Policy ForumEcology

Are U.S. Coral Reefs on the Slippery Slope to Slime?

See allHide authors and affiliations

Science  18 Mar 2005:
Vol. 307, Issue 5716, pp. 1725-1726
DOI: 10.1126/science.1104258

This article has a correction. Please see:

Coral reefs [HN1] provide ecosystem goods and services worth more than $375 billion to the global economy each year (1). Yet, worldwide, reefs are in decline [HN2] (14). Examination of the history of degradation reveals three ways to challenge the current state of affairs (5, 6). First, scientists should stop arguing about the relative importance of different causes of coral reef decline: overfishing, pollution, disease, and climate change. Instead, we must simultaneously reduce all threats to have any hope of reversing the decline. Second, the scale of coral reef management—with mechanisms such as protected areas—has been too small and piecemeal. Reefs must be managed as entire ecosystems. Third, a lack of clear conservation goals has limited our ability to define or measure success.

Large animals, like turtles, sharks, and groupers, were once abundant on all coral reefs, and large, long-lived corals created a complex architecture supporting diverse fish and invertebrates (5, 6). Today, the most degraded reefs are little more than rubble, seaweed, and slime. Almost no large animals survive, water quality is poor, and large corals are dead or dying and being replaced by weedy corals, soft corals, and seaweed (2, 7, 8). Overfishing of megafauna releases population control of smaller fishes and invertebrates, creating booms and busts. This in turn can increase algal overgrowth, or overgrazing, and stress the coral architects, likely making them more vulnerable to other forms of stress. This linked sequence of events is remarkably consistent worldwide (see figure, below).

The slippery slope of coral reef decline through time. CREDIT: MARY PARRISH

Even on Australia's Great Barrier Reef [HN3] (GBR), the largest and best-managed reef in the world, decline is ongoing (9). Australia's strategy, beginning with the vision to establish the world's largest marine park in 1976, is based on coordinated management at large spatial scales. Recently more than one-third of the GBR was zoned “no take,” and new laws and policies to reduce pollution and fishing are in place (10). Evaluating benefits of increased no-take zones [HN4] will require detailed follow-up, but smaller-scale studies elsewhere support increased protection. Two neighboring countries, the Bahamas (11) and Cuba (12), [HN5] have also committed to conserve more than 20% of their coral reef ecosystems. By contrast, the Florida Keys and main Hawaiian Islands are far further down the trajectory of decline (see figure, below), yet much less action has been taken.

Past and present ecosystem conditions of 17 coral reefs, based on historical ecology (6).

The method consists of determining the status of guilds of organisms for each reef with published data, performing a multivariate, indirect gradient analysis on the guild status database, and estimating the location of each reef along a gradient of degradation from pristine to ecologically extinct reefs. Green, Caribbean sites; blue, Australian and Red Sea sites; red, U.S. reefs from the most recent cultural period.

What is the United States doing to enhance its coral reef assets? In the Florida Keys National Marine Sanctuary [HN6], the Governor and the National Oceanic and Atmospheric Administration (NOAA) agreed in 1997 to incorporate zoning with protection from fishing and water quality controls (13). But only 6% of the Sanctuary is zoned no take, and these zones are not strategically located. Conversion of 16,000 cesspools to centralized sewage treatment and control of other land-based pollution have only just begun. Florida's reefs are well over halfway toward ecological extinction and much more impaired than reefs of Belize [HN7] and all but one of the Pacific reefs in the figure above (6). Large predatory fishes continue to decrease (14), reefs are increasingly dominated by seaweed (15, 16), and alarming diseases have emerged (17).

Annual revenues from reef tourism are $1.6 billion (1), but the economic future of the Keys is gloomy owing to accelerating ecological degradation. Why? Without a clear goal for recovery, development and ratification of the management plan became a goal in itself.

Reefs of the northwest Hawaiian Islands [HN8] have been partially protected by isolation from the main Hawaiian Islands (which show degradation similar to that of the Florida Keys) and are in relatively good condition (see second figure). Corals are healthy (2, 18), and the average biomass of commercially important large predators such as sharks, jacks, and groupers is 65 times as great (19) as that at Oahu, Hawaii, Maui, and Kauai. Even in the northwestern islands, however, there are signs of decline. Monk seals and green turtles [HN9] are endangered (20, 21); large amounts of marine debris are accumulating, which injure or kill corals, seabirds, mammals, turtles, and fishes (2, 18, 22); and levels of contaminants, including lead and PCBs are high (18).

