A new computer model by Eric Wolf, estimates the earth will be destroyed by our sun in 1.5 billion years. 
It is a popular idea in science and science fiction that we will one day escape destruction on earth by colonizing other planets. In these scenarios the polluted and spent earth is left behind. But, will there be enough space ships to save us all? What about all the plants and animals we would leave behind? This is a bad way of thinking about the future that can have a negative impact on how we think about the present. We more readily accept pollution and things that harm the planet, when we think that in the distant future, we are going to ditch the earth anyways.
Instead we should plan to save the earth by turning it into a giant space ship, so we can safely move the earth to a higher orbit as the sun becomes a red giant star. Is it too soon to worry about these things? It might take millions of years to safely move the earth to this higher orbit, and transforming the earth into a spaceship may itself take millions of years as well, so we better start now to be sure we have enough time.
Much of the earth as we know it will be lost in this radical transformation into spaceship. In order to preserve natural habitats and places for cities of the future, we will need to greatly increase the total surface area, control the weather, and globally route the flow of fresh water. I have created this animation in Blender to try to capture some of these ideas. I imagine the disk structure as a place for the new cities, where people can enjoy flying around in the lower gravity. The original earth surface enclosed in a protective biosphere, can be maintained for wild animals and returned to its natural state. I placed the rocket booster at the south pole, I imagine we would have to drill to the earths core and reinforce the entire earth through its center from both poles.