Habitat Connectivity

The catastrophic decline around the world of “apex” predators such as wolves, cougars, lions or sharks has led to a huge increase in smaller “mesopredators” that are causing major economic and ecological disruptions, a new study concludes.

The findings, published October 1 in the journal Bioscience, found that in North America all of the largest terrestrial predators have been in decline during the past 200 years while the ranges of 60 percent of mesopredators have expanded. The problem is global, growing and severe, scientists say, with few solutions in sight.

An example: in parts of Sub-Saharan Africa, lion and leopard populations have been decimated, allowing a surge in the “mesopredator” population next down the line, baboons. In some cases children are now being kept home from school to guard family gardens from brazen packs of crop-raiding baboons.

In case after case around the world, the researchers said, primary predators such as wolves, lions or sharks have been dramatically reduced if not eliminated, usually on purpose and sometimes by forces such as habitat disruption, hunting or fishing. Many times this has been viewed positively by humans, fearful of personal attack, loss of livestock or other concerns. But the new picture that’s emerging is a range of problems, including ecosystem and economic disruption that may dwarf any problems presented by the original primary predators.

The elimination of wolves is often favored by ranchers, for instance, who fear attacks on their livestock. However, that has led to a huge surge in the number of coyotes, a “mesopredator” once kept in check by the wolves. The coyotes attack pronghorn antelope and domestic sheep, and attempts to control them have been hugely expensive, costing hundreds of millions of dollars.

The problems are not confined to terrestrial ecosystems. Sharks, for instance, are in serious decline due to overfishing. In some places that has led to an explosion in the populations of rays, which in turn caused the collapse of a bay scallop fishery and both ecological an economic losses.

Source and complete article: ScienceDaily (Oct. 4, 2009)

The Asiatic black bear is now listed as vulnerable, therefore six of the eight species of bear in the world are now officially facing extinction.

The smallest, the sun bear, is the latest to be classified as vulnerable on the Red List of Threatened Species. Four other species – Asiatic black bear, Sloth bear, Andean bear and Polar bear – are also listed as vulnerable.

The giant panda is facing the greatest threat and remains in the endangered category. There is least concern over the European brown bear and the American black bear.

The sun bear found in Souteast Asia, Sumatra and Borneo, will be included in the 2007 Red List drawn up by the World Conservation Union (IUCN). Previously it was known as ‘Data Defficient’ meaning not enough was known about it to give it a classification. Rob Steinmetz, co-chair of the IUCN Bear Specialist Group’s sun bear expert team, said: “Although we still have lot to learn about the biology and ecology of this species, we are quite certain that it is in trouble.

“We estimate that sun bears have declined by at least 30 per cent over the past 30 years (three bear generations), and continue to decline at this rate. Deforestation has reduced both the area and quality of their habitat. Where habitat is now protected, commercial poaching remains a significant threat.

“We are working with governments, protected area managers, conservation groups and local people to prevent extinction of the many small, isolated sun bear populations that remain in many parts of Southeast Asia.”

Bear hunting is illegal throughout Southern Asia, but they suffer heavy losses from poachers, who risk the small chance of being caught against lucrative gains from selling parts. Bile from the bear’s gall bladder is used in traditional Chinese medicine and their paws are consumed as a delicacy. Additionally, bears are often killed when they prey on livestock or raid agricultural crops. Bears simply roaming near a village may be killed because they are perceived as a threat to human life.

Dave Garshelis, co-chair of the Bear Specialist Group, which met earlier this month in Mexico, to update the status of the eight species, said: “Although the bear population estimates for Asia are not as reliable as we would like, we estimate that bears in Southeast Asia are declining at a particularly rapid rate due to extensive loss of forest habitat combined with rampant poaching.”

Bruce McLellan, also a co-chair, said: “An enormous amount of effort and funding for conservation and management continue to be directed at bears in North America where their status is relatively favourable. It is unfortunate that so little is directed at bears in Asia and South America where the need is extreme. We are trying to change this situation but success is slow.”

By Paul Eccleston, Telegraph.co.uk

Climate change wiped out cave bears 13 millennia earlier than thought.

Enormous cave bears, Ursus spelaeus, that once inhabited a large swathe of Europe, from Spain to the Urals, died out 27,800 years ago, around 13 millennia earlier than was previously believed, scientists have reported.

The new date coincides with a period of significant climate change, known as the Last Glacial Maximum, when a marked cooling in temperature resulted in the reduction or loss of vegetation forming the main component of the cave bears’ diet.

