Are humans the most valuable organisms on the planet?

How valuable are humans to the planet is related directly to the question of what do humans add to the planet when compared to the rest of the organisms. When it comes down it to i feel that humans just don't add much and in fact take so much away. We have devastated the living places of countless other living beings, and other effects such has the emissions of toxic chemicals have had a negative effect on the planet. I think that like was said earlier we value humans due to the fact that we are human, however this doesn't make us intrinsically valuable. I'm not sure what organism is more valuable then humans, but I'm going to go ahead and think that there is something out there that adds something to the planet, which is something I feel that humans don't do. Regardless of how valuable we feel we are, or how much "better" we feel i believe that we are not more valuable to the planet then other organisms are.

When we begin to talk about value, we need to define it, other posters have put forth some excellent ideas.
But I wonder, is it possible to place a value on a life form based on it's importance to the over all system? For instance, if you remove say the Dodo bird from an ecosystem, how many other species will be affected? It turns out that this question is incredibly difficult to answer until the said species has been removed. No one expected the calvaria tree to become extinct after the Dodo, but it turned out that the tree needed the bird to help break down the out shell of the seed pods so they could sprout.
Now I don't want to stray too far from the topic, but this illustrates the complexity of life and to think that there are organism of higher or lower value requires an understanding of the global ecosystem we do not yet have.
Now my argument is predicated on using the value system I set forth, it does not hold if, for instance you use "the ability to do good" as others have suggested.


Perhaps we should refine the question before debating an answer?

Thank you, I look forward to any responses.