Well you can still empathize with the pain that other feeling, conscious creatures on Earth experience as a direct result of our actions. It's one thing if a meteor strikes the earth and you simply witness a mass extinction, it's another if you ARE the meteor.

We should care about biodiversity because it affects humans AND because it affects other living things which also have emotions and feel pain and will suffer as a result of what we've done. "Mother Earth" as a concept doesn't exist but other animals do. I think that's what people usually mean by that phrase.