Well, if there is a global environmental crisis and the world "is running out of time", surely that's a good thing? Population growth has been happening at an alarming rate...

the problem is not the decline in population itself but rather the aging. If/when the working population will be outnumbered by those who are retired we’ll have serious problems.

Aging is unavoidable sooner or later as population cannot keep growing forever and we don't want to live in Logan's Run, either. So IMHO this is a red herring: we need to face the inevitable and adapt to it in any case.