Earth Is Not in the Midst of a Sixth Mass Extinction
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 underway 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. [….]So things don’t look so good, no matter where we look. Yes, the victims in the animal world include scary apex predators that pose obvious threats to humans, like lions, whose numbers have dropped from 1 million at the time of Jesus to 450,000 in the 1940s to 20,000 today—a decline of 98 percent. But also included have been unexpected victims, like butterflies and moths, which have declined in abundance by 35 percent since the 1970s.Like all extinction events, so far this one has been phased and complex, spanning tens of thousands of years and starting when our kind left Africa. Other mass extinctions buried deep in earth’s history have similarly played out over tens of thousands, even hundreds of thousands of years. To future geologists, then, the huge wave of extinctions a few thousand years ago as First Peoples spread out into new continents and remote archipelagoes will be all but indistinguishable from the current wave of destruction loosed by modernity and its growing appetites. Surely we’ve earned our place in the pantheon next to the greatest ecological catastrophes of all time: the so-called Big Five mass extinctions of Earth history. Surely our Anthropocene extinction can confidently take its place next to the juggernauts of deep time—the Ordovician, Devonian, Permian, Triassic and Cretaceous extinctions.Erwin says no. He thinks it’s junk science.“Many of those making facile comparisons between the current situation and past mass extinctions don’t have a clue about the difference in the nature of the data, much less how truly awful the mass extinctions recorded in the marine fossil record actually were,” he wrote me in an email. “It is absolutely critical to recognize that I am NOT claiming that humans haven’t done great damage to marine and terrestrial [ecosystems], nor that many extinctions have not occurred and more will certainly occur in the near future. But I do think that as scientists we have a responsibility to be accurate about such comparisons.”Read more at The Atlantic