The idea has theoretical appeal, but the problem of relative scarcity is a big one. In a City of 3,000,000 w/far more people than plants of any particular type, even if a plant weren't damaged (say blackberry, you just pick the berries); the issue of eating all the food meant for the wildlife is a problem, as is consuming the seed meant to repopulate the species.
But many plants are eaten by picking the entire thing or branches/stems etc.
Wild Leek, and Wild Ginger come to mind. These can only sustain limiting picking. Wild Leek can keep up if you remove no more than 10% of what is present in any given year,.
But do you know what was present when you come along and 4 other people have the plants over before you?
Not a huge issue for most common stuff; I mean, if you mistake Mulberry which grows on a tree for raspberry......ummm, there are some gastrointestinal effects if you over indulge, they are 'temporary, but a bit explosive' LOL
There are lots of look-a-like plants, though not that many that are edible are mistakable, mushrooms are clearly an exception. Again, Toronto gets very few Morels or Chanterelles and I'd rather people left them.
Possible, but I think I'd simply be more concerned by run-of-the-mill contamination for anything close to ground level, especially near a street or sidewalk. Dog excrement, road salt, motor oil etc.
