Even conservative calculations show the world is in the midst of a sixth mass extinction that's being caused by our species — and is likely to lead to humanity's demise if unchecked, scientists reported Friday. 
 
 The scientists' analysis, published in the open-access journal Science Advances, follows up on more than a decade's worth of warnings about a rapid loss of global biodiversity. Many experts say the loss has risen to the scale seen during five previous global extinction events — the most recent of which occurred 65 million years ago when the dinosaurs died off. 
 
 The claims provide the theme of Elizabeth Kolbert's Pulitzer Prize-winning book, "The Sixth Extinction." But such claims have drawn skeptical responses as well. The skeptics say it's difficult to judge the "background rate" of extinctions, as well as the current rate of species extinction. 
 
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 Related: Extinction Could Get Worse by 2200, Scientists Say 
 
 The team behind the new study, led by Gerardo Ceballos of the National Autonomous University of Mexico, tried to address such concerns by doubling the commonly cited background rate — going from one species extinction per million species per year to two extinctions. And for the current rate, they turned to a list maintained by the International Union for Conservation of Nature — which they characterized as a conservative accounting. 
 
 Based on those figures, the extinction rate since 1900 has been eight to 100 times higher than the expected background rate, the researchers said. "The particularly high losses in the last several decades accentuate the increasing severity of the modern extinction crisis," they reported. 
 
 "There are examples of species all over the world that are essentially the walking dead," one of the study's co-authors, Paul Ehrlich of Stanford University, said in a news release. 
 
 The researchers noted that amphibians, which account for 7,300 of the species documented by the IUCN, have been particularly hard-hit. "Only 34 extinctions have been documented with a high level of certainty since 1500, yet [more than] 100 species have likely disappeared since 1980," they said. 
 
 Many of the causes for biodiversity loss have been traced to industrialization, deforestation and other, less obvious human factors. For example, in the case of the amphibians, the wave of extinctions have been traced to the rapid spread of a fatal fungus through global shipping. 
 
 Flash Interactive: See When Species Rose and Fell 
 
 Ceballos warned that the human species itself could eventually fall victim to the sixth extinction. 
 
 "If it is allowed to continue, life would take millions of years to recover, and our species itself would disappear early on," he said. 
 
 Although the report paints a depressing picture, Ceballos and his colleagues hold out a slender ray of hope. 
 
 "Avoiding a true sixth mass extinction will require rapid, greatly intensified efforts to conserve already threatened species, and to alleviate pressures on their populations — notably habitat loss, overexploitation for economic gain and climate change," they write. "All of these are related to human population size and growth, which increases consumption (especially among the rich), and economic inequity. However, the window of opportunity is rapidly closing." 
 
 Update for 10 p.m. ET June 19: In the past, Danish environmentalist Bjorn Lomborg has stirred up controversy by arguing that extinction rates won't be as dire as they've been made out to be. In an email to NBC News, Lomborg said the newly published paper appeared to be "well in line with current assumptions ... namely that humanity is definitely causing more extinctions, likely hundreds of times more than the natural background rate." 
 
 Lomborg said the authors' claim that current extinction rate could be as much as 114 times the background rate "definitely sounds plausible," but he took issue with their assessment of the implications for the future. 
 
 "These extinction rates are not likely to persist for many centuries, if even one century, as richer countries can afford to and do reforest, while they also can afford to embark on ever more serious conservation," Lomborg wrote. 
 
 He said that if you run the numbers, the paper suggests 1,508 vertebrate species could go extinct over the course of the next century. (Assuming that there are 66,178 vertebrate species, the formula is 2*114*66178/10000=1508.). 
 
 "This is definitely a problem, but it is not the eradication of the natural world," Lomborg wrote. "It equates to 2.3 percent of all vertebrates over the next 100 years — after which it is likely the problem will decline rapidly because most countries will be rich and care much for the natural world." 
 
 Related: Pope Francis Urges Revolution to Save Earth 
 
 A tally by the International Union for Conservation of Nature shows trends in the extinction of various groups of animal species. Stanford 
 
 In addition to Ceballos and Ehrlich, the authors of "Accelerated Modern Human-Induced Species Losses: Entering the Sixth Mass Extinction" include Anthony Barnosky, Andres Garcia, Robert Pringle and Todd Palmer. ||||| Study reveals rate of extinction for species in the 20th century has been up to 100 times higher than would have been normal without human impact 
 
 The modern world is experiencing a “sixth great extinction” of animal species even when the lowest estimates of extinction rates are considered, scientists have warned. 
 
 The rate of extinction for species in the 20th century was up to 100 times higher than it would have been without man’s impact, they said. 
 
 
 
 Many conservationists have been warning for years that a mass extinction event akin to the one that wiped out the dinosaurs is occurring as humans degrade and destroy habitats. 
 
