Doesn't have to be an asteroid. The Yellowstone supervolcano exploding would be catastrophic enough. What can we do within the limits of our technology to restore Earth's ecology to a safe level? Assuming we are adequately prepared before the event occurs.
I would say the greatest near-term risk to Earth's ecology is humans so probably the best preparation would be not to destroy it in the first place.
After seeing how much trouble something relatively benign like Covid caused I think we would just fight each other. Countries/people with enough resources would make sure they are doing fine and the rest would have to figure something out.
We have a slow motion impact event with climate change, that we didn't do anything to avoid, and we are at a stage where trying to push the brakes when we are going at a 500mph and close enough to wall won't help neither. And we are still accelerating.<p>We as civilization are not willing to prevent that event, nor able to fix/repair what it will do, so what makes you think that we might be able to do anything with faster events like a supervolcano eruption or a big enough asteroid impact?
There’s a good book called “The Precipice” (2020) by Toby Ord that suggests things people can do: <a href="https://en.wikipedia.org/wiki/The_Precipice:_Existential_Risk_and_the_Future_of_Humanity" rel="nofollow">https://en.wikipedia.org/wiki/The_Precipice:_Existential_Ris...</a>
literal and figurative re-seeding.<p>off the top of my head, given unlimited budget, I'd probably have a massive vault of seeds (not just in variety, in quantity, too,) and adequate staff in rotations in a deep-sea bunker. not near a fault line, but deep enough that surface conditions are less likely to impact (no pun intended). Sea vs land because "digging your way out" become less of a problem. If you had a truly unlimited budget, one could imagine an Ark of embryos and a sufficient population of young does of each animal species you sought to preserve.
In the last major extinction event, it was the scrappy and efficient bottom feeders who survived, and the big dopey apex predators and megafauna who didn't.