Want to save the world’s coral reefs? Just listen to them, say scientists

Coral reefs are regarded as the “rainforests of the seas”, providing a significant amount of Earth’s biodiversity. Around 32% of all named marine species live in and around coral reefs, according to the United Nations Environment Programme (UNEP), making them one of the most diverse habitats in the world.

But reefs are, of course, under serious threat from climate change.

Scientists predict that even if global warming doesn’t go beyond 1.5C above pre-industrial levels, up to 90% of coral reefs might disappear by 2050, due to prolonged ocean heat waves.

Warmer water temperatures can result in the phenomenon known as coral bleaching. This is when corals lose the algae called zooxanthellae living in their tissues, causing them to turn completely white. In 2016, 70% of the world’s reefs were damaged, some irreparably, according to BBC Earth.

But there is hope. And it comes in an unexpected form. It turns out reefs emit sound - and those sounds could be crucial in efforts to save them.

Scientists from the UK have used machine-learning to develop an algorithm able to recognize the subtle acoustic differences between a healthy reef and a degraded coral site. "Our findings show that a computer can pick up patterns that are undetectable to the human ear," marine biologist Ben Williams told Science Alert. "It can tell us faster, and more accurately, how the reef is doing."

To capture the coral acoustics, Williams and his team made recordings at various sites in the Spermonde Archipelago, off Sulawesi in Indonesia. The recordings covered four different types of reef habitat: healthy, degraded, mature restored and newly restored. Each type of reef generated a different sound, depending on the amount of coral cover and the sea creatures living and feeding in the area. The team then trained a machine-learning algorithm to detect the different kinds of coral recordings - with their subsequent tests showing that the AI tool was 92% accurate in identifying reef health.

"This is a really exciting development," study co-author and marine biologist Timothy Lamont told Science Alert.

There are other projects underway to help save coral reefs. The Mars Coral Reef Restoration project in Indonesia - where the AI acoustic experiment was carried out - has installed more than 27,000 “reef stars” on more than 40,000 square metres of ocean bed.

Small coral can be attached to the hexagonal structures to kickstart growth. The steel frames also create protective shells where smaller fish can hide from predators, enticing them to stay and help regenerate the entire ecosystem.

The project has so far resulted in 12 times the amount of coral cover and the Mars team is now training up marine park managers globally to help “establish a worldwide network of competent reef builders”.

But everyone can play their part in helping to keep coral reefs out of harm’s way. As countries recover from the COVID-19 pandemic, the tourism industry is poised for a massive rebound which could recover 58 million jobs in 2022 alone.

The World Economic Forum’s Coastal Tourism Challenge programme encourages innovations that enable tourism-dependent coastal communities to maintain and restore the marine environments on which they depend.

Initiatives range from projects that support coastal ecosystems, to ideas that reduce local dependence on tourism. The best submissions are invited to join a community of innovators, which will help their projects gain visibility as well as get access to expert advice.