Deep Ecology, first introduced to the world by Devall & Sessions (1985) in a book by the same name, refers to the inherent worth of all species. This is to be applied regardless of a species' worth for human invention or consumption, including economic concerns. Biological diversity is a core value unto itself, and is to be respected as such.
What is being inferred here is respect for all life ~ the interconnectedness of the whole of Creation. This may be a radical proposition for some to swallow. We have become hooked on the premise that humans are a cut above the billions of other species that share the Earth with us. These species have, almost exclusively, been on the planet longer than we have. Their journey of co-evolution predates the dawn of history.
It is clearly a case of not seeing the forest for the trees. Because one species develops highly advanced logical reasoning, are we to assume superiority in all phases of life? Do we then relegate all other life forms as our possessions, doing with them as we please, ignoring their own need to live up to their destiny and potential? Is it right for us to use other species in laboratory experiments, as if they were unfeeling machines? This is one abhorrent practice that will need to become extinct.
What is true for humans is true for all creatures: No one - not a soul alive - is grist for the mill. Everything and everyone matters.
The Earth is currently undergoing the sixth extinction crisis in its history. This one is different than the previous ones, in that it is altogether human-caused, and happening at a phenomenal pace. As extinction rates rise, entire ecosystems are crashing. Humans will eventually be sucked into this crash.
To prevent this catastrophe from proceeding unchecked, a new way of looking at ourselves within the context of all of Creation must be brought into prominence. Deep Ecology can be this context. As we evolve, there will be a tendency to see the network rather than the hierarchy, the web rather than the throne. As humans gain a more proper perspective of our place in the Universe, it will no doubt leave us a more humble and satisfying existence. No longer the rulers of all we survey, but beautiful pieces of the whole.