We've already felt the first major problem (to the west) of global warming, mass migration. Most recent wars have had environmental issues as part of the cause. Syria's mismanagement of the water table, Rwanda's water shortages. Most conflicts seem to occur near the equator, and in deserts.
Our political system won't cope when a billion people start migrating
Sadly, I think you're right. When you get down to it, wars are usually just one group trying take another group's stuff. The common precursor to large-scale war appears to be 'resource scarcity'. I'm almost beginning to think the 'billions of people migrating' scenario is the more optimistic one.
Our political system won't cope when a billion people start migrating