I unashamedly eat meat. If I have beef, it is from local producers who I know graze year round with only hay as an 'Input'. Chicken and Pork are more problematic of course, but I do ensure they are at least British sourced so well looked after and with low food miles.
The trouble with a vegetarian diet is that all crops are grown as mono-cultures. Yes, I know that field margins are larger than they used to be, but there are, I would suggest, very few insects, which after all are the main base food source, that live in a corn field and those that would like to live in a field of broccoli (cabbage whites for example) are severely discouraged! Whereas, a field that is grazed by animals is an amazing micro ecological miracle because that is how it has developed over millennia. It supports huge numbers of diverse plants and insects, not just grass of which there are in fact a huge number of varieties!
In addition, much of the protein rich vegetables such as soya, lentils and many of the beans that are used, come from far away so have the added issues of Food Miles, destruction of habitats and over use of fertilizers.
As for vegan food, sorry, other than vegetable, so much is actually Ultra Processed. Look at the contents of Vegan 'Cheese'.
Phil