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.

Continue reading

Does hunting impact carnivore recruitment?

Recruitment in a social carnivore before and after harvest” is the title of a recent paper published on the Journal Animal Conservation of the Zoological Society of London that shows collateral impacts of harvesting wolves:

We attributed just 18–38% of pup mortality directly to harvest and suggest that there are indirect effects of harvest on recruitment that may be associated with changes in group size and structure. Models that do not include both direct and indirect effects of harvest on recruitment may underestimate the potential impact of harvest on population growth in social species.”

The article does not have open access and it is available HERE but you can read it in this LINK.

Other recommended reads: http://www.klamathconservation.org/science_blog/conservation/?p=192

Popular Pesticides Linked to Drops in Bird Populations

By Helen Thompson

Let me tell you about the birds and the bees: A family of pesticides called neonicotinoids has been linked with pollinator declines. While their involvement in bee colony collapse is hotly debated, ecologists are wondering: could neonicotinoids impact something further up the food chain?

A study published yesterday in Nature suggests that birds and bees may share a common enemy. Dutch researchers have found a correlation between bird population declines in the Netherlands and higher concentrations of the common neonicotinoid pesticide imidacloprid in surface water.

“There is an alarming trend between declines of local bird populations and imidacloprid in the environment, which needs serious attention to see what we want to do with this pesticide in the future,” says Hans de Kroon, a co-author and plant ecologist at Radboud University in the Netherlands. The researchers posit that the pesticide affects these birds by killing off their bug food supply.

Concerns have been raised about neonicotinoids’ affect on bees since the chemical first emerged on the pesticide scene in the 1990s. What makes them popular is the fact that they’re supposed to only harm insect pests keen to munch on plant leaves. In insects, the pesticide binds to specific receptors in the nervous system, ultimately killing the insect. Continue reading

LESS WILDLIFE MEANS MORE TERRORISM

The harvest of wild terrestrial and aquatic animals each year injects more than $400 billion dollars into the world economy. That harvest provides 15% of the planet’s human population with a livelihood. It’s also the primary source of animal protein for more than a billion of our species. It’s also led to piracy, slavery, and terrorism.

The over-harvest of wild animals, both from land and sea, has created a market defined by low supply and high demand. And that, according to UC Berkeley environmental scientist Justin S. Brashares and colleagues, has led to the proliferation of organized crime in some of the poorest parts of the world. Over-hunting and over-fishing have, at least in part, created conditions where human trafficking and terrorism can thrive.

The reason this is the case comes down to simple economics. “Wildlife declines often necessitate increased labor to maintain yields,” argues Brashares in this week’s issue of Science Magazine. To acquire increasingly scarce resources without the a simultaneous increase in costs, “harvesters of wildlife resort to acquiring trafficked adults and children…A vicious cycle ensues, as resource depletion drives harvesters to increase their use of forced labor to stay competitive.” Continue reading

Why is our wildlife in trouble? Because we’re ignoring science

by Emma Burns
Cattle drovers have won back the right to graze livestock in the Australian Alps – against scientists’ advice. AAP Image/Bob Richardson

From reef dredging, to shark culling, to opening old-growth forests to logging, environmental policies are leaving Australia’s wildlife exposed to threats. The reason, we propose, is that society and government are often ignoring science – particularly ecology.

In a recently published book, more than 80 Australian environment professionals looked at what we have learned from studying ecosystems.

This book is based on long-term field research in numerous ecosystems. From this research, there are examples of science both being used and ignored in management and policy.

There is some good news. Forest studies have led to more sustainable forestry in Tasmania, and potentially soon in Victoria. And new restoration techniques are being trialed to protect endangered woodlands in the Australian Capital Territory.

But there’s still a long way to go. Here are three examples where science is seemingly being ignored by current environmental policy.

Alpine grazing

Under a trial approved by the federal government, cattle are now once again grazing in the Alpine National Park.

