Coral reefs are one of the most diverse and productive ecosystems in the world, containing many species of fish and invertebrates. Coral reefs have a high productivity of 7 g C m-2 d-2, compared to 0.01 g C m-2 d-2 of the surrounding ocean (Hatcher, 1988). Coral reefs are vital to the world’s economy and have been valued at 375 million dollars per year, mainly due to the high recreational uses and coastal protection they provide (Costanza et al., 1997). The highly productive nature of coral reefs means that they are critical to the survival of the tropical ecosystems and hence the people who depend on them (Hoegh-Guldberg, 1999). Their biodiversity has often been described as high as or higher than that of tropical rain forests (Figure 1) and estimates of the number of species on the reefs range from 1-9 million with only 10% having been described (Knowlton, 2001).
However this important resource is under threat from anthropogenic sources and climate change. 50-70% of reefs are at risk due to anthropogenic activities (Hoegh-Guldberg, 1999), even world’s most pristine reef, the outer Great Barrier Reef, is 30% of the way to extinction (Pandolfi et al., 2003). The threats that can be directly attributed to humans are excess nutrients from sewage pollution, recreational use of the reefs by tourists, and the excessive removal of fish. Threats linked indirectly to human activity by the way of climate change are increased episodes of bleaching, increased frequency of storms, ocean acidification, and sea level rise. Natural sources of disturbances are also increasing these include outbreaks of the crown of thorns starfish and diseases. The combination of all these pressures has altered reefs worldwide (Sebens, 1994).
The aim of this website is to provide a summary of the threats to coral reefs. I will be discussing each major threat, how it currently impacts reefs, and how the threat will change in the future due to climate change or increased human activity. I will also discuss how all the threats are linked together in terms of reducing the resilience of the reef.