Fantasy? The world would be overun with herbivors, the planet would be stripped of vegetation in short order and everything would die of starvation.

Carnivores and omnivores are an integral part of our worldwide ecosystem.

Con.
You hve have to eat more volume and more often when you eat vegan to keep up the calorie counts.

Pro.
You use a lot less fossil fuels to procuce began food sources.

Well it would change a lot of things, but what we eat is only one part of the big important changes that need to be made in the world. Population control is another big one, and while those are connected it's not enough to decide what we should eat and how to manage it. No matter what we eat there are too many people. We're consuming and smothering the planet. They're two different but equally important problems.

Pro's : 1. meat is grown in labs also eggs , milk ect. All mass produced.
2. People become healthier due to better diet.
3. Clean Air , Water and soil become hot button political issues as People bcome more concerned about what we consume.
4.Less farm animals reduce greenhouse gasses.
5. People agitate for a just society as they are awakened politically.

Cons

1. Corporations own the means of production and feeding the populace which magnifies power in a few large Corporations.
2. Moving from animal farming to crops leads to a decimation of rural living worldwide. Cities expand and urban crawl and decay increases.
3. People living longer strain the social support systems leading to breakdown of social services and poverty in the elderly.
4. Clean water and air and soil make these resources more valuable than rare earth minerals.Wars are fought over territory. famine and drought lead to massive population contraction.
5. The remaining "owners" live happy long idyllic lives.