak" in the cycle, in which a small amount of organic carbon sinks to the ocean bottom and, over time, is buried as sediment and sequestered from the rest of the carbon cycle.

Rothman found that the critical rate was equivalent to the rate of excess production of carbon dioxide that would result from plugging the leak. Any additional carbon dioxide injected into the cycle could not be described by the loop itself. One or more other processes would instead have taken the carbon cycle into unstable territory.

He then determined that the critical rate applies only beyond the timescale at which the marine carbon cycle can re-establish its equilibrium after it is disturbed. Today, this timescale is about 10,000 years. For much shorter events, the critical threshold is no longer tied to the rate at which carbon is added to the oceans but instead to the carbon's total mass. Both scenarios would leave an excess of carbon circulating through the oceans and atmosphere, likely resulting in global warming and ocean acidification.

The century's the limit

From the critical rate and the equilibrium timescale, Rothman calculated the critical mass of carbon for the modern day to be about 310 gigatons.

He then compared his prediction to the total amount of carbon added to the Earth's oceans by the year 2100, as projected in the most recent report of the Intergovernmental Panel on Climate Change. The IPCC projections consider four possible pathways for carbon dioxide emissions, ranging from one associated with stringent policies to limit carbon dioxide emissions, to another related to the high range of scenarios with no limitations.

The best-case scenario projects that humans will add 300 gigatons of carbon to the oceans by 2100, while more than 500 gigatons will be added under the worst-case scenario, far exceeding the critical threshold. In all scenarios, Rothman shows that by 2100, the carbon cycle will either be close to or well beyond the threshold for catastrophe.

"There should be ways of pulling back [emissions of carbon dioxide]," Rothman says. "But this work points out reasons why we need to be careful, and it gives more reasons for studying the past to inform the present."

Author: Jennifer Chu | Source: Massachusetts Institute of Technology [September 20, 2017]

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New study switches from genetic to metabolic analysis to reconstitute evolutionary process

A new method for analyzing a living being chemical compositions is tested in Andean plants and attest the genesis of species by means of geographic isolation. Scientists analyzed chemical compounds which express specific biogeographic trends in the evolutionary process, validating a Smithsonian hypothesis on the evolution of the genus Espeletia in the process.

A new method for analyzing a living being chemical compositions is tested in Andean plants and attest the genesis 
of species by means of geographic isolation [Credit: Frederico Padilla]

With 72 species currently identified, Espeletia is a plant genus endemic to the paramo, a moist alpine biome unique to the northern Andes. This genus, which inhabits the world's most diverse high-altitude ecosystem, is considered an outstanding example of adaptive success.

Brazilian scientists investigated over Espeletia's diversity and geographic distribution in the paramo; the result, published in Scientific Reports, suggests that researchers might reconstitute more accurately the whole speciation process making use of a relatively unexplored bias in the study of evolutionary science: metabolomics.

Metabolomics refers to an area of study focusing on the chemical substances synthesized by a living organism -- a byproduct of its metabolism -- which is used to map chemical compounds inherent to a given species. In order to do so, a combination of techniques involving plant extracts, geographic data, and multivariate statistics is required. Studies of this kind are usually based on genomics, DNA marker analysis or morphological comparisons.

Researchers at the University of Sao Paulo's School of Pharmaceutical Sciences -- Ribeirao Preto campus (FCFRP-USP), in Brazil, use metabolic fingerprinting for the first time to explain the evolutionary histories and biogeographic characteristics of Espeletia.

"Basically, we took the chemical compositions of the species of Espeletia and their metabolome and found a correlation with their geographic origins. Species present in the same locations display similar chemical profiles. The same link had already been found using molecular markers but on a larger geographic scale. This shows that the geography of the Andes not only determined the evolution of this plant group, and possibly of other plant groups in the region but also shaped the chemical compositions of these species," said Federico Padilla, one of the authors of the article.

Based on a study supported by Sao Paulo Research Foundation (FAPESP) through regular research grant, the article confirms a hypothesis on the origin and migration routes of Espeletia along the northern Andes proposed by researchers at the US National Museum of Natural History, part of the Smithsonian Institution, in the 1990s, which was hitherto partially supported by molecular markers.

According to this hypothesis, the original stock of Espeletia diversified when the first population of the genus started expanding in two directions from the western part of the Cordillera de Merida, the largest massif in Venezuela. One branch moved along the Venezuelan Andes, while the other moved west and southwest along the Colombian Andes and into northern Ecuador.

