Scripps Institution of Oceanography’s 100 Island Challenge uses 3-D photography to monitor how coral reefs change over time in an effort to help local communities save crucial marine ecosystems.

It seems it’s nothing but bad news for coral reefs. Unchecked coastal development has poured pollutants, sediments and excess nutrients into coral habitats. Overfishing has altered reef ecosystems, home to one-quarter of the world’s marine species, while the extermination of sharks is removing the reefs’ top predator. Meanwhile, much of the carbon dioxide dumped into the atmosphere settles into the ocean, increasing its acidity and disproportionately affecting delicate reefs. That CO2, of course, contributes to rising ocean temperatures, which have triggered the unprecedented back-to-back coral bleaching events of 2014–17 that devastated reefs worldwide.

This 3-D model was collected at Flint Island, Southern Line Islands, Republic of Kiribati. One of the most remote and pristine islands on the planet, Flint Island, and the Southern Line Islands as a whole, offer researchers from the Scripps Institution of Oceanography the rare opportunity to study coral reefs in pristine states over the large-scale physical gradients known to influence reef development.

But a group of coral reef specialists at Scripps Institution of Oceanography at the University of California, San Diego, believes at least some reefs have the potential to survive another major bleaching event. That’s if enough of the right kind of data can be collected on how reefs are changing and local communities can be enlisted to manage their reefs so that they are in optimal health when the next surge in ocean temperatures inevitably occurs.

Their conviction is behind a new project dubbed the 100 Island Challenge, an experiment using cutting-edge imaging technology to survey coral reefs in two and three dimensions.

“Our group is in the minority in that we do have hope that not all reefs are going to be dead in 10 to 20 years,” said Jennifer Smith, coprincipal investigator for the 100 Island Challenge and a professor at Scripps.

She pointed to coral species that have adapted to survive a rise in ocean temperature. “We’ve seen in the last few years places that were suffering massive bleaching but then also showed pretty rapid recovery in some of the places that don’t have a human population,” Smith said. “So there’s this idea that if you can manage your reef locally by having good water quality and healthy fisheries, it’s more likely to recover from bleaching more quickly that a reef experiencing runoff, sewage, overfishing and other threats.”

The idea behind the 100 Island Challenge is to capture the variability among reefs across a variety of natural conditions and document how they change over time under pressures both natural and human-made. “We will be able to determine how reefs are affected by things like warming and local human impacts, and how they might be recovering from pressures such as this most recent massive global bleaching event,” said Smith, speaking by phone from the shores of Catalina Island off Southern California, where she had just concluded a class teaching students how to count fish in a kelp forest.

Principal investigator and Scripps professor Stuart Sandin, Smith and their colleagues strategically selected regions to represent different ranges of ocean productivity, human population density and island elevation. That meant nine combinations of islands the team needed to cover to get a representative cross-section of reefs. The team picked 10 islands for each of the nine types, then threw in 10 more to get to 100. “That number seemed to make more intuitive sense from a project branding perspective,” Smith said with a chuckle.

The project is similar to the 50 Reefs initiative, which aims to identify the 50 reefs that are least vulnerable to climate change and have the potential to contribute to the restoration of other reefs in the future. The project is being run out of the University of Queensland in Australia and is headed by coral scientist Ove Hoegh-Guldberg and ocean activist Richard Vevers, featured in the Sundance award-winning documentary “Chasing Coral.”

“There is no longer any reason not to act as if we’re not in an emergency situation to save coral reefs,” Hoegh-Guldberg said. “Big projects like 100 Island Challenge are really the things we need to do to apply conservation tools, measure the baseline to understand impacts and protect as much as we can.”

Sandin’s and Smith’s approach differs from Vevers’ in how the two projects document reefs. Vevers’ method can be likened to Google Street View, while 100 Islands is more like Google Earth. Vevers’ images are basically linear paths through the sea, while 100 Islands photographs a contiguous 1,000 square-ft (100 square-meter) area that can be modeled in three dimensions back in the lab. Sandin and Smith developed the technique with Scripps postdoc Brian Zgliczynski.

Using belt-transect methodology, a well-worn tool for taking a wildlife census, the scientists will swim back and forth across reef sites counting fish. Researchers will document eight sites at each island, placing permanent markers so they can return to the exact same spot and see how it has changed.

“We’re working to partner with local scientists, managers and NGOs in all the locations where we work,” Smith emphasized, “because we’re not just doing this from an academic perspective – we care about ensuring that all imagery gets into the hands of the reefs’ most important users, who are the people who live on and depend on reefs for their livelihoods.”

Smith has no misconceptions about the difficulties inherent in conducting scientific research below the waves. Custom-made writing slates, data sheets preprinted on underwater paper and sign language are among the tools of the trade for scuba-diving scientists. But nothing can prepare an underwater researcher for a switch in the tide. “You can have good visibility and low current then all of a sudden a wall of green water is moving toward you,” Smith said. “Paying attention to where the boat is and where your buddy is at all times is really important.”

It’s all part of the occupational hazards associated with this effort to save reefs from the warming that’s already baked in to the atmosphere. “We need to manage emissions if we want reefs to be around in 100 years,” Smith said, “but carbon emissions are not going to stop tomorrow and there’s things we can do now to help reefs be as healthy as they can be to weather the storm that’s coming.”