I guess I prefer my fantasy a little darker - this optimistic production, somewhat utopic in nature, would not fit in my games. That said, in a more cheerful campaign, PCs could easily be part of the Royal Surveyors Guild, on missions to collect the information for this publication. Such an easy source of hooks to send them on any number of crazy missions for no other reasons than to see what is there.
This would fit in where your campaign had posted want ad's or adventurer's guilds.
In one region of a forest, all of the trees are identical, down to the leaves and the twigs. If the PCs carve something into one of the trees, it could mystically propigate until it covered all of the trees, or could vanish since it was not carved into the one true tree.