That is simply not true. Nordic countries have among the highest population growth of the rich countries. Of course sympathy towards single mothers is part of the reason we never got the severe population decline seen in Germany, Italy and Japan e.g.

The map you show is hard for anybody who doesn't know anything about settlements pattern in various countries. Nordic nations are experiencing population fall in thinly populated remote areas. Because these are large areas, it looks more dramatic than it is.

People are leaving small towns with limited opportunities because they want to live in bigger cities with more variation in opportunities. Mind you limited opportunities doesn't mean there aren't jobs. It just that that young Norwegians and Swedes don't want to work in fishing and mining industry anymore. Often immigrants from eastern europe take over these jobs, saving many small communities from falling apart.