Earth Is Not in the Midst of a Sixth Mass Extinction

[Note:  This item comes from reader Randall Head.  DLH]

Earth Is Not in the Midst of a Sixth Mass Extinction 
“As scientists we have a responsibility to be accurate about such comparisons.”
By PETER BRANNEN
Jun 13 2017
https://www.theatlantic.com/science/archive/2017/06/the-ends-of-the-world/529545/

At the annual meeting of the Geological Society of America, Smithsonian paleontologist Doug Erwin took the podium to address a ballroom full of geologists on the dynamics of mass extinctions and power grid failures—which, he claimed, unfold in the same way.

“These are images from the NOAA website of the US blackout in 2003,” he said, pulling up a nighttime satellite picture of the glowing northeastern megalopolis, megawatts afire under the cold dark of space. “This is 20 hours before the blackout. You can see Long Island and New York City.”

“And this is seven hours into the blackout,” he said, pulling up a new map, cloaked in darkness. “New York City is almost dark. The blackout extended all the way up into Toronto, all the way out to Michigan and Ohio. It covered a huge section of both Canada and the United States. And it was largely due to a software bug in a control room in Ohio.”

Erwin is one of the world’s experts on the End-Permian mass extinction, an unthinkable volcanic nightmare that nearly ended life on earth 252 million years ago. He proposed that earth’s great mass extinctions might unfold like these power grid failures: most of the losses may come, not from the initial shock—software glitches in the case of power grid failures, and asteroids and volcanoes in the case of ancient mass extinctions—but from the secondary cascade of failures that follow. These are devastating chain reactions that no one understands. Erwin thinks that most mass extinctions in earth’s history—global die-offs that killed the majority of animal life on earth—ultimately resulted, not from external shocks, but from the internal dynamics of food webs that faltered and failed catastrophically in unexpected ways, just as the darkening eastern seaboard did in 2003.

“Because it was not clear how to manage that collapse—although after the fact it was clear that it should have been easily contained—it cascaded into failure of grids across the northeastern United States …  I mention this because it turns out that, from a mathematical point of view, the problem of understanding these food webs is exactly the [same] problem as understanding the nature of the power grid. There’s a very rapid collapse of the ecosystem during these mass extinctions,” he said.

I had written to Erwin to get his take on the contemporary idea that there is currently a sixth mass extinction under way on our planet on par with the so-called Big Five mass extinctions in the history of animal life. Many popular science articles take this as a given, and indeed, there’s something emotionally satisfying about the idea that humans’ hubris and shortsightedness are so profound that we’re bringing down the whole planet with us.

Given how severely humans have damaged the natural world over the millennia, it was an idea I found attractive, and it’s one even shared by many geologists and paleontologists. Our destruction is so familiar—so synonymous with civilization—in fact, that we tend to overlook how strange the world that we’ve made has become. For instance, it stands to reason that, until very recently, all vertebrate life on the planet was wildlife. But astoundingly, today wildlife accounts for only 3 percent of earth’s land animals; human beings, our livestock, and our pets take up the remaining 97 percent of the biomass. This Frankenstein biosphere is due both to the explosion of industrial agriculture and to a hollowing out of wildlife itself, which has decreased in abundance by as much as 50 percent since 1970. This cull is from both direct hunting and global-scale habitat destruction: almost half of the earth’s land has been converted to farmland.

The oceans have endured a similar transformation in only the past few decades as the industrial might developed during World War II has been trained on the seas. Each year fishing trawlers plow an area of seafloor twice the size of the continental United States, obliterating the benthos. Gardens of corals and sponges hosting colorful sea life are reduced to furrowed, lifeless plains. What these trawlers have to show for all this destruction is the removal of up to 90 percent of all large ocean predators since 1950, including familiar staples of the dinner plate like cod, halibut, grouper, tuna, swordfish, marlin, and sharks. As just one slice of that devastation, 270,000 sharks are killed every single day, mostly for their tasteless fins, which end up as status symbol garnishes in the bowls of Chinese corporate power lunches. And today, even as fishing pressure is escalating, even as the number of fishing boats increases, even as industrial trawlers abandon their exhausted traditional fishing grounds to chase down ever more remote fish stocks with ever more sophisticated fish-finding technology, global fish catch is flatlining.

[snip]

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