You guys are thinking in way too simple terms. You think that just by introducing stuff like cyanobacteria or mycorrhiza and making them endure Mars' environment will just magically create a breathable atmosphere with just the right nutrients. Even IF that were to magically all happen, ecosystems are INCREDIBLY fucking fickle, even a fart at the wrong direction can create a cascading effect that is catastrophic without a proper biodiversity to suffer the blows properly, such as
>>9306379 create an uncontrolled reaction of a massive scope like utterly toxifying the soil with low ph.
The reason the Earth is a livable planet and Mars isn't is actually far more unique and takes a LONG fucking time to manifest. Not only that, but we have learned to adapt to that very specific concentration of gases and chemicals.
Just think about what happened on Earth:
>volcanic rock with a molten core>nothing can ever live here, no atmosphere, nuffin.>volcanoes release Co2, H2O and NH3 in the meantime>HOWEVER, a fucking planet just comes out of nowhere and collides with it>gases get dejected from the sheer collision force, and in a span of tens or hundreds of thousands of years, they liquify and fall down to form oceans>basic atmosphere is created that replaced the old paper-thin Helium one>underwater thermal vents create carbon molecules that somehow formed from CO2>carbon is able to become more and more complex due to its bonding properties to the point it became an aminoacid and eventually DNA>first lifeform drifts up to the surface in the form of a proto-seaweed>life explodes at an exponential rate, a BAZILLION fucking branches form from that single strand, almost all of them disappearing>the ones that did survive somehow manage to form a symbiotic relationship with a cyanobacterium WITHIN the cell itself that produces O2 as a waste product>the rest is what we have today>mfw there's people thinking we can emulate all that in the span of a few years 