Corals are in fact animals, even though they may exhibit some of the characteristics of plants and are often mistaken for rocks. In scientific classification, corals fall under the phylum Cnidaria and the class Anthozoa. They are relatives of jellyfish and anemones.
There are over 800 known species of reef-building coral worldwide and hundreds of species of soft corals and deep-sea corals. Advances in science and technology have led to new discoveries that are expanding that number regularly. [a] For instance, in March of 2009, scientists discovered seven new species of bamboo coral in deep water off the coast of Hawai`i during a NOAA-funded research mission. In September of 2009, a group of British and American scientists conducting reef surveys in the Galapagos Islands discovered three new coral species and documented colonies of a species previously thought to be extinct.
As with many other types of animals, different species of coral are found in different habitats and different locations around the world. For example, similar but distinct species of Acropora coral have evolved in the Pacific Ocean and the Caribbean.
Corals were once classified as plants, but the French biologist J.A. de Peysonell concluded they were animals in 1753 while studying the western Atlantic. [c]
Coral around the world is in decline due to a variety of threats. Two of the Caribbean Acropora species are listed as threatened under the Endangered Species Act. Additionally, the International Union for Conservation of Nature has listed 27 percent of the reef-building species in threatened categories on its 2008 Red List. An additional 20 percent of the reef-building coral are listed as near threatened and are expected to join a threatened category in the near future. [a] The Status of Coral Reefs of the World: 2008 report states that the world has effectively lost 19 percent of its reefs, with 35 percent threatened or at a critical stage. However, the report shows that 45 percent of the remaining reefs are under no immediate threat of loss, except from the threats posed by climate change. [b]