How old are coral reefs?                                                                                                                

The geological record indicates that the ancestors of modern coral reef ecosystems were formed at least 350 million years ago.  The coral reefs existing today began growing as early as 50 million years ago.  Most established coral reefs are between 5,000 and 10,000 years old.  Although size sometimes indicates the age of a coral reef, this is not always true.  Different species of coral grow at different rates, depending on water temperature, oxygen level, amount of turbulence, and availability of food.

How is a coral reef constructed?

Coral reefs are complex, multi-story structures with holes and crevices shared by various creatures.  If a coral reef can be thought of as a metropolis of the sea, then a coral colony can be thought of as an apartment building with many different rooms and hallways that house different marine species.  Not all coral species build reefs.   The actual architects of coral reefs are hard or stony corals, which are referred to as hermatypic or reef-building corals.  As the polyps of stony corals grow, the produce limestone for their skeletons.  When they die, their skeletons are left behind and are used as foundations for new polyps, which build new skeletons over the old ones.  An actual coral mound or tree is composed of layer upon layer of skeletons covered by a thin layer of living polyps.Other types of animals and plants also contribute to the structure of the reef.   Many types of algae, seaweed, sponge, sediment and even mollusks like giant clams and oysters, add to the architecture of a coral reef.  When these organisms die, they also serve as foundation for new corals.

What are the different types of reefs?

Scientists generally divide coral reefs into four classes:  fringing reefs, barrier reefs, atolls and patch reefs:

Fringing reefs grow near the coastline around islands and continents.  They separate from the shore by narrow, shallow lagoons.  Fringing reefs are the most common type of reef that we see.

Barrier reefs also parallel the coastline but are separated by deeper, wider lagoons.  At their shallowest point they can reach the water's surface forming a "barrier" to navigation. The Great Barrier Reef in Australia is the most famous example and is the largest barrier reef in the world.

Atolls are rings of corals that create protected lagoons and are usually located in the middle of the sea.  Atolls usually form when islands surrounded by fringing reefs sink into the sea or the sea level rises around them (these islands are often the tops of underwater volcanoes).  The fringing reefs continue to grow and eventually form circles with lagoons inside.

Patch reefs are small, isolated reefs that grow up from the open bottom of the island platform or continental shelf.  They usually occur between fringing reefs and barrier reefs.  They vary greatly in size, and they rarely reach the surface of the water.

Coral reefs make a healthy world

Coral reefs are one of the most spectacular and fragile of underwater environments, covering less than one percent of the ocean floor but supporting an estimated twenty-five percent of all marine life.  Even though they are located in the tropics, coral reefs can benefit people and the natural world far beyond their boundaries.

Millions of humans depend on coral reefs

"By one estimate, coral reefs provide economic goods and ecosystem services worth about $375 billion each year to millions of people." (Robert Constanza et. al. 1997)Many countries with coral reefs generate significant portions of their income through tourism.  Studies show that on average, countries with coral reef industries derive more than half of their gross national product from them.  A good example can be found in Bonaire, a small Caribbean island.  Bonaire earns about $23 million USD annually from coral reef activities--yet managing its marine park costs less than $1 million dollars annually.  (F. Talbot and C. Wilkinson, 2001)The variety of marine life and protected beaches supported by coral reefs provide an inviting setting for sightseers, sunbathers, snorkelers, and scuba divers.  In fact, there are more than 8.5 million certified scuba divers in the United States who spend money on dive vacations each year.  In 1997, the State of Florida earned $1.6 billion USD from coral reef and beach related tourism.  For residents of coral reef areas that depend on income from tourism, reef destruction creates a significant loss of jobs in the tourism,marine recreation and sport fishing industries.Coral reefs are also a significant source of protein for millions of people.  For people who live in coral reef areas, coral reefs are part of their lives.  Reefs are directly linked with traditional, spiritual and cultural values of many people who live in reef areas.Coral reef save livesJust like species in the rain forest, reef animals and plants contain medicinal compounds, many of which are just being discovered.  Several important drugs have already been developed from chemicals found in coral reef organisms.  The most famous of these is AZT, a treatment for people with HIV infections, which is based on chemicals extracted from a Caribbean reef sponge.Unique compounds from coral reefs have also yielded treatments for cardiovascular diseases, ulcers, leukemia and skin cancer.  In addition, coral's unique skeletal structure has been used to make our most advanced forms of bone grafting materials.Amazingly, more than half of all new cancer drug research focuses on marine organisms.   The beautiful and fragile creatures of our coral reefs have the potential to make even greater contributions to our lives by providing new cures for life-threatening diseases.

Coral reefs protect the beaches

Another benefit that people received from coral reefs is the guard they keep on our coastlines.  Reefs serve as a buffer, protecting inshore areas from the pounding of ocean waves.  Without coral reefs, many beaches and buildings would become vulnerable to wave action and storm damage.  In on instance, when coral and sand was mined away in the Maldives, it cost $10 million USD per kilometer to build a wall to protect the coastline.  (Coral Reefs, Mangroves and Seagrasses:  A sourcebook for Managers, F. Talbot and C. Wilkinson, 2001)

Animals that live nowhere else

Coral reefs are a high-density location of biodiversity.  This means that the variety of species living on a coral reef is greater than almost anywhere in the world.   When we protect coral reefs, we protect an abundant array of life.Coral reefs provide shelter for nearly one quarter of all know marine species.   Over the last 350 million years, reefs have evolved into one of the largest and most complex ecosystems on the planet.  The reefs are home to over 4,000 species of fish, 700 species of coral, and thousands of other forms of plant and animal life.   Scientists estimate that, in total, more than 1 million species of plants and animals are associated with the coral reef ecosystem.