National Geographic expedition studies reef resilience in Marshall Islands

By Ron Rocky Coloma

For scientists, there are still places in the Pacific where the map feels unfinished.

In the Marshall Islands, that sense of discovery is not just about what remains unknown, but what has endured.

A new expedition by National Geographic Pristine Seas is studying some of the region’s most remote atolls, combining modern science with generations of traditional knowledge to better understand how ocean ecosystems survive in a changing climate.

The three-month expedition, launched in partnership with the Marshall Islands government and the Marshall Islands Marine Resources Authority, will survey seven atolls across the Ralik and Ratik chains. The work supports the country’s Reimaanlok framework, a national approach to conservation that centers community leadership and cultural stewardship alongside scientific research.

The effort also comes as Pacific island nations continue to balance economic needs with environmental protection, particularly as climate change accelerates coral bleaching and shifts marine ecosystems across the region.

Juan Mayorga

For Juan Mayorga, the expedition’s science lead, the Marshall Islands represents a rare opportunity to study ecosystems that have remained largely intact.

“Right now, the Marshall Islands is an extraordinary place to be a scientist. Remote atolls have never been surveyed, and others were first studied over seventy years ago. Most are uninhabited, yet all are under centuries of customary stewardship,” Mayorga said.

“It is the perfect setting to study the impacts of a warming ocean in the absence of most human pressures and to answer one of the most consequential questions in conservation: Can a nation sustain a thriving industrial fishery, feed its people and still harbor reefs of extraordinary ecological richness and beauty? The Marshall Islands is actively answering that.”

That question sits at the center of the expedition. While many coral reef systems face declining biodiversity and increasing stress from warming waters, some of the Marshall Islands’ reefs have shown resilience.

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This expedition aims to test how far that resilience extends.

But the research does not begin in the water. It starts on land, with communities.

“It shapes everything, starting long before we cast off,” Mayorga said. “Months ago, we met with mayors and traditional leaders to share our plans and receive their blessing. Before we begin work at an uninhabited atoll, we first visit the community that holds customary stewardship over those waters. We meet, we listen and we receive permission.”

Even atolls without permanent residents are not considered empty. They are tied to communities that have managed and protected them for generations. Researchers from the Marshall Islands Marine Resources Authority will work alongside the expedition team, contributing local knowledge and helping guide the scientific process.

“Reimaanlok means ‘looking to the future, together.’ That is exactly how we approach this work,” Mayorga said.

That collaboration is especially important in places where little scientific data exists. Several of the atolls included in the expedition have not been formally studied, or were last surveyed decades ago.

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For researchers, that creates a rare moment.

“There is a feeling most people recognize: standing somewhere extraordinary and wondering what the first person to ever see it felt,” Mayorga said. “For some of these atolls, and certainly in the deep sea, we will be that person.”

Still, he emphasized that these places are not newly discovered. They have long been known and cared for by local communities. What is new is the scientific record being built around them.

“When we work without prior data, every observation becomes foundational,” he said.

The expedition will span a wide range of ecosystems, from turtle nesting beaches to deep-sea habitats known as the “twilight zone.” Researchers will document bird colonies, coral reefs and shark populations, while also deploying tools such as environmental DNA sampling and deep-sea submersibles.

Among the most anticipated findings are those related to reef health and predator populations.

“The coral reef ecosystem is at its most intact with sharks as its pulse,” Mayorga said. “When they are abundant, the whole food web tends to follow.”

In other parts of the Pacific, recent expeditions have recorded lower-than-expected numbers of sharks. The Marshall Islands, which has designated itself a shark sanctuary, offers a different possibility.

“I am hopeful we will see that reflected underwater,” Mayorga said. “Abundant, healthy sharks would be the most powerful confirmation that this place is thriving. That protection works.”

The team will also revisit sites with historical data, including Enewetak Atoll and Ailinginae. These comparisons could offer insight into how ecosystems respond over long periods, especially in the face of global changes such as coral bleaching.

“What we hope to find is a resilient ecosystem that has held on against all odds,” Mayorga said. “The people of the Marshall Islands have been reading this ocean for thousands of years, and that knowledge does not live in libraries. It lives in its people."

The team is also focused on establishing ecological baselines, records of what healthy ecosystems look like today.

“In a warming ocean, baselines are how we track what we are losing and what is holding on,” Mayorga said.

Scientists say these baselines could help inform future marine protected areas and guide policy decisions, not only in the Marshall Islands but across the wider Pacific.

Storytelling is another part of that effort. “Science measures the ocean. Storytelling makes people care about it,” Mayorga said.

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