Low natality rate is a dramatic problem in most European nations and in a general way, in populations compossed mainly by europids.
Factors responsible of such situation are, IMO the following:
-Economical: families aim for a better life standards. Hence, they prefear to have less children but offer them better life conditions
-Social: Social roles change. Now both wife and husband have a professional life therefore there are less and less parents who stay home and have little time to spare for rising children
-Ecological: This is the lesser factor maybe, but it has its importance. Up to today only in europid nations (and probably in Japan and China -were natality control policies has been applicated sometimes- aswell) you might found people who feals really concerned by ecological problems including that of OVERPOPULATION. As incredible as it might sound, several families have chosen to not have more than 2 children in the sake of ecological and world overpopulation concerns.
And here we have a big probelm because, if many europeans feel concerned by the overpopulation prospects, is not the case for african, arabs, southern asians and other.
Europeans keep reducing their birth rate for several reasons while in other continents they keep their usual rates, if they do not increase.
My conclusion is that if could be an indirect way of preserving Europe if africans stoped reproducing themselves as rabits
PS: I hope my crudeness won't hurt none.If yes, ps accept my apologizes