Not necessarily true.
To raise quail, you just need 1sqft per bird. 10-20sqft isnt much, specially if you consider that 1 female quail will lay 300+ eggs a year, and that quail mature within 6 weeks of hatching. One could also stack the containers/cages, thus increasing the amount of birds in one area. The major benefit of quail is that they require less food and time to raise vs. raising chickens, being that quails usually eat 1/10th the amount of food than chickens, and only require 6 weeks to mature vs. 6 months.
I have a raised container garden that currently has 30 plants within a 30sqft planter. It provides extreme quality control and adjustment options, as well as a diverse variety of vegetables that provide all the nutrition I would need to survive. Depending on what crops you choose to grow, 20-30 plants would be more than enough to feed a family.
So, with less than 100sqft, one can have a self-sustainable garden/farm that can take care of family, providing that you select the correct crops and livestock to raise. Imagine the possibilities with more space. You might be missing out on some things, like dairy and a massive variety of vegetables and meats; but essentially,, one does not NEED to have an extremely diversified diet, provided that the crops one already has on hand provide sufficient nutrients to sustain you and your family. It becomes more of a complacency issue when you eat the same things all the time. But in a survival situation, as long as you and your family are fed and healthy, who cares about the kid who wants candy or cereal and milk.
Also, by choosing the correct crops, the produce can be traded for what you or your family needs, should such a need arise.
The quail just sit in their cage and gain weight by eating air? Or are you buying food for them that's grown somewhere else?
9,200cal/day out of 100sq ft? LOL
In the real world, sweet potatoes have 390 calories per pound, and really intensive growing in very fertile soil
may produce as much as half a pound per square foot. They take six months to grow, and you do need to rotate, so one crop a year out of any piece of land is about all you can expect.
For a family of four (as per the original article): 9200 calories divided by 390 = just under 24lbs/day. Multiply that by 365 days and you get 8760lbs or 17520 sq ft, which is almost half an acre. Corn is way less space efficient, and takes a bunch more fertilizer. Good luck getting wheat to mature anywhere in Hawaii.
Growing all your own
fruits and vegetables isn't that hard, but trying to grow all the calories that you eat...takes lots of time (and land). Growing all the food your farm animals need just adds another layer of complexity.
Food is cheap because it's grown by machines in large fields that take advantage of economies of scale. Being a peasant in no fun; that's why everybody who can moves to the city and gets a job, even if it only pays $2/day.
Yes, Hawaii needs to be more self reliant, but a return to subsistence agriculture isn't the solution.