USGS Pacific Coral Reefs Website

Reefs at Risk

Bleaching, Disease, and Algal Encrustation

Stressed physiological conditions may threaten the health and sustainability of coral reefs. Black band, brown band, yellow band, and white band diseases have been reported from the Caribbean. In 1994, the first record of black band disease was reported from Hawai‘i.

Underwater photographs, below, taken in 1988 and 1998 of the same coral head, Montastrea annularis, at Grecian Rocks in the Florida Keys demonstrate the degradation of habitat that has occurred in the last decade. This coral has black band disease.

1988

1998

Human Impact on Coral Reefs

Human activities can affect coral reefs in countless ways from overt destructive practices such as cutting channels through reefs to poorly placed anchorages, or environmental pollution. A seldom-considered impact is increasing human population.

Increased tourism in Hawai‘i, for example, means more stress is placed on island resources that ultimately may lead to degraded coral reef habitat. It also means more people visit the reefs, where more corals are broken, collected, or accidently damaged. This raises an ironic question, are we loving the reefs to death?

Coral reefs in urban areas such as those on O‘ahu face problems that are different from Moloka‘i and other islands. Scientists at the USGS and in affiliated institutions are just beginning to map and assess the risks of Hawai‘i urban reefs.

Population increased steadily in the State of Hawai‘i from 1900 to 2000, and it is projected to increase at about the same rate through the year 2025. The number of visitors between 1949 and 2000 has increased much more dramatically. (Sources of data: 2000 US Census and Population and Economic Projections for the State of Hawai‘i DBEDT Series 2025)

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