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World’s sixth mass extinction may be underway: study

World's sixth mass extinction may be underway: studyAFP/File – This file photo shows a colobus monkey kissing his newly born sibling. In the last five centuries, at …

by Richard Ingham and Laurent Banguet Fri Mar 4, 12:58 am ET

PARIS (AFP) – Mankind may have unleashed the sixth known mass extinction in Earth’s history, according to a paper released by the science journal Nature.

Over the past 540 million years, five mega-wipeouts of species have occurred through naturally-induced events.

But the new threat is man-made, inflicted by habitation loss, over-hunting, over-fishing, the spread of germs and viruses and introduced species, and by climate change caused by fossil-fuel greenhouse gases, says the study.

Evidence from fossils suggests that in the "Big Five" extinctions, at least 75 percent of all animal specieswere destroyed.

Palaeobiologists at the University of California at Berkeley looked at the state of biodiversity today, using the world’s mammal species as a barometer.

Until mankind’s big expansion some 500 years ago, mammal extinctions were very rare: on average, just two species died out every million years.

But in the last five centuries, at least 80 out of 5,570 mammal species have bitten the dust, providing a clear warning of the peril to biodiversity.

"It looks like modern extinction rates resemble mass extinction rates, even after setting a high bar for defining ‘mass extinction," said researcher Anthony Barnosky.

This picture is supported by the outlook for mammals in the "critically endangered" and "currently threatened" categories of the Red List of biodiversity compiled by the International Union for Conservation of Nature (IUCN).

On the assumption that these species are wiped out and biodiversity loss continues unchecked, "the sixth mass extinction could arrive within as little as three to 22 centuries," said Barnosky.

Compared with nearly all the previous extinctions this would be fast-track.

Four of the "Big Five" events unfolded on scales estimated at hundreds of thousands to millions of years, inflicted in the main by naturally-caused global warming or cooling.

The most abrupt extinction came at the end of the Cretaceous, some 65 million years ago when a comet or asteroid slammed into the Yucatan peninsula, in modern-day Mexico, causing firestorms whose dust cooled the planet.

An estimated 76 percent of species were killed, including the dinosaurs.

The authors admitted to weaknesses in the study. They acknowledged that the fossil record is far from complete, that mammals provide an imperfect benchmark of Earth’s biodiversity and further work is needed to confirm their suspicions.

But they described their estimates as conservative and warned a large-scale extinction would have an impact on a timescale beyond human imagining.

"Recovery of biodiversity will not occur on any timeframe meaningful to people," said the study.

"Evolution of new species typically takes at least hundreds of thousands of years, and recovery from mass extinction episodes probably occurs on timescales encompassing millions of years."

Even so, they stressed, there is room for hope.

"So far, only one to two percent of all species have gone gone extinct in the groups we can look at clearly, so by those numbers, it looks like we are not far down the road to extinction. We still have a lot of Earth’s biota to save," Barnosky said.

Even so, "it’s very important to devote resources and legislation toward species conservation if we don’t want to be the species whose activity caused a mass extinction."

Asked for an independent comment, French biologist Gilles Boeuf, president of the Museum of Natural History in Paris, said the question of a new extinction was first raised in 2002.

So far, scientists have identified 1.9 million species, and between 16,000 and 18,000 new ones, essentially microscopic, are documented each year.

"At this rate, it will take us a thousand years to record all of Earth’s biodiversity, which is probably between 15 and 30 million species" said Boeuf.

"But at the rate things are going, by the end of this century, we may well have wiped out half of them, especially in tropical forests and coral reefs."

March 5, 2011 Posted by | animal behavior, Animal Related Education, animals, Wild Animals | , , , , , , , | Leave a comment

25% of Wild Mammal Species Are Imperiled

      

BARCELONA, Oct. 6 — At least a quarter of the world’s wild mammal species are at risk of extinction, according to a comprehensive global survey released here Monday.

The new assessment — which took 1,700 experts in 130 countries five years to complete — paints “a bleak picture,” leaders of the project wrote in a paper being published in the journal Science. The overview, made public at the quadrennial World Conservation Congress of the International Union for Conservation of Nature (IUCN), covers all 5,487 wild species identified since 1500. It is the most thorough tally of land and marine mammals since 1996.

