From someone who is not a farmer and doesn't know so much about this, for example could we grow vegetables and feed them to humans directly, rather than feeding grains to cattle?
Take for instance the factory farms which have to constantly ship food in to feed the cattle. Another example is deforestation to create fields for cattle to graze.
I think the OP is right, we need to convince more people that beef is not a sustainable food with the rate at which we consume it today.
People probably wouldn't eat as much meat as they do now if it were from free range, non-grain fed animals.