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article imageSixth great extinction imperils amphibians, birds, mammals and us

By Megan Hamilton     Dec 15, 2014 in Environment
The earth is entering into a dark period of human-caused devastation that is threatening 41 percent of all amphibians, 26 percent of all mammals, and 13 percent of all birds.
We have ourselves to blame for much of this, an acclaimed journal has found.
The Sumatran elephant, Amur leopard, and mountain gorilla are already considered critically endangered, and nearly extinct, but the study points out that other animals now considered as only endangered are also at risk of vanishing in the wild. This includes bonobos, bluefin tuna, and loggerhead turtles, The Guardian explains.
Lynn Szwalkiewwicz
Tasmanian Tiger
Tasmanian Tiger
In every case, human activity is involved, the science journal Nature points out. The seemingly endless march of agriculture is crushing millions of acres of wild lands under the plough every year and leaving animals without homes. The introduction of invasive species, frequently inadvertently helped along by humans is wreaking havoc among native communities of creatures, and pollution and overfishing are killing marine ecosytems.
"Habitat destruction, pollution or overfishing either kills off wild creatures and plants or leaves them badly weakened," Derek Tittensor, a marine ecologist at the World Conservation Monitoring Centre in Cambridge told The Guardian. "The trouble is that in coming decades, the additional threat of worsening climate change will become more and more pronounced and then kill off these survivors."
Complicating the problem is the fact that there are gaps in scientists' knowledge about the diversity of life on earth. Estimates of the total number of species of animals, plants and fungi vary widely from two million to 50 million. Then there's the fact that estimates of current rates of species disappearances also vary widely — from 500 to 36,000 a year. Even at that, researchers have sampled a mere sliver of the planet's biodiversity. Nature notes that most of the unknown groups live in small regions of the world, in habitats that are rapidly being destroyed.
"That is the real problem we face," Tittensor said. "The scale of uncertainty is huge."
Nature based much of the analysis on the latest version of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, released in November. The IUCN evaluated over 76,000 species — a marked increase over earlier editions, Nature reports. However, that is the merest drop in the bucket; only four percent of the more than 1.7 million species that scientists have described. This makes it impossible to come up with any reliable threat levels for at least some groups that haven't been adequately assessed, such as fish, reptiles, and insects, the journal noted.
But some groups can be assessed; among them, amphibians are considered to be the most imperiled — 41 percent are threatened with extinction, and that's due in part to massive epidemics caused by chytrid fungi. The journal pointed out that large percentages of birds and mammals also face serious threats due to the plundering and loss of habitat and due to such destructive activities as hunting.
Costa Rica s beautiful golden toad  declared extinct in 2004.
Costa Rica's beautiful golden toad, declared extinct in 2004.
By Charles H. Smith, vergrößert von Aglarech (U.S. Fish and Wildlife Service) [Public domain], via
To understand just how fragile amphibians are, one only has to look to the story of the golden toad, one of Costa Rica's most iconic animals. Now extinct, the beautiful bright orange toads were once abundant, The Tico Times notes. The little creatures died off in huge numbers during the late 1980's and were declared extinct in 2004. Biologists aren't completely certain what killed off the toads, but temperature increases and the aforementioned fungus are believed to be the main culprits.
First described by scientists in the 1960's, only one of the tiny creatures was seen in 1989. Where once hundreds of the tiny toads could be seen, none have been found since, reports.
This is just one small example of a looming crisis of extinction. As the Guardian notes, all of the data that has been compiled indicates that the Earth is hurtling towards another mass extinction; something that's defined as involving a loss of at least 75 percent of species. It might take one hundred years for this to occur, or it might take one thousand, depending upon the rates of extinction.
The Earth has undergone five mass extinctions, and all of these were caused either by geological or astronomical events — such as the Cretaceous extinction that wiped out the dinosaurs and was heralded by an asteroid that smashed into the planet.
We are responsible for the extinction at hand, The Guardian notes.
"In the case of land extinctions, it is the spread of agriculture that has been main driver," Tittensor noted. "By contrast it has been the over-exploitation of resources — overfishing — that has affected sea life." Add to that rising global temperatures that will likely destroy habitats and kill off more creatures.
Increasing emissions of carbon dioxide from factories and power plants has fueled climate change and, as it dissolves in the oceans, it has made the oceans more acidic and therefore more hostile to sensitive habitats. This means that one-third of all coral reefs, which support more living things than any other ecosystem on Earth, have perished in the last few decades and many marine scientists believe that all of the Earth's coral reefs will vanish before the end of the century, The Guardian notes.
A handout photo received from Australian Institute of Marine Science on October 2  2012 shows bleach...
A handout photo received from Australian Institute of Marine Science on October 2, 2012 shows bleaching on a coral reef at Halfway Island in Australia's Great Barrier Reef
Ray Berkelmans, AIMS/AFP/File
In recent years we have been responsible for the extinction of the golden toad, the thylacine, and the Baiji river dolphin and many thousands of species are under threat.
The Guardian notes that Nature implores governments and groups such as the IUCN to begin an urgent and accurate census regarding the numbers of species on Earth, along with their rates of extinction. This may not be exciting work, the journal notes, but if we wish to protect life on Earth from the worst of our destructive habits, it is of the utmost importance. Otherwise, in such a species depauperate world, we may be sowing the seeds of our own destruction.
As the noted ecologist Paul Ehrlich has said, per The Guardian:
"In pushing other species to extinction, humanity is busy sawing off the limb on which it perches."
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