Since we are talking about biospheres again, I will dredge my ideas on that up from the dead!
Something that always bothers me about planet management is that there is lots of detail in terraforming regarding atmosphere and temperature and other base factors but no attention to the biosphere. Or in other words while its nice to have a planet modified to exactly what I need for an atmosphere to be breathable, what I am basically left with is a dead desert that the game treats as a paradise as far as game play goes. So I propose adding another metric to terraforming that reflects the size, complexity and health of the biosphere.
So that's the basic idea, here are some detailed thoughts.
1.) I propose three metrics for biosphere; mass, health and complexity. Size is a measure of the organic mass of the biosphere. Health is simply a measurement of the abstract condition of whatever biosphere there is. Complexity is a measure of the abstract maturity and value of that biosphere (say in diversity and number of species). So for instance a newly terraformed Mars could have a very healthy biosphere but it might only be fields of simple algae brought by human colonists after only 25 years of settlement so have a very low mass and complexity. On the other hand you discover a new unsettled paradise planet that has a healthy biosphere but also a very large and complex one after billions of years of life developing. Then you might find an ancient desert world that has a very complex biosphere but because it has a small hydrosphere/low temperature/low gravity/active tectonics it has little mass or heath. Each metric affects the same gameplay mechanisms, but you can only get so much benefit from any one while multiple together make for a larger benefit. I believe the obvious current game mechanic that a biosphere would affect is planet morale and population growth rate but an agriculture resource would also be great.
2.) Right now there are no consequences to any industrial activity on a planet. You can mine Earth hollow and nobody will bat an eye. If we gave industrial facilities a pollution value that would provide a very interesting planet management game play device. I have contemplated two ways to work this:
-We can have each industrial facility provide a very slight atmospheric modification and conversely biosphere health and complexity would be affected negatively by the rate of change in atmosphere. You could counteract this using the current in game terraforming facilities or via new research options providing for cleaner industry in several tech levels (giving our Biology/Genetics scientists something useful to do) This would have the added benefit that if you discover an alien world with a very healthy and complex biosphere based on methane you would destroy it if you changed it over to oxygen based in the space of 20 years very much like real life. Environmentalists beware.
-Use a generic pollution metric based on values for each facility and that in turn affects the biosphere. Add a new facility that can counteract these effects on top of the mentioned research.
3.) Biosphere mass is added to a planet via terraforming facilities. We can measure this in weight of biomass and have an optimal mass based on the size of the body and the hydrosphere or whatever other factors we decide are "good" or "bad" for the biosphere. We can restrict this to certain types of atmospheres (Methane over 20% does won't support a biosphere for example), gravity conditions, temperatures, etc. which would let us make sure native biospheres only show up in the real world "habitable zone" of systems or heavily terraformed ones outside of it. Or we could let them develop anywhere making for some truly alien environments. Once biosphere mass is introduced to a planet it has a natural growth rate up to whatever the optimal mass for that planet is. You can rely on that alone or continue to augment it with terraforming facilities, but if you go over the optimal mass you will will negatively affect health and complexity (basically you are over farming). You lose mass through planetary conflict or bombardment or by having a health rate below whatever value chosen (say lose a certain rate at health value 75%, and lose it at a much greater rate at health value under 50%).
4.) Biosphere health is a measure of the whatever biosphere there is based on original planetary conditions in comparison to current ones. The original baseline conditions will gradually shift to current conditions over time. You can rapidly terraform a planet with a native biosphere and cause great degradation, or slowly change it over a century and lose some biosphere but let it adapt to the new conditions over time for the most part. If we are using the atmospheric change mechanism for industrial pollution it will affect biosphere health as above. If we use a generic "pollution" metric it will just degrade the health by the level of pollution combined with whatever terraforming changes are happening.
5.) Biosphere complexity is both naturally occurring and player controlled. It increases naturally at a rate determined by the relationship between mass and health but very slowly (this is naturally a billion year process after all). The player can artificially increase the complexity via a new team mission "environmental seeding" or "species introduction" or whatever which simulates scientists introducing species from other worlds to this one or creating new one is labs specifically for this world (which also gives your biology/genetics scientists something useful to do).
6.) My intended result of this is to make adding biosphere mass and maintaining biosphere health relatively easy to do within the scope of a normal game, while complexity being something you can only affect so much during that same game span. This would mean barring playing through thousands of years Mars will never be as diverse as a an unspoiled Earth and when you discover an alien world with a billion year old biosphere with very high complexity this is something extremely valuable that is to be coveted and protected. Earth of course being one of those. Once you let a world like that be destroyed through conflict or mismanagement there is no getting it back to that level again. I think that all player homeworlds would have such biospheres meaning instead of glassing every NPR world you meet it would be worth it to use ground force invasions (right now there is little reason beyond RP to use ground invasions).
7.) This would provide another reason to colonize less than optimal worlds. Earth might become a planet of low impact facilities like research labs, academies, and financial centers while you move all dirty construction facilities and the like to Luna or Titan.
8.) It adds an environmental aspect to the game beyond the usual 4x slash and burn/grow like a tumor game play. Do I get more value out of maintaining a nursery world with an awesome moral and population growth or by mining every spec of Corundium out of the core? It might be the former or the later. http://aurora2.pentarch.org/index.php?topic=6383.msg65152#msg65152