Tag Archives: extinction

What does 7 Billion People Mean?

Making Sense of 7 Billion People | Wired Science | Wired.com.

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On the last day of October 2011, the global population of an upstart branch of the primate order will reach 7 billion.review smartphone android

What does it mean?

In itself, not much: Seven billion is just a one-digit flicker from 6,999,999,999. But the number carries a deep existential weight, symbolizing themes central to humanity’s relationship with the rest of life on Earth.

For context, let’s consider a few other numbers. The first: 10,000. That’s approximately how many Homo sapiens existed 200,000 years ago, the date at which scientists mark the divergence of our species from the rest of Homo genus, of which we are the sole survivors.

From those humble origins, humans — thanks to our smarts, long-distance running skills, verbal ability and skill with plants — proliferated at an almost inconceivable rate.

 

Some may note that, in a big-picture biological sense, humanity has rivals: In total biomass, ants weigh as much as we do, oceanic krill weigh more than both of us combined, and bacteria dwarf us all. Those are interesting factoids, but they belie a larger point.

We are the .00018 percent, and we use 20 percent.

Ants and krill and bacteria occupy an entirely different ecological level. A more appropriate comparison can be made between humans and other apex predators, which is precisely the ecological role humans evolved to play, and which — beneath our civilized veneer — we still are.

According to a back-of-the-envelope calculation, there are about 1.7 million other top-level, land-dwelling, mammalian predators on Earth. Put another way: For every non-human mammal sharing our niche, there are more than 4,000 of us.

In short, humans are Earth’s great omnivore, and our omnivorous nature can only be understood at global scales. Scientists estimate that 83 percent of the terrestrial biosphere is under direct human influence. Crops cover some 12 percent of Earth’s land surface, and account for more than one-third of terrestrial biomass. One-third of all available fresh water is diverted to human use.

Altogether, roughly 20 percent of Earth’s net terrestrial primary production, the sheer volume of life produced on land on this planet every year, is harvested for human purposes — and, to return to the comparative factoids, it’s all for a species that accounts for .00018 percent of Earth’s non-marine biomass.

We are the .00018 percent, and we use 20 percent. The purpose of that number isn’t to induce guilt, or blame humanity. The point of that number is perspective. At this snapshot in life’s history, at — per the insights of James C. Rettie, who imagined life on Earth as a yearlong movie — a few minutes after 11:45 p.m. on December 31, we are big. Very big.

However, it must be noted that, as we’ve become big, much of life had to get out of the way. When modern Homo sapiens started scrambling out of East Africa, the average extinction rate of other mammals was, in scientific terms, one per million species years. It’s 100 times that now, a number that threatens to make non-human life on Earth collapse.

In regard to that number, environmentalists usually say that humanity’s fate depends on the life around us. That’s debatable. Humans are adaptable and perfectly capable of living in squalor, without clean air or clean water or birds in the trees. If not, there wouldn’t be 7 billion of us. Conservation is a moral question, and probably not a utilitarian imperative.

But the fact remains that, for all of humanity to experience a material standard of living now enjoyed by a tiny fraction, we’d need four more Earths. It’s just not possible. And that, in the end, is the significance of 7 billion. It’s a challenge.

In just a few minutes of evolutionary time, humanity has become a force to be measured in terms of the entirety of life itself. How do we, the God species, want to live? For the answer, check back at 8 billion.

Permian Extinction Harder to recover from than thought

The Sun’ll Come Out Tomorrow? Maybe Not – ScienceNOW.

 

 

Survivors. The dicynodont Lystrosaurus browses on a stand of the lycopsid plant Pleuromeia. These species are two of the “disaster taxa” that proliferated in the wake of the end-Permian mass extinction.

The worst mass extinction of all time did far more than nearly denude the planet of life. This vast catastrophe—probably triggered about 252 million years ago by massive eruptions of the Siberian Traps volcanoes—destabilized life on Earth so drastically, according to a new study, that ecological aftershocks continued to hinder the recovery of life on land for millions of years.

Much of what paleontologists understand about the event, known as the end-Permian extinction, and its aftermath they learned from the fossil record of marine organisms. Up to 95% of known species, including the last of the trilobites, disappeared during the extinction. And the plentiful record of fossil fish and invertebrates indicates that ecosystems in the seas required about 5 million to 8 million years during the following Triassic period to regain their previous diversity and complexity. The story on land, however, has been unclear.

