The River Glaven and its tributaries support a remarkable wealth of wildlife. An array of plants, invertebrates, birds and fishes are present in the river system, many of which are of key conservation concern.
In particular, in its middle reaches, where the river runs over a chalk bed, there are large beds of River Water-crowfoot (Ranunculus penecillatus var. calcareous) cover the river with white flowers in early summer.
The threatened White-clawed Crayfish or “Whitefoot” is also hugely abundant in the middle river, the protection of which has been central to the work of the RGCG.
A rich fish community is present in the Glaven including Brown Trout, Bullhead, Stone Loach, European Eel, Three-spine Stickleback and Brook Lamprey.
More recently, surveys of the lower Glaven and its estuary have revealed the occurrence of important migratory species including Common Smelt, River Lamprey and Sea Trout. The Norfolk Rivers Trust, ZSL and ECON Ecological Consultancy Ltd are currently engaged in surveys and conservation work to help these lesser studied Glaven species in the context of the wider Blakeney Pit and River Stiffkey system.
All in all, the fauna of the River Glaven mark it out as one of the most important rivers in lowland England. Major threats to the river’s valuable flora and fauna include fine sediment pollution linked to soil loss from arable fields, barriers to fish migration and in the case of the White-clawed Crayfish, invasion of the river by American Signal Crayfish.