I could argue that since humans are the most adaptable species on the planet (even if we do change the environment, instead of changing ourselves, we are still adapting), and humans are the most fit, so we deserve to be the dominant species. As Darwin said, the best adapted survive and reproduce. By that token, why shouldn't we continue doing what we're doing, which is making the world an easier place for us to live in?
However, I believe that the world needs to be in balance for everything to work right, and if we keep going in the direction we're heading, our adaptability will be our downfall, and the universe will eventually re-balance itself, with humans in the picture, or not.