Despite the profusion of words I think the AI response basically sums up as "loss of diversity leads to loss of diversity." What diversity is remains undefined. For example, the polar regions are far less diverse than the tropics. But if a region is relatively undisturbed it remains in a natural state which may harbor only a few thousand species as opposed to a tropical habitat that has millions. 

With the risk of repeating myself, I think we only can say when diversity has dipped to the point where there are actual problems. This is the same as saying there are many different ways to define health, but when someone is really sick its fairly obvious.

> Allelic diversity within species is crucial for adaptation to changing environmental conditions.

Comment: there are species which have remain relatively unchanged for many millions of years.  Further, the loss of a particular species may have little or no impact on the ecosystem. And a non-native introduced species can have a decidedly beneficial effect on the system. It was shown that the influx of A. m. scutellata into the tropics increased pollination, which led to increased proliferation of nectar bearing flowers, which in turned helped native pollinators to prosper (the rising tide lifts all boats syndrome). 

In the final analysis, there are people who try to suggest there is a primordial state to which we must strive, ignoring the fact that all nature changes over time and is never the same for long. On the other side there are people who point out that a given ecosystem can be healthy and thriving irrespective of whether the species have been there for millions of years or a hundred. I think we have to set aside preconceived ideas like "the way it was" or "the way it should be" and try to come up with a concept of biological healthiness. 

As an aside, a friend told me of her concern about trace contaminants in bee hives and the need to throw out old combs. I said I can't really worry about everything, especially traces of things which may have little or no impact. I am more concerned about big impacts like black bears (and of course, parasitic mites).

PLB

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