The Case for Strengthening Marine Protections in the Austral and Marquesas Islands

Overview

French Polynesia is home to the world’s largest continuous exclusive economic zone (EEZ), covering nearly 5 million square kilometers (2 million square miles)—an expanse equal to the land area of the European Union. The entire EEZ is designated as the Tainui Atea marine managed area, which spans 118 islands across five major archipelagos: the Austral, Gambier, Marquesas, Society, and Tuamotu. Within Tainui Atea, the government has established two large-scale, no-take marine protected areas (MPAs) and is now working to create more.

The Austral and Marquesas islands, two of the most remote of those archipelagos, harbor rich marine life and natural beauty that contributes greatly to French Polynesia’s economy, particularly tourism and fishing. Their isolation has produced remarkably high levels of species found nowhere else and has left their ocean habitats largely intact.¹

Both archipelagos provide habitat for species classified as overfished, endangered, or critically endangered under international assessments, including oceanic whitetip sharks, Galápagos sharks, and multiple cetaceans. A recent study using tracking data confirms that these waters function as migration corridors for many of these species and that the Marquesas waters are a spawning area for bigeye and yellowfin tuna as well.²

For more than a decade, elected officials and local communities in both archipelagos have called on the French Polynesian government to establish large-scale highly or fully protected areas around their islands. In the Australs, the councils of all five inhabited islands have formally proposed the creation of the Rāhui Nui nō Tuha’a Pae large marine reserve, covering approximately 1 million square kilometers (386,000 square miles).

In 2018, the Marquesas council of mayors (known as CODIM) formally proposed a 430,000-square-kilometer (166,000-square-mile) MPA called Te Tai Nui a Hau—“the big peaceful ocean.” Both proposals would prohibit industrial extractive activities while preserving locals’ artisanal fishing rights.

In June 2025, French Polynesian President Moetai Brotherson signed a law fully protecting the waters around the Society and Gambier Islands. His administration has also committed to adding similar safeguards across at least 500,000 square kilometers (193,000 square miles). This would create the world’s largest network of fully protected MPAs. Work to finalize these designations, including their management, financing, and enforcement mechanisms, is ongoing.

This fact sheet lays out the science supporting the establishment of the new MPAs in the Austral and Marquesas islands.

Joe Fish Flynn Shutterstock

Marquesas Islands: A marine wilderness of global significance

In July 2024, UNESCO recognized the Marquesas Islands—known as Te Henua Enata  (“the land of men”) in the Marquesan language—as a World Heritage Site for their cultural and natural value.³ The designation identified the archipelago as a biodiversity hot spot that is home to irreplaceable and exceptionally well preserved marine and terrestrial ecosystems.

In fact, UNESCO noted that Marquesan waters are among the world’s last marine wilderness areas—virtually free from large-scale industrial activities.

In part because these waters are so undisturbed, they sustain what scientists call a perennial “island mass effect,” in which nutrient-rich waters produce a phytoplankton bloom so dense that it is visible from space.⁴ This bloom supports productivity across all levels of the food chain, creating one of the most biologically rich marine ecosystems in the tropical Pacific.

That is just one of the numerous pieces of scientific evidence of the archipelago’s importance. Others include a 2015 scientific expedition that documented 495 coastal fish species in the Marquesas, 68 of which are found nowhere else on Earth—an endemism  rate of 13.7%.⁵ That ranks the Marquesas as the third-highest region for coral reef fish endemism in the Indo-Pacific region, behind only Hawaii and Rapa Nui (Easter Island).⁶

The Marquesas are also home to 20 species of sharks—including the critically endangered and highly migratory scalloped hammerhead (Sphyrna lewini) and oceanic whitetip (Carcharhinus longimanus)⁷ —along with manta rays, whales, dolphins, turtles, and one of the most diverse seabird communities in the tropical South Pacific. The archipelago is also one of the few known breeding sites in the world for 22 bird species, including the endangered Polynesian storm-petrel (Nesofregetta fuliginosa) and Phoenix petrel (Pterodroma alba), along with Murphy’s petrel (Pterodroma ultima), which ranges thousands of kilometers across the Pacific between feeding trips.

Further, the archipelago was designated an Important Marine Mammal Area by the International Union for Conservation of Nature’s Marine Mammal Protected Areas Task Force in 2021.⁸ Spinner dolphins in the Marquesas are genetically distinct from other Pacific populations—meaning that these animals carry evolutionary adaptations that exist nowhere else. Losing such populations could have untold consequences for other species and the broader ecosystem. Further, melon-headed whales in the Marquesas display a globally unusual pattern of aggregations across multiple islands, a behavior that could play a role in ecosystem balance there.⁹

And the ocean around the Marquesas forms part of the broader Pacific tuna belt, serving as a key spawning area for yellowfin and bigeye tuna and helping to sustain some of the most commercially valuable fisheries in the world.

