Other variables to factor in would include cultural/esthetic ones: how much would a population tolerate a reduction in the idyllic/scenic nature of their landscape, merely to accommodate crops for a rising population?
(This is what I referred to as "quality of life" in another post.)
That math is about animals in a fixed climate who don't do trading. Swiss people do.
And that "how much would a population tolerate a reduction in the idyllic/scenic nature of their landscape" is a very arbitary factor that will strongly depend on who you ask.
You're basically reluctant to accept the fact that such a calculation is possible. That says more about you than the competence of mathematicians and ecologists...
(Btw. I believe switzerland is not trying to be self sufficient anyway, but donimport lots of stuff, like most other countries do)