Behind the iron curtain: How methane-making microbes kept the early Earth warm

For much of its first two billion years, Earth was a very different place: oxygen was scarce, microbial life ruled, and the sun was significantly dimmer than it is today. Yet the rock record shows that vast seas covered much of the early Earth under the faint young sun.

Tiny incubators were used to simulate early Earth conditions, tracking microbial diversity and methane emissions 
over a period of 500 days [Credit: Rob Felt, Georgia Tech]

Scientists have long debated what kept those seas from freezing. A popular theory is that potent gases such as methane -- with many times more warming power than carbon dioxide -- created a thicker greenhouse atmosphere than required to keep water liquid today.

In the absence of oxygen, iron built up in ancient oceans. Under the right chemical and biological processes, this iron rusted out of seawater and cycled many times through a complex loop, or "ferrous wheel." Some microbes could "breathe" this rust in order to outcompete others, such as those that made methane. When rust was plentiful, an "iron curtain" may have suppressed methane emissions.

"The ancestors of modern methane-making and rust-breathing microbes may have long battled for dominance in habitats largely governed by iron chemistry," said Marcus Bray, a biology Ph.D. candidate in the laboratory of Jennifer Glass, assistant professor in the Georgia Institute of Technology's School of Earth and Atmospheric Sciences and principal investigator of the study funded by NASA's Exobiology and Evolutionary Biology Program. The research was reported in the journal Geobiology.

Using mud pulled from the bottom of a tropical lake, researchers at Georgia Tech gained a new grasp of how ancient microbes made methane despite this "iron curtain."

Collaborator Sean Crowe, an assistant professor at the University of British Columbia, collected mud from the depths of Indonesia's Lake Matano, an anoxic iron-rich ecosystem that uniquely mimics early oceans. Bray placed the mud into tiny incubators simulating early Earth conditions, and tracked microbial diversity and methane emissions over a period of 500 days. Minimal methane was formed when rust was added; without rust, microbes kept making methane through multiple dilutions.

Extrapolating these findings to the past, the team concluded that methane production could have persisted in rust-free patches of ancient seas. Unlike the situation in today's well-aerated oceans, where most natural gas produced on the seafloor is consumed before it can reach the surface, most of this ancient methane would have escaped to the atmosphere to trap heat from the early sun.

Author: John Toon | Source: Georgia Institute of Technology [April 17, 2017]

byUnknown

in Ancient Environment, Climate Change, Earth Science, Palaeontology

April 17, 2017

Behind the iron curtain: How methane-making microbes kept the early Earth warm

For much of its first two billion years, Earth was a very different place: oxygen was scarce, microbial life ruled, and the sun was signific...

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Retreating Yukon glacier caused a river to disappear

The massive Kaskawulsh Glacier in northern Canada has retreated about a mile up its valley over the past century.

A Sept. 2, 2016 aerial photo shows the meltwater stream along the toe of Kaskawulsh Glacier, seen on the left, that is 
diverting fresh water from one river to the other [Credit: Dan Shugar/University of Washington Tacoma]

Last spring, its retreat triggered a geologic event at relatively breakneck speed. The toe of ice that was sending meltwater toward the Slims River and then north to the Bering Sea retreated so far that the water changed course, joining the Kaskawulsh River and flowing south toward the Gulf of Alaska.

This capture of one river's flow by another, documented in a study led by the University of Washington Tacoma and published in Nature Geoscience, is the first known case of "river piracy" in modern times. "Geologists have seen river piracy, but nobody to our knowledge has documented it happening in our lifetimes," said lead author Dan Shugar, a geoscientist at the University of Washington Tacoma. "People had looked at the geological record -- thousands or millions of years ago -- not the 21st century, where it's happening under our noses."

River piracy, also known as stream capture, can happen due to tectonic motion of Earth's crust, landslides, erosion or, in this case, changes in a glacial dam. The new study documents one of the less-anticipated shifts that can occur in a changing climate.

Shugar and co-authors Jim Best at the University of Illinois and John Clague at Canada's Simon Fraser University had planned fieldwork last summer on the Slims River, a geologically active system that feeds Kluane Lake in the Yukon. When they arrived in August, the river was not flowing. River gauges show an abrupt drop over four days from May 26 to 29, 2016.

By late summer, "there was barely any flow whatsoever. It was essentially a long, skinny lake," Shugar said. "The water was somewhat treacherous to approach, because you're walking on these old river sediments that were really goopy and would suck you in. And day by day we could see the water level dropping."

Images captured by the European Space Agency’s Sentinel2 satellite in 2015 and 2016 show a dramatic drop in the Slims 
River’s flow. The receding toe of Kaskawulsh Glacier is seen at the bottom. Kluane Lake can be seen at the top of the 
2016 image. Water now flows east and then south via the Kaskawulsh River [Credit: European Space Agency]

The research team puzzled about what to do next. They got permission to use their mapping drone to create a detailed elevation model of the glacier tongue and headwater region. The resulting paper is a geological postmortem of the river's disappearance.

"For the last 300 years, Slims River flowed out to the Bering Sea, and the smaller Kaskawulsh River flowed to the Gulf of Alaska. What we found was the glacial lake that fed Slims River had actually changed its outlet," Shugar said. "A 30-meter (100-foot) canyon had been carved through the terminus of the glacier. Meltwater was flowing through that canyon from one lake into another glacial lake, almost like when you see champagne poured into glasses that are stacked in a pyramid."

