Climate change will definitely make for dramatic changes. Flip a coin between wheat growing areas going from marginal to productive - or to nonexistent - depending on changes in precipitation.

Also, there are rivers that flow south to north. The northern mouth freezes first, melts last, so ice dams causing flooding that makes possibly productive river valleys death traps. No idea if warming might change that to the extent of making some of those river valleys productive, but if it does, there could be quite a shift (huge territory very lightly populated to something else...)