Natural selection will fix it long term. France has higher fertility now because fertility rates dropped there earlier. Natural selection will select for "breeders" long term.

https://akarlin.com/breeders-revenge/

>Then the worm turned. German fertility plummeted after World War I, and even the Nazis with their “Kinder, Küche, Kirche” rhetoric were unable to force a recovery to peak Weimar levels. Meanwhile, the French – long derided for “race decay” by the Anglo-Saxons and the Germans – started to make more babies. Ironically, this began during the Vichy period, at the trough of France’s fortunes, and spread to the rest of the country after 1945; the French have been much more fertile than the Germans ever since. Whereas one 1920s League of Nations demographic projection saw the French population falling from 40 million to 29 million by 1970, it instead soared and now stands at 65 million.

>But why this turnaround?

>I would argue that this historical French dissolution paved the way for present day French virility, and conversely, past German “culture-forced” virility paved the way to present day dissolution. Or to put it in numbers, whereas Germany underwent its fertility 3 generations ago, the France had their about 5 generations ago. Their society has been selecting against those who reproduced less for a while longer, and it is starting to tell.

>The precise details of what will happen in Europe will depend on unknowables, such as the extent to which it becomes Africanized during the 21st century, and the interplay of shifting ethnic proportions with Islamic conversion. However, one minimal thing we can say is that after reaching a minimum sometime in the second half of the 21st century, the share of the indigenous European population will begin to increase again in the 22nd century. They will be concentrated in the small towns and rural areas, and will begin to demographically push back into the Afro-Islamic big cities.