Five reasons why scientist predict that humans will need to colonize other planets in the future?

It has long been scientific projection that man would colonise other planets as insurance against when the Earth became uninhabitable. Please note that all of the following are purely theory, and there is no real evidence to suggest any of them will occur. 1. The possibility of Earth becoming unsustainable due to nuclear war. 2. Overpopulation. 3. Climate change and global warning to the point of causing extinction of most species, and thus a critical threat to humanity. 4. Pollution making the planet virtually uninhabitable. 5. Natural disasters, rendering the planet uninhabitable. 6. Possibility of an asteroid collision. 7. Depletion of Natural Resources.