If the ice-caps melt, they're going straight to the ocean, and the water's gonna become saltwater. Thus, there will be a net decline in freshwater worldwide. Actually, a pretty huge decline -- most of the freshwater in the world is glacial. Simultaneously, glaciers are absolutely vital as the source for the Indus and Ganges rivers, which help feed hundreds of millions of people... as well as a number of other rivers, for that matter. Ice, when not in your driveway, is actually pretty important to the survival of a good chunk of humanity.