Human beings obviously are at risk from an atom bomb, asteroid or some other such cataclysm. But another kind of catastrophe could be just as devastating for our species. If just one of the major seed crops humans depend on were to be taken away, the consequence would be widespread starvation. That's more likely than you might think. There are 2 million varieties of food plants on Earth. Human beings depend for their existence on about 20 of those. In Svalbard, Norway, scientists are squirreling away the crop seeds that could be the key to human survival. Cary Fowler is executive director of what's called the Svalbard Global Seed Vault.