I read this book, Global Warring, by Montreal native Cleo Paskal. It's a real kick in the head.
It's not just food security that's going to be a problem. Water is number one. Energy security is another. You can't make food without water and energy.
But the book takes it beyond the obvious.
For example, changing sea levels will wipe out entire island nations, and reconfigure coastlines. This will affect borders and territorial waters. One possible scenario is, as sea levels rise, the US Gulf coast, which is low-lying, will be inundated while Cuba, which is mountainous, will remain relatively intact. This raises all sorts of issues vis-a-vis that 200 mile zone (although it's not quite respected now.) But Russia is now drilling for oil off Cuba. Uh-oh.
Now multiply that all over the world. The geopolitics are scary.