EcoAlert: Is the Planet’s 6th Mass-Species Extinction in Progress?

Barb_ecology_lg_01 "In one sense we know much less about Earth than we do about Mars. The vast majority of life forms on our planet are still undiscovered, and their significance for our own species remains unknown. This gap in our knowledge is a serious matter: we will never completely understand and preserve the living world around us at our present level of ignorance.

"If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos."

Edward O. Wilson, The world's leading authority on Biodiversity, Emeritus Professor of Biology at Harvard and author of "The Creation: An Appeal to Save Life on Earth."


There is little doubt left in the minds of professional biologists that Earth is currently faced with a mounting loss of species that threatens to rival the five great mass extinctions of the geological past, the most devasting being the Third major Extinction (c. 245 mya), the Permian, where 54% of the planet's species families lost. As long ago as 1993, Harvard biologist E.O. Wilson estimated that Earth is currently losing something on the order of 30,000 species per year — which breaks down to the even more daunting statistic of some three species per hour. Some biologists have begun to feel that this biodiversity crisis — this "Sixth Extinction" — is even more severe, and more imminent, than Wilson had supposed.

With the human population expected to reach 9-10 billion by the end of the century and the planet in the middle of its sixth mass extinction — this time due to human activity — the next few years are critical in conserving Earth’s precious biodiversity. The cause of the Sixth Extinction, Homo sapiens, means we can continue on the path to our own extinction, or, preferably, we modify our behavior toward the global ecosystem of which we are still very much a part.

At a casual glance, the physically caused extinction events of the past might seem to have little or nothing to tell us about the current Sixth Extinction, which is a human-caused event. For there is little doubt that humans are the direct cause of ecosystem stress and species destruction in the modern world through transformation of the landscape, overexploitation of species, pollution, and the introduction of alien species.

The Sixth Extinction can be characterized as  the first recorded global extinction event that has a biotic, rather than a physical, cause, due to massive asteroid impact, volcanic eruptions.  Yet, looking deeper, human impact on the planet is a similar to the Cretaceous cometary collision. Sixty-five million years ago that extraterrestrial impact — through its sheer explosive power, followed immediately by its injections of so much debris into the upper reaches of the atmosphere that global temperatures plummeted and, most critically, photosynthesis was severely inhibited — wreaked havoc on the living systems of Earth, which is precisely what we are doing to the planet right now.

Phase two of the Sixth Extinction began around 10,000 years ago with the invention of agriculture-perhaps first in the Natufian culture of the Middle East. Agriculture appears to have been invented several different times in various different places, and has, in the intervening years, spread around the entire globe.

Agriculture, which began around 10,000 years ago in the Natufian culture of the Middle East, is a major engine driving the Sixth Extinction, represents the single most profound ecological change in the entire 3.5 billion-year history of life. With its invention humans did not have to interact with other species for survival, and so could manipulate other species for their own use nor did humans have to adhere to the ecosystem's carrying capacity, and so could overpopulate.

Homo sapiens became the first species to stop living inside local ecosystems. All other species, including our ancestral hominid ancestors, all pre-agricultural humans, and remnant hunter-gatherer societies still extant exist as semi-isolated populations playing specific roles (i.e., have "niches") in local ecosystems. This is not so with post-agricultural revolution humans, who in effect have stepped outside local ecosystems. Indeed, to develop agriculture is essentially to declare war on ecosystems – converting land to produce one or two food crops, with all other native plant species all now classified as unwanted "weeds" — and all but a few domesticated species of animals now considered as pests.

Yet, upon further reflection, human impact on the planet is a direct analogue of the Cretaceous cometary collision. Sixty-five million years ago that extraterrestrial impact — through its sheer explosive power, followed immediately by its injections of so much debris into the upper reaches of the atmosphere that global temperatures plummeted and, most critically, photosynthesis was severely inhibited — wreaked havoc on the living systems of Earth. That is precisely what human beings are doing to the planet right now: humans are causing vast physical changes on the planet.