Now paleontologist Randall Irmis of the University of Utah and the Utah Museum of Natural History in Salt Lake City and geologist Jessica Whiteside of Brown University propose online today in the Proceedings of the Royal Society B that things were just as tough on dry land as in the seas. Irmis and Whiteside examined fossil vertebrate data sets from southern Africa’s Karoo Basin and the Ural region of Russia. They found that the number of different land-dwelling vertebrate genera dropped during the time interval when the extinction struck. In the post-extinction world, a small cadre of “disaster species” made the most of a bad situation. These survivors, including the “shovel lizard” Lystrosaurus (see picture), were hardy species that could make a living under distressed conditions. Such creatures quickly colonized and dominated the environments that had been shaken up by the mass extinction.

But life was not easy. According to previous geological studies, the global cycle through which carbon is recycled through land, air, and water was disrupted again and again during this time. Previous researchers blamed these cycles on continued volcanic activity. But Irmis and Whiteside propose instead that the perturbations point to a “boom-bust” cycle in which relatively minor changes in temperature, for example, caused some of the surviving species to go extinct. These smaller-scale losses then caused ecosystems to collapse. The events that triggered the end-Permian extinction drastically changed the climate, atmosphere, and other aspects of global ecology, hindering the recovery of life on land during the Early Triassic. Even as survivors of the mass extinction began to recover, the ecosystems they lived in were so fragile that the lingering influences of the end-Permian extinction—such as global warming—could cause those habitats to fail.

This ongoing cycle acted as a reset button, temporarily preventing land vertebrates from evolving the diversity their pre-extinction ancestors had enjoyed. “It seems that the rate of recovery in both marine organisms and terrestrial vertebrates was pretty similar,” Irmis says. “They didn’t really bounce back until the Middle Triassic, some 5 to 6 million years after the extinction.”

Paleontologist Peter Ward of the University of Washington, Seattle, agrees that the new study adds to the big picture of how life recovered from the end-Permian extinction. But our understanding of that time period is still changing, he notes. For one thing, what seems like a long recovery might look shorter as geologists revise figures of how long the Early Triassic actually lasted. If new studies find that the Early Triassic rocks were laid down during a shorter time frame than presently known, then the recovery of Early Triassic life would have happened more rapidly than presently thought.

However long it lasted, the Early Triassic world was likely a harsh one. Citing the work of geologist Lee Kump of Pennsylvania State University, University Park, Ward says that in the millennia after the mass extinction there would have been hot snaps, lowered oxygen levels in lakes and oceans, and possibly the persistence of the poisonous “swamp gas” hydrogen sulfide in the atmosphere. The powerful volcanic eruptions that likely triggered the extinction left a devastating imprint on the planet, which continued to shake up life on Earth even as ecological wounds began to heal.

Javan rhino now extinct in Vietnam

BBC News – Javan rhino ‘now extinct in Vietnam’.

A Javan rhino is captured on camera in Vietnam's Cat Tien National Park (Image: WWF Greater Mekong) Genetic analysis of rhino dung samples revealed that there was only one individual left in Vietnam

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A critically endangered species of rhino is now extinct in Vietnam, according to a report by conservation groups.

The WWF and the International Rhino Foundation said the country’s last Javan rhino was probably killed by poachers, as its horn had been cut off.

Experts said the news was not a surprise, as only one sighting had been recorded in Vietnam since 2008.

Fewer than 50 individuals are now estimated to remain in the wild.

“It is painful that despite significant investment in Vietnamese rhino conservation, efforts failed to save this unique animal, ” said WWF’s Vietnam director Tran Thi Minh Hien.

“Vietnam has lost part of its natural heritage.”

The authors of the report, Extinction of the Javan Rhino from Vietnam, said genetic analysis of dung samples collected between 2009-2010 in the Cat Tien National Park showed that they all belonged to just one individual.

Shortly after the survey was completed, conservationists found out that the rhino had been killed. They say it was likely to have been the work of poachers because it had been shot in a leg and its horn had been cut off.

