Have you ever been down under? No, we're not talking about crawling underneath the kitchen table. We mean Australia!

If you ever visit Australia, you must be sure to check out the Coral Sea off the northeast coast of Queensland. Why? That's where you'll find the world's largest structure made by living organisms — a structure so large it can be seen from outer space. What are we talking? The Great Barrier Reef, of course!

The world's largest coral reef system, the Great Barrier Reef is made up of over 940 islands and 2,900 individual reefs. It stretches over 1,600 miles long across an area of more than 133,000 square miles!

The Great Barrier Reef is made up of and built by billions and billions of tiny organisms called coral polyps. It's one of the world's greatest natural wonders and was named a World Heritage Site in 1981.

It is home to an amazing variety of marine life, including:

  • Over 1,500 types of fish
  • Over 400 types of hard coral
  • One-third of the world's soft corals
  • Over 4,000 types of mollusks
  • Over 130 types of sharks and rays
  • Six different types of threatened marine turtles
  • Over 30 types of marine mammals, including the threatened dugong (sea cow)
  • Over 240 types of birds

Unfortunately, the health of the Great Barrier Reef is threatened today by a variety of factors. Scientists have targeted local fishing practices, pollution, and increased sea temperatures as significant threats to the future of the Great Barrier Reef and the species that call it home.

Population outbreaks of the crown-of-thorns starfish and agricultural runoff are also significant threats. Fortunately, a huge portion of the Great Barrier Reef is protected from human impacts as part of the Great Barrier Reef Marine Park. Despite attempts to limit these threats, scientists estimate the Great Barrier Reef may have lost more than half its coral cover in the last 25 years.

Scientists continue to work on ways to preserve the health of the Great Barrier Reef. It remains one of the most complex natural ecosystems on Earth.

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We sure hope you come to Wonderopolis tomorrow. No one else is here!