efficient energy and transportation systems aren't part of sustainable living? How quite sure how that fits.

The crackpots tend to be the "Everyone, back to nature! Let's all dress in mouldy sheep, mine mud, and eat fallen apples" variety.

True sustainability is about managing both individual impact, and global impact. Efficient energy systems, transportation, and food production might allow a global population of 10Bn to operate on a smaller whatever-footprint than where we are now.

Dealing with a population increase is going to be easier than convincing everyone what is, and how to maintain, a stable population. 1-child-per-family rules are unlikely to hold much sway in what we currently consider 'civilised countries'.