Eating lower on the food chain is definately a good thing, but I wouldn't become vegetarian on environmental grounds alone.
I don't think the issue is that we eat meat, but that too many people eat too much meat. The day the environment needs to be saved by the populace becoming vegetarian is the day there are too many mouths to feed. I bet if we manufactured Soylent Green, we could pack in another 10 billion...but what would be the point.
Personally, I think consuming a largely vegetarian diet occasionally mixed with fish and meat is a healthy and environmentally respectable lifestyle change. However, I don't see vegetarianism as being a more ethical treatment of surrounding life. Despite being inanimate, plants are living beings clutching to life like anything else.
An interesting subset of that reasoning is
fruitarianism.
- LostCause