Well, my decades of pet ownership didn’t kill any birds because they were indoor pets. All sorts of other things, natural and otherwise, killed them without my help. We fed and watered them from time to time, so I think of myself as a net positive re birds.

And is the impact of pet ownership larger than, say, the impact of those involved in sports? Huge amounts of unnatural green spaces are maintained and direct and indirect carbon emissions are created. This directly impacts the former natural population of these areas, usually driving them away or just eliminating them. And I suspect the economic distortion caused by those into sports exceeds those into pets (although there is significant overlap).

Will the authors propose banning sports?

I would think that the impact on the biosphere from having children greatly exceeds having pets. We only had the latter, so I guess we did our part in reducing aggregate damage?