Until recently, small-scale impacts from overfishing and pollution could be managed locally, but thermal stress and coral bleaching [HN10] are already changing community structure of reefs. Impacts of climate change may depend critically on the extent to which a reef is already degraded (8, 23). Polluted and overfished reefs like in Jamaica [HN11] and Florida have failed to recover from bouts of bleaching, and their corals have been replaced by seaweed (2). We believe that restoring food webs and controlling eutrophication [HN12] provides a first line of defense against climate change (8, 23); however, slowing or reversing global warming trends is essential for the long-term health of all tropical coral reefs.

For too long, single actions such as making a plan, reducing fishing or pollution, or conserving a part of the system were viewed as goals. But only combined actions addressing all these threats will achieve the ultimate goal of reversing the trajectory of decline (see the table below).

View this table:

We need to act now to curtail processes adversely affecting reefs. Stopping overfishing will require integrated systems of no-take areas and quotas to restore key functional groups. Terrestrial runoff of nutrients, sediments, and toxins must be greatly reduced by wiser land use and coastal development. Reduction of emissions of greenhouse gases are needed to reduce coral bleaching and disease. Progress on all fronts can be measured by comparison with the past ecosystem state through the methods of historical ecology [HN13] to determine whether or not we are succeeding in ameliorating or reversing decline. Sequential return of key groups, such as parrot fish and sea urchins that graze down seaweed; mature stands of corals that create forest-like complexity; and sharks, turtles, large jacks, and groupers that maintain a more stable food web (4, 5, 6, 24) constitutes success.

This consistent way of measuring recovery (see the second figure) and the possibility of short-term gains set a benchmark for managing other marine ecosystems. Like any other successful business, managing coral reefs requires investment in infrastructure. Hence, we also need more strategic interventions to restore species that provide key ecological functions. For example, green turtles and sea cows [HN14] not only once helped maintain healthy seagrass ecosystems, but also were an important source of high-quality protein for coastal communities (25).

Our vision of how to reverse the decline of U.S. reefs rests on addressing all threats simultaneously (see the table above). By active investment, major changes can be achieved through practical solutions with short- and long-term benefits. Short-lived species, like lobster, conch, and aquarium fish will recover and generate income in just a few years, and benefits will continue to compound over time. Longer-lived species will recover, water quality will improve, and the ecosystem will be more resilient to unforeseen future threats. Ultimately, we will have increased tourism, and the possibility of renewed sustainable extraction of abundant megafauna. One day, reefs of the United States could be the pride of the nation.

HyperNotes Related Resources on the World Wide Web

General Hypernotes

Dictionaries and Glossaries

A glossary of ecology terms is provided by the companion Web site for Essentials of Ecology by C. Townsend, M. Begon, and J. Harper.

A glossary is provided by the Coral Reef Information System.

A glossary is provided by the Marine Protected Areas Center.

A glossary of marine biology is provided by Marine Biology Web.

Web Collections, References, and Resource Lists

The Google Directory provides links to Internet resources in ecology. A section on coral reefs is included.

Academic Info provides an environmental studies gateway.

The Ecology WWW page is maintained by A. Brach, Harvard University Herbaria.

The Ocean Portal is a directory of ocean data and information related Web sites.

Links to Internet resources are included in Marine Biology Web, which is maintained by J. Levinton, Department of Ecology and Evolution, SUNY Stony Brook.

The Digital Library for Earth System Education provides links to educational resources. A selection of biological oceanography resources is included.

The Coral Reef Protection Web site of the U.S. Environmental Protection Agency (EPA) provides links to Internet resources on coral reefs.

Online Texts and Lecture Notes

Ocean World is an educational resource provided by R. Stewart, Department of Oceanography, Texas A&M University. A presentation on coral reefs is included.

Coral Realm is a ThinkQuest student project.

Silent Sentinels: The Future of Corals is a presentation of the Australian Broadcasting Corporation.

An illustrated guide to coral reef ecology is provided by A. Mustard, Southampton Oceanography Centre, UK.