Globally, there has been a sharp increase in the number of rhino poaching cases. Earlier this year, the International Union for Conservation of Nature (IUCN) published a report that said rhino populations in Africa were facing their worst poaching crisis for decades.

An assessment carried out by Traffic, the global wildlife trade monitoring network, said the surge in the illegal trade in rhino horns was being driven by demands from Asian medicinal markets.

Conservation blow

The Vietnam rhino, as well as being the last of the species on mainland Asia, was also the last known surviving member of the Rhinoceros sondaicus annamiticus subspecies – one of three recognised groups of Javan rhino populations.

In detail: Javan rhinoceros

  • Scientific name: Rhinoceros sondaicus
  • The species is listed as Critically Endangered because fewer than 50 individuals remain
  • Weight: 900kg – 2,300kg
  • Height: 1.5m – 1.7m
  • Length: 2.0m – 4.0m
  • Male Javan rhinos possess a single horn about 25cm long
  • It is estimated that they can live for 30-40 years
  • Females reach sexual maturity between 5-7 years, and then give birth to a calf about once every three years

(Source: IUCN/IRF)

Another is already extinct. R. sondaicus inermis was formerly found in north-eastern India, Bangladesh and Burma.

The remaining subspecies, R. sondaicus sondaicus, is now found on Java, Indonesia. However, since the 1930s, the animals – now estimated to number no more than 50 – have been restricted to the westernmost parts of the island.

Bibhab Kumar Talukdar, chairman of the IUCN’s Asian Rhino Specialist Group, said the demise of the Javan rhino in Vietnam was “definitely a blow”.

“We all must learn from this and need to ensure that the fate of the Javan rhino in [Indonesia] won’t be like that of Cat Tien in near future,” he told BBC News.

“Threats to rhinos for their horn is definitely a major problem. But in Indonesia, due to active work done by rhino protection units and national park authorities, no Javan rhino poaching has been recorded in Indonesia for past decade.”

Dr Talukdar observed: “What is key to the success of the species is appropriate habitat management as the Javan rhinos are browser and it needs secondary growing forests.”

He warned that the habitat within the national park on Java serving as the final refuge for the species was being degraded by an invasive species of palm.

“As such, control of arenga palm and habitat management for Javan rhinos in Ujung Kulon National Park is now become important for future of the species.”

New Scientist special about what we do/don't know about Climate change

Climate change: What we do – and don’t – know – New Scientist.

(Image: Maria Stenzel)

There is much we do not understand about Earth’s climate. That is hardly surprising, given the complex interplay of physical, chemical and biological processes that determines what happens on our planet’s surface and in its atmosphere.

Despite this, we can be certain about some things. For a start, the planet is warming, and human activity is largely responsible. But how much is Earth on course to warm by? What will the global and local effects be? How will it affect our lives?Watch movie online A Cure for Wellness (2017)

In these articles, Michael Le Page sifts through the evidence to provide a brief guide to what we currently do – and don’t – know about the planet’s most burning issue.

KNOW

Greenhouse gases are warming the planet

From melting glaciers and earlier springs to advancing treelines and changing animal ranges, many lines of evidence back up what thermometers tell us
Read more

DON’T KNOW

How high greenhouse gas levels will rise

We can’t say how much Earth will warm over the coming years unless we know how much more greenhouse gas will end up in the atmosphere
Read more

KNOW

Other pollutants are cooling the planet

We pump all kinds of substances into the atmosphere. Some of them reflect the sun’s heat back into space and so cool things down
Read more

DON’T KNOW

How great our cooling effects are

Pollutants that form minute droplets in the atmosphere have horrendously complex effects – so it’s far from certain what they mean for global warming
Read more

KNOW

The planet is going to get a lot hotter

Extra carbon dioxide means a warmer world – and then positive feedback effects from things like water vapour and ice loss will make it warmer still
Read more

DON’T KNOW

Just how much hotter things will get

On current trends the temperature rise could exceed 4 °C as early as the 2060s. But even that could be an underestimate
Read more

DON’T KNOW

How things will change in each region

Which regions are going to turn into tropical paradises? Which into unbearably humid hellholes? It would be useful to know. Unfortunately, we don’t
Read more

