Climate change.

Australia is going to burn to cinder. All those little island nations are going to be Atlantisized.

We've got gobs of land. Let's give them space to relocate.

The population of Australia would fit comfortably in Kansas. The entire nation of Kiribati could disappear into Queens or Brooklyn without a trace.

The first generation would work hard, vastly increase the number of neighborhood retailers and food shops, and send all their kids to college. And the second generation would move to Manhattan or L.A. or the Bay Area and become programmers, artists and stand-up comedians.

Win-win.