Heya,
Abandoned bases are correlated to enemy bases, if one goes, the other does as they both utilize the enemy autoplace noise expressions together (If you edit the enemy placement, both are effected proportionally).
With Bio science is only really helpful if you are fighting enemies, otherwise it is useless if in pacifist mode.
The only real upside is getting base movement speed, but at that point you can just fill modular armor with more exoskeletons as you will not need any offensive equipment.
However, despite this, I may add a way to get alien chunks in pacifist mode as well. I can't say the same for abandoned bases.