Thanks to Our Fossil Fuel Addiction, We May Be Setting Ourselves Up for a Catastrophic Natural Event

What is hydrogen sulfide? It smells like farts and rotten eggs. You can find it in swamps, sewers, landfills, volcanic and natural gases, and pretty much everywhere there is a petroleum refinery. Unfortunately, you can also usually find it whenever and wherever you've got mass extinctions.

In fact, it is hydrogen sulfide, rather than killer asteroids or some other interstellar death-bringer, that has possibly become the go-to kill-shot of most mass extinctions in Earth's history.

"It doesn't take much hydrogen sulfide to kill off anything," Gerry Dickens, professor of earth science and paleoceanography at Rice University, explained to AlterNet by phone.

He should know: It was Dickens' work with methane hydrates that completed the puzzle of the Permian-Triassic extinction event, more aptly known as the Great Dying, in the 2002 BBC Horizon documentary The Day the Earth Nearly Died.

During the Great Dying, over 250 million years ago, flood basalts in the Siberian and Emeishan traps unleashed hell on Earth, spewing titanic walls of lava, ash, debris and greenhouse gases into the sky, blotting out the sun and surrounding hundreds of thousands of miles in a biblical inferno for which there is no contemporary analogue, at least in reality.

But even that wasn't enough to wipe out the 96 percent of Earth's marine, terrestrial and plant species claimed by the Great Dying. A growing scientific consensus explains that the death stroke was probably delivered from Earth's anoxic oceans, whose resultant out-of-whack pH balance, once literally defined as the "power of hydrogen," released catastrophic stores of either methane hydrate or hydrogen sulfide into the atmosphere.

Whichever one it was, hydrogen had the power to bring Earth to its knees. And it could happen again.

"It's unannounced stealth nastiness," Peter Ward, professor of biology and paleontology at the University of Washington, declared by phone to AlterNet. "My new book ends with a hydrogen sulfide extinction."

That book, The Medea Hypothesis, posits not one but five hydrogen sulfide extinction events, including the Great Dying, throughout Earth's history. Going further, it flips the Gaia hypothesis on its head by suggesting -- with increasing persuasion, given our current climate crisis of too much carbon dioxide in the air and too little oxygen in the oceans -- that Earth is not seeking an optimal physical and chemical environment for its life.

In fact, Ward argues, its multicellular life is actually suicidal in nature, whose doom will eventually return Earth to the microbes that have dominated most of its history.

Although the truth probably lies somewhere between Gaia and Medea, Ward seems to be right about one thing: Hydrogen sulfide is an unheralded executioner.

"If ancient volcanism raised CO2 and lowered the amount of oxygen in the atmosphere, and global warming made it more difficult for the remaining oxygen to penetrate the oceans, conditions would have become amenable for the deep-sea anaerobic bacteria to generate massive upwellings of hydrogen sulfide," Ward wrote in a Scientific American clarion call titled "Impact from the Deep."Virtually no form of life on the earth was safe."

Ward -- who has also written the books Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us About Our Future; Rare Earth: Why Complex Life is Uncommon in the Universe; and the forthcoming Our Flooded World -- concludes his Scientific American piece with the obvious question: Could it happen again?