Something I don't really talk about much in The Rent Is Too Damn High is the question of what might America overall look like if everyone took my advice and upzoned. I'm sometimes accused of wanting everyplace to look like Manhattan, but at a Manhattan-level density of 71,000 people per square mile the entire population of the United States could fit into San Diego County. And even that is a drastic underestimate since the densest portions of Manhattan are full of office buildings where most of the workers live elsewhere. The United States would be one relatively tiny but extremely bustling coastal metropolis and then a vast howling empty wilderness.
That, of course, would be a ridiculous way to arrange things but the point is that more density in some places is going to mean less density in others. I was reading about the problems of scaling-up grass-based ranching and obviously a major constraint is that to pasture a lot of cows you need a lot of land. And it turns out that the quantity of land on American farms has been in long-term structural decline:
Now to an extent, if this is the trend this is the trend. When land is more valuable in use as houses and offices and stores it makes sense to transform it to nonagricultural uses. But one important reason that there's been growing pressure to turn farmland over to other uses is that we have severe regulatory constraints on the number of people allowed to squeeze into the already-developed parcel. If you turn some neighborhoods of single-family homes into rowhouses and build some more tall apartment buildings on your most expensive land, then there's still plenty of suburban-style land left over for the large share of people who want to live there. Developers don't need to go out and find some new land and turn it into new subdivisions. A country with a growing population is bound to have both infill and greenfield development happening, but the current state of land use regulation in the United States is very heavily biased toward the latter in a way that's destructive to pastoral goals and open space.