>Yes, of course I am talking only of genetic diversity - the very stuff
>which you and I *still* depend on to breath and eat.
Actually genetic diversity has rather little to do with what you
breathe and eat. What you eat almost certainly comes from farms,
and they don't need genetic diversity to operate. Maintaining
diversity would probably permit improvements to farming in the
future, but it's not necessary. The oxygen you breathe effectively
comes from whatever plants fixed the carbon in the food you eat
- in other words, the same farm plants.
The other chemical cycles on this planet like the nitrogen and
sulfur cycles are run by bacteria, and they're doing fine.
The ongoing loss of genetic diversity is quite the catastophe
for non-domesticated life, but for humans and their symbiotes
it's done no significant harm as yet. Even the total conversion
of Planet Earth to Farm Earth would only be a moderate and
manageable problem.