Narya and the Shire

[Flame of Anor]

I should have finished the quote, it continues:

But all such places will soon become islands under siege, if things go on the way they are going. The Dark Lord is putting forth all his strength.

What power could be protecting the Shire enough that when everything else falls it could be one of the last remaining outposts. I mean the Rangers of the North are skilled and very adept but are they really enough power to be able to withstand the Dark Lord for so long when all is failing, and also i doubt they would keep concentration on the Shire that long if everything is going down the crapper, they would most likely focus on their own survival.