Five Sites of Special Scientific Interest (SSSI) have been designated along the River Fal. The river rises on Goss Moor which is both a National Nature Reserve and part of a SSSI. The wetland habitats and western dry heath communities were formed, since the Bronze Age, by the mining of the alluvial tin deposits. South Terras Mine SSSI is also a Geological Conservation Review (GCR) site of national importance and was once a commercial uranium mine. The Crowhill Valley SSSI between Grampound and St Stephen is an ancient woodland dominated by sessile oak on the slopes, and of willow and alder carr on the floodplain which has a rich ground flora. The species list includes many ancient woodland indicators including lichens such as Parmelia endochlora.
