I like to use the nature shrines, they improve planet conditions AND planet value for the whole system. System wide facilities just stack with planet affecting facilities, e.g robotoid fac. (planet) plus Time Shrine (system). So I guess a nature shrine wouldn't even stack with a value improvement plant.
Refer to:
http://www.shrapnelgames.com/ubb/For...ML/001504.html
Edit: UUps, I'm not sure about that value improvement, seems there was a kind of bug in the past
[This message has been edited by PsychoTechFreak (edited 27 April 2001).]