What killed off the giant beasts, climate change or man?

By  for The Guardian,
Earth’s ‘megafauna’ vanished as tribes spread. Now palaeontologists are asking if early humans were the cause
Mammoth

Humans might have played a role in the extinction of the woolly mammoth. Photograph: Andrew Nelmerm/Getty Images/Dorling Kindersley

They were some of the strangest animals to walk the Earth: wombats as big as hippos, sloths larger than bears, four-tusked elephants, and an armadillo that would have dwarfed a VW Beetle. They flourished for millions of years, then vanished from our planet just as humans emerged from their African homeland.

It is one of palaeontology’s most intriguing mysteries and formed the core of a conference at Oxford University las 20th of march when delegates debated whether climate change or human hunters killed off the planet’s lost megafauna, as these extinct giants are known.

“Creatures like megatherium, the giant sloth, and the glyptodon, a car-sized species of armadillo, disappeared in North and South America about 10,000 years ago, when there were major changes to climates – which some scientists believe triggered their extinctions,” said Yadvinder Malhi, professor of ecosystem science at Oxford, one of the organisers of the conference, Megafauna and Ecosystem Function.

“However, it is also the case that tribes of modern humans were moving into these creatures’ territories at these times – and many of us believe it is too much of a coincidence that this happened just as these animals vanished. These creatures had endured millions of years of climate change before then, after all. However, this was the first time they had encountered humans.”

Modern humans emerged from Africa around 70,000 years ago, travelled across Asia and reached Australia 50,000 years ago, a time that coincides with a wave of extinctions of creatures there, including the diprotodon, a species of wombat that grew to the size of a modern hippopotamus. By about 14,000 years ago, humans had reached North America by crossing the land bridge that then linked Siberia and Alaska. Then they headed south.

By 10,000 years ago, Homo sapiens had conquered North and South America at a time that coincided with major megafauna extinctions, including those of the giant sloth and the glyptodon.

“We think of Africa and south-east Asia – with their lions, elephants and rhinos – as the main home of large animals today, but until very recently in our planet’s history, huge creatures thrived in Australia, North America and South America as well,” said Professor Adrian Lister of the Natural History Museum in London. “The question is: why did they disappear in the new world but survive in the old world?

“Some believe it is because large animals in Africa and south-east Asia learned to become wary of human beings and decided to avoid them at all costs. However, I also think climate change may have been involved in the Americas and Australia and that humans only finished off these big animals when they were already weakened by loss of habitats and other climate-related problems.”

The idea that humans were involved in any way in eradicating dozens of species of giant animal when we were still hunter-gatherers has important implications in any case. It was thought, until relatively recently, that it was only when humans invented agriculture several thousand years ago that our species’ relationship with the natural world become unbalanced. Until then, humans had a close affinity with nature. But if ancient hunter-gatherers played a part in wiping out these species of huge animals as long as 50,000 years ago, humanity’s supposed innate harmony with the living world appears misplaced.

More to the point, humanity is still paying the price for the disappearance of the megafauna of the Americas and Australia, the Oxford conference will hear. “There is now a lot of evidence to suggest that large herbivores like gomphotheres, a family of elephant-like animals that went extinct in South America around 9,000 years, played a key role in spreading nutrition in areas like the Amazon. They would eat fruit in the forest, including avocados, and their excrement would then fertilise other areas. That no longer happens and places like the Amazon are today affected by low nutrition as a result,” Malhi said.

Another example is provided by the giant wombat, the diprotodon, which some scientists have argued browsed bush across Australia and kept biomass levels very low. When the diprotodon vanished, plants and shrubs across the outback grew unhindered. The result was major bush fires which, archaeologists have discovered, became a serious problem just after the giant wombat disappeared from Australia.

Diprotodon optatum from the Pleistocene of Australia.

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Tipping point already reached?

A massive crack discovered on Pine Island Glacier in Western Antarctica which scientists now say is headed toward irreversible disintegration. The crack, discovered by an overflight in 2011, will eventually release a massive iceberg. Photo by: NASA.
A massive crack discovered on Pine Island Glacier in Western Antarctica which scientists now say is headed toward irreversible disintegration. The crack, discovered by an overflight in 2011, will eventually release a massive iceberg. Photo by: NASA. 

