Questions and Answers
Global Status of and Threats to Coral Reefs

Q: What are corals?
A: Many people think corals are rocks, but they are actually living animals related to jellyfish and anemones. An individual coral animal is called a polyp. Some live alone, and others live as colonies of thousands of polyps building upon each other. As coral polyps die, their hard skeletons accumulate below the living tissue to form permanent structures called reefs. Coral reefs are the most diverse ecosystem in the ocean, and are second only to tropical rainforests in terms of biological diversity.

Q: Why are coral reefs important?
A: Corals are vital to a healthy ocean. The reefs they build provide 25 percent of all marine fish species with food, reproduction areas and safe havens from predators. Coral reefs also provide people around the world with food, invaluable pharmaceuticals, and economic benefits from commercial fisheries and tourism, as well as protecting coastlines from storms and providing the structure that creates surf. They also create Hawaii’s famous white sand beaches and underwater paradise.

Q: How many types of corals are there?
A: The thousands of known coral species on the planet can be divided into two types — hard corals and soft corals. The hard corals resemble rocks, boulders, or tree trunks. These are the reef builders. The soft corals can look like tree branches or fans. Both are living animals. Hawai‘i has few soft corals and only about 50 species of reef-building corals due to our isolation. The unique nature of our reef ecosystem makes it more vulnerable.

Q: Where are corals found?
A: Corals are found all over the world in shallow, tropical waters as well as on the deep, dark ocean floor. Shallow water reef-building corals have adapted to warm water and rely on being close to sunlight for their survival. Other corals come from the deep sea and survive in cold waters without sunlight. The corals used in tropical fish tanks and as home décor primarily come from shallow water environments. Most precious corals used in jewelry come from the deep seas of the Mediterranean and Pacific Ocean. The Hawaiian Islands have 410,000 acres of living reef in the main islands alone, more than the landmass of O‘ahu.

Q: What’s special about Hawaii’s coral reefs?
A: Hawaii’s coral reef ecosystem, because of its isolation, has more than 1,250 unique species of marine life that can be found only on Hawaii’s reefs. Over 25% of all marine life is endemic to Hawai‘i and scientists are finding new species regularly. The majority of the nation’s coral reefs are found around the Northwestern Hawaiian Islands (the 10 mostly uninhabited islets and atolls extending 1,200 miles northwest of the main Hawaiian Islands).

Q: Why are coral reefs important?
A reef is both a protector and provider – a reservoir of food as well as a buffer against the destructive power of the sea. Hawaii’s coral reefs and nearshore waters are home to more than 7,000 marine life forms – a quarter of them found nowhere else in the world. Hawaii’s cultural traditions and our island way of life are intimately tied to the sea.

Q: What is the current condition of coral reefs throughout the world?
A: Scientists say that we have already lost 20 percent of the world’s coral reefs, and they predict that another 24 percent may be lost in the next 30 years if human impacts are not reduced. The Pacific Ocean contains most of the world’s reefs. Coral reefs were previously thought to be doing well here, but coral coverage has dropped 22 percent in the past 20 years.

Q: What is threatening coral reefs?
A: The primary threats to coral reefs are caused by human activity, including climate change, overfishing, recreational over use, land-based pollution, disease, and invasive species.

Q: How is climate change affecting reefs?
A: Climate change is a threat to coral reefs worldwide because of bleaching, rising sea levels and ocean acidification. Coral bleaching occurs when the symbiosis between corals and their zooxanthellae (single-celled algae that live inside the tissue of reef building corals, providing them with energy) breaks down, resulting in an energy deficit that often leads to the death of the coral host. This is a stress response by the coral that can be caused by various factors, but the most severe and frequent cases are being caused by a rise in sea surface temperature. Hawai‘i is not immune to this threat; in 2002, the first significant bleaching event was documented in the northern three atolls of the Northwestern Hawaiian islands resulting in high rates of coral mortality. Climate change is also causing sea levels to rise, threatening to drown the coral reefs that protect low-lying nations and islands. Finally, the ocean is becoming more acidic due to its intake of increasing levels of carbon dioxide, which may have severe negative consequences for oceanic organisms such as coral reefs.

Q: Why is over-fishing a problem for reefs?
A: Increasing demand for food fish has resulted in over-fishing of not only open ocean commercial fish species such as tuna and swordfish, but key reef species as well. Over-fishing of coral reef species can negatively affect a reef’s ecological balance. For example, herbivorous fishes keep algal growth in check by constantly grazing it from coral reefs. Over-fishing of herbivores can lead to high levels of algae, which can smother and kill corals. From subsistence level fishing to the live fish trade, inadequate fisheries management and destructive fishing practices are resulting in the decline of fish stocks around the world.