KNOW

Sea level is going to rise many metres

Studies of past climate indicate each 1 °C rise in the global mean temperature eventually leads to a 20-metre rise in sea level
Read more

DON’T KNOW

How quickly sea level will rise

Do we have time to get temperatures back down before seas rise by more than a few metres? We have little clue how much room we have for manoeuvre
Read more

DON’T KNOW

How serious the threat to life is

The problem for the plants, animals and people living today is that they and we have adapted to the unusually stable climate of the past few thousand years
Read more

KNOW

There will be more floods and droughts

Warm air holds more moisture. This means more rain or snow overall, and more intense rain or snowfall on average
Read more

DON’T KNOW

Will there be more hurricanes and the like?

A wetter atmosphere will provide more of the fuel that powers extreme events like hurricanes, but it is not clear how often this fuel will be ignited
Read more

DON’T KNOW

If and when tipping points will come

The Amazon could become grassland. Massive amounts of methane could be released from undersea hydrates. And we may not realise in time to do anything about it
Read more

Bat killing fungus identified, but deaths continue

Bat killer identified, but deaths continue – life – 26 October 2011 – New Scientist.Movie Fifty Shades Darker (2017)

A fungus long suspected of killing more than a million batsMovie Camera in the US since 2006 has been pronounced guilty after a series of experiments on captive animals. The tests confirm that “white nose syndrome”, so called because it leaves fuzzy white smudges on the muzzles of its victims, is caused by the Geomyces destructans fungus.

When researchers infected 29 captive little brown bats (Myotis lucifugus) with lab-grown samples of the fungus, they all developed the disease, showing the tell-tale signs and symptoms about three months after infection. None of the 34 controls, which were not infected with the fungus, developed the condition.

Through complementary experiments in which the researchers housed 25 infected bats together with 18 healthy bats, they demonstrated that bats catch the syndrome from each other through physical contact. It cannot spread through the air: healthy bats did not pick up the infection when housed near to, but physically isolated from, diseased bats.

The experiments confirm what many experts had suspected, and rule out the possibility that the fungus preys on sick animals but does not actually cause the disease.

“The discovery allows us to focus our research efforts to develop management and control strategies,” says David Blehert of the National Wildlife Health Center, part of the US Geological Survey in Madison, Wisconsin, who led the research team. “Unfortunately, there’s no silver bullet to kill the fungus.”

Hard to prevent

Most potential solutions have drawbacks, explains Blehert. Applying fungicides in caves might harm plants and other animals living there, and this would have to be done year after year to keep the fungus at bay. Even culling bats in infected caves wouldn’t work, because some infected bats would escape and return, or spread the fungus elsewhere.

Of all the possible solutions, vaccination might provide the best hope, says Blehert, because it would potentially give bats lifelong immunity. He points out that wild foxes, skunks and racoons have been successfully vaccinated against rabies by dropping vaccine-baited food into their habitats from planes.

Earlier this year, a study found that the Geomyces destructans fungus found in US bats is almost identical to one in Europe to which most native bats seem to be resistant. Finding out what makes the European bats resist the fungus could help find ways to protect their US cousins.

The earlier study also raised the possibility that the US fungus originated in Europe and was inadvertently brought to the US by humans. The US Fish and Wildlife Service says that existing precautions issued by the US Geological Survey to stop humans spreading the fungus any further remain essential.

The wildlife service has called for proposals to follow specific research objectives designed to help the US bats. These include identifying the times of the year when the fungus spreads most easily, the factors that affect bat survival, the features of bat-cave environments that might potentially be altered to obstruct spread, and screening for other microbes that may kill the fungus or hamper transmission without harming bats.

Journal reference: Nature, DOI: 10.1038/nature10590

Seaweed Kills Corals by Touch

Seaweed With a Deadly Touch – ScienceNOW.

 

Green plague. In Fiji, rarely fished reefs (top) abound with colorful corals, but seaweeds start their invasions in exploited locales (bottom)

“Attack of the killer seaweed” may sound like a cheesy horror flick, but for many coral species, murderous multicellular algae have become real-life villains. A new study of reefs in the South Pacific suggests that some algae can poison coral on contact. This chemical warfare may be increasing the pressure on struggling reef communities worldwide, researchers say.