"The comparison I make between these big extinction events, prehistoric meteorite-caused or natural event-caused extinctions and the present one," says E.O. Wilson, "is parallel to the difference between a heart attack and cancer. We understand that what we are doing is slow but insidious, and only can be seen when you lay it out over the whole world over a period of decades. The hopeful thing about it is that this cancer can be treated. A lot of damage has been done, and it can be dangerous to us if we really just go on until half the species of organisms are extinct forever. Or we can halt the hemorrhaging.

"In terms of scale, it’s hard to put a figure on it," Wilson adds: "We’re in a pronounced early stage of an extinction event that would probably be, by the end of this century if human activities continue unabated, right up to the Cretaceous level. We’re part way there. Whether you can say its 10 percent there or 25 percent there, a lot of it depends on the organisms you’re talking about. One estimate has it that, particularly when you throw in the mass extinction of the Pacific Island birds, which are the most vulnerable on Earth, something like 20 percent of bird species has been extinguished by human activities."

Biocide is occurring at an alarming rate. Experts say that at least half of the world’s current species will be completely gone by the end of the century. Wild plant-life is also disappearing. Most biologists say that we are in the midst of an anthropogenic mass extinction. Numerous scientific studies confirm that this phenomenon is real and happening right now. Should anyone really care? Will it impact individuals on a personal level? Scientists say, “Yes!”

Critics argue that species disappear and new ones emerge all the time. That’s true, if you’re speaking in terms of millennia. Scientists acknowledge that species disappear at an estimated rate of one species per million per year, with new species replacing the lost ones at around the same rate. Recently humans have accelerated the extinction rate to where several entire species are annihilated every single day. The death toll artificially caused by humans is mind-boggling. Nature will take millions of years to repair what we destroy in just a few decades.

A recent analysis, published in the journal Nature, shows that it takes 10 million years before biological diversity even begins to approach what existed before a die-off. Over 10,000 scientists in the World Conservation Union have compiled data showing that currently 51 per cent of known reptiles, 52 per cent of known insects, and 73 per cent of known flowering plants are in danger along with many mammals, birds and amphibians. It is likely that some species will become extinct before they are even discovered, before any medicinal use or other important features can be assessed. The cliché movie plot where the cure for cancer is about to be annihilated is more real than anyone would like to imagine.

Research done by the American Museum of Natural History found that the vast majority of biologists believe that mass extinction poses a colossal threat to human existence, and is even more serious of an environmental problem than one of its contributors—global warming. The research also found that the average person woefully underestimates the dangers of mass extinction. Powerful industrial lobbies would like people to believe that we can survive while other species are quickly and quietly dying off. Irresponsible governments and businesses would ha
ve people believe that we don’t need a healthy planet to survive- even while human cancer rates are tripling every decade.

A lot of us heard about the recent extinction of the Yangtze river dolphin. It was publicized because dolphins are cute and smart, and we like dolphins. We were sort of sad that we humans were single-handedly responsible for destroying the entire millions-of-years-old species in just a few years through rampant pollution. Unfortunately the real death toll is so much higher than we hear on the news. Only a few endangered “celebrity favorites” get any notice at all.

Since animals and plants exist in symbiotic relationships to one another, extinction of one species is likely to cause ”co-extinctions”. Some species directly affect the health of hundreds of other species. There is always some kind of domino effect. This compounding process occurs with frightening speed. That makes rampant extinction similar to disease in the way that it spreads. Sooner or later—if gone unchecked—humans may catch it too.

Amphibians are a prime example at how tinkering with the environment can cause rapid animal death. For over 300 million years frogs, salamanders, newts and toads were hardy enough to precede and outlive the dinosaurs up until the present time. Now, within just two decades many amphibians are disappearing. Scientists are alarmed at how one seemingly robust species of amphibians will suddenly disappear within a few months.

