No country can be secure if it lacks the things necessary to keep its population alive. This is why food security has become an issue. It's also why more attention should probably be paid to the water scarcity issues that have come up in recent years.
According to the Economist, water scarcity is now a bigger problem than food scarcity. The article here focuses on the water problems in much of the rest of the world, but even the US is having unprecedented problems.
Last year, the US state of Georgia almost ran out of drinking water, and got into a border dispute with Tennessee in order to get the rights to a river in the area. Every year, western mayors spend a large chunk of their time and resources trying to come up with new ways of getting water for their constituents. At the same time, the US is paying for the water for farms in the desert, farms that then proceed to use the least efficient irrigation procedures possible, because they're not the ones paying for the water.
If we cannot get it right, despite our relative abundance of water, what will happen in the poorer countries that are so badly hit? Many theorists expect "water wars" in the near future. The areas with physcial scarcity are all of the danger zones that we spend so much time worrying about for other reasons. It seems that it would be smart to start investing in ways to reduce water use now, so that the booming populations will have access to enough water later. If Georgia and Tennessee can start feuding now over water access, what is likely to happen when two unstable autocratic states (in a world of anarchy, no less) start arguing?