Along the reefs dotting Fiji, overfishing has pitted corals against algae in a battle royale. On swaths of coastline where fishing is restricted, corals such as the tall and branching Acropora millepora rule, says study co-author Mark Hay, a marine ecologist at the Georgia Institute of Technology in Atlanta.

But where Fijians spear lots of herbivores such as bird-beaked parrotfish, few fish remain to prune back the region’s seaweeds, a blanket term for many types of big algae. These algae then creep in, extending their tendrils over close to 60% of the ocean bottom, Hay estimates, and turning waters a sludgy green. Such “seaweed-covered parking lots” aren’t unique to Fiji, either, he says.

Recent studies have hinted that this ocean greenery may be carrying out a subtle chemical war on sensitive reefs. To investigate this covert struggle, Hay and colleagues strung eight different species of Fijian seaweed across growing corals, including A. millepora colonies. True to the researchers’ suspicions, many of these algal species seemed to wield a poison touch. In less than 2 weeks, the test coral often began to discolor and even die where it rubbed against the seaweeds, the team reports today in the Proceedings of the National Academy of Sciences. Faux seaweeds made of plastic had no such effect.

Hay and colleagues then mashed up several of these seaweeds to identify their killer concoction. The key ingredient turned out to be chemicals called terpenes, which some algae use to sicken fish that feed on them. Terpene extracts alone killed off corals, the researchers found. But some algae seemed to be more liberal with their toxins than others, Hay notes. When one particularly nasty specimen called turtle weed (Chlorodesmis fastigiata) rubs against A. millepora, for instance, wide bands of dying tissue girdle the coral.

This seaweed is so nasty, in fact, that most marine herbivores avoid it on sight—except for one species of rabbitfish that quivers with excitement every time it spots this not-so-common algae. That interaction highlights the importance of prudent fishing practices, he adds. If Fijians developed a particular taste for that one rabbitfish, for instance, turtle weed might begin to grow out of control, launching its bid for world, or at least South Pacific, domination. Hay would like to work with Fijians to identify and protect the herbivores most responsible for trimming back deadly seaweeds, giving sensitive corals a fighting chance.

“It’s certainly a novel finding,” says John Bruno, a marine ecologist at the University of North Carolina, Chapel Hill. But not all seaweeds are poisonous, he adds. Many scientists argue that algae—toxins or no—rarely kill off adult corals en masse. Instead, these opportunistic organisms may simply be capitalizing on the slow death of the invertebrates due to pollution, climate change, or other factors. He adds, however, that the seaweeds Hay and colleagues studied would likely be exceptionally toxic to young, coin-sized corals that have yet to grow big and hale.

Terpenes from seaweed are almost certainly not the only reason for the mysterious global decline of corals, says Jennifer Smith, a marine ecologist at the University of California, San Diego. Most scientists rank overfishing, pollution, and warming oceans among the biggest overall contributors. But corals may suffer from other nasty tricks played by seaweed. In a 2006 study, Smith and colleagues sleuthed out that some California algae could take the epidemic route to domination. In the lab, these seaweeds leak huge quantities of dissolved carbon that then fuels the spread of potentially infectious microbes on coral surfaces. “You can imagine that [algae and corals] have evolved over the years different mechanisms for battling each other and fighting these turf wars,” Smith says.

Europe's oceans changing at unprecedented rate

Europe’s oceans changing at unprecedented rate: report | Reuters.

LONDON | Tue Sep 13, 2011 3:26pm EDT

(Reuters) – Europe’s seas are changing at an unprecedented rate as ice sheets melt, temperatures rise and marine life migrates due to climate change, a report by the Climate Change and European Marine Ecosystem Research (CLAMER) project warned.

Scientists examined a mass of EU-funded research on the impacts of climate change on Europe’s marine environment and identified the gaps and priorities for future work.

“Change has been clearly visible and is much more rapid than we thought was possible,” Carlo Heip, chair of the CLAMER project and lead author of the report, told Reuters on Tuesday.

Over the past 25 years, sea water temperatures have increased as Arctic sea ice has melted. The combination of rising sea-levels and increased winds has contributed to the erosion of 15 percent of European coasts, the report said.

Warming has speeded up in the past 25 years at around 10 times faster than the average rate of increase in the 20th century, it added.