Q: What destructive fishing methods are damaging the reef ecosystem?
A: While not a problem in Hawai‘i, destructive fishing with dynamite, cyanide and bleach are destroying not only coral, but also the fragile reef ecosystem in other places around the world. Fishing with gill nets and other non-selective methods can lead to over-fishing as well as direct reef damage. Fishermen often say they have no other option if they are to compete with trawlers and other large-scale commercial fishing enterprises. They are also faced with a smaller supply of fish because of chronic over-fishing. These practices generally are indiscriminate and often result in juveniles being killed in the process. With fewer fish reaching reproductive age, populations continue to decline.

Q: How does tourism affect the reefs?
A: Tourism generates vast amounts of income for key destinations near coral reefs. Responsibly-managed tourism raises awareness about coral reefs and can build support for their preservation. In some places, unregulated tourism can cause damage to the environment upon which the industry depends. Physical damage to the coral reefs can occur through continued contact from careless swimmers, divers, and poorly placed boat anchors. Hotels and resorts may also discharge increased levels of sewage and wastewater into the ocean, polluting the water and encouraging the growth of algae, which competes with corals for space on the reef.

Q: How does coastal development impact the reefs?
A: The growth of coastal cities and towns generates a range of threats to nearby coral reefs. Where space is limited, airports and other construction projects may be built on land reclaimed from the sea. Sensitive habitats can be destroyed or disturbed by dredging activities necessary for these developments. Dredging for deep-water channels or marinas, and the dumping of waste materials also destroys reefs. Where land development alters the natural flow of water, greater amounts of fresh water, nutrients and sediment can reach the reefs causing further degradation. Nutrient-rich water causes fleshy algae and phytoplankton to grow in suffocating amounts known as algal blooms. Coral reefs are biological assemblages adapted to waters with low nutrient content, and the addition of nutrients favors species that disrupt the balance of the reef communities.

Q: What other forms of pollution damage reefs?
A: Coral reefs need clean ocean water to thrive. Increased amounts of sewage discharge from inadequate or aging treatment plants, septic systems, and cesspools disrupts the nutrient balance in coastal waters, altering water quality and harming coral reefs. In addition, litter, waste oil, fertilizers, and other land-based pollutants are damaging reefs worldwide. Items thrown in streams, water ways and storm drains such as green-waste are not good for the reefs.

Q: What are invasive species and why are they a problem?
A: Species that have been moved intentionally or unintentionally into areas where they do not occur naturally are called “introduced species” or “alien species.” Where natural controls such as predators are lacking, alien species may multiply rapidly, taking over their new environment, drastically altering the ecosystem and out-competing local organisms. Native species can also become invasive when natural systems have been altered. For example, native and non-native algal species can overgrow and smother corals when herbivores have been removed from the system, causing adverse environmental, economic and socio-cultural impacts.

Q: Is having a home aquarium a problem?
A: It is estimated that nearly 2 million people worldwide keep marine aquaria. The great majority of marine aquaria are stocked with species caught from the wild. This rapidly developing trade is leading to the movement of fish species across borders. Threats from the trade include the use of cyanide in collection, over-harvesting of target organisms and high levels of mortality associated with poor collection practices and insensitive shipping. Some regulation, including certification of sustainable practices, is in place to raise industry standards (contact the Marine Aquarium Council). In West Hawai‘i, there is a management plan that sets aside Fish Replenishment Areas that are closed to aquarium fish collection.

Q: Is the trade of coral jewelry a threat?
A: The most valuable and widely traded corals used for jewelry are red and pink corals, known as Corallium. The United States is the world’s largest documented consumer of precious red corals, with more than 26 million pieces imported from 2001 to 2006. Having been fished for more than 5,000 years in the Pacific and the Mediterranean, precious corals have shown serious signs of decline in just the past two decades.

Click here for more reef facts at www.HawaiiReef.net or try these links:

Learn more about coral jewelry and decor: Too Precious to Wear

Learn about consumer seafood choices and fishing: Seafood Choices Alliance; Fair Catch

Learn about endangered species

Learn about invasive species: Habitattitude; List of invasive species

Learn about pollution in storm drains and take 9 Simple Actions to protect coral reefs

Learn about fish feeding and the Fish Friendly Business Alliance

Watch a video about Reef Etiquette

Learn about Papahānaumokuākea Marine National Monument