Brignall Banks is a Site of Special Scientific Interest

Site of Special Scientific Interest

A Site of Special Scientific Interest is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based upon...

 in the Teesdale

Teesdale (district)

Teesdale was, from 1974 to 2009, a local government district in County Durham, England. Its council was based in Barnard Castle and it was named after the valley of the River Tees....

 district of south-west County Durham

County Durham

County Durham is a ceremonial county and unitary district in north east England. The county town is Durham. The largest settlement in the ceremonial county is the town of Darlington...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. It consists of a narrow belt of woodland

Woodland

Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...

 on the steep slopes of the valleys of the River Greta

River Greta

The River Greta is a river in Cumbria, England. It is a tributary of the River Derwent and flows through the town of Keswick.The source of the river is to be found near to Threlkeld at the confluence of the River Glenderamackin and St. John's Beck...

 and its tributary, Gill Beck, just west of the village of Brignall

Brignall

Brignall is a village in the Pennines of England, situated close to Barnard Castle. It was historically located in the North Riding of Yorkshire but along with the rest of the former Startforth Rural District it was transferred to County Durham for administrative and ceremonial purposes on 1 April...

 and about 6 km south of Barnard Castle

Barnard Castle

Barnard Castle is an historical town in Teesdale, County Durham, England. It is named after the castle around which it grew up. It sits on the north side of the River Tees, opposite Startforth, south southwest of Newcastle upon Tyne, south southwest of Sunderland, west of Middlesbrough and ...

.

It is one of the largest expanses of semi-natural woodland in North-east England; a number of scarce species are present, indicating that it is ancient woodland.

A varied lichen flora includes several species that are sensitive to air pollution and rare in County Durham, including some, such as Thelotrema lepadinum and Graphis scripta, that are indicator species for ancient woodland.