As someone who has dedicated thousands of hours and dollars to pursuing permaculture food production, I question its effectiveness as a mass-scale food production system. It has significant limitations, and unfortunately, the kind of dispirited article cited here is what you get when the wildly optimistic claims don't line up with the reality of permaculture.

First, when it comes to growing food on trees, in most climates it takes many years for a tree to reliably generate a substantial number of calories. I have a mixed orchard of 52 trees that are five years old or older, and of these trees about 15% produce a significant number of edible calories. And yes, all the trees are healthy. Some produce no fruit, and some produce fruit that is destroyed by insects because I don't spray pesticides.

Second, permaculture is often not up to the task of dealing with a wave of insect pests before it destroys your crop. As one example, there is no native predator that effectively controls the invasive exotic brown marmorated stink bug, yet these pests can roll through your orchard and garden like an army.

Third, the nutrient boost created by nitrogen fixing plants is often overstated. The many moral virtues of hairy vetch pale in comparison to the effectiveness a jug of Miracle-Gro pellets when it comes to quickly growing plants that you intend to eat.

Fourth, what many people claim is permaculture or sustainable food production is really neither. I watch in amusement when people point to these urban gardens where tilapia waste water feeds hydroponic lettuce, but everyone seems to ignore the fact that the tilapia are fed processed fish food and the whole operation would be a bubbling bacterial soup in about 24 hours if the electricity (thanks, grid!) were to be cut off.

Fifth, permaculture is a discipline absolutely overflowing with people who loudly proclaim its effectiveness, and yet if you asked them how many calories they consumed in the last month that were produced with permaculture principles, the answer would vary from a tiny fraction to zero. People like to talk about, but very few are doing it in a way that puts food on the table 24/7/365.

And finally, I can think of no food production system less suited to the impoverished urban dweller than permaculture. Permaculture takes a long time, a large area, and a detailed knowledge of ecosystems to produce a significant amount of food. None of these are attributes of your average urban dweller. If you're going to get depressed about not bringing permaculture to the inner city in a way that actually fills bellies on a daily basis, then you need to grow some St. John's Wort (great in a partial sun guild) and treat your depression.