"Historically, this kind of analysis has been based on molecular markers. However, genetic analysis is unable to determine specific biogeographic trends with satisfactory precisions in groups that have evolved recently, such as the genus Espeletia, for which it merely identifies two groups, the Venezuelan and Colombian species, " Padilla said.

Metabolites data point evolutionary adaptation

The Smithsonian hypothesis was confirmed by an analysis of the secondary metabolites (i.e., the chemical compounds involved in plants' adaptations to the ecosystem), which pointed to patterns of geographic distributions and chemical diversifications in the Andean paramos.

"Each kind of marker has advantages and disadvantages," said Professor Fernando Batista da Costa , Padilla's supervisor and a co-author of the article published in Scientific Reports. "Unlike animals, plants can't move in order to adapt to this or that environment. Instead, they produce a vast array of chemical compounds that help them adapt to the place where they grow."

The rugged topography of the Andes makes the paramo a highly fragmented biome, biologically and geographically comparable to an archipelago in which "islands" of open grassland vegetation are separated by dense forests or deep valleys that prevent plant species from communicating with other paramos.

According to the article, this geographic isolation is a particularly influential factor for species with limited seed dispersal and a lack of long-distance pollinators, as is the case for Espeletia.

"We prove that their isolation favored allopatric speciation, meaning speciation occurring in separate regions because of geographic barriers. Darwin proposed this kind of speciation in his evolutionary theory as a result of his observations in the Galapagos Archipelago. He saw there that different islands had different species and that these species were related to each other," Batista da Costa said.

The researchers' analyses of the chemical compositions showed that species of Espeletia in different paramos differ not only genetically and morphologically but also chemically.

"In each paramo, most species accumulate different chemical compounds that may possibly be linked to their adaptation to that particular geographic area," Padilla said. "We demonstrate, using chemical evidence, that allopatric speciation occurred in these paramos and groups of species, as had been proposed in the 1990s."

Application of metabolomics in other areas

According to the researchers, this approach can be used to study practically all of a plant's metabolites at the same time.

"In classical phytochemistry, we studied one plant at a time and usually identified a few chemical substances," Padilla said. "With the new techniques and equipment, such as the liquid chromatography coupled with mass spectrometry that we used, we can now assemble 100 or more plant extracts, analyze them all at the same time, and obtain a data matrix potentially representing more than 1,000 chemical compounds."

The researchers stress that analogous models to that described in the article can be used to obtain metabolic fingerprints for other plants with the aim of analyzing their biogeographic and evolutionary histories.

"This new model can be used in agriculture, or for medicinal plants, or even by the police, for example, to identify the origin of marijuana consumed in a particular region," said Batista.

Source: Fundação de Amparo à Pesquisa do Estado de São Paulo [September 19, 2017]

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When it comes to the threat of extinction, size matters

Animals in the Goldilocks zone -- neither too big, nor too small, but just the right size -- face a lower risk of extinction than do those on both ends of the scale, according to an extensive global analysis.

Extinction risks are greater for animals at the small and large ends of the scale 
[Credit: Oliver Day, Oregon State University]

Reporting today in the Proceedings of the National Academy of Sciences, researchers who determined body masses for thousands of vertebrate animal species showed that the largest and smallest species face a greater risk of extinction than do mid-sized animals.

Disproportionate losses at the large and small ends of the scale raise the likelihood of significant changes to the way natural ecosystems function in forests, grasslands, oceans and even rivers and streams -- "the living architecture of the planet," the researchers wrote.

"Knowing how animal body size correlates with the likelihood of a species being threatened provides us with a tool to assess extinction risk for the many species we know very little about," said William Ripple, a distinguished professor of ecology at Oregon State University and lead author of the study.

Ripple and colleagues from the United States, Australia and Switzerland looked at the more than 27,000 vertebrate animal species assessed by the International Union for the Conservation of Nature in the so-called Red List. About 4,400 are threatened with extinction.

Among the groups of animals evaluated were birds, reptiles, amphibians, bony fishes, cartilaginous fishes (mostly sharks and rays) and mammals.

The largest animals are threatened principally with harvesting by humans. "Many of the larger species are being killed and consumed by humans, and about 90 percent of all threatened species larger than 2.2 pounds (1 kilogram) in size are being threatened by harvesting," said Ripple.

