An ethic to supplement and guide the economic relation to land presupposes the existence of some mental image of land as a biotic mechanism. We can be ethical only in relation to something we can see, feel, understand, love or otherwise have faith in.

The image commonly employed in conservation education is ‘the balance of nature.’ For reasons too lengthy to detail here, this figure of speech fails to describe accurately what little we know about the land mechanism. A much truer image is the one employed in ecology: the biotic pyramid. I shall first sketch the pyramid as a symbol of land, and later develop some of it implications in terms of land-use...

Extracted from "Land Ethic" by Aldo Leopold. 1947.