The causes of biocide are a hodge-podge of human environmental “poisons” which often work synergistically, including a vast array of pollutants, pesticides, a thinning ozone layer which increases ultra-violet radiation, human induced climate change, habitat loss from agriculture and urban sprawl, invasions of exotic species introduced by humans, illegal and legal wildlife trade, light pollution, and man-made borders among other many other causes.

In a new study by University of California, Berkeley, paleobiologists assess where mammals and other species stand today in terms of possible extinction, compared with the past 540 million years.

"If you look only at the critically endangered mammals—those where the risk of extinction is at least 50 percent within three of their generations—and assume that their time will run out, and they will be extinct in 1,000 years, that puts us clearly outside any range of normal, and tells us that we are moving into the mass extinction realm," said Anthony D. Barnosky, UC Berkeley professor of integrative biology, a curator in the Museum of Paleontology and a research paleontologist in the Museum of Vertebrate Zoology.

"If currently threatened species—those officially classed as critically endangered, endangered and vulnerable—actually went extinct, and that rate of extinction continued, the sixth mass extinction could arrive within as little as 3 to 22 centuries," he said.

Nevertheless, Barnosky added, it's not too late to save these critically endangered mammals and other such species and stop short of the tipping point. That would require dealing with a perfect storm of threats, including habitat fragmentation, invasive species, disease and global warming.

"So far, only 1 to 2 percent of all species have 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. "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."

Coauthor Charles Marshall, UC Berkeley professor of integrative biology and director of the campus's Museum of Paleontology, emphasized that the small number of recorded extinctions to date does not mean we are not in a crisis.

"Just because the magnitude is low compared to the biggest mass extinctions we've seen in a half a billion years doesn't mean to say that they aren't significant," he said. "Even though the magnitude is fairly low, present rates are higher than during most past mass extinctions."

"The modern global mass extinction is a largely unaddressed hazard of climate change and human activities," said H. Richard Lane, program director in the National Science Foundation's Division of Earth Sciences, which funded the research. "Its continued progression, as this paper shows, could result in unforeseen – and irreversible – negative consequences to the environment and to humanity."

The study originated in a graduate seminar Barnosky organized in 2009 to bring biologists and paleontologists together in an attempt to compare the extinction rate seen in the fossil record with today's extinction record. These are "like comparing apples and oranges," Barnosky said. For one thing, the fossil record goes back 3.5 billion years, while the historical record goes back only a few thousand years.

In addition, the fossil record has many holes, making it is impossible to count every species that evolved and subsequently disappeared, which probably amounts to 99 percent of all species that have ever existed. A different set of data problems complicates counting modern extinctions. Dating of the fossil record also is not very precise, Marshall said.

"If we find a mass extinction, we have great difficulty determining whether it was a bad weekend or it occurred over a decade or 10,000 years," he said. "But without the fossil record, we really have no scale to measure the significance of the impact we are having."

"This paper, instead of calculating a single death rate, estimates the range of plausible rates for the mass extinctions from the fossil record and then compares these rates to where we are now."

Barnosky's team chose mammals as a starting point because they are well studied today and are well represented in the fossil record going back some 65 million years. Biologists estimate that within the past 500 years, at least 80 mammal species have gone extinct out of a starting total of 5,570 species.  The team's estimate for the average extinction rate for mammals is less than two extinctions every million years, far lower than the current extinction rate for mammals.

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

After looking at the list of threatened species maintained by the International Union for Conservation of Nature (IUCN), the team concluded that if all mammals now listed as "critically endangered",  "endangered" and "threatened" go extinct, whether that takes several hundred years or 1,000 years, Earth will be in a true mass extinction.

"Obviously there are caveats," Barnosky said. "What we know is based on observations from just a very few twigs plucked from the enormous number of branches that make up the tree of life."

"Our findings highlight how essential it is to save critically endangered, endangered and vulnerable species," Barnosky added. "With them, Earth's biodiversity remains in pretty good shape compared to the long-term biodiversity baseline. If most of them die, even if their disappearance is stretched out over the next 1,000 years, the sixth mass extinction will have arrived."

The Daily Galaxy via University of California – Berkeley

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