Not only that, former permafrost is highly unstable almost by definition: as soon as it starts melting it starts shifting. This is already starting to be an infrastructure issue, as roads and bridges built on/in permafrost degrade at very high rate when it thaws.
And that's before considering the cool methane bombs. Nothing says stability like your field or house being replaced by a 40m deep crater.
And then, obviously, global warming / permafrost melting doesn't magick a more reasonable insolation. Even ignoring soil quality factors, agricultural yields start degrading as you go further towards the poles because the seasons and sheer amount of sun are crap.
When sea level rise then the salty water infiltrates into the ground water and makes vast amounts of soil infertile, from what I understand a much larger area than the zone lost directly to flooding. This will destroy massive wealth and push rural farmers inland, in conflict with each other or the wild areas.