A paleontologist has suggested that the Earth might be ultimately inhospitable to life, and that life itself might be the primary reason for shutting down Earth as a habitable planet.
In the past 50 years, it has become commonplace to think of Earth as a nurturing place, straining mightily to maintain equilibrium so that life might continue and flourish.
The Gaia hypothesis, named for the ancient Greek goddess of Earth, even put forth the idea that our planet behaves as a kind of giant organism, with its complex systems finely tuned to compensate when one system gets out of kilter.
But actually, it is the Gaia view that is out of kilter, according to Peter Ward, a University of Washington paleontologist.
In a new book, he suggests the planet ultimately is inhospitable to life, and that life itself might be the primary reason.
Rather than Gaia, he invokes the darker Medea from Greek mythology.
"The Medea hypothesis says life is already shutting down Earth as a habitable planet. Not just the diversity of life, but the actual biomass," Ward said. "Life keeps evolving, and there are unintended, often negative, consequences," he added.
In the 208-page book, Ward argues that humans have to use engineering to manage their environment or face potential extinction if the Earth is left to manage itself.
"The engineering I'm talking about is not girders and sky shields. It's engineering microbes to take over food production and energy production," he said.
According to Ward, microbes have undergone evolution, a sort of natural engineering, throughout Earth's history, and humans have the ability to guide such changes to clean the environment, for example, or regulate carbon dioxide (CO2) in the atmosphere.
Currently, CO2 is at 380 parts per million and rising, creating a greenhouse effect that most climate scientists say will greatly increase temperatures around the world, with some severe consequences.
Ward noted that throughout Earth's history, carbon has been stripped from the atmosphere and stored in trees, rocks, even the oceans.
He said those processes will continue until atmospheric CO2 drops to 10 parts per million, a point at which no plants can live.
Once plants are gone, within 20 million years, the oxygen will plummet to 1 percent of the total atmosphere and life as we know it will end.
"Then, you've gotten to a point where it will be forever impossible to get diversity of life back. It will be forever impossible to regain an oxygen-rich atmosphere. That's not Gaia. It's the opposite of Gaia," said Ward.