Science Center Objects

Explore the fascinating undersea world of coral reefs. Learn how we map, monitor, and model coral reefs so we can better understand, protect, and preserve our Nation's reefs.

Coral head that looks like lettuce sits on sandy bottom in clear blue water and is surrounded by brightly colored fish.

Cerulean damselfish dart around lettuce coral off the Cape Range National Park along the Ningaloo Coast in Western Australia. USGS researchers combined forces with Australian colleagues in this UNESCO World Heritage Site to conduct the most extensive study of how erosion of reefs contribute sand to the beaches—a coast’s natural armor. With the threat of a rising sea and changes to the climate, understanding this connection can tell us how resilient the coast will be.

Coral reefs are unique ecosystems of plants, animals, and their associated geological framework. Coral reefs cover less than 0.5 percent of the earth's surface, but are home to an estimated 25 percent of all marine species. Second only to tropical rainforests in size and complexity, some scientists estimate that more than one million species of plants and animals are associated with coral reefs. Coral reefs are also of great economic importance to those who live on or visit islands in the Pacific and Atlantic Oceans. Reefs shelter and provide nursery grounds for many commercially and culturally important species of fish and invertebrates, they protect the islands' harbors, beaches, and shorelines from erosion and wave damage by storms, and they are vital to the marine tourism industry. These diverse ecosystems provide valuable goods and services worth about $4 billion each year to the U.S.’s coastal communities. Yet, as important as coral reefs are, these ecosystems are being threatened worldwide.

More than 8,500 square miles (22,000 square kilometers) of coral reef habitat is found in U.S. waters. Most of these coral reefs still appear to be relatively healthy, but some areas of dead and dying coral have been found in recent years. The causes of this degradation are poorly known, but are probably in part related to human activities.

View from a grassy, vegetated hill looking down on a tropical beach with many tall buildings lining the coast.

Photograph of waves breaking over the fringing coral reef that protects the shoreline of Waikīkī and infrastructure of Hawaiʻi's capital, Honolulu.
Credit: Brian Schmidt, licensed under CC BY 3.0 via Wikimedia Commons

The U.S. Geological Survey (USGS), working closely with academic institutions, state, and other Federal agencies, is spearheading an effort to better understand the geologic and oceanographic controls on the structure and processes of our Nation's coral reef ecosystems.

This web site is a gateway to USGS studies of coral reefs. We focus on the geophysical processes that influence the health and sustainability of coral reefs. From this work we are gaining new insight into the structure of coral reefs, providing the basis for future monitoring, and understanding better both the influences of natural processes and impacts of human activities on coral reef health. These efforts will help to preserve and protect the biodiversity, health, and social and economic value of these remarkable habitats.

Read more coral reef facts.

Underwater view of coral in some shades of pink where it is alive, shades of brown and green where it's dying.

Underwater photograph off Molokaʻi Hawaiʻi, showing some of the impacts of land-based pollution, such as terrestrial sediment, on coral reefs: burial by sediment, algal overgrowth, and coral bleaching.

Learn about our current studies by topic.

Climate Change and Land-use Histories

We are developing new and unique oceanographic and environmental archives from coral skeleton records to better understand the compounding effects of land-use and environmental change on coral reef health.

Hydrogeology and Reef Health

We are conducting geophysical and geochemical research to address questions about coastal groundwater-to-reef flow and coral reef health, with the goal of informing management decisions related to planning and implementing activities in priority watershed-coral reef systems.

Reef Hydrodynamics and Sediment Processes

We are developing a better understanding how tides, waves, currents, and both land- and reef-derived sediment influence the development of coral reefs and their adjacent shorelines.

Role of Reefs in Coastal Protection

We are combining ocean, engineering, ecologic, social, and economic modeling to provide a high-resolution, rigorous, spatially-explicit valuation of the coastal flood protection benefits provided by coral reefs and the cost effectiveness of reef restoration for enhancing those benefits.

Reef Resource Assessments - Planning for the Future

We are mapping and assessing all of the important geologic and oceanographic factors to identify those coral reefs most at risk and those reefs that are potentially the most resilient and the most likely to recover from natural and human-driven impacts.

Also, learn about our studies by location:

  1. Guam
  2. Hawai‛i
  3. Kaho‛olawe
  4. Kaua‛i
  5. Kwajalein Island
  6. Lāna‛i
  7. Maui
  8. Moloka‛i
  9. O‛ahu
  10. Puerto Rico
  11. Roi-Namur Island
  12. Tutuila

Please also see the associated Coral Reef Ecosystem Studies (CREST) Project website.

Our partners are numerous and include: