Yet in fact, the economy is a subsystem of the earth’s ecosystem, its biosphere. You see, any economic system – like barter, slavery, feudalism, socialism, or capitalism – is a human invention. Since humans are just one of the earth’s many species (albeit a powerful species, what with our written words and our weapons), any invention of ours is a subsystem of the earth’s ecosystem. Once we understand that (which is not my opinion, but plain fact), it leads to other insights. – Annie Leonard; The Story of Stuff