But I haven't seen any alternative scenarios either. If there is a population readjustment, what we might call a disorderly retreat from 7 billion to 1 billion or less, it will likely wipe out any groundwork in the process.

There isn't any solid evidence that 10 billion or more people can't be sustainably provided for, so I don't understand why so many assume that the population will implode. We have ample nuclear fuel for millions of years at 1000 times the global energy demand now and thats been demonstrated on a large scale (say all of france) without even bothering getting into the argument that renewables can also provide energy to power civilization.

I guess it depends on whether one thinks of your estimates as being able to see into the future or as hypothetical, and on whether it really is just a matter of energy as to being able to provide all of the resources and food that we we consider vital, without severely damaging our habitat, for a population of 10 billion, at moderate standards of living.

I'm sure many people disagree with both.

I'm sure many people disagree with both.

I know many do. On the later point, its based on undemonstrated assertions that there are somehow components that aren't producable by energy despite reasonable evidence to the contrary.

On the former, they're just plain wrong.