"Gone" - Animal Extinction - the greatest threat to mankind

By Julia Whitty - with excerpts from MotherJones

...In the final stages of dehydration the body shrinks, robbing youth from the young as the skin puckers, eyes recede into orbits, and the tongue swells and cracks. Brain cells shrivel and muscles seize. The kidneys shut down. Blood volume drops, triggering hypovolemic shock, with its attendant respiratory and cardiac failures. These combined assaults disrupt the chemical and electrical pathways of the body until all systems cascade toward death.

Such is also the path of a dying species. Beyond a critical point, the collective body of a unique kind of mammal or bird or amphibian or tree cannot be salvaged, no matter the first aid rendered. Too few individuals spread too far apart, or too genetically weakened, are susceptible to even small natural disasters: a passing thunderstorm; an unexpected freeze; drought. At fewer than 50 members, populations experience increasingly random fluctuations until a kind of fatal arrhythmia takes hold. Eventually, an entire genetic legacy, born in the beginnings of life on earth, is removed from the future.

Scientists recognise that species continually disappear at a background extinction rate estimated at about one species per million per year, with new species replacing the lost in a sustainable fashion. Occasional mass extinctions convulse this orderly norm, followed by excruciatingly slow recoveries as new species emerge from the remaining gene-pool, until the world is once again repopulated by a different catalogue of flora and fauna.

From what we understand so far, five great extinction events have reshaped earth in cataclysmic ways in the past 439 million years, each one wiping out between 50 and 95 per cent of the life of the day, including the dominant life forms; the most recent event killing off the non-avian dinosaurs. Speciations followed, but an analysis published in Nature showed that it takes 10 million years before biological diversity even begins to approach what existed before a die-off.

Today we're living through the sixth great extinction, sometimes known as the Holocene extinction event. We carried its seeds with us 50,000 years ago as we migrated beyond Africa with Stone Age blades, darts, and harpoons, entering pristine Ice Age ecosystems and changing them forever by wiping out at least some of the unique megafauna of the times, including, perhaps, the sabre-toothed cats and woolly mammoths. When the ice retreated, we terminated the long and biologically rich epoch sometimes called the Edenic period with assaults from our newest weapons: hoes, scythes, cattle, goats, and pigs.

But, as harmful as our forebears may have been, nothing compares to what's under way today. Throughout the 20th century the causes of extinction - habitat degradation, overexploitation, agricultural monocultures, human-borne invasive species, human-induced climate-change - increased exponentially, until now in the 21st century the rate is nothing short of explosive. The World Conservation Union's Red List - a database measuring the global status of Earth's 1.5 million scientifically named species - tells a haunting tale of unchecked, unaddressed, and accelerating biocide.

When we hear of extinction, most of us think of the plight of the rhino, tiger, panda or blue whale. But these sad sagas are only small pieces of the extinction puzzle. The overall numbers are terrifying. Of the 40,168 species that the 10,000 scientists in the World Conservation Union have assessed, one in four mammals, one in eight birds, one in three amphibians, one in three conifers and other gymnosperms are at risk of extinction. The peril faced by other classes of organisms is less thoroughly analysed, but fully 40 per cent of the examined species of planet earth are in danger, including perhaps 51 per cent of reptiles, 52 per cent of insects, and 73 per cent of flowering plants.

By the most conservative measure - based on the last century's recorded extinctions - the current rate of extinction is 100 times the background rate. But the eminent Harvard biologist Edward O Wilson, and other scientists, estimate that the true rate is more like 1,000 to 10,000 times the background rate. The actual annual sum is only an educated guess, because no scientist believes that the tally of life ends at the 1.5 million species already discovered; estimates range as high as 100 million species on earth, with 10 million as the median guess. Bracketed between best- and worst-case scenarios, then, somewhere between 2.7 and 270 species are erased from existence every day. Including today.

We now understand that the majority of life on Earth has never been - and will never be - known to us. In a staggering forecast, Wilson predicts that our present course will lead to the extinction of half of all plant and animal species by 2100.

You probably had no idea. Few do. A poll by the American Museum of Natural History finds that seven in 10 biologists believe that mass extinction poses a colossal threat to human existence, a more serious environmental problem than even its contributor, global warming; and that the dangers of mass extinction are woefully underestimated by almost everyone outside science. In the 200 years since French naturalist Georges Cuvier first floated the concept of extinction, after examining fossil bones and concluding "the existence of a world previous to ours, destroyed by some sort of catastrophe", we have only slowly recognised and attempted to correct our own catastrophic behaviour....

