“In the great commons at Gaia’s Landing we have a tall and particularly beautiful stand of white pine, planted at the time of the first colonies. It represents our promise to the people, and to Planet itself, never to repeat the tragedy of Earth.”
— Lady Deirdre Skye, “Planet Dreams”
In the game, Tree Farms are an expensive base facility that require Environmental Economics to construct. The most obvious effect they have is to provide a multiplicative bonus to energy channeled toward economy and psych in the base. The dual effect is analogous to the Research Hospital, but yielding extra energy credits instead of research.
However, it also provides another benefit that the game just refers to as “forest” in the interface. What that ends up meaning is that a Tree Farm improves the nutrient yield of every forest tile worked by the base by one. Since forests always yield one nutrient, this means that they now yield two. Because of the math around population growth, this now means that forests are now self-sustaining – population can grow on forests up until the base habitation limits. Since forests override the underlying terrain yields and grow on their own, this seemingly-small benefit really implies the ability to cheaply and effectively colonize even the most bleak deserts of Chiron.
Upon constructing the first Tree Farm, the player is treated to a reprise of Lady Deirdre’s introductory quote. Given the fact that Tree Farms come after the final resource cap is lifted, they certainly come after the time of the “first colonies”. She can’t be literally talking about the construction of the first Tree Farm as modeled by the game. But the choice of this quote here is definitely intended to get the player to associate Tree Farms with the Gaian reverence for the ecology of Planet.
It’s worth thinking a little more deeply about that. As we’ve already seen, the game supports two distinct terraforming strategies. The first is the intense, specialized, supply-crawler focused, mines-and-boreholes approach. And the second is the more eco-friendly forest and fungus approach. The Tree Farm is the key facility that makes the second approach workable. Without it, there just aren’t enough nutrients to go around to make the second approach competitive.
But there’s an additional benefit to Tree Farms that is kept immediately hidden for narrative reasons. After the first fungus pop makes it clear to the faction leader (and thus the player) that the fungus is somehow related to the strange psychic Planet voice, Reynolds tries to present a choice to the player with regard to his faction’s stance toward the planet. Does he want to exploit the Planet for maximum human benefit, or does he want to seek to find a way to coexist with it? The Morganites generally serve as the philosophical tradition most closely tied to the first standpoint, while the Gaians serve as the exemplars of the second. But no matter what your faction, Reynolds wants you to feel like you have a free choice in the matter.
So, in order to support this, base facilities that are tightly associated with ecological balance or harmony with Planet all have a special feature. Each one built after the first fungal pop raises the clean mineral limit by one for every base throughout the faction’s territory! It’s not just local. The net effect is that, if a faction invests heavily in Tree Farms, it greatly reduces the ecodamage reported by all of their bases.
This effect mitigates highly-polluting boreholes just as well as it does cleaner minerals from forests. But once a player has chosen to spend all the money or minerals on expensive Tree Farms, it naturally nudges him toward a more forest-based economy in order to get his money’s worth. This is just another small example of how Reynolds carefully tied together the gameplay considerations with the desired narrative effect in order to suck the player deeper into the imagined world of SMAC. For a first time player, this all happens invisibly in the background, yielding either a war or an uneasy truce with Planet depending on his thematic choices.