The Site is a representative northern European coastal archipelago formed by 360 islands and islets with shallow marine waters, which provide important breeding sites for large numbers of seabirds and waterfowl. The Site supports breeding of species such as the common tern (Sterna hirundo), the black guillemot (Cepphus grille) and the common guillemot (Uria aalge), and there are also considerable populations of the great cormorant (Phalacrocorax carbo) and the European shag (Phalacrocorax aristotelis). The Eurasian otter (Lutra lutra) regularly uses the Site. The vegetation on the main islands has been shaped by traditional grazing and harvesting, and the ceasing of these activities is very likely to trigger vegetation succession. The islands are also used for recreation and tourism. Horsvær has been an important Site for monitoring the lesser black-backed gull population under the SEAPOP seabird monitoring programme since 2008.