Cities -can- be more environmentally friendly than the equivalent population living in a more rural setting -IF- you're comparing roughly equivalent standards of living.
And there lies the rub. A) It is entirely possible that China will screw up something in their planning resulting in poorer environmental outcomes. B) This demographic shift will almost certainly come matched with an economic uplifting, and regardless of efficiencies of scale and density (which is what a city gives you), the increase in standard of living (and therefore energy and other related 'products') can result in increased environmental damage.
For starters, what are these people currently burning to keep warm and cook their food? And how will that change if they become middle-class city-dwellers?
It depends. Coal, charcoal, wood. The house where my father grew up vented smoke/exhaust from the fires in the kitchen under a hard clay bed built into the house to keep the family warm in the winter.
You can see the effect of years of exposure to soot on the faces of people who live in rural China (and, I daresay, anyone who lives in similar circumstances). These people are not living particularly environmentally clean lives right now (although, to be fair, they probably do consume far fewer manufactured goods than their city-dwelling brethren).
Something of interest is the prevalence of solar water heaters, both in urban and rural areas. They are surprisingly common, much better than heating water using fire or electricity, and affordable even to those outside the cities.
That video doesn't tell us much, but I think this could be an incredible opportunity to rethink what cities are. If they're making them all anyway, why not create them sustainable? It's a bunch of farmers, so give them plots of land to feed themselves with. Make self-sufficient earthships instead of houses that require utilities.
Sadly, the video says this is meant to increase the economy, get them buying more stuff. I imagine that there will be a very efficient system for shipping all these people into massive factories to make plastic crap, so that all these newly converted consumers can buy more plastic crap, 98% of which ends up in landfills within 2 years, which I suppose is what they'll be using their old farmland for! lol.
Education of girls and urbanization are the most effective ways to slow the birth rate. Without doing that, environmental preservation is not going to be possible.
In fact it has the other kind of birth-rate problem, a looming demographic crunch due in large part to the one-child policy. And of course a mysteeerious gender imbalance to go with it.
