Why are coral reefs in peril and what is being done to protect them?

Coral reefs can be damaged by natural processes, such as storms, but they are increasingly at risk from human activities. Oil spills and pollutants can threaten entire reefs. Excessive nutrients from land sources, such as sewage and agricultural fertilizers, promote the growth of algae that can smother corals. Other organisms harmful to corals, such as crown-of-thorns starfish, multiply when the species that prey on them are removed.

Coral productivity is also decreased when land developments for agriculture, industry, and housing increase sediment transported from land into coastal waters as runoff. This clouds the waters and blocks light necessary for photosynthesis by algae living in corals. Corals face serious risks from various diseases. When corals are stressed, they often expel the algal symbionts that are critical to their health in a process commonly known as coral bleaching. One known cause of coral bleaching is increases in ocean temperatures, possibly due to global warming.

Scientists worldwide are working to understand the impacts of natural processes and human activities on the health and sustainability of coral reefs. The USGS is contributing to the effort to understand the biological and geological controls that affect our Nation's coral reefs. USGS coral reef research focuses on detailed mapping of reefs, the development of monitoring techniques, studying reefs' geologic growth and development, and how they are affected by water quality, fishing, and sedimentary and hydrologic processes. These efforts will help provide information that is essential if coral reefs are to be saved.

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Date published: April 30, 2019

Coral Reef Barriers Provide Flood Protection for More Than 18,000 People and $1.8 Billion Worth of Coastal Infrastructure and Economic Activity Annually

Today, the U.S. Geological Survey (USGS) released the findings of a new, in-depth study titled “Rigorously Valuing the Role of U.S. Coral Reefs in Coastal Hazard Risk Reduction,” – funded in part by the U.S. Department of the Interior’s (DOI) Office of Insular Affairs

Date published: March 29, 2018

New Control Methods Can Help Protect Coral Reefs from Invasive Species

Honolulu, Hawaii – Control efforts such as the removal of shipwrecks and application of chlorine may help mitigate the damaging effects of corallimorph, which is a type of invasive anemone, on valuable coral reefs in the Central Pacific Ocean, according to a new U.S. Geological Survey study.

Date published: January 25, 2017

Florida Corals Tell of Cold Spells and Dust Bowls Past, Foretell Weather to Come

Boulder corals in the waters of Dry Tortugas National Park, 70 miles from Key West, contain evidence that confirms a centuries-old sea temperature cycle linked to rains, droughts and hurricanes.

Date published: October 1, 2015

Many Atolls May be Uninhabitable Within Decades Due to Climate Change

SANTA CRUZ, Calif. — A new study shows that the combined effect of storm-induced wave-driven flooding and sea level rise on island atolls may be more severe and happen sooner than previous estimates of inundation predicted by passive “bathtub” modeling for low-lying atoll islands, and especially at higher sea levels forecasted for the future due to climate change.

Date published: July 22, 2015

Climate Change Reduces Coral Reefs’ Ability to Protect Coasts

SANTA CRUZ, Calif. — Coral reefs, under pressure from climate change and direct human activity, may have a reduced ability to protect tropical islands against wave attack, erosion and salinization of drinking water resources, which help to sustain life on those islands.

Date published: September 9, 2014

Ocean Warming Affecting Florida Reefs

Late-summer water temperatures near the Florida Keys were warmer by nearly 2 degrees Fahrenheit in the last several decades compared to a century earlier, according to a new study by the U.S. Geological Survey.

Date published: May 13, 2014

Coral Reefs are Critical for Risk Reduction & Adaptation

Stronger storms, rising seas, and flooding are placing hundreds of millions people at risk around the world, and big part of the solution to decrease those risks is just off shore. A new study finds that coral reefs reduce the wave energy that would otherwise impact coastlines by 97 percent.

Date published: July 10, 2013

New Approach to Measuring Coral Growth Offers Valuable Tool for Reef Managers

A new more sensitive weight-based approach for monitoring coral growth in the wild has been developed by U.S. Geological Survey researchers leading to more definitive answers about the status of coral reefs.

Date published: March 30, 2011

2,000 Year-old Deep-sea Black Corals call Gulf of Mexico Home

For the first time, scientists have been able to validate the age of deep-sea black corals in the Gulf of Mexico. They found the Gulf is home to 2,000 year-old deep-sea black corals, many of which are only a few feet tall. 

