That is true of the current intermediate technology level. If we manage to develop sufficiently advanced technology that we no longer need to use the Earth to support ourselves, it could change.
Given environmentalists proposing to turn the whole Earth into a nature reserve, the answer I would like to be able to give is, "Sure, have fun. I'm off to the asteroid belt to find some dead matter to turn into computational substrate. Send me some postcards."
Interesting recent article from Ben-Nun et al. (doi:10.1038/nmeth.1706) in the high-impact journal Nature Methods.
As I understand it, they express reprogramming factors in the adult cells (e.g., fibroblasts) of two endangered species (here and here) to convert them into induced pluripotent stem cells.
They then cryopreserve these pluripotent stem cells, in the hopes that they can eventually be used to increase the number and genetic diversity of these two species.
However, this will require two additional technologies which, crucially, are still in development:
1) the generation of germ cells from pluripotent stem cells, and
2) the development of assisted reproductive technologies for related monkeys and rhinos.
In the meantime, these pluripotent stem cells will simply remain in cryopreservation.
What does this remind you of? In what ways is it different, such that it can be published in a high status journal? Are those differences informative in any way?