The indicator; Coverage of protected areas in relation to marine areas shows temporal trends in the mean percentage of each important site for marine biodiversity (i.e., those that contribute significantly to the global persistence of biodiversity) that is covered by designated protected areas.

Protected areas, as defined by the International Union for Conservation of Nature (IUCN; Dudley 2008), are clearly defined geographical spaces, recognized, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values.

The status "designated" is attributed to a protected area when the corresponding authority, according to national legislation or common practice (e.g., by means of an executive decree or the like), officially endorses a document of designation. The designation must be made for the purpose of biodiversity conservation, not de facto protection arising because of some other activity (e.g., military).

Sites contributing significantly to the global persistence of biodiversity are identified following a globally-accepted criteria. These Key Biodiversity Areas encompass (a) Important Bird & Biodiversity Areas (b) Alliance for Zero Extinction sites

The indicator does not measure the effectiveness of protected areas in reducing biodiversity loss, which ultimately depends on a range of management and enforcement factors not covered by the indicator

Protected Areas: World Database on Protected Areas, DEFRA-JNCC

Key Biodiversity Areas: World Database of Key Biodiversity Areas

UK country boundary: ONS Open Geography portal

This indicator is calculated from data derived from a spatial overlap between digital polygons for protected areas from the World Database on Protected Areas (UNEP-WCMC & IUCN 2020) and digital polygons for marine Key Biodiversity Areas (from the World Database of Key Biodiversity Areas, including Important Bird and Biodiversity Areas, Alliance for Zero Extinction sites, and other Key Biodiversity Areas).

Sites are classified as marine Key Biodiversity Areas by undertaking a spatial overlap between the Key Biodiversity Area polygons and an ocean raster layer (produced from the ‘adm0’ layer from the database of Global Administrative Areas (GADM 2019)), classifying any Key Biodiversity Area as a marine Key Biodiversity Area where it had ≥5% overlap with the ocean layer (hence some sites were classified as both marine and terrestrial).

The value of the indicator at a given point in time, is based on year of protected area establishment and computed as the mean percentage of each Key Biodiversity Area currently recognised that is covered by protected areas.

it is straightforward to disaggregate to national and regional levels. The indicator can be disaggregated according to different protected area management categories (categories I–VI) to reflect differing specific management objectives of protected areas.