The Coral Reef Information System (CoRIS) of the National Oceanic and Atmospheric Administration (NOAA) provides access to NOAA coral reef information and data products, especially those derived from NOAA's Coral Reef Conservation Program. A collection of essays about coral reefs is included.

Other U.S. government resources on coral reefs include the U.S. Coral Reef Task Force, NOAA's Coral Health and Monitoring Program (CHAMP), and the EPA's Coral Reef Protection.

ReefBase is a global information system on coral reefs. A photo gallery and country-level data and information on coral reefs are included.

The International Coral Reef Action Network (ICRAN) is a global partnership of coral reef conservation groups and scientists working to halt and reverse the decline in the health of the world's coral reefs.

ICRAN's International Coral Reef Information Network provides information about coral reefs and tools and resources.

A study guide on coral reefs is provided in PDF format by D. Krupp, Department of Natural Sciences, Windward Community College, University of Hawaii.

D. Eernisse, Department of Biological Sciences, California State University, Fullerton, provides lecture notes for a marine biology course.

K. S. Kilburn, Department of Biological Sciences, Old Dominion University, Norfolk, VA, offers lecture notes and other resources for an ecology course.

P. Ganter, Biology Department, Tennessee State University, Nashville, provides lecture notes for an ecology course.

H. D. Mooers, Department of Geology, University of Minnesota, Duluth, provides lecture notes in PDF format for a field course on coast coral reef geology.

General Reports and Articles

A September 2002 report to Congress entitled A National Coral Reef Action Strategy is made available by CoRIS.

Status of Coral Reefs of the World: 2004 (2) is made available in PDF format by the Australian Institute of Marine Science, which also makes available a 2004 book by J. Hill and C. Wilkinson titled Methods for Ecological Monitoring of Coral Reefs: A Resource for Managers.

The 8 May 2001 issue of the Proceedings of the National Academy of Sciences had an article by N. Knowlton titled “The future of coral reefs” (8).

The February 2003 issue of Ecological Applications had a supplement on the science of marine reserves.

The 29 June 2004 issue of the Proceedings of the National Academy of Sciences had an article by A. Balmford et al. titled “The worldwide costs of marine protected areas.”

The 27 July 2001 issue of Science had a Review by J. B. C. Jackson et al. titled “Historical overfishing and the recent collapse of coastal ecosystems” (5).

The 15 August 2003 issue of Science had a Report by J. M. Pandolfi et al. titled “Global trajectories of the long-term decline of coral reef ecosystems” (6) and a Review by T. P. Hughes et al. titled “Climate change, human impacts, and the resilience of coral reefs” (23).

Global Trade and Consumer Choices: Coral Reefs in Crisis, edited by B. Best and A. Bornbusch, is the proceedings of a 2001 AAAS symposium.

Numbered Hypernotes

1. Coral reefs. The Coral Kingdom is a collection of images in the NOAA Photo Library. A Coral Reef Photobank is provided by the International Coral Reef Information Network. The Marine Programme of the World Conservation Monitoring Center offers a presentation on coral reefs with maps of their location. The United Nations Atlas of the Oceans offers an introduction to coral reefs with links to Internet resources. Resources on coral reefs are provided by the Fish and Wildlife Research Institute of the Florida Fish and Wildlife Conservation Commission. NOAA's National Ocean Service offers educational material on coral reefs. Coral Reefs: A Guided Tour is provided by NOAA's Office of Response and Restoration. An introduction to coral reefs is presented by T. Turner, Science and Mathematics Division, University of the Virgin Islands. F. J. Jochem, Marine Biology Program, Florida International University, offers lecture notes on coral reefs and coral reef development for a course on marine biology and oceanography.

2. Reefs in decline; threats to reefs. The 2002 report State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States is available in PDF format from the National Centers for Coastal Ocean Science. The National Marine Sanctuary Foundation makes available in PDF format a slide presentation by J. Pandolfi titled “Coral reefs and the history of their degradation” from the 2002 Capitol Hill Oceans Week. ReefBase provides a section on threats to coral reefs. The International Coral Reef Initiative provides country status reports. The Hawaii Coral Reef Initiative Research Program provides information on threats to reefs, as well as detailed reports by island. The World Resources Institute provides publications and resources from its Reefs at Risk project; included are country summaries and case studies. Florida's Fish and Wildlife Research Institute makes available in PDF format the 2002 executive summary (15) and the 2003 executive summary of the EPA/NOAA Coral Reef Evaluation and Monitoring Project. The 17 July 2003 issue of Science had a report by T. A. Gardner et al. titled “Long-term region-wide declines in Caribbean corals” (3). ReefGuardian International provides links to news articles and meetings related to the threats to coral reefs. Status of Coral Reefs of the World: 2004 has a chapter on global threats to coral reefs.

3. Great Barrier Reef, Australia. UNESCO's World Heritage Centre provides information on the Great Barrier Reef. The Great Barrier Reef Marine Park Authority (GBRMPA) provides information about the Great Barrier Reef Marine Park and ReefEd, a gateway to information about the reef. GBRMPA makes available information on Great Barrier Reef protective zoning. Status of Coral Reefs of the World: 2004 has a chapter on the status of coral reefs in Australia and Papua New Guinea.

4. No take zones. The International Society for Reef Studies provides a briefing paper (in PDF format) on marine protected areas in management of coral reefs. The Marine Protected Areas Center provides information resources related to the marine protected areas of the United States. The Division of Aquatic Resources, State of Hawaii, makes available in PDF format the March 2005 publication titled “Marine protected areas in Hawaii.” Oceanus makes available a 1 February 2005 article by M. J. Fogarty and S. A. Murawski titled “Do marine protected areas really work?” The 30 November 2001 issue of Science had a report by C. M. Roberts et al. titled “Effects of marine reserves on adjacent fisheries” and a related News of the Week article by D. Malakoff titled “Reserves found to aid fisheries.” The 12 April 2002 issue of Science had a News Focus article by D. Malakoff titled “Picturing the perfect preserve.” The 6 December 2002 issue of Science had a report by E. Sala et al. titled “A general model for designing networks of marine reserves.”

5. Coral reef protection in the Bahamas and Cuba. ReefBase provides information on reefs and protected marine areas in the Bahamas and information on reefs and the protected marine areas in Cuba. The World Resources Institute's 2004 report Reefs at Risk in the Caribbean includes information on Cuba and the Bahamas. The Bahamas Reef Environment Educational Foundation provides information about no-take marine reserves and a 13 January 2002 press release about their establishment. The Bahamas Environment Science and Technology Commission makes available in PDF format a February 2005 draft report on the state of the Bahamas' environment with sections on coral reefs and marine protected areas. Medioambiente.cu provides information (in Spanish) about marine protected areas in Cuba. Status of Coral Reefs of the World: 2004 includes a chapter with information on Bahamian and Cuban coral reefs.

6. Florida reefs and the Florida Keys National Marine Sanctuary. The World Resources Institute's Reefs at Risk in the Caribbean provides information on Florida reefs. NOAA's Encyclopedia of the National Marine Sanctuaries provides an introduction to the Florida Keys National Marine Sanctuary. The Florida Keys National Marine Sanctuary provides information about coral reefs and a collection of Internet links; information about Florida Keys marine zoning is provided, and the Final Management Plan is made available in PDF format. The U.S. Marine Protected Areas Center provides a case study of the Florida Keys coral reefs. The Dustan Lab, Department of Biology, University of Charleston, provides information about the Florida Keys coral reef monitoring project. Status of Coral Reefs of the World: 2004 has a chapter with information about the reefs of Florida and the U.S. Caribbean.

7. Information on the reefs of Belize is provided by ReefBase. The World Resources Institute's 2004 report Reefs at Risk in the Caribbean includes information on the coral reefs of Belize. Status of Coral Reefs of the World: 2004 includes a chapter with information on Belize reefs.

8. Coral reefs of the northwestern Hawaiian islands. NOAA's Encyclopedia of the National Marine Sanctuaries has a section on the Northwestern Hawaiian Islands. The Northwestern Hawaiian Islands Coral Reef Ecosystem Reserve provides a FAQ and information about the region and maps. NOAA's Ocean Explorer Web site has a presentation about a research trip to the northwestern Hawaiian islands. The Hawaii Coral Reef Initiative Research Program makes available in PDF format the interim report titled Coral Reef Ecosystems of the Northwestern Hawaiian Islands (18).

