EKU (Eastern Kentucky University) hosts a series of lectures called the Chautauqua Lectures, and I attended the first of the season on Tuesday, given by marine biologist Sylvia Earle.
In addition to bearing witness to the enormity and beauty of what's below the surface of the oceans (and hammering home the mantra that the earth is really blue, not green!), Earle touched on the problems of commercial fishing and how it is depleting populations of various (edible) sea critters, and pointing out how these practices have numerous negative impacts on these ecosystems. (And since ocean life generates a significant amount of the oxygen we breathe, it's not just a problem for the fish, etc.)
This got me thinking again about something I've been thinking about already: the ecological considerations supporting vegetarianism. I located a nice paper which states the issue clearly: "An Ecological Argument for Vegetarianism," by Peter Wenz.
Peter Singer's arguments for vegetarianism have never quite worked for me, not because animal suffering isn't bad, but precisely because there's nothing wrong with eating an animal that lived a decent animal life. (Of course, he would say that most of the meat that's readily available isn't from animals that enjoyed such privilege.) I'm still mulling over Cora Diamond's very different approach, which, roughly, involves the thought that seeing other animals as our kin should lead to the further insight that we shouldn't eat them: we don't eat our kin (see "Eating Meat and Eating People," Philosophy, Vol. 53, No. 206 (Oct., 1978)). I've yet to read a recent essay by Stanley Cavell that engages Diamond's ideas (as well as John McDowell's response), but it's on the shelf, waiting.
Nevertheless, I tend to find the ecological considerations most compelling. Waste not, want not, or something to that effect.