"Harvesting of these larger animals takes a variety of forms including regulated and unregulated fishing, hunting and trapping for meat consumption, the use of body parts as medicine and killing due to unintentional bycatch," the authors wrote.

Meanwhile, threats to the smallest animals may be grossly underestimated. The smallest species with high extinction risk consist of tiny vertebrate animals generally less than about 3 ounces (77 grams) in body weight. These diminutive species are mostly threatened by loss or modification of habitat. Examples include the Clarke's banana frog, sapphire-bellied hummingbird, gray gecko, hog-nosed bat and the waterfall climbing cave fish. Small species that require freshwater habitats are especially imperiled.

Different conservation strategies will be needed to address threats to the largest and smallest animals, the scientists said. Well known mammals at the large end of the scale -- whales, elephants, rhinos, lions -- have been the target of protection programs, but conservation attention is also needed for large-bodied species that are not mammals. They include large fish, birds, amphibians and reptiles such as the whale shark, Atlantic sturgeon, Somali ostrich, Chinese giant salamander and the Komodo dragon.

Human activity seems poised to chop off both the head and tail of the size distribution of life, the authors added, which will fundamentally restructure many ecological communities.

Source: Oregon State University [September 18, 2017]

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Old fish few and far between under fishing pressure

Like old-growth trees in a forest, old fish in the ocean play important roles in the diversity and stability of marine ecosystems. Critically, the longer a fish is allowed to live, the more likely it is to successfully reproduce over the course of its lifetime, which is particularly important in variable environmental conditions.

A large, old yelloweye rockfish [Credit: Victoria O'Connell]

A new study by University of Washington scientists has found that, for dozens of fish populations around the globe, old fish are greatly depleted -- mainly because of fishing pressure. The paper, published in Current Biology, is the first to report that old fish are missing in many populations around the world.

"From our perspective, having a broad age structure provides more chances at getting that right combination of when and where to reproduce," said lead author Lewis Barnett, a UW postdoctoral researcher at the School of Aquatic and Fishery Sciences and the Joint Institute for the Study of the Atmosphere and Ocean.

In forestry, a tree farm with only 20-year-old trees may be healthy and productive, but the loss of old-growth trees should not go unnoticed. The giant trees have unique traits that support a number of animal and plant species and make for a diverse, robust ecosystem. In a similar sense, the same is true for old fish.

"More age complexity among species can contribute to the overall stability of a community," Barnett said. "If you trim away that diversity, you're probably reducing the marine food web's ability to buffer against change."

The designation of an "old fish" varies from species to species, depending on life history. Some types of rockfish might live to 200 years, while few herring live past age 10.

After female fish release eggs, many factors must align for a healthy brood to hatch and grow to adult size. Because the marine environment is so variable, species might go a whole decade between successful broods. Older fish in a population have more years to produce eggs, increasing the chance for success over time.

The face of an old halibut fish [Credit: Andrea Pokrzywinski]

"In the marine world, the success rate of producing new baby fish is extremely variable," said co-author Trevor Branch, a UW associate professor of aquatic and fishery sciences. "I think of old fish as an insurance policy -- they get you through those periods of bad reproduction by consistently producing eggs."

In addition to having more opportunities to reproduce, older fish also behave differently than younger fish. As they age, some fish change what they eat and where they live in the ocean. They also take on different roles in the marine food web, sometimes becoming a more dominant predator as they get older, and bigger.

When you take old fish out of the mix, the diversity and stability of an ecosystem can suffer, the authors explain.

"Big fish are in a lot of ways different from smaller fish," said co-author Tim Essington, a UW professor of aquatic and fishery sciences. "Having that diversity acts as a hedge against risk and helps stabilize the system a bit."

The researchers looked at model output gathered from commercial and recreational fisheries and scientific observations that describe the status of fish populations over the years. In their analysis of 63 populations living in five ocean regions worldwide, they found that the proportion of fish in the oldest age classes has declined significantly in 79 to 97 percent of populations, compared with historical fishing trends or unfished figures, respectively. The magnitude of decline was greater than 90 percent in 32 to 41 percent of the groups.

This is mainly due to fishing pressure, the researchers say. In general, the longer a fish lives, the more encounters it has with fishing gear, and the greater the likelihood it will be caught. However, some environmental factors like disease and pollution might also contribute to the loss of old fish.

