The purpose of conservation

In a letter to Science George M. Woodwell, a respected ecologist, criticizes the whole idea of setting conservation priorities.

The objective of conservation is the preservation of a fully functional biosphere as the only human habitat. That entails preservation of the full range of genetic potential in species, the species in all of its intrinsic diversity.

Every concept in this quotation is meaningless unless it is carefully qualified or, better, quantified. The objective - only one? Of whom? His objective with his own money? All biological diversity? Tom Fenchel has said that if you look hard enough every individual is different. How can you preserve all the diversity in species when individual organisms change, reproduce and die all the time? Fully functional biosphere? Full compared to what? Why should we preserve the functionality of the biosphere when we can actually aim at increasing it, as we have always done?