- cows need a lot of land. If you used that land for e.g. efficient crops instead (and if people ate that instead of all that beef) you would free up a lot of land which you could use for other things (say, plant trees for example)
- cows need to eat a lot of feed to produce 1 calorie of beef. It is much more efficient to produce 1 calorie of vegetables and let people eat those vegetables directly instead of having it go through a cow first
- cows emit a lot of methane
- deforestation to produce more feed (like e.g. soy) is indeed also a factor
- cows need a lot of land. If you used that land for e.g. efficient crops instead (and if people ate that instead of all that beef) you would free up a lot of land which you could use for other things (say, plant trees for example)
- cows need to eat a lot of feed to produce 1 calorie of beef. It is much more efficient to produce 1 calorie of vegetables and let people eat those vegetables directly instead of having it go through a cow first
- cows emit a lot of methane
- deforestation to produce more feed (like e.g. soy) is indeed also a factor