Millions of tons of plastic waste enter the world's oceans every year, but the impact this has on coral reefs has yet to be properly studied.

Reefs are crucial to the health of the marine ecosystem which humans rely on, but they are dying around the globe. It is estimated that more than 275 million people around the globe are dependent on reefs for food, storm protection and tourism income, highlighting the need to protect them.

Now, a new study, published in the journal Science, has found that around 11.1 billion plastic items are lodged in coral reefs in the Asia-Pacific region and that this waste increases the risk of coral disease from 4% to 89%.

For the study, an international team of scientists examined more than 150 reefs in the Asia-Pacific region between 2011 and 2014, finding plastic on a third of them. Those near Indonesia were the most heavily polluted, while Australian reefs were covered in the least plastic.

The researchers also found that the presence of plastic in reefs meant coral diseases were 20 times more likely to occur. Previous research has indicated that this may be because plastic debris can cause stress to coral by depriving it of light and oxygen, while providing a gateway for pathogens.

Furthermore, the authors also predict that the number of plastic items entangled in coral reefs in the Asia-Pacific could increase to a staggering 15.7 billion by 2025.

As humanity continues to burn fossil fuels, reefs are already under increasing threat from rising ocean temperatures and ocean acidification, which result in harmful coral bleaching. Plastic pollution simply exacerbates these threats.

"Coral disease outbreaks can ravage reefs," Drew Harvell from Cornell University, an author of the study, told IBTimes UK. "These infectious diseases are responsible for huge losses of live coral, especially given that outbreaks often follow bleaching events, doubling the the amount of coral killed."

In this context, cutting down on plastic waste - in addition to reducing other threats such as overfishing - is crucial to give reefs a helping hand in their battle with climate change.

"The results from this new research are sobering, but there is hope if we act now to mitigate the most significant threats facing corals and the vulnerable human communities who depend on them," said Douglas N. Rader, a co-author of the study.

"If we increase the abundance of fish, we can improve the health of coral ecosystems, making them more resilient to climate change and maximizing their value to the people who depend on them. While fighting overfishing does not directly undo disease risks caused by plastic, fixing overfishing could well help offset damage done to individual corals," he said.

Not only do coral reefs contain incredible biodiversity but they are also effective wave-breakers, a feature that will become increasingly important to coastal communities as oceans rise and storms become more frequent with climate change.