From 1986 to 2006, sea surface temperature rises for European waters were three to six times higher than the global average.

“Scenario simulations suggest that by the end of the 21st century, the temperature of the Baltic Sea may have increased by 2 to 4 degrees centigrade, the North Sea by 1.7 degrees, and the Bay of Biscay by 1.5 to 5 degrees,” the report said.

Melting ice sheets and glaciers add more uncertainty. Current estimates for 2100 suggest European sea levels could rise 60 cms and up to 1.9 meters at some British coasts.

Sea level rise threatens populations in all low-lying areas of Europe, but countries such as Britain, France and the Netherlands could be less vulnerable because they are rich enough to adopt coastal protection measures.

Changes in the marine food chain have also occurred as organisms have migrated to the Atlantic from the Pacific via seasonal ice-free passages through the Arctic.

While some species can thrive in other oceans, any major upheaval to the marine ecosystem could have devastating effects, the report said.

CLAMER also found that some bacteria strains were becoming more prevalent and could be a potential threat to human health. For example, cholera strains have increased in the North Sea over the past 50 years, perhaps due to temperature change.

Among its many recommendations, CLAMER urged more study of seal-level changes due to ice sheets breaking up or melting, coastal erosion, temperature changes, ocean acidification, marine ecosystems and circulation changes.

“The main message is we need to keep our fingers on the pulse,” said Heip.

The full report is available at: www.clamer.eu/

(Editing by Janet Lawrence)

'Dinosaur Killer' Asteroid Parent Now Doubted

Was the ‘Dinosaur Killer’ Unfairly Charged? – ScienceNOW.

 

 

Wanting to bring the master evildoer, not just a henchman, to justice is human enough. So when planetary scientists traced the asteroid that wiped out the dinosaurs 65 million years ago back to a rampaging rock named Baptistina in the asteroid belt there was palpable satisfaction that the ultimate culprit seemed to have been nailed.

But now a group of astronomers is challenging that claim. Baptistina did blast another asteroid to smithereens, sending a devastating shower of debris into the inner solar system, but that cataclysmic collision probably came too late to have sent the dino killer to Earth, they argue.

The original CSI-like case against Baptistina involved an odd link between an asteroid’s size and the ability of sunlight to move it across the asteroid belt. In their 2007 Nature paper, planetary scientists William Bottke, David Vokrouhlický, and David Nesvorný of the Southwest Research Institute (SwRI) in Boulder, Colorado, identified asteroids whose similar orbits mean they are members of the “family” of asteroids formed in a collision between asteroids 170 and 60 kilometers in diameter, 40-kilometer-diameter Baptistina being the largest survivor.

By assuming how reflective Baptistina family members are, the SwRI group could estimate the size of each asteroid from the amount of visible light they reflected. Their sizes, in turn, determined how quickly sunlight could ease debris away from the collision. As each fragment absorbs solar energy, it radiates the heat away to give an ever-so-gentle rocketing effect. That nudging could have driven fragments toward a known orbital spot from which Jupiter’s gravity could fling them toward Earth. Judging by how far from the collision Baptistina family members have gotten, the group estimated that the collision occurred about 160 million years ago, early enough for the solar-driven rocketing to drive a 5- or 10-kilometer fragment to the jumping-off point to Earth by 65 million years ago.

But now team members on the Wide-Field Infrared Survey Explorer (WISE) mission dispute this line of evidence in a paper just out in The Astrophysical Journal. Joseph Masiero of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, and colleagues report that WISE has returned estimates of the size of 100,000 asteroids, the Baptistina family among them. These estimates are more accurate than those the SwRI group had because WISE detects infrared light, not the visible spectrum. The SwRI group had to assume a reflectivity, but the WISE infrared measurements yielded actual measurements of reflectivity that are four times larger than the SwRI group had assumed. That in turn gave smaller sizes, faster moving fragments, and therefore a younger collision time—about 80 million years ago—than the SwRI group had calculated.

“This doesn’t give the remnants from the collision very much time to … get flung down to Earth 65 million years ago,” says Amy Mainzer, a co-author and the principal investigator of the asteroid phase of WISE at JPL. So instead of the Baptistina collision being ultimately responsible, another, as-yet-undated collision may have been responsible. Or the dino killer was a random asteroid that happened to wander out of the asteroid belt then.