These findings could inform fisheries management, which often sets limitations based on the total weight of fish caught over a season without considering factors such as the size or age of a fish. The authors suggest fishing methods to protect young and old fish by prohibiting the harvest of fish below and above a specific size range. Other solutions include closing certain areas to fishing permanently, or rotating areas where fishing can take place each year to let fish grow older and bigger -- similar to agricultural crop rotations that allow the soil to recover between planting cycles.

Author: Michelle Ma | Source: University of Washington [September 14, 2017]

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Earth's oldest trees in climate-induced race up the tree line

Bristlecone pine and limber pine trees in the Great Basin region are like two very gnarled, old men in a slow-motion race up the mountaintop, and climate change is the starting gun, according to a study from the University of California, Davis.

Gnarled, dead bristlecone pine trees, which can live more than 5,000 years, stand where young limber pine grow 
around them. Limber pine is beginning to colonize areas of the Great Basin once dominated by bristlecones 
[Credit: Brian Smithers/UC Davis]

The study, published in the journal Global Change Biology, shows that the tree line has been steadily moving upslope over the past 50 years in the Great Basin. The region extends from California's Sierra Nevada, across Nevada to Utah's Uinta Mountains. Its north and south are framed by the Columbia and Colorado rivers' watersheds.

The study also found that limber pine is successfully "leapfrogging" over bristlecone pine. They are growing in soils once almost completely dominated by bristlecone pine, and they are moving upslope at a faster rate than the bristlecone pine.

Charging upslope

"We are seeing very little regeneration anywhere in bristlecone ranges except in the tree line and, there, limber pine is taking all the good spots," said the study's corresponding author Brian Smithers, a Ph.D. candidate in the Department of Plant Sciences at UC Davis. "It's jarring because limber pine is a species you normally see further downslope, not at tree line. So it's very odd to see it charging upslope and not see bristlecone charging upslope ahead of limber pine, or at least with it."

Dead bristlecone pines stand among limber pine trees on the California side of the White Mountains, 
part of the Great Basin region [Credit: Brian Smithers/UC Davis]

The study concludes that if bristlecone pine trees are unable to advance upslope because they are blocked by limber pine, bristlecones could face a reduction of their range and possibly local extinctions.

Earth’s oldest living trees

Bristlecone pine trees are Earth's oldest individual trees and can live for more than 5,000 years. No spring chicken, limber pine trees can live 2,000 years or more.

Both tree species have seen many climate changes during their time on Earth -- from extremely warm periods to ice ages -- and have slowly advanced across the landscape. Over millennia, bristlecone pine trees have moved from the lowlands of the Great Basin up to the current tree line. But, the study notes, neither bristlecone nor limber pine have ever experienced climate change and temperature increases as rapidly as what has been occurring in recent decades.

Bristlecone pine trees grow on soils and in conditions where few other species can live. But limber pines in the 
Great Basin region, such as California’s White Mountains, are beginning to give them some competition 
[Credit: Brian Smithers/UC Davis]

Legacy effects

Smithers said he doesn't expect bristlecone pine adult trees to be impacted much by current climatic shifts, as those trees are well-established. But how, if and where new bristlecone pine trees will regenerate is less certain, particularly as other species like limber pine take up valuable space for them to germinate.

"The things we're doing today have legacy effects for thousands of years in the Great Basin," Smithers said. "When those trees do start to die, they won't likely be replaced because it's just too hot and dry."

The study suggests that land managers identify the specific bottlenecks for a species to live long enough to reproduce, and focus on that stage. For long-lived trees like bristlecone and limber pines, the bottleneck is at the time of their initial establishment, not hundreds and thousands of years into their adulthoods.

Author: Kat Kerlin | Source: University of California - Davis [September 14, 2017]

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Climate change challenges the survival of fish across the world

Climate change will force many amphibians, mammals and birds to move to cooler areas outside their normal ranges, provided they can find space and a clear trajectory among our urban developments and growing cities. But what are the chances for fish to survive as climate change continues to warm waters around the world?

Fish species in many river systems, including the John Day River pictured, will face the challenge of coping 
with warmer waters in the future [Credit: University of Washington]

University of Washington researchers are tackling this question in the first analysis of how vulnerable the world's freshwater and marine fishes are to climate change. Their paper, appearing online in Nature Climate Change, used physiological data to predict how nearly 3,000 fish species living in oceans and rivers will respond to warming water temperatures in different regions.

