More and more people cross international borders because their lives have been ruined by an earthquake, flood, drought, or hurricane. But they face a black hole of international law. No major migrant destination country allows people legal entry for this reason.
Humanitarian permission may be given to enter rich countries for other reasons. If violence has ruined your life in the country you live in, you may qualify to enter as a "refugee" or "asylee," as 16 percent of US immigrants did last year (PDF). Equally, if your life was ruined back home by a natural disaster and you enter a rich country without authorization, many countries won't immediately send you back. But the world has so far decided that the right amount of new, authorized migration because of natural disasters—no matter how horrific—is zero.