OK the question was raised about no backyards in cities. Much can still be done even by apartment dwellers.

In many major cities it is not uncommon for homing pigeons to be raised on rooftops. Pigeons while not as big are a meat source. Don't like pigeons, what about a dove cote? You might even get away with rabbits. Although chicken might be a bit much if only because of the noise factor.

For growing crops there is container gardening. Think of it as smaller scale raised bed gardening. This can be accomplished on rooftops and on balconies.

There has in the past movements for groups to raise community gardens in nearby vacant lots.

Yes! In any of these you might suffer vandalism and outright theft. They are possibilities. And there are many other ways a city bound apartment dweller can raise quite a bit of their own food.