Oinkoink's idea sounds like a good one.
Edit: After reading some more, I have to say I really think environment should have a greater effect, but not on smaller nations, and not in this way. I mean does a nation with 10K citizens really have terrible environmental concerns. It should really only be larger nations that get hit hard with this. A small new nation shouldn't have to worry about the environment both for introduction reasons and for RP. Maybe have infra or population levels where environment starts to make more of a difference similar to infra jumps. Right now environmental concerns seem to leave the largest nations the least effected, which strikes me as odd. I like making environment matter, and having it effect population makes sense to me, but this hurts the wrong people. It needs work.
PS - I would have loved a little warning. I switched 4 of my border walls for guerrilla camps 2 days before this went into effect, and now I'm 5 improvements beyond my population, and in the middle of a war .