Scientists map coral reefs off northern Australia

Over 1,000 previously unmapped coral reefs have been discovered stretching across northern Australia, with scientists identifying the massive marine habitats without leaving the office.

Led by the Australian Institute of Marine Science (Aims) in partnership with the University of Queensland, the Marine and Coastal Hub project has mapped a vast stretch of underwater ecosystems from Western Australia’s Houtman Abrolhos through to western Cape York in Queensland.

Hidden beneath sediment-rich waters, the reefs have largely been invisible to conventional surveys and historically overlooked in conservation and coastal development planning. Previously, the best mapping of the northern coastline was found on maritime charts that failed to distinguish between coral and rocky reefs, as they were designed simply to warn vessels to stay clear of hazards.

Aims e-Atlas project manager Eric Lawrey said the breakthrough was 12 years in the making, sparked by the rise of satellite imagery such as Google Earth. eAtlas is a website and mapping system that contains research, maps and data for tropical Australia.

While most people were zooming in on their own homes, Lawrey was scanning the northern Australian coastline, noticing what appeared to be coral reefs and wondering why they were absent from official maps. The challenge, he noted, was that even on a clear day, the reefs were obscured by the region’s highly turbid water.

“If you look at any one satellite image, the water just looks like turquoise paint and you can’t really see reefs,” said Lawrey.

“But if we overlay 200 images of the area, taken at different times, to create a composite image, all the swirly patterns of the moving water move around and average out while the reefs are constant,” he added. “Their signal gets reinforced and they become much clearer. It allows us to peek deeper into the water column than we could in one image.”

The digital expedition required 700 hours of painstaking work to digitise and classify the reefs. The effort has resulted in the first comprehensive view of coral reef boundaries across northern Australia, successfully mapping more than 3,600 coral reefs and 2,900 rocky reefs.

Lawrey noted the region harbours a similar quantity of reefs to the Great Barrier Reef, albeit much smaller in individual size.

“It’s a vast set of reefs that’s been largely unknown about,” he said. “Well, maybe I should say unmapped, because I'm sure people that are there, or locals, know about all these places.”

Funded by the Australian government under the National Environmental Science Program, the project's success was almost a victim of its own ambition. “The number of reefs we found inshore was a surprise,” said Lawrey. “It became a bit of a problem for our project because we had to map so many of them.”

The final datasets have been made openly available through public data portals, such as eAtlas. By revealing what lies beneath the northern coastal waters, the project is expected to pave the way for stronger environmental protection of marine ecosystems that have spent decades hidden in plain sight.

Aims has been at the forefront of leveraging technology to monitor and protect Australia’s marine ecosystems. In 2021, it teamed up with Accenture to monitor the health of coral reefs using computer vision.

Using a database of underwater imagery, the technology has automated the analysis of coral ecosystems, allowing researchers to track reef health and understand how specific coral species respond to stressful scenarios, such as devastating coral bleaching events.