 But the authors of a study published on Friday said that even when they analysed the most conservative extinction rates, the rate at which vertebrates were being lost forever was far higher than in the last five mass extinctions. 
 
 The Earth stands on the brink of its sixth mass extinction and the fault is ours Read more 
 
 “We were very surprised to see how bad it is,” said Dr Gerardo Ceballos of the National Autonomous University of Mexico. “This is very depressing because we used the most conservative rates, and even then they are much higher than the normal extinction rate, really indicating we are having a massive loss of the species.” 
 
 Previous studies have warned that the impact of humans taking land for buildings, farming and timber has been to make species extinct at speeds unprecedented in Earth’s 4.5bn-year history. 
 
 Ceballos said that his study, co-authored by Paul R Ehrlich who famously warned of the impact of humanity’s “population bomb”, employed better knowledge of natural or so-called background extinction rates. He said it was conservative because it looked only at species that had been declared extinct, which due to stringent rules can sometimes take many years after a species has actually gone extinct. 
 
 Under a “natural” rate of extinction, the study said that two species go extinct per 10,000 species per 100 years, rather than the one species that previous work has assumed. 
 
 Modern rates of extinction were eight to 100 times higher , the authors found. For example, 477 vertebrates have gone extinct since 1900, rather than the nine that would be expected at natural rates. 
 
 “It’s really signalling we’ve entered a sixth extinction and it’s driven by man,” said Ceballos. 
 
 Facebook Twitter Pinterest Noah’s Ark and the General Deluge - a colour lithograph published in New York by Muller and Company, c 1870 by an unknown artist. Photograph: Corbis 
 
 However, Prof Henrique Miguel Pereira, the chair of the Group on Earth Observations Biodiversity Observation Network, said that the new paper did not add anything revolutionarily new. 
 
 “They argue that recent extinction rates are up to 100 times higher than in the past. I think it improves our documentation of the process but it does not yet confirm a sixth mass extinction. I tend to think we have a major biodiversity crisis, but it would take either a fast acceleration of current extinction rates or a couple of centuries at current extinction rates, for the current process to become a sixth mass extinction.” 
 
 The team behind the new analysis said “rapid, greatly intensified efforts” would be needed to stop or slow the extinctions currently underway. 
 
 Ceballos pointed to the Pope Francis’s encyclical on the environment, which was published on Thursday and lamented the loss of the world’s biodiversity, and interventions by Barack Obama, as signs of hope. “These important figures are starting to really grasp the problem,” he said. 
 
 On why people should be worried about the rate of extinctions, he said: “People say that’s really sad, but why does it affect me? There are many reasons we should care. We are the species that are causing the loss of all these other species.” 
 
 But the most important reason, he said, was that by losing species humanity was losing what enabled us to have a “good standard of living”. 
 
 The paper, Accelerated modern human–induced species losses: Entering the sixth mass extinction, was published in the journal Science Advances. ||||| Earth has entered its sixth mass extinction with animals now dying out at 100 times the normal rate, scientists have warned. 
 
 Humans have created a toxic mix of habitat loss, pollution and climate change, which has already led to the loss of at least 77 species of mammals, 140 types of bird since and 34 amphibians since 1500. 
 
 They include creatures like the dodo, Steller’s Sea Cow, the Falkland Islands wolf, the quagga, the Formosan clouded leopard, the Atlas bear, the Caspian tiger and the Cape lion. 
 
 Scientists at Stanford University in the US claim it is the biggest loss of species since the Cretaceous-Tertiary mass extinction which wiped out the dinosaurs 66 million years ago. 
 
 “Without any significant doubt that we are now entering the sixth great mass extinction event," said Professor Paul Ehrlich, at the Stanford Woods Institute for the Environment. 
 
 “Species are disappearing up to about 100 times faster than the normal rate between mass extinctions, known as the background rate. 
 
 “Our calculations very likely underestimate the severity of the extinction crisis. There are examples of species all over the world that are essentially the walking dead.” 
 
 Humans were responsible for wiping out the dodo 
 
 Using fossil records and extinction counts from a range of sources, the researchers calculated the normal ‘background rate’ of extinctions and compared it with a conservative estimate of current extinctions. 
 
 Natural population changes in the wild usually lead to two species of mammals dying out every 10,000 years. But the current rate is 114 times that level. 
 
 And humans have been responsible for animal decline going much further back. In the islands of tropical Oceania, up to 1800 bird species are estimated to have gone extinct in the last 2,000 years. 
 
 It is likely that early humans were also responsible for wiping out the huge megafauna which used to live in Australia including a huge giant wombat a marsupial lion and a flesh-eating kangaroo. 
 
 Currently one in four mammals is at risk of going extinct and 41 per cent of amphibians. Many now only survive in captivity. 
 
 A giant wombat which used to live in Australia 
 
 "If it is allowed to continue, life would take many millions of years to recover, and our species itself would likely disappear early on," said lead author Gerardo Ceballos of the Universidad Autónoma de México. 
 