“Mammals are definitely declining, and the driving factors are habitat destruction and over-harvesting,” said Jan Schipper, the paper’s lead writer and the IUCN’s global mammals assessment coordinator. The researchers concluded that 25 percent of the mammal species for which they had sufficient data are threatened with extinction, but Schipper added that the figure could be as high as 36 percent because information on some species is so scarce.

Land and marine mammals face different threats, the scientists said, and large mammals are more vulnerable than small ones. For land species, habitat loss and hunting represent the greatest danger, while marine mammals are more threatened by unintentional killing by pollution, ship strikes and being caught in fishing nets.

While large species such as primates (including the Sumatran orangutan and red colobus monkeys in Africa) and ungulates (hoofed animals such as Africa’s Dama gazelle and the Malaysian tapir) may seem more physically imposing, the researchers wrote that these animals are more imperiled than smaller creatures such as rodents and bats because they “tend to have lower population densities, slower life histories, and larger home ranges, and are more likely to be hunted.”

Primates face some of the most intense pressures: According to the survey, 79 percent of primates in South and Southeast Asia are facing extinction.

Conservation International President Russell A. Mittermeier, one of the paper’s writers and a primate specialist, said animals in the region are being hit with “a triple whammy.”

“It’s not that surprising, given the high population pressures, the level of habitat destruction, and the fairly extreme hunting of primates for food and medicinal purposes,” he said in an interview. He added that some areas in Vietnam and Cambodia are facing “an empty forest syndrome,” as even once-populous species such as the crab-eating macaque, or temple monkey, are “actually getting vacuumed out of some areas where it was common.

In some cases, the scientists have a precise sense of how imperiled a species has become: There are 19 Hainan gibbons left in the wild on the island off China’s southeast coast, Mittermeier said, which actually counts as progress because there used to be just a dozen.

With others, including the beaked whale and the jaguar, researchers have a much vaguer idea of their numbers despite technological advances — such as satellite and radio tagging, camera tracking and satellite-based GPS (global positioning system) mapping. The authors of the assessment wrote that most land mammals occupy “areas smaller than the United Kingdom,” while “the range of most marine mammals is smaller than one-fifth of the Indian Ocean.”

The report on mammals came on the same day that the IUCN updated its “Red List” — a separate periodic survey of nearly 45,000 species of plants and animals — and concluded that 32 percent are threatened with extinction. Its scientists added 20 of the world’s 161 species of grouper to the list of those at risk of extinction, along with several tarantula species.

Jonathan Baillie, who directs conservation programs at the Zoological Society of London, said: “It’s a continual decline in all cases.”

Not all of the news was grim yesterday: IUCN officials said that the La Palma giant lizard, believed to be extinct for 500 years, was rediscovered last year in the Canary Islands and is now considered critically endangered.

The writers of the mammals assessment said the observed declines are not inevitable. “At least 5 percent of currently threatened species have stable or increasing populations,” they wrote, “which indicates that they are recovering from past threats.”

Said Mittermeier: “It comes down to protecting habitats effectively, through protected areas, and preventing hunting and other forms of exploitation.” As one example of how conservation can be effective, he noted that in areas where scientific researchers work, animals stand a much better chance of surviving. “Where you have a research presence, it’s as good or better than a guard force,” he said.

Schipper offered the model of the U.S. effort to bring back the black-footed ferret, which was essentially extinct on the North American prairie as of 1996. “Now it’s endangered, which, in this case, is a huge improvement,” he said. “When governments and scientists commit resources to a project, many species can be recovered.”

Monday’s reports come as researchers have been documenting effects of human-generated greenhouse gases. In a paper published Thursday in the journal Geophysical Research Letters, a team at the Monterey Bay Aquarium Research Institute found that ocean acidification spurred by carbon emissions will cause sound to travel farther underwater, because increasingly acidic seawater absorbs less low- and mid-frequency sound.

By 2050, the researchers predicted, sounds could travel as much as 70 percent farther in parts of the Atlantic Ocean and other areas, which may improve marine mammals’ ability to communicate but also increase background noise, which could prove disorienting.

“We understand the chemistry of the ocean is changing. The biological implications of that we really don’t know,” said ocean chemist Keith Hester, the lead writer. “The magnitude to which sound absorption will change, based mainly on human contribution, is really astounding.”

By Juliet Elperin, Washington Post Staff Writer, Tuesday, October 7, 2008; Page A13

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