Bottke doesn’t see a problem. Indeed, the WISE results “if anything … make our story stronger,” he writes in an e-mail. The SwRI group’s 2007 calculations show that “lots of things escape from the Baptistina family right away … decreasing the age of the Baptistina family is not a problem.”

Before, the collision was so early that the dino killer would have had to have been among the sparse debris that reached Earth long after the collision, Bottke says; with a more recent collision, far more Baptistina fragments would have been raining toward Earth 65 million years ago. Bottke’s argument “provides a good counterpoint to the conclusions reached by the WISE team,” writes dynamicist Derek Richardson of the University of Maryland, College Park. Now perhaps the prosecution and the defense can work on a settlement.

Climate Change Endangers Cutthroat Trout

Iconic Fishes Face New Threat – ScienceNOW.

They’re not spectacular like marlins, but trout are among the most legendary—think A River Runs Through It—and lucrative fish of mountain rivers and lakes. Across the western United States alone, trout fishing generates hundreds of millions of dollars annually. But trout habitat will likely be cut in half by 2080 due to warming rivers and altered patterns of flooding, according to a large study published today. “It’s fairly shocking to us, as biologists,” says co-author Kurt Fausch of Colorado State University, Fort Collins.

The study, published online today in the Proceedings of the National Academy of Sciences, is the first to tease apart the probable impacts of climate change on common trout species. This is not a case of winners and losers; the four species examined by the team are all likely to decline to varying degrees. The good news for fans of fly-fishing is that the rainbow trout, beloved for its large size, will suffer the smallest impact. On the other hand, the results will further alarm conservationists concerned about the plight of native cutthroat trout.

By running several climate models and plugging in data on habitat characteristics and fish present at 9890 locations in the Rocky Mountains and Great Basin, the team of scientists created predictions for trout habitat across more than 1 million square kilometers of the western United States. They factored physical aspects of habitat—water temperature, patterns of flooding—as well as competition among species. Here’s what the study concludes about the future of trout:

Rainbow trout (Oncorhynchus mykiss): Introduced beginning in the 1800s for fishing, these trout live in larger rivers than do the other species. They typically grow up to 110 centimeters long and are relatively easy to catch.Increases in water temperature will restrict their range, but rainbow trout dodge a bullet. Climate change will mean more frequent and intense winter floods, which can scour away eggs laid in the fall, but rainbow trout spawn in the spring. The size of their habitat is predicted to decline by 35%.

Brown trout (Salmo trutta): Smaller than rainbow trout, they are the most temperature tolerant among the four species and like warmer temperatures. They have the ill fortune to spawn in the fall, so the increased flooding will make many streams inhospitable. Their habitat is predicted to decline by 48%.

Cutthroat trout (Oncorhynchus clarkii): The range of these native fish has already shrunk by more than 85% due to competition from introduced species. Two subspecies have already gone extinct. Warming temperatures and continued competition primarily from rainbow trout are predicted to reduce suitable habitat by a further 58%.

Brook trout (Salvelinus fontinalis): Runts compared with the other species, brook trout are the biggest losers in 2080. Because they spawn in the fall, the increase in winter flooding is expected to reduce their suitable habitat by 77%—a surprising amount given their success at invading new habitat. “I did not expect brown trout to decline so much,” says co-author Seth Wenger, a biologist with Trout Unlimited, a conservation organization in Boise.

Frank Rahel, a fish ecologist at the University of Wyoming in Laramie, who was not involved with the study, says the findings help paint the big picture for trout this century. “They’re very sobering results that will catch people’s attention,” he says. Not much can be done to reduce the impact of winter floods, but managers already try to keep streams cooler by planting trees and shrubs.

Mystery Fossils Link Fungi to Ancient Mass Extinction

Mystery Fossils Link Fungi to Ancient Mass Extinction | Wired Science | Wired.com.

By Scott K. Johnson, Ars Technica

Of the five mass extinctions in the Earth’s past, one stands above the rest in magnitude: the Permian-Trassic extinction, known as the Great Dying. It saw the disappearance of almost 60 percent of all families, and over 80 percent of all genera — in the ocean, that added up to about 96 percent of all species. The cause of this event, 250 million years in the past, is still a matter of debate.

