[javajosh]

My assessment for most of my life has been if most of the world's ~10k 'strategic' megaton-scale warheads exploded in air over Earth's major cities it would kick up enough dust to kill the sun for several years, which would kill off a large fraction of Earth's flora and fauna, akin to a major volcanic eruption or asteroid collision.

There would still be life of the smaller sort, and deep in the oceans of course. Only a terribly unlucky cosmic event, like a nearby supernova spewing enough neutrinos at us could kill literally all life, even in the cracks and crevices.

[thaumasiotes]

That is an ephemeral change. It takes very little time for the biosphere to make a full recovery. You're talking about a small, brief, suppression of the biosphere. And you're calling it "destruction of the biosphere".

[javajosh]

Yes, and when a forest burns down I call it the destruction of a forest even though it can grow back because that's how language is used.

[thaumasiotes]

Even if you're talking about the fires in Yellowstone in 1988, the only way to call that "destruction of the forest" is if you define the forest as being the trees. That's a defensible choice.

(And temperate forests "burn down" all the time as part of their normal operations.)

But you can't define the biosphere as "the species that go extinct in a particular scenario". You're stuck with the whole thing, which is not going to notice whatever humans do. It would make as much sense to call it "destruction of the biosphere" if I moved a rock thirty feet.

[astrange]

Burning down is part of the natural lifecycle of many forests, and they actually suffer when modern land management stops natural fires.