The tag boundary=forest is approved https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dforest
I was hoping to use this tag to display the boundaries of state forests in my country in a similar manner as many of the protected area boundaries are rendered. Currently only the name of the forest only is displayed on the standard layer of OSM and most are complex multi-polygon areas and I feel it is important to see where the boundaries are as strict conditions apply within these bounds.
+1, I would like this implemented also. I am working in commercial Forest land, corporately owned land in the US that’s enrolled in a state property tax program. No protection so no boundary=protected_area; not a leisure=nature_reserve, so boundary=Forest and sub areas land use=forest, natural=water, wetland, as described on the wiki page for tag:boundary=forest. Example; https://www.openstreetmap.org/relation/14051942
Mapnik currently renders the following:
Miscellaneous - framed areas
National park / Nature reserve boundary=national_park / leisure=nature_reserve.
It would fit to add boundary=Forest the same class of a green frame.
For state and National forests I have been using the boundary=protected_area and leisure=nature_preserve to get the desire rendering, again per the US Public Lands/#US Forest service suggested tags. Those can be considered protected areas, class=6 generally with sustained use of natural resources. Since they are in public ownership I would say they are protected (from urban development, land use change), but that can be uncertain if mineral rights are not held publically or if leased for exploitation. Or not protects if the public forest land is sold or exchanged but then owner=, operator= will change anyway and the previous protection gone.
If there is a conservation easement then the boundary=protected_area, leisure=natural_reserve seems to fit for private lands too. But there-in lies the gap, unprotected Forest land for which landuse=forest is too specific.