The reserve is primarily of botanical interest, for example for populations of Cerastium nigrescens, a plant unique to Unst.
[1] Keen of Hamar was designated a special area of conservation on 17 March 2005.
The site is of outstanding interest for the interaction of plants with the thin, chromium metal-rich soil.
Scottish Natural Heritage provides further information on its SSSI site management statement.
This article about a Site of Special Scientific Interest in Scotland is a stub.