Coral reefs are one of the most diverse ecosystems on this planet. They are home to numerous species of marine life and offer a plethora of benefits both to natural ecosystems and to the human population. Coral reefs bring in enormous funds to coastal countries through tourism, fishing, and discoveries of new biochemicals and drugs (Hoegh-Guldberg 1999). Additionally, they provide natural coastal protection and building materials (Hoegh-Guldberg 1999). However, coral reefs are experiencing massive die-outs all around the world.
Climate change is the greatest global threat to coral reef ecosystems. Scientific evidence now clearly indicates that the Earth’s atmosphere and ocean are warming, and that these changes are primarily due to greenhouse gases derived from human activities.
Climate change will affect coral reef ecosystems, through sea level rise, changes to the frequency and intensity of tropical storms, and altered ocean circulation patterns. When combined, all of these impacts dramatically alter ecosystem function, as well as the goods and services coral reef ecosystems provide to people around the globe.
Warmer water temperatures brought on by climate change stress corals because they are very sensitive to changes in temperature. If water temperatures stay higher than usual for many weeks, the zooxanthellae they depend on for some of their food leave their tissue. Without zooxanthellae, corals turn white because zooxanthellae give corals their color. White, unhealthy corals are called bleached. Bleached corals are weak and less able to combat disease.
Bleaching events on coral reefs around the globe were observed in 1998 (West and Salm 2003). In some Pacific islands, a little bit of bleaching is common in the summer; however, there have been times when bleaching is particularly bad in this region (Craig 2009). For example, larger than normal bleaching events in the National Park of American Samoa occurred in 1994, 2002, and 2003 (Craig 2009). As climate change continues, bleaching will become more common, and the overall health of coral reefs will decline.