Two hundred years from now, the planet could look very different. This week two landmark studies revealed that West Antarctica’s ice sheet is in a state of seemingly inevitable collapse linked to climate change. The slow-motion collapse would by itself eventually lead to a rise in global levels of 3.6-4.5 meters (12-15 feet), overrunning many of the world’s islands, low-lying areas, and coastal cities. The only silver lining is that scientists conservatively estimate that the collapse could take 200-1,000 years.

“There’s been a lot of speculation about the stability of marine ice sheets, and many scientists suspected that this kind of behavior is under way,” said Ian Joughin, a glaciologist with the University of Wisconsin, who co-authored a study in Science focusing on a key glacier in the region, Thwaites Glacier. 

The team found that Thwaites Glacier is in a state of rapid retreat, which likely cannot be halted. By itself, the Thwaites Glacier would raise global sea levels by almost 2 feet; however, the Thwaites Glacier is also the stop gap to the much larger West Antarctica ice sheet. Once the Thwaites Glacier is gone, nothing will prevent the full ice sheet from melting, according to researchers, adding another 10-13 feet. 

A high-resolution map of Thwaites Glacier's thinning ice shelf. Warm water, driven by stronger winds, is cutting into the bottom of the floating shelf on the glacier. Scientists now believe the glacier's melt is inevitable. Map by: David Shean/University of Washington.
A high-resolution map of Thwaites Glacier’s thinning ice shelf. Warm water, driven by stronger winds, is cutting into the bottom of the floating shelf on the glacier. Scientists now believe the glacier’s melt is inevitable. Map by: David Shean/University of Washington.

Moreover these estimates only account for Western Antarctica, and not other ice losses across the continent or in Greenland. 

Joughin and his team used airborne lasers to better map the topography of the ground beneath Thwaites Glacier, giving them the most accurate view yet of how melting will occur. 

But, Joughin told Climate Progress that their findings were “conservative” and “do not include all the feedbacks.” While they note that the likeliest timeline given current information is 200-500 years, the team also didn’t run a worst-case scenario, meaning the ice loss could occur even faster. 

The Science study was complemented by other research from NASA on six glaciers in same region–including Thwaites–which came broadly to the same conclusion: the melting of the region’s glaciers has passed a tipping point. This team used satellite and airborne measurements to record the melting of the glaciers since the early 1990s and better map the topography. 

“The collapse of this sector of West Antarctica appears to be unstoppable,” noted co-author Eric Rignot, with the University of California and NASA, whose study was published in Geophysical Research Letters. “At this point, the end appears to be inevitable.” 

Unfortunately, the team found no hills or mountains that could slow the melt. 

The findings also mean that the recent Intergovernmental Panel on Climate Change (IPCC) may already be out of date. The landmark report in September did not include melting from Antarctica in its estimates of sea level rise, which ranged from 0.28 meters to 1 meter (0.9-3.2 feet) by 2100. 

While melting in the region is extremely complex, but both studies agree that stronger winds–possibly linked to climate change, the hole in the ozone layer or both–have pushed warmer waters underneath the glaciers, unhinging them. 

“The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating parts of the glaciers,” added Rignot. 

While West Antarctica’s great melt may be inevitable, whether it takes a couple hundred years or a thousand may depend, at least partly, on how much fossil fuels are burned in the future, according to the researchers. 

Iceberg in the Amundsen Sea off of Western Antarctica. As the glaciers melt, they often birth massive icebergs. Photo by: NASA.
Iceberg in the Amundsen Sea off of Western Antarctica. As the glaciers melt, they often birth massive icebergs. Photo by: NASA.

Citations:

  • I. Joughin et al. Marine Ice Sheet Collapse Potentially Underway for the Thwaites Glacier Basin, West Antarctica. Science, 2014.
  • Rignot et al. Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011. Geophysical Research Letters, 2014.


