This article is focusing only on near-future resources needed for habitation. Probably just for the first 10 years of habitation. During the long run, the asteroid belt objects can come into place, and many other techniques I have read about. Stay tuned and I promise I will write about them in a later chapter.

I talked previously in my series about the Planetary Act:

"Terraforming in the long run
Some other preliminary studies cover the introduction of certain bacteria and algae, that could survive in the current Martian environment and if spread in a sufficiently big enough area could thrive and contribute to the gradual martian atmospherical composition change. However this is not allowed yet, under the Planetary Protection act. This is in place due to the fact that Mars has a high probability of hosting life which could be endangered by introducing new forms of life."

from: https://steemit.com/mars/@alexdory/can-we-make-enough-breathable-air-in-our-future-mars-colony-colonization-of-mars-series

I really appreciate your concern, it is also one of mine as I really believe that we will find some sort of evidence of life there ( at least past). It seems more unlikely not to find evidence of life as all the criteria are currently being met.