There is no scientific case for the trial. Since the 1940s scientists have been monitoring the alpine ecosystems.

For instance we know that hard-hooved animals such as cattle, sheep, horses, deer and pigs have significant negative impacts. These include changes to species composition, ecosystem dynamics, and fewer herbs such as Billy Buttons and Snow-daisies.

These studies also clearly demonstrate that grazing by domestic livestock does not reduce the frequency or severity of fire in the Australian alps, and can actually increase the risk of fire, as grazing encourages growth of flammable shrubs.

As a consequence of these studies, grazing of sheep and cattle had been phased out of most alpine areas. It poses a clear threat to the alpine ecosystem and natural heritage values of Alpine National Park, and we know that when grazing stops, the alpine ecosystems recover — albeit slowly, and future recovery is unlikely to be as robust as past recovery because environmental conditions are changing.

Alpine Billy Button Photo by Henrik Wahren

Culling fruit bats

Queensland and New South Wales are currently culling fruit bats, despite evidence that culls do not reduce health risks or work.

The threatened spectacled flying fox (Pteropus conspicillatus), targeted as part of the culls, also falls under conservation regulations and provides free services for human society, such as dispersal of pollen and seeds. But many humans fear them because of Hendra virus, and dislike them because urban camps are smelly and noisy, and because they damage commercial fruit crops.

Spectacled Flying-foxes Photo by A. McKeown

Regular calls are made for their conservation status to be downgraded and for management interventions such as camp removal and culling to be adopted. But a ten-year study that we referred to of the habits of spectacled flying foxes demonstrates that apparently simple solutions like moving or destroying camps will ultimately fail because the species is nomadic — naive individuals are always arriving at camps meaning that camps easily re-establish at the site or nearby.

The often repeated claims that flying-fox populations are exploding are also not supported by the research.

Forest management

Recently Prime Minister Tony Abbott suggested that too much forest is locked away from logging and blames “green ideology” for this. We don’t need ideology driving decision making about forest management but more science would be good.

Research on the effects of the 2009 Black Saturday fires in Victoria shows that a decline in hollow bearing trees, which is leading to declines in some fauna, has been linked to these high severity fires and a long history of timber harvesting. On the basis of this research, as well as economic factors, there is a public campaign to change this area’s land tenure from State Forest to National Park.

Professor David Lindenmayer proposes a Giant Forest National Park

However this research is specific to forests in Victoria, and the story may be different in other forest systems. Each system in question needs independent research.

How do we get more science in policy?

Environmental scientists, researchers and policy-makers have a “social imperative” to increase scientific knowledge in policy. Alongside our work on ecosystems, we developed a policy handbook to guide policy makers. And we encourage more ecologists, and their institutions, to distill and communicate their science in similar ways.

It’s not too late, but scientist and policy-makers need to work together and act with the urgency, scale and intelligence needed to meet our environmental challenges.

The book and policy handbook referred to in this article were supported by the Terrestrial Ecosystem Research Network. TERN has catalysed collaborations between researchers dedicated to ecological research but who would have been unlikely to work together without support from TERN.

Source: http://theconversation.com/why-is-our-wildlife-in-trouble-because-were-ignoring-science-27226

Drastic population fluctuations explain the rapid extinction of the passenger pigeon

The number of passenger pigeons went from billions to zero in mere decades, in contrast to conventional wisdom that enormous population size provides a buffer against extinction. Our understanding of the passenger pigeon’s extinction, however, has been limited by a lack of knowledge of its long-term population history. Here we use both genomic and ecological analyses to show that the passenger pigeon was not always super abundant, but experienced dramatic population fluctuations, which could increase its vulnerability to human exploitation. Our study demonstrates that high-throughput–based ancient DNA analyses combined with ecological niche modeling can provide evidence allowing us to assess factors that led to the surprisingly rapid demise of the passenger pigeon.

