Asteroids will inevitably wreck non-human life---survival allows space colonization that stops it

Now, some philosophers have argued that we have no obligations to human beings who are not even born, but that is surely mistaken.14 Otherwise we would have no obligation, say, to prevent the accumulation of dangerous materials next to the new-born wing of a hospital, on the grounds that those materials will not reach a critical stage in less than ten years. A possible explosion then will kill people not yet born now. And there might even be some who think that humanity is not worth saving. Making a case for what is right amounts to providing reasons for action, compelling reasons for those who might be called upon to make great efforts.15 And it is difficult to imagine that humanity as a whole will come to hate itself to the degree of accepting extinction. As for those who love spiders and ragweed more than their fellow humans, they might consider that large cosmic collisions in the past may have wiped out between 75% (65 M years ago) and 96% of marine species on Earth (presumed collision at the end of the Permian, 252 M years ago).16 We will not be saving just ourselves. And, incidentally, by colonizing space we will also be taking other terrestrial life with us into the heavens, for we will need plants and at least small animals for food, just as we will want flowers and other ornamental vegetation. Some insects and many bacteria will be essential to the survival of the other terrestrial life, and so they must also accompany us. In the case of a final disaster, it is likely that people would try to save as much of terrestrial life as they could place in space.