What causes ecological damage in Alpha Centauri (Alien Crossfire)?

I have been getting a lot of Ecological Damage in my cities for no apparent reason. I have all the base facilities that help Ecology and none of the ones that damage it (like a Genejack Factory). All of my cities are surrounded with forests...in fact, the only terraforming I do (apart from roads) is planting trees.

What's really interesting is that sometimes I get Eco damage mid-turn! Insane amounts!

I'm not sure what causes it, because I checked the Help and I don't have anything that is documented to cause it.

There are 2 things however that I do and I think they might be related:

Nerve gas pods
Tectonic missiles

None of them are documented as eco-damaging, but I'm out of options here...

My question is: what are the undocumented sources of eco damage in SMAC?

Edit: The eco damage I get is from cities. I can see the indicator appear in seemingly random cities sometimes mid-turn. This means that I check all my cities at the start of the turn, and I see zero eco damage. Then at the end of the turn there is an insane amount...I summed it up and sometimes my eco damage goes over 100 total.

I can also share a save game file.

Solution 1:

It would appear that your use of neve gas pods may be the culprit, on the grounds that nerve gas is considered an atrocity. As to your question, though, the Fandom wiki for SMAC says the following under the Causes section on the Ecological damage (SMAC) page:

It is determined by the number of terraforming enhancements you have built in range of that base, and the number of minerals the base is receiving by any means. Committing atrocities such as the use of nerve gas will cause the planet to attack you, unless the Planetary Council has voted to eliminate the ban on them. The same is true with using planet busters but the damage is more severe.

If enough boreholes are built, the planet will heat up and melt the ice caps flooding everyone. Voting to launch solar shades helps with this, and you can use formers to raise your land.

Ecological damage can be altered by making choices in the Social Engineering menu that affect Planet.

You can also build Base Facilities and Secret Project to help, or plant trees to reduce it.

From the Gamepedia wiki for SMAC, the Ecology page goes into more detail under the Precise Formula section:

The ecological damage formula is complex:

For each base total the number of Mines, solar collectors, farms, soil enrichers, roads, mag tubes, Condensers, echelon mirrors, and thermal boreholes. Items in squares which are actually being worked count double.

Add an extra +8 for each Borehole, +6 for each Mirror, and +4 for each Condenser.

Subract 1 for each Forest.

Halve if base has Tree Farm, and Eliminate if also has Hybrid Forest.

Divide this value by 8, and reduce by up to 16 plus number of previous damages. Set this number aside.

Take the number of minerals produced this turn (but not from Orbit)

If result from 5 was reduced by less than 16+#, reduce result 6 by remaining amount.

Divide minerals by 1 plus number of Centauri Preserve, Temple of Planet, and Nanoreplicator facilities.

Sum the values of (5) and (8), and add +5 for each major atrocity.

If Alpha Prime is at perihelion (20 years out of every 80), double your value.

Take the resulting number and compute:

Ecology% = (ValueFromStep10) * Difficulty * Technologies * (3-PLANET) * LIFE / 300

Difficulty = Normally 3, but 5 on two highest two difficulty levels.

Technologies = Number of technologies discovered

PLANET = Social Engineering PLANET value

LIFE = Native life level (1-3) from Custom Start