I see natures reserve's now help reduce pollution (-3).  I built multiple reserves in one of my cities (across multiple territories) but only saw pollution was reduced by -3, do reserves only  count once? 

They only work for the territory they are situated in. As pointed out by SmileyD, you can see that next to the name of the territory by moving the mouse cursor over the pollution icon.

That said, it is still possible for them to have an impact on global pollution.

If territory A has 5 nature reserves and had -15 pollution score, and territory B has 2 nature reserves but 10 pollution from districts, that will give your civilization a total pollution score per turn of -15 + (10-6)= -11 pollution. You will still have an overall negative score even if you have a few very polluted territories. I have used this to reduce global pollution to zero by building all nature reserves I can and watching carefully how many Maker's quarters I have.

Keep in mind that each territory has also its own pollution threshold, so you will still want to not overdo pollution per territory.

Thank you guys for your helpful responses.  In regards to SmileyD's suggestion about not building over natural modifiers, if you do have build over some (for adjacency bonus reasons) can you build the reserve on top of the existing district once you unlock the tech?

Once you build something over a natural reserve spot, you destroy it completely - caves, oases, coral reefs et cetera. They can not be restored at a later part of the game. You are better off leaving those natural reserve spots intact as they can give you not only a reduction to pollution, but influence and good FIMS yields.

Melliores wrote:

Once you build something over a natural reserve spot, you destroy it completely - caves, oases, coral reefs et cetera. They can not be restored at a later part of the game. You are better off leaving those natural reserve spots intact as they can give you not only a reduction to pollution, but influence and good FIMS yields.

i've been ransacking quater from cities captured precisely to "restore" the natural modifiers after clearing the ruins on top... even though the tile visual yield count don't show, they do add to the exploitation at least going by mouse roll over info

HumanKid wrote:

Melliores wrote:

Once you build something over a natural reserve spot, you destroy it completely - caves, oases, coral reefs et cetera. They can not be restored at a later part of the game. You are better off leaving those natural reserve spots intact as they can give you not only a reduction to pollution, but influence and good FIMS yields.

i've been ransacking quater from cities captured precisely to "restore" the natural modifiers after clearing the ruins on top... even though the tile visual yield count don't show, they do add to the exploitation at least going by mouse roll over info

Yeah i often do that as well, since very rarely does the AI build good districts

Nature Reserves aren't able to be built on River Springs... Hey programmer, you forgot 1 !!

SmileyD wrote:

Nope, but they do only count on the territory itself. As in if the territory itself doesn't have a reserve it wont reduce pollution. So you have to plan your makers quarters to be in a territory with a lot of potential reserves. You can seek the exact value next to the administrative center building.

Btw i do find that district to be incredibly good, because if you plan ahead and don't build over anomalies. You can actually have a lot of pollution buildings and still be at negative pollution, also it exploits all resources on the tile and gives you influence on top.

The funny thing is, even before the pollution bonus on the reserves, or in general not knowing reserves were a thing, I disliked building on special tiles I liked preserving them. So it was a cool little bonus when I was able to build reserves for the first time lol

Well, arguably it is better to leave them open, because they tend to have multiple yields and building anything that can't exploit all of it over them is a waste. Issue here is that in most cases infrastructure-bonus and adjacency will override what meager yields terrain could have. I do wonder if they'd be more gamechanging and noticeable if they'd provide truly insane yields, easily reaching +10.