9. Monk seals and green turtles. The University of Michigan Museum of Zoology's Animal Diversity Web has entries for the green sea turtle and the Hawaiian monk seal. NOAA's Encyclopedia of the National Marine Sanctuaries provides information on the monk seal and green turtle. Presentations on Hawaiian monk seals and green sea turtles are included in curriculum materials on Earthtrust's Hawaii's Marine Wildlife Web site. The Seal Conservation Society provides information on the Hawaiian monk seal.

10. Coral bleaching; climate change and coral reefs. GBRMPA offers an introduction to coral bleaching and mass bleaching events. NOAA's Coral Health and Monitoring Program offers an introduction to coral bleaching. Information about monitoring coral reef bleaching is provided by NOAA's Coral Reef Watch. Current Operational Coral Bleaching HotSpots are presented by NOAA's Office of Satellite Data Processing and Distribution. The Australian Institute of Marine Sciences offers coral bleaching resources. The Reef Education Network provides information about climate change and coral reefs. The CRC Reef Research Centre offers a presentation on coral bleaching; a January 2002 brochure titled “Coral bleaching and global climate change” is also available. The 27 October 2000 issue of Science had a News of the Week article by D. Normile titled “Warmer waters more deadly to coral reefs than pollution.”

11. Jamaican reefs. The World Resources Institute's 2004 report Reefs at Risk in the Caribbean includes information on the coral reefs of Jamaica. Status of Coral Reefs of the World: 2004 includes a chapter with information about Jamaican reefs.

12. Eutrophication is defined in the FAO fisheries glossary. NOAA's National Centers for Coastal Ocean Science makes available a feature about estuarine eutrophication.

13. Historical ecology. Historical ecology is defined on the French Project Web site of C. Crumley, Department of Anthropology, University of North Carolina. An introduction to applied historical ecology is provided by the U.S. Geological Survey's Fort Collins Science Center, which also makes available in PDF format a 1999 article by T. W. Swetnam, C. D. Allen, and J. L. Betancourt titled “Applied historical ecology: Using the past to manage for the future.” R. Sagarin, Department of Environmental Health Sciences, University of California, Los Angeles, offers a research presentation on historical ecology. The American Society for Environmental History provides links to Internet resources. Oosthoek's Environmental History Homesite provides links to Internet resources related to environmental history.

14. Sea cows. Wikipedia has an entry on the order Sirenia, which includes dugongs and manatees. The Columbia Encyclopedia has an article on sirenians (or sea cows). Animal Diversity Web has entries for manatees and dugongs. GBRMPA offers a fact sheet on dugongs (sea cows) and links to related resources. The CRC Reef Research Centre makes available in PDF format an April 2002 brochure titled “Dugongs in the Great Barrier Reef.” The United Nations Environment Programme's Division of Early Warning and Assessment provides (in PDF format) the February 2002 publication titled “Dugong status report and action plans for countries and territories.”

15. J. M. Pandolfi is at the Centre for Marine Studies and in the Department of Earth Sciences, University of Queensland, St. Lucia, Queensland, Australia. J. B. C. Jackson is at the Smithsonian Tropical Research Institute, Balboa, Republic of Panamá, and at the Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, La Jolla, CA. N. Baron is at the National Center for Ecological Analysis and Synthesis, Santa Barbara, CA. R. H. Bradbury is at the Centre for Resource and Environmental Studies, Australian National University, Canberra. H. M. Guzman is at the Smithsonian Tropical Research Institute. T. P. Hughes is at the Centre for Coral Reef Biodiversity, School of Marine Biology, James Cook University, Townsville, Australia. C. V. Kappel and F. Micheli are at the Hopkins Marine Station, Stanford University. J. C. Ogden is at the Florida Institute of Oceanography, St. Petersburg. H. P. Possingham is in the Department of Mathematics and the School of Integrative Biology, University of Queensland. E. Sala is at the Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography.


  1. 1.
  2. 2.
  3. 3.
  4. 4.
  5. 5.
  6. 6.
  7. 7.
  8. 8.
  9. 9.
  10. 10.
  11. 11.
  12. 12.
  13. 13.
  14. 14.
  15. 15.
  16. 16.
  17. 17.
  18. 18.
  19. 19.
  20. 20.
  21. 21.
  22. 22.
  23. 23.
  24. 24.
  25. 25.
View Abstract

Navigate This Article