That second lake drains via the Kaskawulsh River in a different direction than the first. The situation is fairly unique, Shugar said, since the glacier's toe was sitting on a geologic divide.

Clague began studying this glacier years ago for the Geological Survey of Canada. He observed that Kluane Lake, which is Yukon's largest lake, had changed its water level by about 40 feet (12 meters) a few centuries ago. He concluded that the Slims River that feeds it had appeared as the glacier advanced, and a decade ago predicted the river would disappear again as the glacier retreated.

"The event is a bit idiosyncratic, given the peculiar geographic situation in which it happened, but in a broader sense it highlights the huge changes that glaciers are undergoing around the world due to climate change," Clague said.

A close-up view of the ice-walled canyon at the terminus of the Kaskawulsh Glacier, with recently collapsed ice blocks. 
This canyon now carries almost all meltwater from the toe of the glacier down the Kaskawulsh Valley 
and toward the Gulf of Alaska [Credit: Jim Best/University of Illinois]

The geologic event has redrawn the local landscape. Slims River crosses the Alaska Highway, and its banks were a popular hiking route. Now that the riverbed is exposed, Dall sheep from Kluane National Park are making their way down to eat the fresh vegetation, venturing into territory where they can legally be hunted. With less water flowing in, Kluane Lake did not refill last spring, and by summer 2016 was about 3 feet (1 meter) lower than ever recorded for that time of year. Waterfront land, which includes the small communities of Burwash Landing and Destruction Bay, is now farther from shore. As the lake level continues to drop researchers expect this will become an isolated lake cut off from any outflow.

On the other hand, the Alsek River, a popular whitewater rafting river that is a UNESCO world heritage site, was running higher last summer due to the addition of the Slims River's water.

Shifts in sediment transport, lake chemistry, fish populations, wildlife behavior and other factors will continue to occur as the ecosystem adjusts to the new reality, Shugar said.

"So far, a lot of the scientific work surrounding glaciers and climate change has been focused on sea-level rise," Shugar said. "Our study shows there may be other underappreciated, unanticipated effects of glacial retreat."

The Kaskawulsh Glacier is retreating up the valley because of both readjustment after a cold period centuries ago, known as the Little Ice Age, and warming due to greenhouse gases. A technique published in 2016 by UW co-author Gerard Roe shows a 99.5 percent probability that this glacier's retreat is showing the effects of modern climate change.

"I always point out to climate-change skeptics that Earth's glaciers are becoming markedly smaller, and that can only happen in a warming climate," Clague said.

Source: University of Washington [April 17, 2017]

byUnknown

in Canada, Climate Change, Ecosystems, Natural Heritage, North America

April 17, 2017

Retreating Yukon glacier caused a river to disappear

The massive Kaskawulsh Glacier in northern Canada has retreated about a mile up its valley over the past century. A Sept. 2, 2016 aerial pho...

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Stalagmites store paleoclimate data

The North Atlantic Oscillation (NAO) is the dominant atmospheric pressure mode over the North Atlantic that plays a significant role in determining the winter climate in Europe.

Zoolithen Cave in Burggaillenreuth with flowstones, stalactites, and stalagmites
[Credit: Jasper Wassenburg]

Depending on the prevailing state of the NAO, Europe experiences mild or very cold winters and even strong storms. Geoscientists based at Johannes Gutenberg University Mainz (JGU) in Germany are currently reconstructing the fluctuations of the NAO over the last 10,000 years with the aim of being able to predict future developments.

For this purpose, they use stalagmites obtained from subterranean caves as natural climate archives and are examining new indicators of climate change to retrieve climate information that is as accurate as possible. Initial results indicate that it is likely that the NAO will respond to the melting of the Arctic ice cap in the future, with consequences for our climate, environment, and society as a whole.

Dr. Jasper Wassenburg works with stalagmites from caves in the Middle Atlas, a mountain range in the northwest of Morocco. Stalagmites are calcium carbonate deposits that grow from the floor of a cave upwards due to precipitation of calcium carbonate minerals deposited from the dripwater. Calcite is the most common form of calcium carbonate although in some cases it can also be aragonite. "Aragonite, if well preserved, can be dated with remarkable precision. So we prefer aragonite stalagmites over calcitic ones," explained Wassenburg, who is a member of the research team headed by Professor Denis Scholz at the Institute of Geosciences at Mainz University.

The incorporation of chemical elements in speleothems, which is the term scientists use for the secondary mineral deposits in caves, is often depending on changes in the environment. These elements are known as climate proxies because they provide indirect evidence of climatic history. Wassenburg's study of seven speleothem samples obtained from Morocco, India, France, Spain, and a cave known as the Hüttenbläserschachthöhle in Germany's Sauerland region is the first attempt to identify in detail the concentrations at which trace elements tend to be incorporated in aragonite. "We have been able to demonstrate that the concentration of uranium in aragonite stalagmites is a very precise indicator of prehistoric rainfall patterns," he added. This means that stalagmites can tell us qualitatively how much it rained 200,000 years ago.

The Bab Mafraque cave in the Middle Atlas in Morocco with flowstones and stalactites 
[Credit: Jasper Wassenburg]

Reconstruction of the North Atlantic Oscillation as far back as the onset of the current interglacial period

Uranium and strontium concentrations and the relative ratios of oxygen isotopes were also analyzed in order to obtain information on past rainfall for a recent study of past NAO variability. The NAO index reflects the difference in atmospheric pressure between the Icelandic Low to the north and the Azores High to the south. One particular phenomenon of interest is that if the NAO brings dry weather to Europe, it rains in Morocco—and vice versa. The weather of the northwestern region of Morocco seems to react particularly sensitive to changes in the NAO. In this case, the samples used by Dr. Jasper Wassenburg came from a fairly small cave in which the host rock is dolomite. The Grotte de Piste is located in the Atlas Mountains at an elevation of some 1,250 meters above sea level. It is 70 to 80 meters in extent and 15 to 20 meters from floor to ceiling.