In a study published in Boreas, researchers suggest it was this deterioration in food supply that led to the extinction of the cave bear, one of a group of ‘megafauna’ – including woolly mammoth, woolly rhinoceros, giant deer and cave lion – to disappear during the last Ice Age.

They found no convincing evidence of human involvement in the disappearance of these bears. The team used both new data and existing records of radiocarbon dating on cave bear remains to construct their chronology for cave bear extinction.

“Our work shows that the cave bear, among the megafauna that became extinct during the Last Glacial period in Europe, was one of the earliest to disappear,” said Dr Martina Pacher of the Department of Palaeontology at the University of Vienna. “Other, later extinctions happened at different times within the last 15,000 years.”

Dr Pacher carried out the research alongside Professor Anthony J. Stuart of the Natural History Museum, London, and the University of Durham.

Many scientists previously claimed that cave bears survived until at least 15,000 years ago, but Dr Pacher and Professor Stuart claim that the methodology of these earlier studies included many errors in dating as well as confusion between cave bear and brown bear remains.

The pair also concluded, from evidence on skull anatomy, bone collagen and teeth, that these extinct mammals were predominantly vegetarian, eating a specialised diet of high-quality plants. Compared with other megafaunal species that would also become extinct, the cave bear had a relatively restricted geographical range, being confined to Europe, which may offer an explanation as to why it died out so much earlier than the rest.

“Its highly specialised mode of life, especially a diet of high-quality plants, and its restricted distribution left it vulnerable to extinction as the climate cooled and its food source diminished,” said Dr Pacher.

The brown bear, with which Ursus spelaeus shares a common ancestor, was spread throughout Europe and much of northern Asia and has survived to the present day.

“A fundamental question to be answered by future research is: why did the brown bear survive to the present day, while the cave bear did not?” said Professor Stuart. Answers to this question may involve different dietary preferences, hibernation strategies, geographical ranges, habitat preferences and perhaps predation by humans.

Cave bears were heavily built animals, with males growing up to around 1000kg. The maximum recorded weight of both Kodiak bears and polar bears – the largest bears living today – is 800kg, with averages of around 500kg.

Scientists have recovered a large quantity of cave bear remains from many cave sites, where they are believed to have died during winter hibernation. Caves provide an ideal environment for the preservation of these remains.

Despite over 200 years of scientific study – beginning in 1794 when a young anatomist, J. Rosenmüller, first described bones from the Zoolithenhöhle in Bavaria as belonging to a new extinct species, which he called cave bear – the timing and cause of its extinction remain controversial.

By far the best source of information on the appearance of cave bears in the flesh is to be found in red pigment cave paintings in the Grotte Chauvet in the Ardèche region of southern France. These are the only depictions in Palaeolithic art that can be attributed unambiguously to the cave bear.

http://en.wikipedia.org/wiki/Cave_bear

source SCIENCE, 13 OCTOBER 2006

Why are Polar Bears falling through the sea ice? Scientists have found the first unequivocal evidence that the Arctic region is warming at a faster rate than the rest of the world at least a decade before it was predicted to happen.

Climate-change researchers have found that air temperatures in the region are higher than would be normally expected during the autumn because the increased melting of the summer Arctic sea ice is accumulating heat in the ocean. The phenomenon, known as Arctic amplification, was not expected to be seen for at least another 10 or 15 years and the findings will further raise concerns that the Arctic has already passed the climatic tipping-point towards ice-free summers, beyond which it may not recover.

The Arctic is considered one of the most sensitive regions in terms of climate change and its transition to another climatic state will have a direct impact on other parts of the northern hemisphere, as well more indirect effects around the world.

Although researchers have documented a catastrophic loss of sea ice during the summer months over the past 20 years, they have not until now detected the definitive temperature signal that they could link with greenhouse-gas emissions.

However, in a study to be presented later today to the annual meeting of the American Geophysical Union in San Francisco, scientists will show that Arctic amplification has been under way for the past five years, and it will continue to intensify Arctic warming for the foreseeable future.

Computer models of the global climate have for years suggested the Arctic will warm at a faster rate than the rest of the world due to Arctic amplification but many scientists believed this effect would only become measurable in the coming decades.

The Independent

By Steve Connor, Science Editor
Tuesday, 16 December 2008

Photo credits: Peter Evins – WWF Canada, Jonathan Hayward – AP