Coral reefs are one of the most biologically diverse ecosystems on the planet, despite being found only between 30 degrees north and 30 degrees south of the equator. They are actually formed by living organisms called polyps, which can only survive in water no deeper than 30m, to allow photosynthesis, and at 16 - 24 degrees celcius.
Despite being home to over 4000 species of fish, sponges, worms, crustaceans, mollusks, echinoderms (starfish, urchins etc.) sea turtles and sea snakes. They are one of the most sensitive and fragile ecosystems known to man.
Because of this, they have suffered decline in recent times for several reasons, both man-made and natural. Global Warming is having a negative effect on coral reefs, by way of increased sea-levels and increase in temperature of the seas.
Man is having the greatest impact on this beautiful ecosystem.
Agriculture and pollution - Surface run-off of chemicals and fertilizers damage coral reefs by creating nutrient rich waters, which promote the growth of algae, which is bad for corals.
Leisure activities - Both diving and boating have a negative impact on the corals themselves and by scaring off the wildlife.
With the current rates of destruction, 70% of the world's coral reefs will be lost within 50 years. Because they are so important to the economies of the nations where they are found, governments are implementing Marine Protection Zones to control human activities and minimize the impacts that we have on this natural wonder.
The Great Barrier Reef off the north east coast of Australia, which is the largest reef system on Earth is even visible from space!