These life-forms and their life strategies compose what we might think of as the "body" of the desert, with some species the lungs and others the liver, the blood, the skin. The trend in scientific investigation in recent decades has been toward understanding the interconnectedness of the bodily components, i.e. the effect one species has on the others. The loss of even one species irrevocably changes the desert (or the tundra, rainforest, prairie, coastal estuary, coral reef, and so on) as we know it, just as the loss of each human being changes his or her family forever.

Nowhere is this better proven than in a 12-year study conducted in the Chihuahuan desert by James H Brown and Edward Heske of the University of New Mexico. When a kangaroo-rat guild composed of three closely related species was removed, shrublands quickly converted to grasslands, which supported fewer annual plants, which in turn supported fewer birds. Even humble players mediate stability. So when you and I hear of this year's extinction of the Yangtze river dolphin, and think, "how sad", we're not calculating the deepest cost: that extinctions lead to co-extinctions because most living things on Earth support a few symbionts, while keystone species influence and support myriad plants and animals. Army ants, for example, are known to support 100 known species, from beetles to birds. A European study finds steep declines in honeybee diversity in the past 25 years but also significant attendant declines in plants that depend on bees for pollination - a job estimated to be worth £50bn worldwide. Meanwhile, beekeepers in 24 American states report that perhaps 70 per cent of their colonies have recently died off, threatening £7bn in US agriculture. And bees are only a small part of the pollinator crisis.

One of the most alarming developments is the rapid decline not just of species but of higher taxa, such as the class Amphibia, the 300-million-year-old group of frogs, salamanders, newts and toads hardy enough to have preceded and then outlived most dinosaurs. Biologists first noticed die-offs two decades ago, and, since then, have watched as seemingly robust amphibian species vanished in as little as six months. The causes cover the spectrum of human environmental assaults, including rising ultraviolet radiation from a thinning ozone layer, increases in pollutants and pesticides, habitat loss from agriculture and urbanisation, invasions of exotic species, the wildlife trade, light pollution, and fungal diseases. Sometimes stressors merge to form an unwholesome synergy; an African frog brought to the West in the 1950s for use in human pregnancy tests likely introduced a fungus deadly to native frogs. Meanwhile, a recent analysis in Nature estimated that, in the past 20 years, at least 70 species of South American frogs had gone extinct as a result of climate change...

Vacariu is the western director of the Wildlands Project, the conservation group spearheading the drive to rewild North America—to reconnect remaining wildernesses (parks, refuges, national forests, and local land trust holdings) through corridors, on a continentwide scale. The idea came into being 15 years ago, a hybridization between activism and science, when Earth First founder Dave Foreman teamed with Michael Soulé, professor emeritus at the University of California-Santa Cruz and one of the founding fathers of conservation biology.

Rewilding is bigger, broader, and bolder than humans have thought before. Many conservation biologists believe it's our best hope for arresting the sixth great extinction. E.O. Wilson calls it "mainstream conservation writ large for future generations."

To save Earth's living membrane, we must put its shattered pieces back together. Only "megapreserves" modelled on a deep scientific understanding of continent-wide ecosystem needs hold that promise. "What I have been preparing to say is this," wrote Thoreau more than 150 years ago. "In wildness is the preservation of the world." This, science finally understands...

The Wildlands Project has also identified the five most critically endangered wildlife linkages along the spine, each associated with a keystone species. Grizzlies already pinched at Crowsnest Pass on Highway Three, between Alberta and British Columbia, will be entirely cut off from the bigger gene pool to the north if a larger road is built. Greater sage grouse, Canada lynx, black bears and jaguars face their own lethal obstacles further south...

The truth is that wilderness is more dangerous to us caged than free - and has far more value to us wild than consumed. Wilson suggests the time has come to rename the "environmentalist view" the "real-world view", and to replace the gross national product with the more comprehensive "genuine progress indicator", which estimates the true environmental costs of farming, fishing, grazing, mining, smelting, driving, flying, building, paving, computing, medicating and so on. Until then, it's like keeping a ledger recording income but not expenses. Like us, the Earth has a finite budget.