One of the thornier things about the existence of super-heroes in the DCU is that, "realistically" (an admittedly dicey word), on a planet teeming with hundreds of super-heroes, some things just shouldn't be a problem any more. And I'm not talking about multifacted, difficult-to-solve issues like world hunger or peace in the Middle East, I'm talking about things like:
Large Scale Forest Fires
With all the Supermen, Green Lanterns, Flashes, and so forth running around on the planet, there's really no excuse for any decent-sized forest fire in the DCU to gain any traction.
Giant Hurricanes Making Landfall
The nice thing about hurricanes is that you can see them coming. If it looks like they're catastrophically big and about to hit a population center, some Green Lanterns, Flashes, and Red Tornados can steer them away. Probably.
Big Time Flooding
Again, there are lots of folks on the planet who can literally change the course of mighty rivers. It would seem that most flooding disasters should be severely mitigated in the DCU.
And that's not even getting into how much Climate Change should probably have been addressed by the Big Brain characters.
Anything else that really shouldn't be much of an issue in the DCU?