[whswhs]

tshiggins: I was just rereading some of Jo Walton's essays on SF classics, and in one of them she comments that in Heinlein's juveniles (published in the purportedly optimistic 1940s and 1950s), there is a running theme of an overpopulated, oppressively governed Earth from which people are emigrating to other worlds, often imperfectly terraformed or with hazardous native life. So it's a classic theme, not just a recent one. Though I always remember the conversation near the end of Farmer in the Sky where an ecologist says that if you have emigration to other planets, you reduce the stress on the Earth population and people will have more children in response . . .

On the other hand, that assumes population growth, and most of the developed world, from Sweden to China, is faced with population decline, or so it appears. But I suppose you could premise an Earth where accumulated biochemical hazards have drastically reduced fertility and other planets offer a better chance of having children . . .