There is scarcity - resources aren’t evenly distributed. You can’t have a fruit farm on the tundra, and you can’t mine uranium on Hawai‘i. It’s not possible to locally sustain a city in Arizona (ie food and water). A significant adjustment of the lifestyle to which we’ve become accustomed would be required.

More locally, I live on some prime farmland, with (usually) ample water and some pretty decent climate for a wide variety of crops. Our country is busy converting this into poorly built housing and warehouse space. There are also large portions of the country wholly inhospitable to farming, which are disdained. A similar concept is the ongoing market gardening of vegetables in the California desert. Some people are big on urban gardening and that’s fantastic, but it’s not going to supply the caloric needs even if it’s all potatoes. Vertical farms conveniently leave out the massive energy inputs (not just light and heat and water, but fertilizer and pest control too).

If we continue to abuse the resources which we have available, humanity is doomed.