Source: http://news.mongabay.com/2014/0514-hance-west-antarctica-melt.html#O7qRjxuTOQK9oxy5.99

Every tree matters: Even a little deforestation alters climate

by Bill Laurence

Thinking about knocking down a few trees in the backyard?  Think again.  Felling even a handful of trees can change the local climate, according to a new study.

Think twice before cutting...

Think twice before cutting…

It’s been known for some time that clearing forests can have regional-scale impacts on climate by reducing evapotranspiration (the emission of water vapor by plants, which cools the land) and changing albedo (how much solar radiation gets reflected away from the ground surface).

But now it appears these effects happen at surprisingly small scales.  Especially in warmer parts of the world, clearing even a football field-sized area is enough to provoke significant heating of the immediate area.

That’s an important insight.  Folks living in tropical and subtropical areas often complain that deforested lands are unpleasantly warm, less productive for farming, and more prone to harboring diseases.

So, spread the word: Cutting down trees doesn’t just have a global impact, by increasing carbon emissions; or a regional impact, by changing evapotranspiration and albedo.

Killing trees also has a sizable local impact, meaning it directly affects the quality of life of those living nearby.

Source: http://alert-conservation.org/issues-research-highlights/2014/4/16/every-tree-matters-even-a-little-deforestation-alters-climate

Severe impacts of climate change

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The impacts of climate change are likely to be “severe, pervasive, and irreversible,” the chair of the Intergovernmental Panel on Climate Change said Sunday night in Yokohama, Japan, as the world’s leading climate experts released a new survey of how our planet is likely to change in the near future, and what we can do about it.

Here’s what you need to know:

  1. We’re already feeling the impacts of climate change. Glaciers are already shrinking, changing the courses of rivers and altering water supplies downstream. Species from grizzly bears to flowers have shifted their ranges and behavior. Wheat and maize yields may have dropped. But as climate impacts become more common and tangible, they’re being matched by an increasing global effort to learn how to live with them: The number of scientific studies on climate change impacts, vulnerability, and adaptation more than doubled between 2005, before the previous IPCC report, and 2010. Scientists and policymakers are “learning through doing, and evaluating what you’ve done,” said report contributor Kirstin Dow, a climate policy researcher at the University of South Carolina. “That’s one of the most important lessons to come out of here.”
  2. Heat waves and wildfires are major threats in North America. Europe faces freshwater shortages, and Asia can expect more severe flooding from extreme storms. In North America, major threats include heat waves and wildfires, which can cause death and damage to ecosystems and property. The report names athletes and outdoor workers as particularly at risk from heat-related illnesses. As the graphic below shows, coastal flooding is also a key concern.

    risks chart

  3. Globally, food sources will become unpredictable, even as population booms.Especially in poor countries, diminished crop production will likely lead to increased malnutrition, which already affects nearly 900 million people worldwide. Some of the world’s most important staples—maize, wheat, and rice—are at risk. The ocean will also be a less reliable source of food, with important fish resources in the tropics either moving north or going extinct, while ocean acidification eats away at shelled critters (like oysters) and coral. Shrinking supplies and rising prices will cause food insecurity, which can exacerbate preexisting social tensions and lead to conflict.
  4. Coastal communities will increasingly get hammered by flooding and erosion. Tides are already rising in the US and around the world. As polar ice continues to melt and warm water expands, sea level rise will expose major metropolitan areas, military installations, farming regions, small island nations, and other ocean-side places to increased damage from hurricanes and other extreme storms. Sea level rise brings with it risks of “death, injury, ill-health, or disrupted livelihoods,” the report says.
  5. We’ll see an increase in climate refugees and, possibly, climate-related violence.The report warns that both extreme weather events and longer-term changes in climate can lead to the displacement of vulnerable populations, especially in developing parts of the world. Climate change might also “indirectly increase” the risks of civil wars and international conflicts by exacerbating poverty and competition for resources.
  6. Climate change is expected to make people less healthy. According to the report, we can expect climate change to have a negative impact on health in many parts of the world, especially poorer countries. Why? Heat waves and fires will cause injury, disease and death. Decreased food production will mean more malnutrition. And food- and water-borne diseases will make more people sick.
  7. We don’t know how much adaptation is going to cost. The damage we’re doing to the planet means that human beings are going to have to adapt to the changing climate. But that costs money. Unfortunately, studies that estimate the global cost of climate adaptation “are characterized by shortcomings in data, methods, and coverage,” according to the IPCC. But from the “limited evidence” available, the report warns that there’s a “gap” between “global adaptation needs and the funds available.”
  8. There’s still time to reduce the impacts of global warming…if we cut our emissions.Here’s the good news: The IPCC says that the impacts of climate change—and the costs of adaptation—will be “reduced substantially” if we cut our emissions of greenhouse gases.

