In a recent talk, Steven Hawking expressed the need for humanity to colonize other worlds in order to avoid extinction. He spoke specifically about the eminent threats to human survival, like asteroid collisions and nuclear war, as well as the development of near light travel. He also spoke of his own determination to go into space.
It struck me while reading about this talk, that colonizing other worlds would involve a lot more than just the technology to get there. We would need to survive there. And even a planet that already supports life of some kind isn't likely to have everything on hand that human beings would need to survive. It's most likely that we would need to engineer environments on new worlds to make homes for ourselves. A biosphere transplant.
The leading Paleontologist Richard Leakey, in a speech at Cameron University in 2001, stressed the need to preserve genetic diversity of species "in order to ensure our tenure on this planet." I think he's right, and I would also take that a step further. We need to preserve genetic diversity of species in order to ensure our tenure in the universe. The worlds we may find to call home outside this solar system will almost certainly run the full spectrum of environments that can support life. To create viable biospheres on such worlds, we may need creatures as diverse as carrier pigeons and woolly mammoths. All the more reason for us to be careful with our environment.