Sharp Photography

The Austral Islands: Rich ecosystems, deep roots in conservation

The Austral Islands—French Polynesia’s southernmost archipelago—lie in relative isolation between Australia and South America. Spanning one-fifth of French Polynesia’s waters, the Australs contain five inhabited islands—Rimatara, Rurutu, Tubuai, Raivavae and Rapa—and the uninhabited Maria Atoll and Marotiri rocks.

Part of a key biological network

The archipelago sits between tropical and temperate zones, creating the only “temperate-tropical” transition ecosystem in French Polynesia and supporting species assemblages that overlap with those of New Zealand’s Kermadec Islands and the Pitcairn Islands, a British overseas territory.¹⁰

A comprehensive scientific inventory compiled in 2014 by Pew and the Institute for Pacific Coral Reefs (IRCP-CRIOBE), based on input from 30 experts across four field expeditions,¹¹ found that the waters off the island of Rapa alone harbor 112 coral species, 150 algae species, and 383 species of coastal fish, 10% of which exist only there. Research published in 2019 identified Rapa as one of the last confirmed marine predator refuges in the entire Indo-Pacific—a remote site where large predators still dominate the food web as they did before industrial fishing.¹² That status makes Rapa irreplaceable in the global conservation portfolio.

Across the archipelago, the inventory identified 455 species of mollusk, with more than 20% of them—98 species—endemic. The Australs also host three species of sea turtles, 10 marine mammal species, 14 shark species, four ray species, 60 pelagic fish species, and the most diverse array of seabirds in French Polynesia, with 23 of the territory’s 28 breeding species. Further, the crystal clear waters off Rurutu are among the best locations on Earth to observe humpback whales.¹³

French Polynesia's 2023 Tainui Atea management plan identifies the archipelago's seamounts as a priority for research and protection. These underwater features disrupt deep ocean currents, pulling nutrient-rich water toward the surface that then attracts concentrations of marine life—fish, sharks, and mammals—that would otherwise be dispersed across the open ocean.¹⁴

Seamounts also carry significant cultural importance to local communities. A 2025 study commissioned in coordination with Pew Bertarelli Ocean Legacy found seamounts named in oral tradition, and some specific ones tied to family lineages and governed for generations with rules for access and seasonal closure.¹⁵ The Arago seamount, for example, is linked to the Teariki family of Rurutu and figures prominently in regional fishing tradition.

The study points toward a need to respect local culture and customs in government ocean protections, especially given that Polynesians have successfully stewarded their environment for millennia. For example, the Austral communities have a deep tradition of marine stewardship rooted in rāhui—the Polynesian practice of allowing ecosystems to recover by restricting human activity within them. The island of Rapa has long maintained a coastal rāhui, and the five inhabited islands have collectively proposed that any marine reserve be managed through a governance structure—a central committee for the archipelago alongside local committees for each island—that honors the rāhui tradition.¹⁶

Protection would bring opportunities for new discoveries

Another potential benefit of expanding ocean protections in the Austral and Marquesas islands is the chance for scientists to discover new species, some of which could directly benefit humankind if, for example, they are found to have uses in medicine, as some marine life has in the past.

Two recent studies show how much marine biodiversity in French Polynesia has gone undocumented. A 2023 molecular survey identified more than 100 distinct sponge species in French Polynesian waters.¹⁷ A separate study published the same year combined traditional taxonomy with DNA barcoding—a technique that reads genetic markers from physical specimens to distinguish species that look identical under a microscope—and produced a revised inventory of 702 marine plant and algae species, roughly double the previous count.¹⁸

The genetic data revealed two findings that matter for conservation planning. First, each of French Polynesia’s five archipelagos contributed a distinct set of species, with many found in only one place. From a biodiversity standpoint, that means that protection in one archipelago does not carry over to the others. Second, a significant share of the species detected through DNA barcoding have not yet been formally described, meaning that the 702 species count may be conservative.