Source: http://climatedesk.org/2014/03/if-this-terrifying-report-doesnt-wake-you-up-to-the-realities-of-what-were-doing-to-this-planet-what-will/

Amazon Inhales More Carbon than It Emits, NASA Finds

Old-growth Amazon tree canopy in Tapajós National Forest, Brazil.Old-growth Amazon tree canopy in Tapajós National Forest, Brazil. A new NASA study shows that the living trees in the undisturbed Amazon forest draw more carbon dioxide from the air than the forest’s dead trees emit. Image credit: NASA/JPL-Caltech

A new NASA-led study seven years in the making has confirmed that natural forests in the Amazon remove more carbon dioxide from the atmosphere than they emit, therefore reducing global warming. This finding resolves a long-standing debate about a key component of the overall carbon balance of the Amazon basin.

The Amazon’s carbon balance is a matter of life and death: living trees take carbon dioxide out of the air as they grow, and dead trees put the greenhouse gas back into the air as they decompose. The new study, published in Nature Communications on March 18, is the first to measure tree deaths caused by natural processes throughout the Amazon forest, even in remote areas where no data have been collected at ground level.

Fernando Espírito-Santo of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., lead author of the study, created new techniques to analyze satellite and other data. He found that each year, dead Amazonian trees emit an estimated 1.9 billion tons (1.7 billion metric tons) of carbon to the atmosphere. To compare this with Amazon carbon absorption, the researchers used censuses of forest growth and different modeling scenarios that accounted for uncertainties. In every scenario, carbon absorption by living trees outweighed emissions from the dead ones, indicating that the prevailing effect in natural forests of the Amazon is absorption.

Until now, scientists had only been able to estimate the Amazon’s carbon balance from limited observations in small forest areas called plots. On these plots, the forest removes more carbon than it emits, but the scientific community has been vigorously debating how well the plots represent all the natural processes in the huge Amazon region. That debate began with the discovery in the 1990s that large areas of the forest can be killed off by intense storms in events called blowdowns.

Espírito-Santo said that the idea for the study arose from a 2006 workshop where scientists from several nations came together to identify NASA satellite instruments that might help them better understand the carbon cycle of the Amazon. In the years since then, he worked with 21 coauthors in five nations to measure the carbon impacts of tree deaths in the Amazon from all natural causes — from large-area blowdowns to single trees that died of old age. He used airborne lidar data, satellite images, and a 10-year set of plot measurements collected by the University of Leeds, England, under the leadership of Emanuel Gloor and Oliver Phillips. He estimates that he himself spent a year-and-a-half doing fieldwork in the Amazon.

“It was a difficult and audacious study, and only Espírito-Santo’s dedication made it possible,” said Michael Keller, a research scientist at the U.S. Forest Service and co-author of the study.

Correlating satellite and airborne-instrument data with ground observations, Espírito-Santo and his colleagues devised methods to identify dead trees in different types of remotely sensed images. For example, fallen trees create a gap in the forest canopy that can be measured by lidar on research aircraft, and dead wood changes the colors in a satellite optical image. The researchers then scaled up their techniques so they could be applied to satellite and airborne data for parts of the Amazon with no corresponding ground data.

“We found that large natural disturbances — the sort not captured by plots — have only a tiny effect on carbon cycling throughout the Amazon,” said Sassan Saatchi of JPL, also a co-author. Each year, about two percent of the entire Amazon forest dies of natural causes. The researchers found that only about 0.1 percent of those deaths are caused by blowdowns.

This study looked only at natural processes in Amazonia, not at the results of human activities such as logging and deforestation, which vary widely and rapidly with changing political and social conditions.