The results of analysis of the speleothems from the north-west of Morocco were compared with a rainfall reconstruction obtained from other cave deposits from the Bunkerhöhle or Bunker cave in western Germany. This enabled the climate researchers to trace back the fluctuations of the NAO over the past 11,000 years to the end of the last Ice Age. The best reconstruction previously available went back only 5,200 years. "We were surprised to discover that the situation during the early Holocene 11,000 years ago was quite different to that of today. The weather regimes in Europe and Morocco seem to have behaved similarly so that wet weather in Europe also meant more rain in Morocco," explained Wassenburg. This positive correlation disappeared at some point during the transition from the early Holocene to the mid-Holocene.

The researchers postulate that this was attributable to a major reduction in the melt water contribution from the Laurentide Ice Sheet that still covered large areas of North America at the end of the Ice Age. "The pattern of the North Atlantic Oscillation is not as stable as we thought," stated Professor Dennis Scholz and added that the NAO will probably also be influenced by today's melting of the Greenland Ice Sheet, with potential effects on the atmosphere, the oceans, and other biological phenomena, including farming and fishing. The team plans to conduct further research in order to reconstruct the changes of the NAO over the last 10,000 years.

The findings are published in Geochimica et Cosmochimica Acta and Nature Geoscience.

Source: University of Mainz [April 11, 2017]

byUnknown

in Ancient Environment, Climate Change, Earth Science, Geology, Germany, Morocco, Palaeontology

April 11, 2017

Stalagmites store paleoclimate data

The North Atlantic Oscillation (NAO) is the dominant atmospheric pressure mode over the North Atlantic that plays a significant role in dete...

Read More

Food webs entangle humans in complex relationships with animals, crops and the environment

Reconstructed food webs from the Ancestral Puebloan southwestern United States show the complexity and interconnectedness of humans, other animals, crops and the environment, in an area of uncertain climate and resources, according to researchers, who think climate change and human decisions then, may shed light on future human choices.

Square Tower House in Mesa Verde National Park [Credit: Nate Crabtree]

"As southwestern archaeologists, we know that Ancestral Puebloan people were intrinsically connected to the environment," said Stefani Crabtree, postdoctoral fellow in human behavioral ecology in the Department of Anthropology, Penn State. "But, most food webs have omitted humans."

Traditionally, food webs, while they map the interaction of all the animals and plants in an area, usually do not emphasize the human component. Crabtree and colleagues created a digital food web that captures all categories of consumers and consumed, can be defined for specific time periods and can also represent food webs after major food sources or predators disappear from the area. If an area suddenly becomes devoid of deer or humans or corn, for example, a food web of that situation can show where predators went to find prey, or which prey thrived for lack of a predator.

These knockout food webs -- webs missing a specific predator or prey -- show the changes and pressures on the food sources substituted for the missing ones, or the changes that occur when pressure is removed by removing a major consumer. The researchers report the results of their study in the Journal of Archaeological Science.

"When people show up in the area around A.D. 600 they bring corn," said Crabtree. "It takes a while for critters to get used to it, but eventually, everything that eats vegetation, eats corn and prefers it."

Humans bringing corn into an area is a major disruption of the existing food web. Planting corn means clearing fields to displace whatever plants and animals were there, creating a high-energy plant source of food and switching plant eaters to the preferred higher-calorie food source.

In the American Southwest, the Ancestral Puebloan people eventually preyed on their deer population enough so that they deer were no longer a reliable source of food. To compensate for this, they began to domesticate turkeys for food. Turkeys need to be fed corn if they are captive and that competes with corn for human consumption. At this time, corn made up 70 to 80 percent of Ancestral Puebloans' food and so feeding turkeys altered the food web.

A sample food web with red nodes representing primary producers, orange nodes primary consumers, yellow-orange 
nodes omnivores, true-yellow nodes are true carnivores. This draft food web was created with the program 
Network3D from foodwebs.org [Credit: Stefani Crabtree, Penn State]

To create the food web, the team identified all the common, noninvasive species in the area. They then added species that were found in archaeological sites, but were absent from the modern lists. In some food webs, components are identified by their function, so all humming birds are considered flying pollinators, but in this case each type of humming bird received its own place in the web, linked to what it ate and what, if anything, ate it. This produced a very complicated web, but supplied exceptional redundancy.

"In the insect world it is harder to get at the data," said Crabtree. "We have not been able to get at good databases so we aggregate at the functional level -- pollinators or bloodsuckers for example."

The exception to individual web entries then are invertebrates -- insects, spiders, snails, etc. -- that were classified by their function. Invertebrates are organized to the level of order and then grouped by function. With insects, for example, the researchers would group butterflies and moths that pollinated and sipped nectar, together in one group.

The overall food web had 334 nodes representing species or order-level functional groups with 11,344 links between predator and prey.

The researchers realize that there are differences in the environment between now and the Ancestral Puebloan period, but many things, such as pinon-juniper woodlands and sage flats are the same. Enough similarity exists for this approach to work.

