Is there hard evidence that this is bad? Resource depletion is among the highest risks to civilization. Seems straightforward that severe population decline should be desired, and voluntary refraining from reproduction should be welcome. (Please don't just extrapolate the trend till extinction. See http://xkcd.com/605/ . )
We're not Pandas. Ressource depletion is only a problem if our ressource consumption doesnt evolve. And it will evolve.
In the worst case, it could bring the bloody end of civilization as we know it.
I agree that society and technology could evolve us through a much more desirable path. But the more time we can buy for that to happen, the better.