I think that at the moment we overeat on meat causing overfarming, deforestation, etc. However, if the whole world suddenly would give up eating animals, we would equally create an imbalance. The key is, as usual, BALANCE. Me for instance, I eat meat or fish only 2 or 3 times per week. Afterwards, I don't even feel like it anymore. If everybody started to put a few vegan or vegi days into his diatary plan, we would already achieve a lot.