The other institutions participating in the study are the University of New Hampshire, Durham; the Universities of Leeds and Nottingham, U.K.; Oxford University, U.K.; James Cook University, Cairns, Australia; U.S. Forest Service International Institute of Tropical Forestry, Puerto Rico; EMBRAPA Satellite Monitoring Center, Campinas, Brazil; National Institute for Research in Amazonia, Manaus, Brazil; EMBRAPA Eastern Amazonia, Santarém, Brazil; National Institute for Space Research (INPE), São José dos Campos, Brazil; the Missouri Botanical Garden, Oxapampa, Peru; and the Carnegie Institute for Science, Stanford, Calif.

NASA monitors Earth’s vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

Source: http://www.jpl.nasa.gov/news/news.php?release=2014-084

For more information about NASA’s Earth science activities in 2014, visit: http://www.nasa.gov/earthrightnow

Iconic island study on its last legs: genetic rescue needed for Isle Royale’s inbred wolves

by Emma Marris

Rolf Peterson/Minneapolis Star Tribune/MCT/Newscom

Since 1958, ecologists have watched wolf and moose populations on Isle Royale in Lake Superior wax and wane in response to each other, disease and the weather. But for the longest predator–prey study in the world, the wolf is now at the door. Devastated by inbreeding, the wolf population has dropped from 30 individuals a decade ago to just 10 spotted in field counts so far this year, leading the US National Park Service to consider importing new animals for a ‘genetic rescue’.

Now, nature is intervening — and could either save the landmark project without the need for tranquillizer darts and wolf crates, or sound its death knell. As temperatures plummeted last month, Lake Superior froze for the first time in six years. The 24-kilometre ice bridge could let wolves from the Canadian mainland cross to the US island, bringing an influx of genes (see ‘Wolf island’). But project scientists say that the opposite is more likely: free to roam, the last wolves could leave the island in search of mates. 

That would put an end to a study that has provided textbook ecology lessons for generations. It has shown how predation can structure populations of prey: when wolf numbers plummet, moose populations tend to soar (see ‘Ecosystem in flux’). And it has offered insights into wolf behaviour, moose physiology, the life cycle of moose ticks and how wolves might be driven to form packs to ward off scavengers such as ravens, rather than for any hunting advantage.

Through the decades, the search for cause and effect in the ecosystem has been rendered much easier by isolation from the mainland’s human and animal populations. Occasionally, however, Lake Superior freezes. The very first wolves came to Isle Royale over an ice bridge in the early 1940s, some 30 years after the first moose. The lake froze nearly every year at the beginning of the study, but that has changed. The most recent ice bridge was in 2008; before that, the last one was in 1997, when a wolf that biologists called ‘the old grey guy’ came to the island. He sired 34 pups and provided a rare boost of genes that doubled the population by the mid-2000s.

Whether any wolves have crossed this year’s ice bridge will not be clear immediately. The scientists are conducting their annual population survey, and are flying along the island shore in their Super Cub plane two or three times a week, but snow fills wolf tracks very quickly. If new wolves do arrive, their presence will probably be confirmed in the coming months, when DNA is extracted from faeces samples.

Source: John Vucetich/Rolf Peterson

John Vucetich, co-leader of the project and an ecologist at Michigan Technological University in Houghton, says that the need for an influx of genes is becoming urgent. In the past two decades, wolf skeletons have displayed spinal deformities that can painfully pinch nerves and affect gait and generally reduce fitness. According to work led by Vucetich and Rolf Peterson, also an ecologist at Michigan Technological University, this might explain why the number of moose needed to support a given number of wolves has increased: the predators’ attacking efficiency may be compromised (J. Räikkönen et alBiol. Conserv. 142, 1025–1031; 2009).

For Vucetich, genetic rescue is required not so much to maintain the continuity of the study as to preserve the ecosystem. Moose eat balsam fir trees. When the moose population expands, unchecked by predation, fewer fir seedlings can grow large enough to ‘escape’ into the canopy above the reach of moose and reproduce. There is already a missing generation of trees from between about 1910, when the moose arrived on the island, and 1940, when the wolves came. Most of Isle Royale’s balsam firs are thus either older than 100 years and near the end of their lives, or young and short enough to be browsed to death. If the trees do not achieve escape in the next decade or so, says Vucetich, “large portions of Isle Royale are not going to generate balsam fir, which is a really basic component of a boreal forest ecosystem”.

