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Shallow water (less than ~150 m water depth) coral reefs are seafloor structures built from the calcium carbonate skeletons of marine organisms. Reefs buffer shorelines from waves, storm surges, and tsunamis and help to protect ~200 million of the world's coastal dwellers from flooding, erosion, property damage, and loss of life. Reefs support high levels of biodiversity; they are home to up to 25% of all ocean species. Developing nations in tropical regions rely on coral reef fisheries for food security. Coral reefs are also an economic driver for tourism, supporting jobs in the hotel, sport fishing, diving, clothing, and gear industries.
While coral reefs are valued for the economic and environmental services they provide, they are also significantly threatened. Since the 1970s, there has been a 70%–80% decrease in the abundance of reef-building corals along U.S. coastlines. Projections indicate that up to 66% of the world's remaining coral reefs will continue to degrade in the coming decades due to ocean warming and acidification. Additional local, regional, and global stressors such as disease, overfishing, land-based pollution, and invasive species have caused a cascading loss of reef-building organisms, biodiversity, and reef-habitat structure.
The CMHRP contributes to coral reef research by integrating geologic, physical, and biogeochemical information to determine the drivers and quantify the rates of past and modern coral reef formation and degradation, as well as characterize the impact of reef loss on seafloor structure and oceanographic processes. CMHRP studies identify local and global threats to reef ecosystems and provide a perspective on the health and resilience of and the risks to U.S. coral reefs within a global context. CMHRP scientific results are used by partnering agencies and nongovernmental organizations to guide conservation and protection strategies for critical refuge habitats and Endangered Species Act-listed species. CMHRP research complements the contributions of partnering agencies (e.g., National Park Service, U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, Environmental Protection Agency, and other Federal, state, and local agencies), which lead long-term monitoring programs, map habitats, and conduct biologically and ecologically oriented research on coral reefs.
Past and Current Successes
Results from CMHRP research have shown that reef degradation in the U.S. Caribbean and Florida Keys has already caused significant loss of seafloor elevation, increasing coastline vulnerability to waves and storms. The CMHRP has also found that environmental conditions in some Pacific and Caribbean reefs protect them from the factors driving degradation such as ocean warming and acidification. The CMHRP has shown that in places (e.g., Hawai‘i, Guam) submarine groundwater delivers far more nutrient contamination to reefs than rivers, leading to increased bio-erosion and loss of reef structure. These and other studies seek to establish the historical and contemporary conditions of coral reefs to inform forecasts about future changes in response to stressors such as changing ocean temperature and chemistry, coastal land use, and sea level.
The CMHRP will continue to support the resource management needs of partnering agencies by developing coral reef qualitative threat indices that reflect the impact of climate change, sea level rise, changing land use, restoration activities, and resource extraction, and by assigning risk levels to U.S. coral reef resources. An extension of the CMHRP's National Assessment of Coastal Change Hazards will address the vulnerability of coral reef coastlines, which are currently not explicitly included. These risk assessment activities will, in turn, inform numerical modeling to forecast the response of coral reefs to various stressors under a range of scenarios for twenty-first century change. As the program responsible for supplying the geologic expertise for U.S. coral reef studies, the CMHRP will continue to refine methods for detailed seafloor surveying in these settings and for more accurate measurement and prediction of seafloor elevation loss.
Explore the CMHRP Decadal Strategic Plan, and visit our Coral Reef project pages
This geonarrative constitutes the Decadal Strategic Plan of the USGS's Coastal and Marine Hazards and Resources Program for 2020 to 2030.