The Dead Mire

I have lived among the anchorites of Telredor for some time, $N, and in that time I've come to know the marsh quite well. Recently, I've started to notice a disturbing change in the land to the northeast.$B$BVirtually all life there has begun to wither and die, seemingly without explanation. I have a few ideas as to what might be happening, but they are little more than speculation. If you were to bring me a sample of the soil in that area, I may be able to get to the bottom of this mystery.