The team did not produce just one overall food web, but also food webs corresponding to three archaeological locations and three time periods of Ancestral Pueblo occupation in the area -- Grass Mesa Pueblo for Pueblo I, Albert Porter Pueblo for Pueblo II and Sand Canyon Pueblo for Pueblo III. They began with using archaeological assemblages from these sites incorporating all human prey and all human predators into the food web. Then they included the prey of the primary prey of humans and then predators of these human-prey species. Prey, in this case, includes animals, insects and plants.

A coyote preying on an entire clutch of baby rabbits in Boulder County, CO. [Credit: Mindy Wilkinson]

When creating knockout food webs, the researchers included only those species that were found in reasonable quantities in the archaeological assemblages at those times.

"Knockout food webs are one of the best ways to understand how people interact with the environment," said Crabtree. "Because we can remove something, predator or prey, and see what would happen."

When major changes in climate variables such as drought, heat and lack of snowpack are factored in, the balance in the food web may become unstable. When food becomes scarce, most mobile creatures, animals and insects move to another location. During the time of the Ancestral Puebloans, this was possible and eventually, these people moved to the area of the Rio Grande in New Mexico and other places in New Mexico and Arizona.

"We didn't have a long-term plan during the 600 years of Ancestral Pueblo habitation in the Mesa Verde region," said Crabtree. "We don't have a long-term plan today either. We don't even have a four-year plan. Some people are pushing us to look closely at climate change."

In the past, people migrated, said Crabtree. Unless we figure out better strategies, where are we going to migrate out to? We do not have a place to go, she said.

What people plant and eat has a great effect on the environment and on ecosystems. In the end, those choices will impact human survival, according to the researchers.

This work is part of a collaboration of researchers creating resolved food webs from a variety of places. Crabtree believes that she can compare this project to others that include humans in other geographical areas to help understand ecosystems with humans in them.

Author: A'ndrea Elyse Messer | Source: Penn State University [April 10, 2017]

byUnknown

in Americas, Archaeology, Climate Change, Ecosystems, Environment, North America, USA, Wildlife

April 10, 2017

Food webs entangle humans in complex relationships with animals, crops and the environment

Reconstructed food webs from the Ancestral Puebloan southwestern United States show the complexity and interconnectedness of humans, other a...

Read More

First oceans may have been acidic

One way to understand how ocean acidity can change, for example, in response to rising carbon dioxide (CO2) levels, is to look to the history of seawater acidity. Dr. Itay Halevy of the Weizmann Institute of Science has looked to the distant past -- all the way back to Earth's earliest oceans. The model he developed, together with Dr. Aviv Bachan of Stanford University, suggests that the early oceans, right around the time that life originated, were somewhat acidic, and that they gradually became alkaline. The study, published in Science, sheds light on how past ocean acid levels were controlled by CO2 in the atmosphere, an important process for understanding the effects of climate change.

Dr. Itay Halevy of the Weizmann Institute of Science has looked to the distant past -- all the way back to Earth's earliest 
oceans. The model he developed, together with Dr. Aviv Bachan of Stanford University, suggests that the early oceans,
 right around the time that life originated, were somewhat acidic, and that they gradually became alkaline 
[Credit: Weizmann Institute of Science]

Acidity and alkalinity are measured on the pH scale of 0-14. On this scale, 7 is neutral, higher is alkaline, lower is acidic. At around 8.2, today's oceans are mildly alkaline, and we know that rising CO2 levels are currently increasing the oceans' acidity (decreasing pH).

Halevy, of the Weizmann Institute's Earth and Planetary Sciences Department, explains that billions of years ago "the early Sun was dimmer, even though we don't have evidence for a much colder climate. We think that this is because the early atmosphere had more of the greenhouse gas CO2 than at present, and that as the Sun got brighter, CO2 levels decreased," says Halevy.

CO2, and water produce carbonic acid, so it stands to reason that the early oceans would have been more acidic. But higher early CO2 levels would also have resulted in acidic rainwater and this, in turn, could have led to higher rates of chemical weathering of Earth's rocky crust, washing down ions that would partly neutralize the acidity of CO2. Which effect is the stronger? This has been unclear; thus previous models of the history of seawater pH have come up with everything from high values to low.

The model that Halevy and Bachan developed accounts for these processes and the way in which they influence the fluxes of ions into and out of ocean water. According to their model, the acidifying effect of higher CO2 levels dominated, and the early oceans had a lower-than-present pH.

"On a very fundamental level," says Bachan, "we show that the pH of the ocean has been controlled by a few simple processes for all of geologic time."

Putting numbers to the proposed pH, Halevy says that three to four billion years ago, the pH of ocean water was somewhere between 6.0 and 7.5 -- between that of milk and human blood. Halevy: "This gives us some clues as to the conditions under which life emerged in the early oceans."

"We had an early ocean more acidic than today in which primitive life thrived and chemical cycles were balanced; but if we want to apply this insight to today, we have to remember that this balance of acids and bases was maintained over geological timescales -- millions of years," he adds. "Today's acidification from CO2 is much more rapid, so this model does not apply to the short-term problem. Hundreds of thousands of years from now, the oceans will have found a new balance, but between now and then, marine organisms and environments may suffer."

Source: Weizmann Institute of Science [April 08, 2017]

byUnknown

in Ancient Environment, Climate Change, Earth Science, Oceans, Palaeontology

April 08, 2017

First oceans may have been acidic

One way to understand how ocean acidity can change, for example, in response to rising carbon dioxide (CO2) levels, is to look to the histor...

Read More

Rising temperatures, not droughts, increased warfare among the Maya, claims new study

The reason for the collapse of Mayan civilisation has been hotly debated, but now scientists claim they have an answer - climate change.