To assess the role of human disturbances in species’ extinction requires an understanding of the species population history before human impact. The passenger pigeon was once the most abundant bird in the world, with a population size estimated at 3–5 billion in the 1800s; its abrupt extinction in 1914 raises the question of how such an abundant bird could have been driven to extinction in mere decades. Although human exploitation is often blamed, the role of natural population dynamics in the passenger pigeon’s extinction remains unexplored. Applying high-throughput sequencing technologies to obtain sequences from most of the genome, we calculated that the passenger pigeon’s effective population size throughout the last million years was persistently about 1/10,000 of the 1800’s estimated number of individuals, a ratio 1,000-times lower than typically found. This result suggests that the passenger pigeon was not always super abundant but experienced dramatic population fluctuations, resembling those of an “outbreak” species. Ecological niche models supported inference of drastic changes in the extent of its breeding range over the last glacial–interglacial cycle. An estimate of acorn-based carrying capacity during the past 21,000 y showed great year-to-year variations. Based on our results, we hypothesize that ecological conditions that dramatically reduced population size under natural conditions could have interacted with human exploitation in causing the passenger pigeon’s rapid demise. Our study illustrates that even species as abundant as the passenger pigeon can be vulnerable to human threats if they are subject to dramatic population fluctuations, and provides a new perspective on the greatest human-caused extinction in recorded history.

This article contains supporting information online at http://www.pnas.org/content/suppl/2014/06/13/1401526111.DCSupplemental/pnas.1401526111.sapp.pdf

Reference:

Chih-Ming HungPei-Jen L. Shaner,Robert M. ZinkWei-Chung Liu,Te-Chin ChuWen-San Huang, Shou-Hsien Li

Drastic population fluctuations explain the rapid extinction of the passenger pigeon PNAS 2014 published ahead of printJune 16, 2014,

http://www.pnas.org/content/early/2014/06/11/1401526111?

How Many Wolves Died for Your Hamburger?

by  Population and Sustainability Director, Center for Biological Diversity

 

When you bite into a hamburger or steak, you already know the cost to the cow, but what about the wolves, coyotes, bears and other wildlife that were killed in getting that meat to your plate?

There are a lot of ways that meat production hurts wildlife, from habitat taken over by feed crops to rivers polluted by manure to climate change caused by methane emissions. But perhaps the most shocking is the number of wild animals, including endangered species and other non-target animals, killed by a secretive government agency for the livestock industry.

Last year Wildlife Services, an agency within the Department of Agriculture, killed more than 2 million native animals. While wolf-rancher conflicts are well known, the death toll provided by the agency also included 75,326 coyotes, 3,700 foxes and 419 black bears. Even prairie dogs aren’t safe: They’re considered pests, blamed for competing with livestock for feed and creating burrow systems that present hazards for grazing cattle. The agency killed 12,186 black-tailed prairie dogs and destroyed more than 30,000 of their dens.

The methods used to kill these animals are equally shocking: death by exploding poison caps, suffering in inhumane traps and gunned down by men in airplanes and helicopters.

How many of the 2 million native animals were killed to feed America’s meat habit? No one really knows. This is where the secrecy comes in: While we know that they frequently respond to requests from the agricultural community to deal with “nuisance animals,” Wildlife Services operates with few rules and little public oversight. That’s why the Center for Biological Diversity, where I work, has called on the Obama administration to reform this rogue agency to make it more transparent and more accountable. Despite the growing outcry from the public, scientists, non-governmental organizations and members of Congress, the federal agency shows no signs of slowing its killing streak.

There are two important ways that you can help rein in Wildlife Services. First, sign our online petition demanding that the Department of Agriculture create rules and public access to all of the agency’s activities. Second, start taking extinction off your plate. Our growing population will mean a growing demand for meat and for the agency’s deadly services, unless we take steps to reduce meat consumption across the country. By eating less or no meat, you can reduce your environmental footprint and help save wildlife.

Source: http://www.huffingtonpost.com/stephanie-feldstein/how-many-wolves-died-for-your-hamburger_b_5535494.html