A unicorn is described as having the legs of a deer, the tail of a lion, the head and body of a horse. It possesses a single horn which is white at the base, black in the middle and red at the tip. Its body is white, its head red, and its eyes are blue. Clearly, the only thing unreal about a unicorn is in the combination of its parts. That is, a unicorn is less than the sum of its parts, assuming, that is (with a prayerful nod to Anselm of Canterbury), that existing in reality trumps existing in the mind, or in this case existing in the mind as in a series of disarticulated parts that are themselves very real.
When an ecosystem is described as greaterthan the sum of its parts, as it was in Eugene Odum’s holistic conception of it, what is meant is that when the biotic components of ecological communities interact with the abiotic realm (that is, the formerly living and the never-alive), certain properties of the whole emerge that cannot be readily predicted from an analysis of the component parts. This claim, made on behalf of the larger units of nature, was persuasive to generations of ecologists influenced by Odum’s textbook, first published in 1953 and now in its posthumously published 5th edition (2005). However, in as much as Odum’s notion of the ecosystem manifests a Balance of Nature perspective it has almost universally fallen out of favor in ecology and, like the unicorn, is emphatically relegated to myth and fancy.
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