oil wars, water wars
All the fighting at the moment is linked to oil reserves, but with a growing population, many of whom are in warmer countries, potential climate change, extremely poor resource management in every country, future wars will be water wars.
Some Middle Eastern countries have something like 97% of water from desalination, and so really briny shorelines where they pump out the waste, that's only going to compound. Once they run out of free oil to desalinate sea water then the vast cities of huge Tower blocks and ski ramps will get deserted and desertified in a heartbeat. And considering how much water is squirted onto motorway trees the whole way through the scorching desert, that time is going to come.
We're damn lucky here in the UK to have so much water, no matter how poorly we manage it. Maybe we'll become a super power again...