A team of researchers have found a link between temperature increase and growing conflicts among the Maya 
in the lowlands of the Yucatán Peninsula. Pictured are reconstructions of a Mayan fresco found in 
"The Temple of the Murals" at an ancient Maya archaeological site called Bonampak
 in Chiapas, Mexico [Credit: Shutterstock/Leon Rafael]

Researchers believe that hot weather made the Mayans more aggressive and therefore likely to fight one another.

As crops failed due to the rising temperatures leaders waged war for power which lit the fuse of their eventual demise around 900 AD, the study says.

With crops levels low Mayan leaders could no longer rely on brash festivals or building projects to keep their sujects happy.

So they resorted to power struggles and war instead which finished the mysterious civilisation off.

Maya civilisation thrived for more than 2,000 years with its heyday being 300 to 900 AD.

They built the earliest cities and created the first writing systems in the Americas.

For hundreds of years the Mayas dominated large parts of the Americas until, mysteriously in the 8th and 9th century AD, a large chunk of the Maya civilisation collapsed.

Researchers catalogued inscriptions related to violence on stone monuments and compared them to temperature and rainfall records for the lowlands of the Yucatán Peninsula, which includes mordern-day Mexico, Guatemala and Belize.

Researchers found a  total of 144 different conflicts in more than 30 major centres, according to Seeker.

'The change in conflict levels between 350 and 900 AD was considerable,' they wrote in the paper, which is published in Quaternary Science Reviews.

'We found that there was a substantial increase in conflict in the approximately 500 years covered by the dataset.

'The number of conflicts increased from zero to three every 25 years in the first two centuries to 24 conflicts every 25 years near the end of the period.' 

Conflict could not be explained by drought but rather by hot weather, which experts say works in two ways.

One is psychological - several studies suggest hot weather might have made the Maya more aggressive.

The second is economic - as temperature rose above 30°C (86°F) crops failed more frequently which in turn led to conflict.

'Instead, it's probably better to consider the increase in warfare in a way that we often think about warfare today — namely as a tool for the elite to maintain support,' said co-author Professor Mark Collard, an archaeologist at the University of Aberdeen in Scotland.

As crop yields decreased a ruler could no longer rely on opulent festivals and building projects to maintain support and so would have resorted to war to maintain power, experts believe.

The study has implications for debates about contemporary climate change - and whether we can learn important lessons from what happened to the Maya.

Dozens of theories have attempted to explain the Classic Maya Collapse, from epidemic diseases to foreign invasion.

'Most obviously, we need to know whether the effect is a regional one, specific to the Maya area, or one that holds for other parts of the world,' Professor Collard said. 

Author: Phoebe Weston | Source: Daily Mail [April 07, 2017]

byUnknown

in Americas, Archaeology, Belize, Central America, Climate Change, Guatemala, Mexico

April 07, 2017

Rising temperatures, not droughts, increased warfare among the Maya, claims new study

The reason for the collapse of Mayan civilisation has been hotly debated, but now scientists claim they have an answer - climate change. A t...

Read More

When peaceful coexistence suddenly turns into competition

Biologists agree that climate change reduces biological diversity. The specific processes that ultimately cause species to go extinct have, however, been little studied so far. Scientists at the German Centre for Integrative Biodiversity Research (iDiv) and the Leipzig University have now discovered that as temperatures rise, the complex relationships between species are changing. Prey species not only become stronger competitors for scarce resources, but also more preyed upon. These findings have now been published in the renowned journal Proceedings of the Royal Society B.

The larger prey species used in the experiment, the springtail Folsomia candida 
[Credit: Andy Murray]

To find out how rising temperatures could affect species diversity, biologists from the German Centre for Integrative Biodiversity Research (iDiv) and the Leipzig University have developed a simple experiment: they covered the bottoms of Petri dishes with litter material, then put in two species of springtails, that is, arthropods only a few millimetres in size; they then added mites feeding on springtails. Subsequently, in some of the Petri dishes, they increased the ambient temperature from 13.5°C to 18.5°C and for some other Petri dishes to 23.5°C. In those Petri dishes, the temperatures were respectively 10 degrees higher than the conditions to which the animals had been exposed in long-term cultures over the years. This created simplified miniature ecosystems under climate change conditions, in which the springtail species that peacefully coexist in the wild represented the prey, and the mites represented the predators. For two months, the researchers then observed how the interactions between the three species developed with different temperatures.

The smaller prey species, Proisotoma minuta. Springtails are tiny soil animals that use a tail-like
appendage for jumping [Credit: Andy Murray]

Madhav P. Thakur, the lead author of the study, explains the initial hypothesis of the Leipzig scientists: "We had actually been expecting that the smaller of the two springtail species would cope better with higher temperatures than the larger species. Their need for food is generally lower, so that it should increase less sharply under the new conditions." The actual results took the researchers by surprise: After two months, the smaller springtail species had completely disappeared in the warmer Petri dishes, whereas the larger species had managed to survive.

The predatory mites, Hypo aculifer, under the microscope 
[Credit: Tom Künne]

The study authors suspect that the smaller species was doomed due to two reasons: On the one hand, it was under a higher risk of being eaten. At higher temperatures, the predator's need for food also increases due to the generally elevated metabolism. Smaller prey are probably easier pickings than larger animals, because it is harder for them to escape from predators. On the other hand, the members of the smaller species were clearly and significantly less successful at adapting to the altered conditions—even though it is generally advantageous at higher temperatures to have a small body size. "This apparent paradox could be explained by the fact that the smaller springtail species was less able to acclimate to warmer environments, that is, to adapt its metabolism to the higher temperature, and simultaneously suffered a heavy predation. In contrast, the larger prey species could cope better with the new conditions and also more successfully escaped predation," says Thakur, who is a scientist at the iDiv research centre and the Leipzig University.

