I'm pretty sure that you can't be atheist unless you are talking about a religion, such as Islam or Judaism or Christianity, which claims that there IS a "God." If your religion worships a "life force" and celebrates the living things around you it'd be pretty hard to be an atheist, I suspect.

People confuse materialism with atheism as well. If you believe it's all over when your biological shell no longer functions, that's materialism. If you believe that there is no church-defined "God", that's atheism. Yes, they can go hand-in-hand, but they are not the same.