New research reveals the dire threat that climate change poses to coral reefs, one of the most important ecosystems in the world.

Within 20 years, 70-90% of coral reefs will likely die. By 2100, there could be few to none left.

Photos show what vibrant reef systems currently look like, and what could happen to them in the future because of climate change.

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Coral reefs are dying.

Between 70% and 90% of all reef systems could disappear within the next two decades because of pollution and climate change, according to new research.

That projection, which researchers from the University of Hawaii Manoa presented at annual Ocean Sciences Meeting last week, suggests that by the end of the century, there could be few to no suitable sites for coral reefs anywhere in the world.

Coral reefs cover less than 1% of Earth's surface, but they provide a home for over 25% of all marine life. Millions of people rely on them for food, medicine, protection from storms, and employment in tourism sectors.

But corals are highly sensitive to water temperature, and climate change is causing oceans to warm and become more acidic. Some studies suggest half of the world's coral reefs have already died.

The new research also found that by the end of the century, there will be very few locations where human efforts to restore coral habitats would be viable at all.

"Trying to clean up the beaches is great, and trying to combat pollution is fantastic. We need to continue those efforts," Renee Setter, the lead researcher on the project, said in a statement. "But at the end of the day, fighting climate change is really what we need to be advocating for in order to protect corals and avoid compounded stressors."

Here's what bright, biodiverse coral reefs look like, and the dead shells they could become.