Cataract bog

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; 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. Bogs get water from the atmosphere, while fens get their water from groundwater seepage.

Cataract bogs inhabit a narrow, linear zone next to the stream and are partly shaded by trees and shrubs in the adjacent plant communities. Algae growing on the rocks can make the surface slippery and dangerous for those exploring a cataract bog.