Should Earth become a planet of vegetarians?

When I saw that headline on a story in The Guardian, it was like I’d been waiting for it. It struck me as both amusing, in its implication that vegetarianism would be a tough fate even though we’d likely be healthier for it, and also as an inevitability, with which I’d already come to terms.

But the story itself is not funny.
Here was the lead paragraph:

Vertical farms could help feed cities, save land and reduce pollution

New York City has one of the most recognizable skylines in the world. It’s famously tall buildings provide maximum occupancy for minimum space, making an ideal situation for a rapidly growing population.
When millions of immigrants flocked to America in the late 1800’s, the need for space to put them all caused the city to grow up instead of out and skyscrapers sprouted like weeds.
The human population is growing. By the year 2050, it is estimated that we will be another 3 billion people. By that time 80 percent of the world’s population will live in urban areas.