AMER. ZOOL., 34:115-133 (1994) Biodiversity of Coral Reefs: What are We Losing and Why? 1 KENNETH P. SEBENS Department of Zoology, University of Maryland, College Park, Maryland 20742 SYNOPSIS. Coral reefs are threatened by numerous anthropogenic impacts, some of which have already had major effects worldwide. These unique tropical environments harbor a high diversity of corals, reef invertebrates, fish and other animals and plants. In most taxa, the species diversity of reef-associated organisms is poorly understood because many of the spe- cies have yet to be collected and described. High coral mortality has been associated with natural events such as hurricanes, predator outbreaks and periods of high temperature, but has also resulted from excess nutrients in sewage and from specific pollutants. Reef corals and associated organ- isms are also threatened by the possibility of global warming which will result in rising sea levels and periods of increased temperature stress, and which may also bring increased storm frequency and intensity. Although the recent extensive episodes of coral bleaching in the Caribbean and eastern Pacific cannot be causally related to global warming at this time, the close link between bleaching and temperature suggests that global warming will result in severe changes in coral assemblages. Major reef destruction has followed outbreaks of the predatory seastar Acanthaster planci in the Pacific. Although this is considered part of a natural distur- bance cycle, there are indications that altered land use patterns and reduc- tion of predators on this seastar by human activities may have increased the severity of outbreaks. Recreational and commercial use of reefs has also increased, and has caused extensive damage, especially near areas of high population density. One of the most obvious and widespread losses to reef biota is the reduction in fish populations from intense overfishing in most reef areas of the world. Coasts without adequately managed reefs have suffered intense overfishing for both local and export purposes, to the point where the positive effects offishon those reefs have been com- promised. The combination of these destructive factors has altered reefs in all localities, and many that were once considered protected by distance and low population density are now being exploited as well. On the pos- itive side, improved understanding of ecological processes on reefs com- bined with concerted conservation efforts have managed to protect some extensive areas of reef for the future. INTRODUCTION the past few decades. Coral reefs are fre- Coral reefs of the world: Distribution quently described as the marine equivalent and diversity of tropical rain forests, given their high spe- !-,•„ j i L- i • * L *J cies diversity and the similarity of certain Ecolog,stsand coral biologists have noted stnlcluri y rocesses (Conne|| ^, 78 Jack . son.99, T h epa ra .Se,sdo no ,end,here, co ra , reefs £ most parts Jf the wortd over beleaguered terrestrial ecosystems as humans seek to exploit their numerous insZL&^u^^&W ^sources. Coral itself is used as a building the American Society of Zoologists, 27-30 December material, reefs are destroyed by coastal 1992, at Vancouver, Canada. development, and reef fish are being severely 115 Downloaded from https://academic.oup.com/icb/article/34/1/115/111574 by guest on 05 December 2023