The Great Barrier Reef site in Australia was inscribed on the World Heritage List in 1981. The site is the world’s most extensive stretch of coral reef with probably the richest animal diversity anywhere. There are over 1,500 species of fish, about 400 types of coral, 4,000 types of mollusk (including the small giant clam, Tridacna maxima, pictured here), and a diverse assemblage of sponges, anemones, marine worms, crustaceans, and many other invertebrate and vertebrate species.