> Why should I expect that to result in us killing each other over arable farm land, any more than we're killing each other over arable farm land now?
Arable farmland and access to fresh water have been a fairly common thing for people to kill each other over historically, including in the modern era. To the extent we aren't, its because many countries have reached settled states with their neighbors that are stable given a relatively stable distribution of those resources.
Major shifts would leave large existing populations without support and others newly prosperous, giving the former little to lose and the latter something quite valuable to defend.
Yeah, but those without are going to be continents away from those 'with'. Not really in a position to fight, especially as they're starving. Not talking knights in armor fighting over a moor here.
> Yeah, but those without are going to be continents away from those 'with'.
No, they aren't. The US will be one of the losers, Canada one of the winners (again, ignoring effects of variability, etc.) And lots of the relative winning/losing pairs are going to be immediate neighbors.
> Not really in a position to fight, especially as they're starving.
There'll be a whole long period where the losses will be to established economic position rather than mass starvation. Its not going to be "breadbasket today, wasteland tomorrow". There'll be a long period where declining economic position, rising food prices, and less food security (and similar effects with water in place of food) will be evident and starvation visible down the road before mass starvation -- and its in that period that there will be strong pressures on governments to reverse that position by any means at their disposal.
Arable farmland and access to fresh water have been a fairly common thing for people to kill each other over historically, including in the modern era. To the extent we aren't, its because many countries have reached settled states with their neighbors that are stable given a relatively stable distribution of those resources.
Major shifts would leave large existing populations without support and others newly prosperous, giving the former little to lose and the latter something quite valuable to defend.