Actually Vikings invaded much of western Europe as well as Ukraine earlier starting in 800AD in response to Carolus Magnus proselytism, and it is contested that they were "murdering and pillaging". Most probably this vision was propagated by their enemies in the Christian world.

We do not know for the "mass famines", but this time was the Medieval Warm Period (800–1300). It is thought that between c. 950 and c. 1100 was the Northern Hemisphere's warmest period since the Roman Warm Period.

https://en.wikipedia.org/wiki/Viking_Age

Ok. "Oppressed people of Ukraine invited vikings (ie russians) to rule them." I do not know much history, but this snippet from Putin's speech from 2014 comes to mind.

The historical reality is quite different.

https://en.wikipedia.org/wiki/Varangians#Kievan_Rus'

According to some semi-official sources I found with a quick Googling, Sweden was mostly self-sufficient up until the mid-90's. Dunno how many people lived there during the 90's, but I take it that it was more than a million?

Of course, things will change once harvests will start failing, and if you guys had just a bad of a harvest as we had this year (Finland), then it doesn't matter if 50% or 10% of the food comes from local sources; you're going to be reliant on imports anyway.

Yes. But this was accomplished with heavy machinery and fertilization, which are based on imported oil. In Northern Norway you can find most pitiful attempts of agriculture above the arctic circle, indicating that the land was overpopulated and even the sea was overfished.

Interesting times ahead for us people up here then... Good thing I grow my own potatoes.