One calorie of vegetables is a lot less carbon-intensive to produce than a calorie of meat. As for meat replacement alternatives to help people adjust to a die

One calorie of vegetables is a lot less carbon-intensive to produce than a calorie of meat. As for meat replacement alternatives to help people adjust to a diet with less/no meat: Plant-based meat substitutes (these have become a lot better in recent years), in vitro meat production (still a few years off), or just more beans/lentils in the diet to replace the lost protein.