http://www.nytimes.com/2009/12/22/science/22angi.html?ref=nutrition Exactly what I've been thinking about ever since taking plant biology classes in college. The only way I can think of eating that's more "ethical" than other ways, therefore, is eating low on the food chain to preserve as many resources and lives as possible, or eating consciously in a way that preserves and protects our ecosystems to the greatest extent.
Cause, really, chlorophyll, phloem, blood, mitochondria, chloroplasts... how are they really all that different?