In both examples I was presenting a conflict between a use and preservation. Biologically, the tortoise population, or any organism, needs a certain area to support a self-sustaining non-inbreeding population. At some point with the tortoises there needs to be a line drawn, if they are to survive. Society has to decide where that line is and how large it is.

Same with human population. The earth has an (approximate) absolute limit of humans. The more people, the fewer free-living natural resources. Those magnificent million-plus bison herds on the Great Plains are doing just fine, right? Society, as a whole, will need to decide on how many people there will be. I am certainly not suggesting that a single person should make that decision.

It seems to me that jumping to solutions such as lock up zillions of acres for a turtle, limit humans to a population of X is a really neat deflection to get away from dealing with the question of just how we wish to share the planet in the future. There is no one answer stat than if we do not decide, we have decided to wipe it all out.