To establish micro ecosystems, the researchers filled Petri dishes with litter and added the animals 
[Credit: Madhav P. Thakur]

If these findings were extrapolated to the natural world, this could mean that in the future, some animal species will not only be burdened by increasing energy needs through rising temperatures, but will also be under threat due to the changing interactions between species. Thus, there is not only an increased competition for scarce resources among species on the same tier of the food chain, but also a higher probability of being eaten by predators as climate continues to warm. "This study once again demonstrates how little we understand about and can predict the complex interactions between species under future environmental conditions. Further studies with more complex communities and various model systems are urgently required here, to generate a comprehensive understanding," says Prof Dr Nico Eisenhauer, the senior author of the study.

A mite attacks a larger prey species – without success. Then it goes for a smaller prey species ... 

[Credit: Tom Künne]

The scientists had deliberately opted for using springtails in their study. These animals are not only easy to keep in the laboratory, but also play a crucial role in nature as decomposers of dead animal and plant material. If their species richness decreases due to climate change, some of their functions could be lost, and many processes within the ecosystems might unravel.

Source: German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig [April 06, 2017]

byUnknown

in Biodiversity, Biology, Climate Change, Evolution

April 06, 2017

When peaceful coexistence suddenly turns into competition

Biologists agree that climate change reduces biological diversity. The specific processes that ultimately cause species to go extinct have, ...

Read More

Paintings, sunspots and frost fairs: Rethinking the Little Ice Age

The whole concept of the 'Little Ice Age' is 'misleading', as the changes were small-scale, seasonal and insignificant compared with present-day global warming, a group of solar and climate scientists argue.

Analysis of extreme temperatures in the Central England Temperature (CET) thermometer record. Part (b) shows the 
lowest monthly average in each winter whereas part (c) shows the hottest monthly average in each summer. In both 
cases blue shows lower temperatures, and red shows higher temperatures than the long-term average. The cold winter 
months match up very well with the years in which frost fairs were held (vertical mauve lines) or years when the Thames
 was reported as frozen solid (vertical orange lines). However these years are not usually also associated with colder 
summers, unless there was a large volcanic eruption (measured from the sulphates that it deposited in polar ice sheets)
 such as Tambora in 1815. The top panel (a) shows the level of solar activity as seen in sunspot numbers (from 
telescopic observations and deduced from Carbon-14 stored in tree rings). It can be seen that, contrary to common
 claims, the Thames did not freeze more often during the Maunder minimum (c.1660-1710). Thames freezing events
 ceased after the demolition of the old London bridge in 1825 and the installation of the embankments, completed
 in 1870 (both dates marked with black lines): the faster flow meant that the river no longer froze, even when 
temperatures fell to values that had previously caused freezing [Credit: M. Lockwood]

Explanations for the cooling to Earth's climate, thought to have occurred between the 16th and 19th centuries, include low solar activity, volcanic eruptions, human changes to land use and natural climatological change.

But in a new paper in Astronomy & Geophysics, the house journal of the Royal Astronomical Society, Professor Mike Lockwood, of the University of Reading, and his collaborators, note that the temperature shift was smaller than that seen in recent decades resulting from the emission of greenhouse gases, and that although low solar activity may have been one driving factor, it certainly was not the only one.

Professor Lockwood said: "Commentators frequently refer to the Little Ice Age in discussions on climate change. We wanted to carry out a comprehensive study to see just how reliable the evidence is for a cooler climate, how big an impact it really had and how strong the evidence for a solar cause really was.

"On the whole the Little Ice Age was a manageable downturn in climate concentrated in particular regions, even though places like the UK had a larger fraction of cold winters. Our research suggests that there is no single explanation for this, that warm summers continued much as they do today and that not all winters were cold."

Researchers scrutinised historical records, such as the accounts of 'frost fairs' when the River Thames froze solid, and looked at the paintings from the era, such as the landscapes of Pieter Bruegel the Elder, with 'Hunters in the Snow' depicting a cold winter scene. Both of these are cited in support of the Little Ice Age concept.

"The Hunters in the Snow", Pieter Bruegel the Elder, 1565 [Credit: Kunsthistorisches Museum, Vienna, Austria]

From around 1650-1710, and to a lesser extent from 1790-1825, periods respectively known as the Maunder and Dalton Minima, sunspot numbers were unusually low, an indication that the surface of the Sun was slightly cooler. This external influence is often suggested as an explanation for the colder conditions.

The Reading-led team looked at the various pieces of evidence in more detail. They compared direct temperature records and proxy data such as ice records, with the years when the Thames was frozen over (whether or not a frost fair took place), and with the indications of solar activity.

Historical climate change is assessed through a variety of means. The Central England Temperature (CET) dataset tracks temperature from 1659, making it the oldest and longest running meteorological instrumental data sequence in the world. This direct record is supplemented by studies of biological proxies such as tree rings, corals, insect numbers and molluscs, all sensitive to climate change.