Date published: November 20, 2008

Reversing Coral Reef Decline in Hawai`i — A New Look at a Critical Problem

New discoveries about how even small amounts of sediment can severely impact fragile ocean coral and suggestions about solutions are illustrated and described in a new book written by a team of U.S. Geological Survey (USGS) scientists and their colleagues. Coral reefs are in decline worldwide, and a leading cause is the runoff of sediment and pollutants from nearby land surfaces.

Date published: January 4, 2008

Coral Reef Builders Vulnerable to Ocean Acidification

As pH declines in the world's oceans, the effects on coral reefs could be more harmful than previously thought. This pH decline, a process known as "ocean acidification," occurs due to absorption of carbon dioxide from the atmosphere. As a result, the growth of reef builders may be severely inhibited.

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March 22, 2019

Why are coral reefs in peril and what is being done to protect them?

A short video on information related to coral reefs and the USGS.

April 26, 2018

PubTalk 4/2018 - Coral Reefs

Title: The Role of U.S. Coral Reefs in Coastal Protection - Rigorously valuing flood reduction benefits to inform coastal zone management decisions

  • Coral reefs are a first line of coastal defense
  • We can account for the physical defense that reefs provide
  • We can provide value-based information to guide restoration efforts at management-relevant
Coral Bleaching and Disease: Effects on Threatened Corals and Reefs
April 17, 2016

Coral Bleaching and Disease: Effects on Threatened Corals and Reefs

Coral Bleaching and Disease: Effects on Threatened Corals and Reefs: White plague disease caused major coral mortality following bleaching in 2005.

USGS research diver over coral reef in the Dry Tortugas
April 5, 2016

USGS research diver over coral reef in the Dry Tortugas

USGS research diver over coral reef in the Dry Tortugas

SCUBA Diver Collects Corals for Paleoclimate
December 31, 2015

SCUBA Diver Collects Corals for Paleoclimate

A USGS SCUBA Diver Collects a Core from a Coral Using a Hydraulic Drilling System in the U.S. Virgin Islands. USGS Image (I. Kuffner).

Attribution: Land Resources
September 24, 2015

PubTalk 9/2015 — Coral Reefs, Climate Change, and Atoll Sustainability

Will Micronesians become the U.S.'s first climate change refugees?

by Curt Storlazzi, USGS Research Geologist and Oceanographer

  • Sea level is rising, threatening low-lying atoll islands throughout the western Pacific Ocean
  • Climate change is degrading the coral reefs that atoll islands have developed upon, decreasing
April 15, 2015

Resilience Potential of Coral Reefs in the Mariana Islands

This webinar was conducted as part of the "Climate Change Science and Management Webinar Series" held in partnership between the USGS National Climate Change and Wildlife Science Center and the FWS National Conservation Training Center. Webinar Summary: Reducing coral reef vulnerability to climate change requires that managers understand and support the natural resilience

March 31, 2015

Exploring Causes of Coral Disease

The Hawaiian Islands’ beautiful ocean and beaches attract more than 8.5 million tourists each year. The USGS aims to help Hawaii preserve its underwater natural resources by tracing how oceanography may influence coral disease outbreaks. Looking into contaminants in the freshwater, or how quickly a bay may or may not flush, will help enrich future and past studies about

Image: Fire Coral Bleaching
September 6, 2014

Fire Coral Bleaching

Colonies of “blade fire coral” that have lost their symbiotic algae, or “bleached,” on a reef off of Islamorada, Florida. Hard and soft corals are presently bleaching- losing their symbiotic algae – all over the coral reefs of the Florida Keys due to unusually warm ocean temperatures this summer. Months with waters warmer than 85 F have become more frequent in

June 26, 2014

PubTalk 6/2014 — Into the Abyss

Living Without Light

by Nancy Prouty, Research Oceanographer 


  • As archives of natural and human activities, deep-sea corals are windows to the past.
  • Scientific studies of these slow-growing and long-living animals lead to good stewardship for healthy ecosystems.
  • Deep-sea coral communities are
Image: Sampling Diseased Coral
August 6, 2012

Sampling Diseased Coral

USGS scientist Thierry Work takes a sample from diseased coral at Tunnels Reef on the north shore of Kauai, Hawaii

Attribution: Natural Hazards
coral reef
June 25, 2012

A Healthy Coral Reef

Taken at Palmyra National Wildlife Refuge