Sites of Special Scientific Interest (SSSIs)

SSSIs are Britain's most important wildlife and geological sites. They are protected under the Wildlife and Countryside Act of 1981. There are 5,300 in Great Britain, covering 16,270 square kilometres or 7% of the land. Most are in private ownership.

All four of the waterside SSSIs in the Calder catchment are located in the upland area. They protect acid moors, heaths, mires and acidic flushes. below this the nature value of the river system is limited, although there are some sites of regional interest and value.