The North Bull Island has evolved over the last 200 years into a unique coastal environment on the north shore of Dublin Bay. The island became Ireland�s first bird sanctuary in 1931 and has since been declared a UNESCO Biosphere Reserve in 1981, National Nature Reserve in 1988 (S.I. 231 of 1988 and S.I. 232 of 1988), Special Area of Conservation (SAC 000206) under the EU Habitats Directive and a Special Protection Area for birds (SPA S.I. No. 211/2010 under the Birds Directive 2009/147/EC). The island is also a Wetland of International Importance under the Ramsar Convention (Site 406) due to the large concentrations of birds present during migration and in winter.

A number of scarce and rare plants occur on the island. Three are protected by the Flora Protection Order 1999. A rare liverwort Petalophyllum ralfsii is listed under Annex II of the Habitats Directive and is therefore a species of high conservation value.