Warning: My criticism of Leopold is based only upon cursory familiarity with his work. I should want to learn more.
When Leopold, his various disciples, and others who shy away from taking responsibility for the adventure that is human artifice endorse their particular vision of a "natural" order of human communities (which, as Carrico has observed, often includes an appeal to nature as a moral category), they are still exercising their distinctive emotional and cognitive muscles with which only we, as political animals, have yet been endowed. No act of powerful human volition--not even the act of dreaming of a "state of nature" where humans try awkwardly to disrobe themselves of their artificial clothes (by "clothes" I mean everything we build atop the edifice of nature, including our political institutions, symphonies and financial markets)--can expunge that volition. There aren't very many kinds of animals (or cyborgs or other agents, if any) who could do what Leopold did, or who could do what Leopold wanted us to do with our politics (assuming the particular desires Leopold happened to proclaim are even possible to achieve in practice). And so far as I can tell, all of those exceptionally-endowed agents fit reasonably well in the category of the "human". Not even Leopold could escape from embodying human exceptionalism! (Nonetheless, one wonders whether he actually thought he had plucked his vision from an ethereal Tree of Truth rather than simply used his imagination--like all political animals--to invent his vision.)
Whether we like it or not, we are increasingly responsible for life on this planet. Rather than deny our special role, why shouldn't we embrace it?
(I'm trying not to sound human-racist, but as usual, it's difficult.)
(Acknowledgment: Thanks to Walter Truett Anderson for inspiration.)