Protections would also benefit high-seas fisheries

By acting now, while fishing pressure on these waters remains relatively low even as activity on the surrounding high seas increases, the French Polynesian government would help sustain healthy ecosystems that support artisanal and commercial fisheries within its waters and contribute to the recovery of tuna stocks across the wider Pacific.¹⁹

For example, bigeye tuna is one of the most commercially valuable tuna species in the Pacific and faces fishing pressure, including of juveniles, elsewhere in the region. By protecting bigeye spawning areas around the Marquesas, the government could safeguard a community of tuna that continually replenishes the regional stock.²⁰

This approach complements the United Nations Agreement on Marine Biodiversity of Areas Beyond National Jurisdiction—also known as the BBNJ treaty or High Seas Treaty—which creates the first legal mechanism for establishing MPAs in international waters and sets new standards for environmental review of activities on the high seas.²¹ It also reflects the growing scientific agreement that designating large-scale offshore MPAs on a precautionary basis helps to maintain ecosystem functions and pelagic habitats amid rising high-seas fishing pressure.²²

In one relevant precedent, researchers in 2016 found measurable spillover of yellowfin and bigeye tuna from the Papahānaumokuākea Marine National Monument near Hawaii into adjacent fisheries, an outcome they attributed to protection inside the boundary.²³ At approximately 1.5 million square kilometers (579,000 square miles) and highly protected since 2016, Papahānaumokuākea is comparable in scale and remoteness to the proposed Austral and Marquesas designations.

Other research has also found that protecting intact spawning and nursery habitat creates source populations that replenish stocks that are under pressure in surrounding waters.²⁴

For the Austral and Marquesas—where artisanal fishing is central to food security and local economies—acting before external fishing pressure escalates further is a science-based strategy.

Low-cost, effective surveillance technology

Fortunately, the French navy maintains a permanent patrol capability in French Polynesia and can leverage recent technological advances to monitor such large MPAs. Specifically, the navy uses satellite synthetic-aperture radar, which detects more than 95% of vessels longer than 50 meters and approximately 80% of vessels between 25 and 50 meters—the size classes that conduct industrial fishing—regardless of whether their tracking transponders are active.²⁵

Overwhelming community support

The vast majority of French Polynesians support establishing MPAs in the Austral and Marquesas islands. A 2024 poll of 1,378 of the territory’s residents, commissioned by Pew Bertarelli Ocean Legacy and conducted by Alvea Consulting, found that 92% of respondents back the safeguards, an increase from 78% and 73% support for the Rāhui Nui nō Tuha’a Pae and Te Tai Nui a Hau proposals, respectively, in 2019.²⁶ In the 2024 poll, nearly 80% of respondents also said that the ocean is insufficiently protected and that they favored conservation measures covering more than half of the territory’s waters and lagoons.

Climate adaptation value

Studies show that ocean areas with large-scale, strong, comprehensive, and long-term protections are more resilient to climate change than are unprotected areas. Experts say French Polynesia's existing marine protections may be one reason the region is experiencing milder climate impacts than in other parts of the world.²⁷

And, in fact, the lower projected climate impact in French Polynesia makes its protected reefs particularly valuable as refugia for a wide variety of species.²⁸

As ocean warming, acidification, and extreme events intensify across the Pacific, maintaining intact, protected ecosystems in lower-exposure regions becomes increasingly important for preserving functioning systems that can serve as source populations for recovery in areas that experience more severe impacts.²⁹

Conclusion

Given the strong scientific evidence, community support, and economic rationale for extending full protection to the Austral and Marquesas archipelagos, Pew Bertarelli Ocean Legacy encourages the government of French Polynesia to deliver on its commitment and designate new MPAs. Doing so would honor the rāhui tradition, help meet the food security and cultural needs of island communities, and contribute to healthier and more sustainable fisheries throughout the Pacific region.

Endnotes

1. Bernard Salvat et al., "Environnement Marin Des Îles Australes," The Pew Charitable Trusts and Institut Recifs Coralliens Pacifique, 2015, https://www.pew.org/-/media/assets/2016/01/environnementmarindesilesaustrales.pdf. Rene Galzin et al., "Diversity of Coral Reef Fish at Rapa Island (French Polynesia)," Cybium 30 (2006): 221–34, https://www.researchgate.net/publication/286979685_Diversity_of_coral_reef_fish_at_Rapa_Island_French_Polynesia. Jean Tröndlé and Michel Boutet, "Inventory of Marine Molluscs of French Polynesia," Atoll Research Bulletin (2009): https://repository.si.edu/items/749a3e56-e89b-4e9f-91db-5ce10e632f19. Jean-Yves Meyer and Elin Claridge, Terrestrial Biodiversity of the Austral Islands, French Polynesia (Paris: French National Museum of Natural History, 2014). Patrick Weigelt, Walter Jetz, and Holger Kreft, "Bioclimatic and Physical Characterization of the World's Islands," Proceedings of the National Academy of Sciences 110, no. 38 (2013): 15307–12, https://www.pnas.org/doi/10.1073/pnas.1306309110.
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