Low birth rate of white people, or whatever group is in control.
I’ve always assumed that it was a dog whistle to nationalism and racism at some level, along with birthrates needed to prop up the system requiring infinite growth, the profits of which are primarily diverted to those already wealthy instead of growth in the social services needed to help an aging population.
The point is to install a new subway. Would you install a subway with the expectation that massive earthworks be installed to protect said cities and otherwise flooded subways?
Many of our subway-worthy cities are coastal. As sea levels rise they can either have flooded subways or attempt to build massive levees to hold the ocean back and skip the subways.
Building smaller homes should be in that list of things to do to reduce energy demand. None of these giant, leaky McMansions like they build in Texas housing tracts.
All for it.
Unfortunately where I live grass or plantings for a lawn above a certain height gets you a letter and possibly a citation from the town. You’d have to rip out the whole lawn and “landscape” the space. Not sure how much good that would do as you’d constantly have to maintain it so as not to leave all the dead plants around as the flowers died.
That said, one can still do a lot with lawn space to make it at least low-mow with various plants and flowers that will still look great and provide something for insects to eat.