The first time UQ Marine Remote Sensing Senior Research Fellow Dr Chris Roelfsema went diving on a tropical coral reef in 1988, he couldn’t believe the vast beauty of these precious underwater ecosystems. It was in that moment, awestruck by the colour and calm of the reef, that he decided he would dedicate his life’s work to protecting them.
He remembers the clear tropic waters off the coast of Egypt bustling with sea life and coral of all kinds – a far cry from the frigid, murky Holland lakes he completed his first 500 dives in.
“When I was 14 years old, a friend asked me if I would join him on an introductory dive in a swimming pool with the local scuba dive club, so I did. And since then, the longest interval that I haven't dived was for six weeks,” Dr Roelfsema said.
“In Holland, it was freezing cold and the visibility was maybe three metres – whereas good visibility would be five metres. The water temperature varied between two and 18 degrees and on average was probably eight or 10 degrees – so you can imagine how much nicer it was to be in tropical waters.
“Today, I work to protect the reef simply because I love it. There's no doubt about it – the more we can take care of coral reefs, and the more knowledge we have about it, the better we can manage it and preserve it for future generations, as we need it.”
When Dr Roelfsema was approached in late 2017 to join an international partnership aiming to map and monitor the world’s coral reefs, he and his colleagues from UQ’s Remote Sensing Research Centre (RSRC) were ready to accept the challenge to lead the mapping component.
The Allen Coral Atlas project, named for the late Microsoft co-founder Paul G Allen, was initially funded by Allen’s philanthropic organisation, Vulcan Inc. Allen and the late coral reef scientist, Professor Ruth Gates, had worked together to help the world’s coral reefs and the communities surrounding them with the support of satellite image provider Planet.
ASU’s Professor Greg Asner and his team now lead the project and its monitoring system development, while National Geographic is the engagement lead. Back on home soil, Dr Roelfsema and the RSRC team are the mapping lead for the project.
The Atlas was built using high-resolution Planet Dove satellite imagery and advanced analytics to map and monitor the world’s coral reefs in unprecedented detail.
These habitat maps show the globe’s estimated 230,000 coral reef locations and compositions of coral/algae, seagrass, rock, rubble and sand. The monitoring system developed by ASU uses Sentinel 2 Satellite imagery to assess in bi-weekly time series whether coral bleaching is occurring in the mapped coral habitat if ocean temperatures are above normal.
According to Dr Roelfsema, the process of creating the Atlas was much akin to piecing together a mosaic – but with machine learning and object-based analysis used to expedite the process.
“Our process involved gathering information for set areas on the reef, jumping in the water and taking photos – these are then used to characterise what's there,” Dr Roelfsema said.
“We can’t go everywhere, so we approached the international coral reef community to share data with us, and as such have integrated over 500 data sets – making it a truly joint effort.
“We try to locate field data in such a way that we go to all extremities of the reef. So not only at the nice healthy areas of reefs, but also the not so nice areas too. We map everything, not only coral – but things like seagrass, sand and algae.
“We then combine the information from the field with pixels of the satellite image, and use machine learning to find all other pixels in the satellite images globally that have the same look.
“We use our knowledge of the ecology, depth, waves and characteristics of the reef bottom to clean up the maps, and are guided by the additional data sets and specially developed relationship rules using object-based analysis.”
The RSRC then developed a cloud-based processing approach using Google Earth Engine. This combined depth data and low tide image mosaics, provided by the ASU team, with field data and their machine learning and object-based procedures to produce the maps and a quality assessment.
This extensive process led to the first comprehensive global map of all the world’s shallow coral reefs being published to the Allen Coral Atlas website.
Background image: UQ's Heron Island Research Centre.
Prior to the Atlas, no single consistent data set or map of the world’s reefs was available to stakeholders and researchers that provided information on the seabed. Now, anyone with internet access can view maps and download high-quality data that has never been available at this global scale.
The impact of this international partnership is broad-reaching. The Atlas has improved the capacity for scientists, policymakers and reef managers globally to protect and preserve the reef in real-time.
“The Atlas directly benefits any reef researcher or manager who doesn't have the funding and doesn’t have a map that describes the environment that they’re in charge of,” Dr Roelfsema said.
“For example, Sri Lanka didn't have maps of their reef. We provided the maps, and this had a positive impact because it directly resulted in reef protection by the government.
“More recently, a paper came out where researchers assessed the amount of seagrass in the Central Pacific, and they also used the Atlas to derive this information – making that research possible. So, it's helping facilitate further research and management.”
The Atlas itself is a great tool that can be used in high schools, where students learn more about coral reefs, by downloading and examining the data sets for any reef on Earth.
According to Dr Roelfsema, it’s “mind blowing” to have completed the beta maps of all the world’s reefs, and he hopes that the Atlas inspires users to consider the importance that coral reefs and the surrounding ocean have on our everyday lives.
“There is a quote by marine biologist Sylvia Earle, and she says ‘Knowing is the key to caring, and with caring, there is hope that people will be motivated to take positive actions. They might not care even if they know, but they can’t care if they are unaware.’ And I couldn’t agree more," he said.
“It’s important that people know that they depend on the coral reef, and that their livelihoods are influenced by what's in the ocean. It’s a truly symbiotic relationship, and so we must do all that we can to preserve it.”
"This work could not have been done without the support of UQ's RSRC Coral Mapping Team, the School of Earth and Environmental Sciences and Faculty of Science professional staff, and our many international collaborators. All involved can be proud as they are part of mapping the world's coral reef at a level of detail not seen before."