The reconstruction of ancient marine environments is an important task of the Earth Sciences, of great interest to geology, pure and applied, to oceanography and climatology, as well as to such fields as ecology and evolution. In principle, such reconstructions are based on the actualistic approach of "the present is the key to the past." Since the deciphering of past environmental changes, either nat ural or man-made, has considerable bearing on planning, the past may provide a key to the future. Paleoenvironmental interpretations in the marine realm are based to a great extent on assemblages of fossils recovered from ancient sediments in outcrops and from land-based or submarine drillings. Observable lateral sequences of assemblages in contemporaneous strata, the known or assumed functional or adaptive significance of preserved skeletal struc tures, as well as their evolution through time and space, provide by themselves indications of ancient environmental settings. In some cases even present-day eco logical considerations may be derived from analysis of fossils.

Coral reefs are the largest landforms built by plants and animals. Their study therefore incorporates a wide range of disciplines. This encyclopedia approaches coral reefs from an earth science perspective, concentrating especially on modern reefs. Currently coral reefs are under high stress, most prominently from climate change with changes to water temperature, sea level and ocean acidification particularly damaging. Modern reefs have evolved through the massive environmental changes of the Quaternary with long periods of exposure during glacially lowered sea level periods and short periods of interglacial growth. The entries in this encyclopedia condense the large amount of work carried out since Charles Darwin first attempted to understand reef evolution. Leading authorities from many countries have contributed to the entries covering areas of geology, geography and ecology, providing comprehensive access to the most up-to-date research on the structure, form and processes operating on Quaternary coral reefs.