Many scientists familiar with Isle Royale support genetic rescue, especially because human activity has contributed to the current population crash. Climate change has led to the decreasing frequency of ice bridges. Canine parvovirus, probably caught from a domestic dog, caused the wolf population to fall from around 50 to 14 in the early 1980s. And in 2012, three wolves were found dead in an abandoned mining pit. Given this history of human influence, the argument that leaving the wolves alone would be allowing nature to take its course does not sway most ecologists.

David Mech, a US Geological Survey wolf biologist based in St Paul, Minnesota, argues in favour of “watchful waiting”. He says that much can be learned from studying how inbreeding affects population persistence, and that the knowledge would be useful for conservation biologists, who often need to nurture small, inbred populations of endangered species. He is not convinced that the wolves will die out; they have hit low numbers before and bounced back, he notes. And even if they do disappear, new wolves can be brought in quickly.

But Vucetich says that it could be five years before the last wolf dies and scientists confirm its demise, and another five before federal bureaucracies approve a genetic rescue and a pack develops into a predation force. He fears that a decade without significant moose predation would leave the fir trees devastated.

Phyllis Green, superintendent of the Isle Royale National Park, is considering three alternatives: doing nothing; watchful waiting followed by reintroduction if the population hits zero; or genetic rescue. She has not initiated a formal decision-making process, and will not commit to a timeline, but says that she wants to make a decision in consultation with her regional and national directors “before we run out of options”.

She is proceeding cautiously, she says, in part because of the implications of her decision. The mandate of the National Parks Service, as enshrined in a 1916 Act of Congress, is to “conserve the scenery and the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations”. Generally, this has meant a hands-off approach, but a genetic rescue could set a precedent for interventions to counteract the effects of climate change in other parks.

Green knows that many scientists are in favour of genetic rescue, but she also hears from “wilderness-oriented” advocates who urge her not to intervene. “It is one of the wicked problems,” she says.

Nature 506, 140–141 (13 February 2014) doi:10.1038/506140a

Source: http://www.nature.com/news/iconic-island-study-on-its-last-legs-1.14697

Bitter winter, pup survival alter Isle Royale wolf debate

Article by: JOSEPHINE MARCOTTY

Healthy pups and frigid weather change the scientific debate on Isle Royale

In the upper left, the male and female alpha wolves of this pack on Isle Royale rebuke one of their new pups born last year on Isle Royale. Photo: JOHN VUCETICH,

It’s only February, and already it’s been an extraordinary winter for the wolves of Isle Royale.

At least two new healthy pups, and perhaps three, have survived their first perilous months of life — proof that the famous wolves, which number less than a dozen, may not be dwindling after all.

And twice this winter, the bitter cold that has halted shipping across Lake Superior has also created temporary ice bridges across the 20-mile channel between Isle Royale and the Minnesota-Ontario mainland, raising the tantalizing possibility that once again wolves could either leave the island or arrive on their own four feet.

Both developments are likely to only confound a precedent-setting decision that faces the National Park Service: whether to intervene in nature’s course and bring new wolves onto the island in an effort to preserve them and the critical balance between the predators and their primary prey, moose. Conservationists say the decision could establish new policy on managing critical species in national parks everywhere and even change the definition of wilderness as a place where only nature is allowed to rule.

The wolves, which once numbered as many as 50, are at their lowest ebb since researchers first began tracking them in the 1950s and are closely followed by naturalists all over the world. Scientists running the Isle Royale wolf study today, from Michigan Technological University say they fear that even with the new pups, they could die out, largely as a result of inbreeding.

At best, the new pups “might extend the amount of time the population can bump along,” said Rolf Peterson, who has been studying the wolves and moose along with John Vucetich for years.