The most likely culprit is the prolific volcanism of the Siberian Traps— the erupted basalt still covers about 2 million square kilometers — but other events may have also played a role. Evidence for a massive destabilization of methane hydrates on the seafloor (a phenomenon described as “The Big Burp”), ocean anoxia and even contemporary asteroid impacts have all been found.

A couple of recent papers in the journal Geology have brought some new information to the discussion, and may help make the picture just a little bit clearer.

 

One source of significant mystery has been the nature of the organic microfossils that are common in rocks dated to the time of the extinction worldwide. The tiny fossils resemble filamentous colonies of cells, but have evaded positive identification.

Some researchers think they are the remains of fungi, while others argue that they are algae instead. There’s evidence on both sides, but the two scenarios represent very different conditions. The fungus indicates a widespread dying of woody vegetation, while algae suggest extensive swamps forming along river systems.

A paper published this month shows that the microfossils are almost identical morphologically to a group of pathogenic soil fungi that can infect trees. If its authors have identified these correctly, it fits in well with an overall picture showing loss of forests and topsoil. The demise of tree species is clear in pollen studies, and there is a lot of evidence for greatly accelerated soil erosion, including increased sediment deposition in deltas with lots of soil-derived organic debris.

Modern studies show that drought stress and UV damage, both of which could be caused by the massive releases of volcanic gases from the Siberian Traps, can make trees susceptible to fungal infection.

Connecting a fungus to a global mass extinction may seem tenuous, but the authors point out that processes down in the world of the very small are often overlooked in any extinction discussions. They summarize by saying, “There may have been a variety of other globally operating environmental stress factors, but whatever sequence of events triggered ecosystem destabilization on land, the aggressiveness of soil-borne pathogenic fungi must have been an integral factor involved in Late Permian forest decline worldwide.”

Separately, another recent paper has pinned down the timing of the extinction. It’s not considered to have been as sudden as the End Cretaceous extinction that killed off the dinosaurs, but the precise timeline has been tough to get a handle on, and estimates have varied.

The research group looked at some marine Permian-Triassic rocks in China that recorded cyclical global climate patterns. Climate controlled the amount of terrestrial sediment that was deposited in this area, which shows up as changes in grain size through the rock layers. Using a device that measures magnetic susceptibility, they were able to precisely quantify changes in grain size across the rock layers. Together with some uranium-lead isotopic ages, they were able to pick out the orbital cycles that control climate, including the prominent 400,000-year eccentricity cycle, and use them to precisely date the extinction interval.

A couple of interesting things show up in the data. For one, minima in several of the orbital cycles coincide shortly before the start of the extinction period. (Think of three sine waves with different wavelengths — at certain points in time, all three troughs will line up by chance.) That could have made for some unusual climatic conditions. Additionally, the effect of the 100,000-year orbital cycle on climate seems diminished for as long as 2 million years afterward.

It’s dangerous to extrapolate to the big picture from records like this, but there’s enough there to warrant further investigation of the orbital forcings.

In the end, they found that the extinction took 600,000 to 700,000 years to play out. This is consistent with the idea that several events acted in concert to destabilize ecosystems and cause the loss of so many species, meaning a significant length of time would be needed. It was simply a nasty time to be a living thing on planet Earth. Some advice for any time travelers out there — steer well clear of the Great Dying.

Image: Photomicrographic comparison of fossil and modern filamentous fungal structures. A: Sclerotium of modern Rhizoctonia aff. solani, aggregated monilioid hyphae (Paul Cannon/Centre for Agriculture and Biosciences International, CABI). B: Modern R. solani, branched monilioid hyphae (Lane Tredway/American Phytopathological Society). C, D: Late Permian Reduviasporonites stoschianus, branched monilioid hyphae. E: R. stoschianus, aggregated hyphae with dominant narrow cells. F: R. stoschianus, aggregated monilioid hyphae. G: R. stoschianus, segment of small intact disk-like sclerotium. Scale bar for all images is 100 ?m.

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Citation: Geology, 2011. DOI: 10.1130/G32126.1 and Geology, 2011. DOI: 10.1130/G32178.1