Siachen, one of the largest glaciers outside the polar regions, belongs to India or to Pakistan, depending upon whom you ask. This 40-mile-long behemoth, which originates at about 19,000 feet altitude and terminates at nearly 12,000 feet, is shrinking because of climate warming and environmental degradation caused by the militarization of this disputed territory. What's at stake when this ice giant's spring and summer meltwater slows to a trickle sometime this century? A key water source for hundreds of millions of Asians — a frightening thought.