Is Alien aggression global or is it on a per-nest basis?

According to another question about alien aggression, alien aggression can be lowered by:

they also become less hostile if an alien nest actually exists within the borders of your city, eventually becoming friendly.

But that leaves me wondering if the aliens become friendly for that nest or city, or do the aliens become friendly globally.

Is alien aggression tracked globally in Beyond Earth?

Alien aggression is tracked locally in Beyond Earth, so the aliens would become friendly only for that nest.

It has been proposed that alien aggression be global here, but has not yet been implemented.

Source 1 (A great read, recommended for any civ-beyond-earth player)