Pristinity and pristineness are recorded in some dictionaries (though for some reason not in the better ones), and they are attested on the Internet--though their incidence is relatively low. You can certainly use them and be understood, as in your example sentence.

However, I find them awkward and would usually avoid them; don't know if others feel the same way.

I would rephrase your sentence: Let us preserve the forest primeval in its pristine condition.

Webster führt es hier unter den "Related Words" an, hat aber keinen eigenen Eintrag dazu : 

http://www.webster-dictionary.org/definition/...

Novelty

Webster's 1913 Dictionary

 ... newfangleness, newness, nonimitation, novelness, nowness, originality, ornament, plaything, presentness, pristineness, rage, rawness, recency, recentness, ...

#5: Daher habe ich auf das (wenigstens selten verwendete) pristineness gewechselt. Danke für den Hinweis nochmal.

@#9 - The affixing of a Germanic suffix to a Latinate root doesn't bother us at all; we do it all the time without batting an eye. One example comes to mind: sordidness, where "sordid" comes (indirectly) from Latin sordidus, just as "pristine" comes from Latin pristinus.

But I would finesse the whole issue. Rather than joining any Coalition for the Conservation of Pristinity, I'd sooner ally myself with the Bloc for Keeping Things Unchanged.