In a series of e-mails sent from the island this week, Peterson said that even now the number of wolves is too small to keep the moose population in check and the forest ecosystem in balance. Since 2006, moose numbers have more than doubled to nearly 1,000. That’s far less than their peak of nearly 2,500 more than 30 years ago, but the rate of growth is dramatic.

The huge mammals depend on balsam firs, one of the primary species of trees on the island, as a major part of their diet. If they eat too many, then other trees would take over and, in the long run, neither wolves or moose would survive.

But other wolf experts disagree, including David Mech, a wolf expert with the U.S. Geological Survey in Minnesota. Mech said that the wolves’ population is perilously low, but that it has bounced back before, and that the pups are evidence that it can again. Many of the wolves, he said, are only now at the best age for breeding, and this year could see even more and larger litters, he said.

“Those wolves are not nonreproductive,” he said. “In another year or two they could produce some more.”

Precarious

In the meantime, scientists say they provide valuable information on reproduction, genetics and ecology. This week, the prestigious journal Nature weighed in with an editorial.

“A declining island wolf population underlines the influence that humans have on nature,” it read. It points out that the whole system is “highly artificial.” Wolves and moose have been on the island less than 100 years, and in the 1980s the wolf population was nearly wiped out by canine parvovirus, an infection likely brought to the island by someone’s pet. (Dogs are no longer allowed.)

Meanwhile, climate change — also caused by humans — is greatly reducing the chances for the ice bridges that brought wolves to the island in the first place, it said.

Once a near seasonal event, the bridges have become increasingly rare. The last one formed in 2008, when two wolves collared with tracking devices disappeared, perhaps to the mainland. The last bridge before that was in 1997, when a wolf named “Old Gray Guy” appeared on the island and went on to sire dozens of puppies, providing an infusion of new genes that researchers credit with saving the population from demise.

This year satellite images show that two bridges have formed and then been broken again by wind, the latest in early February, said Peterson.

Isabelle’s fate

Isabelle, a five-year-old female, is not attached to either of the two packs on Isle Royale. Photo: ROLF PETERSON

Meanwhile, as humans fret about the wolves’ survival and the meaning of wilderness, Isabelle waits. She is, literally, a lone wolf on Isle Royale and a prime candidate to mate with a new arrival, should one come, or take off across an ice bridge, researchers said.

Isabelle was born in 2008 to one of the two packs on the island, but, as wolves often do, left the pack in 2012 to find a mate. The pickings are few — and all the males are related to her. That inhibits mating in wolves as well as people, Peterson said.

In addition, lone wolves are vulnerable to attacks from breeding packs in the relentless competition for the right to reproduce.

Because she wears a tracking collar, the researchers have been able to follow her lonely and persecuted life. Last year they saw three other wolves chase her to the edge of the water and attack her with all the ferocity they use to bring down a 900-pound moose. They left her wounded and bleeding on the edge of the ice. When the researchers left last winter, they weren’t sure if they would see her again.

“But she has survived,” Vucetich announced on the research study’s blog in late January. “It would not be surprising if she’s learned to kill moose by herself. A wolf that can do so is better than most.”

Isabelle is now 5, a prime age to mate. About one in 10 wolves will strike off on their own and try to start new packs, and some will travel for hundreds of miles in their search. On Isle Royale, however, the wolves are trapped — unless there is an ice bridge.

No one knows what’s in the heart of a wolf, but Peterson said he thinks it’s quite possible, that given the chance, Isabelle will head out. Mech said that as long as there are potential mates on the island, she’s more likely to stay put.

The chances that a wolf would come from the mainland are also very small, researchers said. It’s known to have happened only three times in the island’s history. And today mainland wolves face a treacherous path across roads, yards and urban areas — never mind 20 miles of shifting ice.

Still, the survival of the three pups and the renewed possibility of ice bridges may have bought the National Park Service some time. Phyllis Green, park superintendent, is weighing three options: doing nothing, reintroducing wolves if their numbers hit zero or a “genetic rescue” by bringing a few new wolves to mate with those that are in residence.

Peterson and Vucetich said they favor genetic rescue. And Isabelle, if she had a vote, would likely agree.

Source: http://www.startribune.com/local/245704671.html