 Professor Ehrlich said that government must start working together to conserve threatened species. 
 
 Despite the gloomy outlook, there is a meaningful way forward, according to Ehrlich and his colleagues. 
 
 "Avoiding a true sixth mass extinction will require rapid, greatly intensified efforts to conserve already threatened species, and to alleviate pressures on their populations - notably habitat loss, over-exploitation for economic gain and climate change," the study's authors write. 
 
 Many types of wolves have become extinct including British and Falkland Island varieties 
 
 Earth has experienced five recognised mass extinctions. The Ordovician-Silurian mass extinction of 443 million years ago saw 83 per cent of sea life wiped out. In the Late Devonian mass extinction which followed 90 million years later three quarters of life on Earth became extinct . The Permian mass extinction of 248 million years ago was nicknamed The Great Dying as 96 per cent of species died out. Then 48 million years later half of Earth’s species were wiped out by climate change and asteroid impacts. The final one marked the end of the dinosaurs. 
 
 Dr Mike Barrett, WWF-UK’s Director of Science and Policy said, ‘These findings echo those of WWF’s Living Planet Report which highlighted a 52 per cent decline in vertebrate populations over the last 40 years. 
 
 "If this trend is not reversed it is easy to see how more extinctions could take place and it is further evidence that we clearly need to do more to protect wildlife and their habitats." 
 
 The research was published in the journal Science Advances. 
 
 10 most endangered species 
 
 South China tiger 
 
 Native to the southern Chinese provinces of Fujian, Guangdong, Hunan and Jiangxi the tiger had a population of 4,000 in the 1950s but it is no thought longer to exist in zoos. 
 
 Sumatran elephant 
 
 As more of Sumatran forest becomes converted for agricultural uses, the elephant has faced a critical loss of habitat. A 2007 study estimated there were less than 2,800 remaining in the wild. 
 
 Amur leopard 
 
 The world's rarest cat is believed to be making a comeback with at least 57 confirmed animals now confirmed Russia. Just 30 animals existed in 2007. But the animal is still vulnerable to hunters. 
 
 Atlantic goliath grouper 
 
 Despite the US issuing a moratorium on hunting the big fish in 1990, the animal remains critically endangered. 
 
 Gulf porpoise 
 
 The Gulf porpoise is now one of the rarest mammals in the world, with a global population estimated at under 100 in 2014. The last remaining porpoises live in North America's Gulf of California and experts expect it to become extinct by 2018. 
 
 Northern bald ibis 
 
 The bird’s natural habitat of North Africa, European and the Middle East has been plagued with war and civil unrest and now only one population exists in Morocco, with just a few hundred remaining. 
 
 Attempts are currently underway in Austria, Spain and Italy to breed the animals for reintroduction into the wild. 
 
 Hawksbill turtle 
 
 The 20,000 strong female population is under severe threat by hunters seeking their brown and gold shells. 
 
 Black rhinoceros 
 
 The black rhino has suffered the most drastic decline in total numbers of all rhino species and was officially declared extinct in the wild in 2011. However a major conservation effort has seen numbers swell to 5,000 and now the animals are kept under armed guard. 
 
 Pygmy three-toed sloth 
 
 Found on Panama's uninhabited Escudo de Veraguas island, a 2012 study found fewer than 80 sloths were still living because of habitat loss by loggers. 
 
 Chinese pangolin 
 
 Used extensively as a food, and for Chinese medicines, the pangolin has declined by 94 per cent since the 1960s. Exact numbers have been difficult to estimate because the creature is solitary and nocturnal.
– Feeling upbeat? Enough of that: Planet Earth is undergoing a sixth mass extinction that will likely annihilate the human race unless we can curb the trend, scientists say. According to a new paper, the current rate of species extinction outpaces the natural rate far more than anyone knew, NBC News reports. The analysis "employed better knowledge" of Earth's natural extinction rate, the Guardian reports, upping the number from one extinction per million species annually to two extinctions. It then compared that to a current extinction rate that study authors consider conservative. Presto, they got a rate since 1900 that's eight to 100 times worse than the natural one. "We were very surprised to see how bad it is," says study leader Gerardo Ceballos. "This is very depressing." "If it is allowed to continue, life would take millions of years to recover, and our species itself would disappear early on," says Ceballos. But nations can reverse the crisis—which has been linked to deforestation, industrialization, and other human factors—by conserving threatened species and lowering pressures on their populations, the paper says. So far critics seem to buy the paper's basic math but doubt that species extinction will continue at this high rate for centuries. "It is likely the problem will decline rapidly because most countries will be rich and care much for the natural world," writes one environmentalist. Earth has seen five other mass extinctions, including one 443 million years ago that killed off 83% of sea life, and the most recent, which wiped out the dinosaurs 66 million years ago, the Telegraph notes.