I've heard from a bunch of different sources that most land humans use for farming is specifically for animal agriculture and that if everyone went vegetarian, something like 20% of the land would be required.

I'm hoping that if lab grown meat takes off and becomes affordable for your average person, we might be able to give back some of the land that was de-forested for animal agriculture back to nature.

Energy usage is a self-imposed problem. We know how to generate massive amounts of electricity with zero emissions: nuclear energy. Insane self-described environmentalists successfully lobbied to make nuclear reactors nearly impossible to build in most Western countries, much to the delight of the coal industry. But laws can be changed, and if we're choosing between changing a law, and an environmental disaster, we should obviously change the law.

I'm pro-lab-grown-meat though; if it's a tasty source of protein that reduces animal suffering and reduces the environmental impact of the meat industry, why not?

What's this "we" stuff, you speak like we already have one world government and as if I'm responsible for providing food for people all over the globe. The future is regionalization, not more globalization. War is already killing globalism and it will intensify soon.