Birth control + communal farming, sounds great, might work in North America, guaranteed to not work in many other parts of the world. Why? Culture, availability of land, and not enough time.
Firstly, changing some people’s minds about birth control is practically a death sentence to them. In some cultures having a big family is a social status. Having lots of kids is a sign of success. Forcing birth control on them “for the good of the planet” is akin to asking your average American to give up a single detached home and instead squeeze your family of 4 into a studio apartment.
Land availability, a huge problem in many parts of the world. Communal or not, the fact remains that farmland is quickly diminishing because people are building houses on farmland. Communal farms means people need to live relatively close to the field, which means building even more houses on farmland. Yes, we could cut down more trees to make more land but wait, isn’t that worse?
Time, time is a huge factor. What crops grow in the winter where you live? Where I live, basically nothing, and winter is a cruel 5 months of the year. Out of the remaining 7 months we have to consider that organic crops take a long time to mature. What if a drought hits? What if a storm destroys the crops? Even if they are harvested, they have a short shelf life. How many people will have to starve due to poor timing?