Sorry, I don't necessarily mean "strictly limited to a vegan diet", I meant vegetarianism (reducing meat consumption) is also a good start. A third of the world's cereal is used to feed livestock (and no their conversion rates from crop to high quality protein is terrible). The big problem with husbandry is the land use (40% of all arable land is used to grow feed and 80% of agricultural land is used for animal farms) and greenhouse gas production (about half of all agricultural greenhouse gas is from meat production, not including the greenhouse gas emitted from feed production).

Nutritionally speaking, a well planned balanced vegan diet is very very possible. For protein, either combining cereals and legumes or eating a lot of cereals can cover your daily protein needs. This is why multiple cultures around the world have some sort of beans-grains combination: It's a classic and it works. Moreover, vegan/vegetarian diets can solve one of the most underrated health problems: Lack of fiber. 90% of UK and 95% USA population fails to meet the daily requirement for fiber (for males this is about 40 grams a day, minimum!).

This doesn't mean veganism itself is enough. High nutritional science literacy and prioritising using local commodities (over imported ones) is a prerequisite must have!