A cataract bog is a rare ecological community formed where a permanent stream flows over a granite outcropping. The sheeting of water keeps the edges of the rock wet without eroding the soil, but in this precarious location no tree or large shrub can maintain a roothold. The result is a narrow, permanently wet, sunny habitat. While a “cataract bog” is host to plants typical of a bog, it is technically a fen, not a bog. Bogs get water from the atmosphere, while fens get their water from groundwater seepage.