It would be interesting to see if a court would grant a prescriptive easement to make it more convenient for climbers or other recreationists to get to the far end of the Nears when a piece in the middle closes. After all, climbers or hikers will still have access to the far end of the Nears by walking out the Millbrook Ridge Trail and descending between The Nears and The Bayards. A prescriptive easement would merely make such access more convenient...A claim of right-of-way to get from one portion of a private property to another portion of the same private property, by the most convenient route, will be a difficult case to make.
Prescriptive easements, generally, are only granted for transit as far as I know.
According to my reading, the language of prescriptive easment in New York state refers to "use" of land, not to whether that use is necessary or convenient, and it does not restrict the definition of use to transit, even if the majority of court cases involve that issue. There is another type of easement, Easement by Necessity, that would presumably fail in the case of getting from one part of the Nears to the other. But the conditions for prescriptive easement are that the owner of the land is legally able but fails to bring an action against the users for the ten-year statute of limitations, that the use must be known to the landowner and continuous during the ten year period, and must be without permission from the owner of the land.
And again, if such claim is made, regardless of whether or not it is successful, then property owners everywhere along the ridge, and elsewhere, will have strong motivation to close their properties as a defense against the possibility of such claims being made against them in the future.
But if, god forbid, it ever came to actual legal actions, then closing land to prevent future action would have to be balanced against the possibility of having to defend against suits provoked by the closing, so the decision doesn't seem to me to be entirely clear-cut. Moreover, it doesn't seem to me that closing the property is enough to prevent prescriptive easment claims, in fact is to some extent a precondition for such claims, which require that the use be "hostile." The landowners might have to make an ongoing effort to bring actions against trespassers. And oddly enough, it seems that a sure-fire way to prevent such claims in the future would be to grant access permission, in which case a prescriptive easment cannot be claimed, and then landowners could deny access in the future without any exposure to the prescriptive easement argument.
Another way, going forward, to prevent future prescriptive claims would be to interfere with the "continuous use" condition that must be in effect for a ten year-period. It seems to me that even a single documented one-day closing, say every year, would be more than enough to prevent "continuous" use.
So if I owned land climbers have been using for fifty years, I think I'd go down to my local town hall and try to file something, if this is possible, indicating I have granted permission for climbing on my land except for absolute closures on Christmas, Yom Kippur, and the last day of Ramadan, and then by god I have a Muslim Patrol on Christmas, a Christian Patrol on Yom Kippur, and a Jewish Patrol on Ramadan to make damn sure no one was on my land on those sacred days. End of presecriptive easement claims as far as I can tell, and who knows, maybe world peace as a side benefit.
I'm just a lowly mathematician way, way, way, out of my depth here. I just went off and read a bunch o' legalese and then mouthed off about it. It's probably a genetic defect, I come from a family of lawyers. If McCarthy ever sees this, he's gonna toast my ass so bad I'll be standing for a year. He already thinks I've exceeded my pay grade on the history of Gunks climbing.
But hypotheticals notwithstanding (bread and butter for those of us in the theory business), one can only pray that some kind of meeting of the minds can prevent an escalation that ever even approaches these scenarios.