Why ethical? How ethical?

“We can be ethical only in relation to something we can see, feel, understand, love, or otherwise have faith in.”--Aldo Leopold 

I support this idea because I think we, as human beings, are born to think in a relatively anthropocentric way, which means we usually care about something starting from caring about ourselves. This is instinctive because our feelings originated from every neuro, every impulse in our body and mind are those that affect our decisions at the first place. At the very beginning of human species, trees are cut to make shelters, and animals are consumed to provide energy for survival. That is--we started consuming "resources" for our basic needs, not wants. Then we desire more, and consume more--to satisfy our wants, our psychological need--possibly the feeling of being admired. As a result, people around the world would worship land, water, trees, flowers, etc.

Is this idea wrong? I don't think so--it actually means that we are ethical to everything we know, because everything in this world is related to us in someway. If we don't know or understand something, we would, of course, know how it could affect us, and therefore would not even notice it. If we cannot notice it, we are not in relation to it, how could we feel ethical in relation to it?