The Great Barrier Reef is one of the most spectacular places on the planet — here's what it looks like as it dies off

• The Great Barrier Reef is one of the most biodiverse places in the entire world, worth billions of dollars.
• But it's in real danger of being killed off as greenhouse gas emissions warm the water and make it more acidic, which causes coral bleaching and can kill it.
• There's a real chance the Great Barrier Reef could be killed within the next couple of decades, leaving a dead structure that could take thousands of years of recover, if it ever can.

One of the most spectacular natural environments on the planet is also one of the most vulnerable, and if people aren't careful, there's a good chance it could be destroyed altogether.

Located off the northeastern coast of Australia, the Great Barrier Reef — made up of more than 3,860 separate coral reefs, according to some measures — is such a massive natural structure that it can be seen from space.

It's home to countless organisms and it's a huge draw for tourism. It's the most biodiverse of all UNESCO Heritage Sites and the most extensive coral reef ecosystem on the planet.

But just like all coral reefs, it's vulnerable to human activity, which means that it's in real danger of dying off.

It's not just local activities like fishing and pollution that damage the corals that make up the Great Barrier Reef, though those do have detrimental effects. The biggest overall threat to reef health — both off the coast of Australia and around the world — comes from the carbon dioxide emissions that cause climate change.

The broader consequences of reef loss are devastating, both for natural environments and for the people that depend on them.

As a recent study in the journal Nature Geosciences explained, the Great Barrier Reef has come back from near-death experiences before — five times in the last 30,000 years. That shows recovery is at least theoretically possible, but in those cases, it took hundreds or thousands of years.

Here's what's happening to make the Great Barrier Reef so vulnerable.

SEE ALSO: The quest to save the fragile reefs Earth's oceans depend on

According to one recent study published in the journal Nature, the Great Barrier Reef is made up of 3,863 coral reefs, with over 400 species of coral building up those reefs.

Source: Nature

Corals are animals — translucent creatures that form huge colonies and create a variety of structures.

Certain types of algae populate the structures, which gives reefs bright colors and helps them derive energy from the sun as well as from nutrients and plankton in the water.

The environments these creatures create are crucial — a quarter of fish species spend some part of their life cycle in reefs, which means their loss could have catastrophic effects on fish populations and the many people who depend on them for food or income.