I'm halfway thorugh The World is Blue: How Our Fate and the Ocean's Are One by Sylvia A. Earle. The author is a marine biologist (and the Explorer in Residence at the National Geographic Society) and this book is about the wonderful creatures in the ocean, anything from tiny bacteria to the largest whales.
The book laments the destruction that we are doing with pollution and other careless acts, and she argues that by destroying our ocean's resources we are robbing ourselves of countless treasures, both known and also undiscovered. Its amazing how diverse the life is in our world's oceans. They speculate that there may be tens of millions if not more undiscovered species there ranging from fish to microorganisms. When we destroy habitat we may be destroying living organisms that we don't even yet know exist, and in our ignorance we may be causing even more harm than we imagine.