"Climate change is happening. We need tools to try to identify areas that are going to be the most at risk and try to develop plans to conserve these areas," said lead author Lise Comte, a postdoctoral researcher in the UW's School of Aquatic and Fishery Sciences. "It's important to look at the organisms themselves as we cannot just assume they will all be equally sensitive to these changes."

The researchers compiled data from lab experiments involving nearly 500 fish species, conducted over the past 80 years by researchers around the world. These standardized experiments measure the highest temperatures fish are able to tolerate before they die. This analysis is the first time these disparate data from lab experiments have been combined and translated to predict how fish will respond in the wild.

The researchers found that overall, sensitivity to temperature changes varied greatly between ocean-dwelling and freshwater fish. In general, marine fish in the tropics and freshwater fish in higher latitudes of the Northern Hemisphere were the most at risk when water temperatures warmed, the analysis showed.

This figure shows the risk that freshwater fish (top) and marine fish (bottom) could exceed their thermal limits 
by the year 2070. Blue indicates a low risk and red shows a high risk [Credit: University of Washington]

"Nowhere on Earth are fish spared from having to cope with climate change," said senior author Julian Olden, a UW professor of aquatic and fishery sciences. "Fish have unique challenges -- they either have to make rapid movements to track their temperature requirements, or they will be forced to adapt quickly."

Using years of data -- and relying on the fact that many fish species are taxonomically related and tend to share the same thermal limits -- the researchers were able to predict the breaking-point temperature for close to 3,000 species. Regional patterns then emerged when those data were paired with climate-model data predicting temperature increases under climate change.

For example, fish in the tropical oceans are already living in water that is approaching the upper range of their tolerance. They might not have much wiggle room when temperatures increase slightly. By contrast, in freshwater streams in the far north, fish are accustomed to cooler water temperatures but have much less tolerance for warming waters. Since the effects of climate change are acutely felt in high latitudes, this doesn't bode well for fish in those streams that have a small window for survivable temperatures.

Fish will either migrate, adapt or die off as temperatures continue to warm, the researchers explained. Given past evolutionary rates of critical thermal limits, it's unlikely that fish will be able to keep up with the rate at which temperatures are increasing, Olden said. The ability to move, then, is imperative for fish that live in the most critical areas identified in this analysis.

Currently, dams and other infrastructure may block fish from getting where they might need to be in the future; fish ladders and other means to allow fish to circumvent these barriers could be more readily used, although the effectiveness of these structures is highly variable.

Additionally, actions to restore vegetation along the edges of streams and lakes can help shade and reduce water temperature for the benefit of fish.

"Fishes across the world face mounting challenges associated with climate change," Olden said. "Looking forward, continued efforts to support conservation strategies that allow species to respond to these rapid changes are needed."

Author: Michelle Ma | Source: University of Washington [September 13, 2017]

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Study: Asia's glaciers face massive melt from global warming

Scientists say one-third of the ice stored in Asia's glaciers will be lost by the end of the century even if the world manages to meet its ambitious goal of keeping global warming below 1.5 degrees Celsius, affecting water supplies for millions of people on the continent.

International trekkers pass through a glacier at the Mount Everest base camp, Nepal. Scientists say a third of the ice stored 
in Asia’s glaciers will be lost by the end of the century even if global warming stays below 1.5 degrees Celsius 
[Credit: AP/Tashi Sherpa]

In a paper published in the journal Nature, researchers in the Netherlands also examined what would happen if average global temperatures rise beyond 1.5 degrees Celsius (2.7 degrees Fahrenheit) by the end of the century. They concluded that almost two-thirds of the ice in Asia's glaciers could vanish, if no effort is made to curb climate change.

"In regions where glacier melt water is an important part of the river flow, the retreating glaciers can become a problem," Philip Kraaijenbrink, a University of Utrecht geographer who led the study, said.

"There are many people living in basins that have their rivers originating in Asia's high mountains, such as the Indus, Ganges and Brahmaputra," Kraaijenbrink said. "In these basins, the river water is used for irrigation of cropland, drinking water and for hydropower dams."

The 1.5-degree target was set at the international climate conference in Paris two years ago, but experts say it would require a massive shift to the world economy.

In total, the researchers compared 110 climate simulations and found that high mountain glaciers in Asia tended to experience greater levels of warming than the global average. All glaciers analyzed already are losing mass except those in the Kunlun Mountains of western China.

