Gaia Save Us! Not So Fast, part three. The Great Extinctions

 This is the third in a series of essays.

 One of the great insights of modern science has been that the ecosystem of the Earth as a whole might be self-regulating, that is, it regulates its systems (temperature, geology, atmospheric chemistry, biology) the way a body regulates itself. It adds a new dimension to the meaning of Mother Earth. This is an insight usually attributed to James Lovelock, who called the Earth Gaia, and extended by the late, great biologist Lynn Margulis. Neither one of them intended to imply that the Earth was a goddess; Lynn Margulis particularly told me so. Gaia is a self-regulating systems, not a goddess.

In this series of essays, I wish to explain that Earth has a regulatory system, which you can call Gaia if you like. But this system is very unresponsive except on the largest scales of time and space. Don’t trust Gaia to solve any of our current ecological problems.

This third essay is about how Gaia did not save us from mass extinctions. The previous essay was November 8.

You have heard about the event (the Terminal Cretaceous Event) that caused the dinosaurs (except birds, which are dinosaurs) to become extinct. Dinosaurs have caught everyone’s imagination, and even more dramatic is the fact that it was almost certainly a giant asteroid slamming into the Earth that caused the dinosaurs to die. Dinosaurs and an asteroid—it doesn’t get much more dramatic than that. Of course, the asteroid did not have to hit all the dinosaurs. It caused a massive firestorm that baked many of them, and thick smoke that brought years of darkness, freezing the survivors. Surely Gaia could not prevent asteroids from hitting the planet and cannot be faulted for the Cretaceous extinction.

But there was an earlier, much larger, extinction event, at the end of the Permian Period, about 250 million years ago. Although it did not involve an asteroid, it did involve one of the largest volcanic eruptions in Earth history, which poured lava over much of Siberia. It was a long, slow eruption. If you lived away from the eruption site, you might not have noticed anything on a day to day basis. But it did put a lot of sulfur dioxide into the upper atmosphere, which not only cooled the Earth but also poisoned the oceans, gradually.

The end of the Permian was also when all the continents crashed together to form the supercontinent Pangaea, which means the “whole earth.” This, in itself, would have made a major contribution to extinction, since many species live in shallow waters around the continents. One big continent has less shallow water around it than numerous, smaller continents. Also, to the extent that the climate was hospitable at the start of the Permian, it probably was not at the end. The middle of this giant continent of Pangaea, far from the coastal rains, would have been dry, much like the Gobi Desert today. Gaia has no control over continental movements, no more than over volcanic eruptions, which are both aspects of plate tectonics, and thus cannot be faulted for the Permian extinction.

A Gaia that cannot protect us from mass extinctions is of little help to the Earth. Gaia has no mind and is slow. It may have saved Earth from becoming an ice planet or a hellish one. But on a day to day, or million year to million year, basis, it is of little help to the planet.