Continuing with Leopold; from The Land Ethic (1949):
"We can be ethical only in relation to something we can see, feel, understand, love, or otherwise have faith in."
This statement relates to his concern over the urbanization of this country and resulting detachment from the land. For as we remove ourselves from the land we become less aware of how it functions. Regardless of where we live - downtown Minneapolis or downtown Herman - we depend on it. Yet we loose that realization of dependency as we become urbanized and indeed we find that "food comes from the grocery store".