Right now the explosion of the human population, which will peak sometime in this century or the next before declining, is destroying earth's natural habitats. I see the decrease in demand for human labor as a good thing in the long run, although there are lots of unfortunate short-term effects which hopefully we can mitigate.
The decrease in global human population is already being test-run in a few countries, and the effects are mild so far: very low unemployment rates, stable or declining property prices. One worry is paygo pension systems, but that is a small price to pay for what we have to do in the end. I simply do not understand the fear of a falling demand for labor and a falling population.