The authors draw comparisons with the ice ages proper. Cores taken from Antarctic ice allow global temperatures to be inferred, by measuring the proportions of deuterium (2H), a heavier atom of hydrogen, and of the heavier oxygen atom 18O, compared with their lighter 'normal' counterparts. It takes more energy to evaporate water with a higher proportion of these atoms, and they are more easily lost from rainfall, before they are deposited in ice found nearer the poles. The changing proportion of these atoms then allows researchers to assess how the temperature has changed over millions of years.

From these comparisons, the scientists argue that the description of the period as an Ice Age is misleading, as temperatures in that period fell far less than in a glaciation. During the Little Ice Age (LIA), the average temperature in the northern hemisphere fell by around 0.5 degrees. In contrast, in the most recent major glaciation that came to an end around 12,000 years ago, global temperatures were typically 8 degrees Celsius colder than today.

"Haymaking", Pieter Bruegel the Elder, 1565 [Credit: Kunsthistorisches Museum, Vienna, Austria]

Frost fairs also seem to be a poor indication of overall climate, as they often did not take place despite the Thames freezing, partly for many reasons including puritanical authorities or safety as lives were lost when the ice melted. The ending of the frost fairs had nothing to do with climate change or solar activity, instead being due to the increased river flow when the original London Bridge was demolished in 1825, and the first Victoria embankment opened in 1870. Both of these prevented the river from freezing completely, despite many subsequent cold winters.

Selective use of art historical evidence appears to reinforce the illusion of a prolonged cold spell. Yet 'Hunters in the Snow', depicting a January scene, is part of a series by Bruegel known as 'The Twelve Months'. Seven of these paintings may have been lost, but 'The Gloomy Day' (February), 'Haymaking' (July), and 'The Return of the Herd' (November) all give no indication of unusually cold conditions. Consistent with this, Lockwood and his team note that even at the height of the LIA period, colder European winters were still accompanied by many warm summers.

For example, 1701 is close to the lowest point of the Little Ice Age, yet in both Paris and London the summer was reported as being unbearably hot and the CET for July that year is the 10th hottest on record, with average temperatures for the month reaching 18.3°C. The year 1676 is the second hottest June on record at 18.0°C, yet it too was in the middle of a run of cold winters. Such high summer temperatures do not fit at all with the name "Little Ice Age".

Much more dramatic variations can result from large volcanic eruptions. Samalas, a volcano which erupted in 1257 in what is now Indonesia, ejected large amounts of dust into the atmosphere, causing a temporary cooling effect. The years between 1570 and 1730, corresponding to the coldest part of the LIA, also saw continuous lower level volcanic activity that may have suppressed temperatures. Volcanic eruptions undoubtedly cause both cold winters and cold summers. One of the clearest examples was the Tambora eruption of July 1815, which caused the next year to be called "the year without a summer".

Professor Lockwood said: "This study provides little solace for the future, as we face the challenge of global warming. Solar activity appears to be declining at present, but any cooling effect that results will be more than offset by the effect of rising carbon dioxide emissions, and provides us with no excuse for inaction."

Source: Royal Astronomical Society [April 04, 2017]

byUnknown

in Ancient Environment, Climate Change, Earth Science, Europe, Palaeontology

April 04, 2017

Paintings, sunspots and frost fairs: Rethinking the Little Ice Age

The whole concept of the 'Little Ice Age' is 'misleading', as the changes were small-scale, seasonal and insignificant compa...

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Future CO2 and climate warming potentially unprecedented in 420 million years

New research led by the University of Southampton suggests that, over the next 100 to 200 years, carbon dioxide concentrations in the Earth's atmosphere will head towards values not seen since the Triassic period, 200 million years ago. Furthermore, by the 23rd century, the climate could reach a warmth not seen in 420 million years.

A living Ginkgo leaf (left) and fossil (right). Density of stomata in such leaves is proxy of atmospheric CO2 in past 
[Credit: Dana Royer]

The study, published in Nature Communications, compiled over 1200 estimates of ancient atmospheric carbon dioxide (CO2) concentrations to produce a continuous record dating back nearly half a billion years. It concludes that if humanity burns all available fossil fuels in the future, the levels of CO2 contained in the atmosphere may have no geologically-preserved equivalent during this 420 million year period.

The researchers examined published data on fossilised plants, the isotopic composition of carbon in soils and the oceans, and the boron isotopic composition of fossil shells. Gavin Foster, lead author and Professor of Isotope Geochemistry at the University of Southampton, explains: "We cannot directly measure CO2 concentrations from millions of years ago. Instead we rely on indirect 'proxies' in the rock record. In this study, we compiled all the available published data from several different types of proxy to produce a continuous record of ancient CO2 levels."

This wealth of data shows that CO2 concentrations have naturally fluctuated on multi-million year timescales over this period, from around 200-400 parts per million (ppm) during cold 'icehouse' periods to up to 3000 ppm during intervening warm 'greenhouse' periods. Although evidence tells us our climate has fluctuated greatly in the past (with the Earth currently in a colder period), it also shows the current speed of climate change is highly unusual.

Carbon dioxide is a potent greenhouse gas and in the last 150 years humanity's fossil fuel use has increased its atmospheric concentration from 280 ppm in the pre-industrialisation era to nearly 405 ppm in 2016. However, it's not just CO2 that determines the climate of our planet, ultimately it is both the strength of the greenhouse effect and the amount of incoming sunlight that is important. Changes in either parameter are able to force climate change.

