Corals – an ecosystem at risk

08 May 2009 | News story

Over one-quarter (27%) of the world’s 845 species of reef-building corals have been listed as threatened on the 2008 IUCN Red List of Thretened Species™, and an additional 20% are considered Near Threatened. Reef-building corals are essential habitat for many species of fish and invertebrates making them the most biologically diverse ecosystems in the ocean.

Coral reefs in the Caribbean region have been impacted by recent, rapid population declines of two key species: Staghorn Coral (Acropora cervicornis) and Elkhorn Coral (Acropora palmata), both of which have been listed as Critically Endangered.

The primary threats to corals are climate change and localized stresses resulting from destructive fishing, declining water quality from pollution, and the degradation of coastal habitats. Climate change causes rising water temperatures and more intense solar radiation, which lead to coral bleaching and disease often resulting in mass coral mortality. A 2008 study by IUCN found that 566 of 799 warm-water reef-building coral species are likely to be susceptible to the impacts of climate change.

A further threat to corals is ocean acidification as a result of increasing levels of atmospheric carbon dioxide. This is reducing ocean carbonate ion concentrations and the ability of corals to build skeletons.

“When corals die off, so do the other plants and animals that depend on coral reefs for food and shelter, and this can lead to the collapse of entire ecosystems.” states Kent Carpenter, IUCN Species Programme.

Globally, the Indo-Malay-Philippine Archipelago or the “Coral Triangle” has the highest number of species in threatened categories. This region is also known as the epicenter of marine biodiversity, and has the highest coral species richness.

Although they have been impacted by localized warming events, coastal development, and other human activities, coral reefs in the South and Eastern Pacific have lower numbers of threatened species. In any region, the potential loss of these coral ecosystems will have huge cascading effects for reef-dependent species, and on the large number of people and nations that depend on coral reef resources for economic and food security.