Let’s do a thought experiment.

About 251 million years ago, there was an enormous extinction event. No one knows why for sure, but one theory is … global warming. 90% of marine species and 70% of terrestrial vertebrates were wiped out. Left behind? Mostly fungus.

If animals, plants, and ecosystems have value in and of themselves, we must view the Permian-Triassic extinction event as an almost unfathomable tragedy, far worse than anything human history has witnessed. It ought to make us tremble, shake faith in a benevolent deity.

But it doesn’t. We don’t view it as a tragedy that dwarfs any human violence, starvation, or disease, not really. Some might say it is, but I’ll venture nobody on the planet feels it to be such.

It’s just something that happened. Indeed, though it was the worst, it was but one of seven major extinction events — including the one we’re living through now, the fastest.

Now: imagine we wipe ourselves out, along with more than half the other extant species on earth. In 250 million years, should there be creatures capable of studying the past, do you think they will shed tears for us? Not likely. We too will just be something that happened.

The earth will not have suffered appreciably. As long as the basic chemical building blocks of life persist, the planet can easily weather many more extinction events. The solar system produces life and it produces death, in cycles, and there’s no reason to think this isn’t the cosmically appropriate thing for it to do. Humanity is just one weapon in a species-destroying arsenal that includes asteroids, mega-volcanos, plate tectonics, and gamma ray bursts.

What, then, is environmentalism? We want to save the set of ecosystems and species that happen to exist at this point in the earth’s history. Why this set? What makes it more special than the six other sets that have come and gone?

Here’s an obvious answer: This set includes us.

We want to save our own asses, not because we’re more worthy than the millions of others that have come and gone from earth, but because their our asses. We want to save the ecosystems and species now extant because they’re the ones we know and can survive in.

The earth wouldn’t care if the atmosphere got warmer and fewer species survived, but we would. We want to live. And we want to have good lives.

A good life for homo sapiens means an atmosphere within a particular energy equilibrium. It means a rich, diverse biosphere — not just the minimum required for brute survival, but a full, wondrous, aesthetically rich panoply.

That’s what we fight for, the kind of environmentalist I am. Before on this blog I’ve used the term anthropocentrism, but perhaps I’ll adopt David Shariatmadari’s slightly slightly truculent "hard green" for its superior memetic potential.