"Due to nuclear reactions in stars, like our sun, over time they become brighter," adds co-author Dan Lunt, Professor of Climate Science at the University of Bristol. "This means that, although carbon dioxide concentrations were high hundreds of millions of years ago, the net warming effect of CO2 and sunlight was less. Our new CO2 compilation appears on average to have gradually declined over time by about 3-4 ppm per million years. This may not sound like much, but it is actually just about enough to cancel out the warming effect caused by the sun brightening through time, so in the long-term it appears the net effect of both was pretty much constant on average."

This interplay between carbon dioxide and the sun's brightness has fascinating implications for the history of life on Earth. Co-author Professor Dana Royer, from Wesleyan University in the US, explains: "Up until now it's been a bit of a puzzle as to why, despite the sun's output having increased slowly over time, scant evidence exists for any similar long-term warming of the climate. Our finding of little change in the net climate forcing offers an explanation for why Earth's climate has remained relatively stable, and within the bounds suitable for life for all this time."

This long-term view also offers a valuable perspective on future climate change. It is well recognised that the climate today is changing at rates well above the geological norm. If humanity fails to tackle rising CO2 and burns all the readily available fossil fuel, by AD 2250 CO2 will be at around 2000 ppm - levels not seen since 200 million years ago.

Professor Foster adds: "However, because the Sun was dimmer back then, the net climate forcing 200 million years ago was lower than we would experience in such a high CO2 future. So not only will the resultant climate change be faster than anything the Earth has seen for millions of years, the climate that will exist is likely to have no natural counterpart, as far as we can tell, in at least the last 420 million years."

Source: University of Southampton [April 04, 2017]

byUnknown

in Ancient Environment, Climate Change, Environment, Fossils, Geology, Natural Heritage

April 04, 2017

Future CO2 and climate warming potentially unprecedented in 420 million years

New research led by the University of Southampton suggests that, over the next 100 to 200 years, carbon dioxide concentrations in the Earth...

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Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to the Earth's carbon cycle, a finding that has global implications as the bulk of Earth's glaciers shrink in response to a warming climate.

The Cotton Glacier stream in the McMurdo Dry Valleys region of Antarctica, where MSU researchers 
Heidi Smith and Christine Foreman sampled glacier runoff in 2012, in shown in this aerial photo 
[Credit: Christine Foreman]

Heidi Smith, a postdoctoral researcher, and Christine Foreman, associate professor of chemical and biological engineering, both of the Center for Biofilm Engineering in MSU's College of Engineering, were co-authors of a paper published in the prestigious journal Nature Geoscience.

Titled "Microbial formation of labile organic carbon in Antarctic glacial environments," the article was co-authored by researchers at the University of Colorado at Boulder, the U.S. Geological Survey, Stockholm University in Sweden and the Max Planck Institute for Marine Microbiology in Germany.

The paper challenges the prevailing theory that microorganisms found in glacial meltwater primarily consume ancient organic carbon that was once deposited on glacial surfaces and incorporated into ice as glaciers formed.

"We felt that there was another side to the story," said Smith, the paper's lead author. Smith earned a Ph.D. in ecology and environmental sciences in MSU's Department of Land Resources and Environmental Sciences in 2016, with Foreman as her adviser.

"What we showed for the first time is that a large proportion of the organic carbon is instead coming from photosynthetic bacteria" that are also found in the ice and that become active as the ice melts, Smith said. Like plants, those bacteria absorb carbon dioxide and in turn provide a source of organic matter.

The research team made the discovery after sampling meltwater from a large stream flowing over the surface of a glacier in the McMurdo Dry Valleys region of Antarctica in 2012.

Afterward, Smith spent two months at the Max Planck Institute for Marine Microbiology in Bremen, Germany, with support from the National Science Foundation's flagship interdisciplinary training program, the Integrative Graduate Education and Research Traineeship. There, she worked with colleagues to track how different carbon isotopes moved through the meltwater's ecosystem, allowing the team to determine the carbon's origin and activity.

The researchers ultimately found that the glacial microbes utilized the carbon produced by the photosynthetic bacteria at a greater rate than the older, more complex carbon molecules deposited in the ice, because the bacterial carbon is more "labile," or easily broken down. The labile carbon "is kind of like a Snickers bar," meaning that it's a quick, energizing food source that's most available to the microbes, Smith said.

Moreover, the researchers found that the photosynthetic bacteria produced roughly four times more carbon than was taken up by the microbes, resulting in an excess of organic carbon being flushed downstream. "The ecological impact of this biologically produced organic carbon on downstream ecosystems will be amplified due to its highly labile nature," Foreman said.

Although individual glacial streams export relatively small amounts of organic carbon, the large mass of glaciers, which cover more than 10 percent of the Earth's surface, means that total glacial runoff is an important source of the material. Marine organic carbon underpins wide-ranging ecological processes such as the production of phytoplankton, the foundation of the oceans' food web.

As glaciers increasingly melt and release the organically produced, labile carbon, "we think that marine microbial communities will be most impacted," Smith said. "We hope this generates more discussion."

In a "News and Views" commentary accompanying the article in Nature Geoscience, Elizabeth Kujawinski, a tenured scientist at Woods Hole Oceanographic Institution, called the team's work "an elegant combination" of research methods.

Taken together with another study published in the same issue of Nature Geoscience, about microbial carbon cycling in Greenland, Smith's paper "deflates the notion that glacier surfaces are poor hosts for microbial metabolism," according to Kujawinski. The two studies "have established that microbial carbon cycling on glacier surfaces cannot be ignored," she added.

Source: Montana State University [April 04, 2017]

byUnknown

in Antarctic, Biology, Climate Change, Ecosystems, Environment, Natural Heritage

April 04, 2017

Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to...

Read More