Tuna is one of the most overfished species on a global scale. GreenSeas Tuna is apparantly dolphin safe, but I don't know of large scale commercial fishing methods that do not have a significant by-catch of other species such as turtles, other fish, sharks etc. All the by-catch is discarded dead back into the ocean. Even if GreenSeas tuna avoids unsustainable practices, I don't think that eating tuna is actually helping the seas and making them "green".