A Kashmiri nomad tends to his heard of sheep and goats as he crosses a glacier near Dubgan, 70 kilometers (43 miles) 
south of Srinagar, India. Scientists say a third of the ice stored in Asia’s glaciers will be lost by the end of the century
 even if global warming stays below 1.5 degrees Celsius. Bakarwals are nomadic herders of India's Jammu-Kashmir 
state who wander in search of good pastures for their cattle. Every year in April-May more than one hundred thousand 
people from the nomadic Bakarwal tribes arrive in the meadows of Kashmir and parts of Ladakh from areas of the
 Jammu region with their flocks of cattle and sheep. After crossing snowy mountains with their cattle and belongings, 
Kashmir valley's lush green meadows become their home from April to September, after which they begin their 
return journey. This seasonal shifting of "homes" ensures a regular flow of income for the families 
[Credit: AP/Dar Yasin]

Taking into account the effect on melting levels of rubble covering some of the glaciers, they concluded that the amount of ice lost from Asian glaciers is almost proportional to the amount of warming they experience, though with some regional variations.

"Even if temperatures stabilize at their current level, mass loss will continue for decades to come until a new equilibrium is reached," the researchers said.

Kraaijenbrink acknowledged that a scenario in which global warming remains under 1.5 degrees Celsius is optimistic.

"We are aware that more extreme, business-as-usual scenarios are possibly a more likely future," he said.

In a comment published along with the study, J. Graham Cogley of Trent University in Canada said the researchers' glacier model "has some innovative features that might raise eyebrows among glaciologists, but it is difficult to find fault with it as a pioneering effort."

"The authors have shown that achieving the 1.5 Celsius target will conserve a substantial fraction of Asia's water resources and that, if we fail in this regard, we will pay in direct proportion to the extent of the failure," Cogley said.

Author: Frank Jordans | Source: The Associated Press [September 13, 2017]

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Cold region 'tipping point' now inevitable

The decline of cold regions called periglacial zones is now inevitable due to climate change, researchers say.

Intense soil frost churning at Kilpisjarvi, northwestern Finland, at 800 metres above sea level 
[Credit: uha Aalto]

Periglacial zones, where there is often a layer of frozen ground known as permafrost, make up about a quarter of Earth's land surface and are mostly found in the far north and south, and at high altitudes.

Scientists from the universities of Exeter and Helsinki and the Finnish Meteorological Institute examined natural processes caused by frost and snow which take place in these zones.

Their findings suggest that -- even with optimistic estimates of future carbon emissions -- areas covered by periglacial zones will reduce dramatically by 2050, and they will "almost disappear" by 2100.

This would have a major impact on landscapes and biodiversity, and could trigger climate "feedbacks" -- processes that can amplify or diminish the effects of climate change.

"The results suggest that profound changes can be expected in current periglacial zones regardless of climate change mitigation policies," said Dr Juha Aalto, of the University of Helsinki and the Finnish Meteorological Institute.

"Unfortunately, it seems that many of the frost-driven processes we studied are already at the margin of the climate in which they can exist."

The scientists studied four processes which take place in periglacial zones, including snow accumulation sites and "frost churning" -- which refers to mixing of materials caused by freezing and thawing.

"Our results forecast a future tipping point in the operation of these processes, and predict fundamental changes in ground conditions and related atmospheric feedbacks," Dr Aalto added.

Dr Stephan Harrison, of the University of Exeter's Penryn Campus in Cornwall, said: "The project used very high-resolution climate and land surface models to demonstrate that geological processes and ecosystems in high latitudes (the far north and south) will be fundamentally altered by climate change during this century."

Even based on the optimistic RCP2.6 estimate for future carbon emissions, the researchers predict a 72% reduction in the current periglacial zone in the area of northern Europe they studied.

By 2100, periglacial zones in will only exist in high mountain regions, they say.

Professor Miska Luoto, of the University of Helsinki, said: "The anticipated changes in land surface processes can feedback to the regional climate system via alterations in carbon cycle and ground surface reflectance (light reflected by snow and ice) caused by the increase of shrub vegetation to alpine tundra.

"Our results indicate significant changes in Northern European plant life. Many rare species can only be sustained in areas of intense frost activity or late-lying snow packs, so the disappearance of such unique environments will reduce biodiversity."

The paper is published in the journal Nature Communications.

Source: University of Exeter [September 11, 2017]

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