In Krugman's obituary for Paul Samuelson, he mentioned that one of his contributions is he clarified the idea of welfare for economists, and the common good. Economists have a very well defined notion of social welfare, that is entirely human centric, but at least it is clear and well defined.
I do concede that animals and plants must fit in there somewhere, but since I have yet to come across a good definition, I tend not to use use it.
This interesting nytimes article questions whether killing brussels sprouts is any better than killing a pig for food?
This is particularly relevant when it comes to the issue of climate change, since if we just consider the impact of humans, climate change has arguably negligible impact 0 +/- 2% of GDP say the best estimates (of course extreme events are possible). But the impact on plants and animals is tricky. Many animals will die, though plants on the whole stand to benefit. And was it wrong for say the mammals to kill the dinosaurs (as some theories suggest)?