In the prefaceto the island's 1992 draft plan, Skomer as a producer of the public goods of biodiversity  was described as one of the few offshore islands in Southern Britain holding exceptionally large seabird colonies of international importance.  In particular the colony of Manx Shearwaters is one of the largest in the world and there are important populations of the southern race of the Guillemot and of Puffins and Razorbills.

The islands produces other exceptional public goods including the unique Skomer Vole and an important breeding population of Grey Seals. It is nationally important for its lichens, a number of scarce invertebrates have been recorded and it is recognised as a site of high geological interest. There are also extensive remains of a late prehistoric community and the ruins of an 18th Century farm.

Management is targeted mainly at the protection of the breeding habitat of the seabirds.