Located 155 miles northwest of the Hawaiian Archipelago lies one of the world’s largest marine protected areas: Papahānaumokuākea National Monument. Only recently overtaken by Antarctica’s Ross Sea, the monument boasts a large, tropical, and biodiverse community. The fishing exclusion zone of Papahānaumokuākea covers 583,000 square miles, an area larger than all national parks in the U.S. combined, since President Barack Obama quadrupled its size in 2016. In addition to extending the monument’s boundary, President Obama prohibited commercial fishing out to the 200-mile limit of the exclusive economic zone. International and unclaimed waters beyond 200 miles from the Hawaiian coastlines still remain open for commercial use. However, with an area this vast, ecologists and economists hoped the U.S. reserve would effectively protect the over 7,000 marine species native to the area.
Researchers know that marine protected areas (MPAs) protect endangered species vulnerable to coral bleaching, ocean acidification, and warming seas. Coral reefs in MPAs, although among the healthiest in the world and far from direct human interaction, are impacted by global shifts. Papahānaumokuākea serves as a sanctuary for endangered populations like blue whales, sea turtles and Hawaiian monk seals. A quarter of the species found in the monument are found nowhere else in the world, so this exclusion zone plays a key role in maintaining biodiversity in Pacific seas.
However, experts believed that conservation efforts through all kinds of MPAs were largely ineffective when addressing species targeted by fisheries, like tuna. Because fish travel long distances, it was assumed no MPA would be large enough to shelter these populations and allow for recovery. Papahānaumokuākea, however, is over four times the size of California. Researchers at the University of Hawai’i at Manoa knew the reserve could challenge this assumption.
A study published in Science in October of this year demonstrated spillover benefits from Papahānaumokuākea into increased fishing yields in the surrounding waters for tuna species central to Hawaiian diet and culture. Fisheries operating just outside the exclusion zone experienced benefits not directly intended by the reserve; instead, they noticed positive consequences of the intended conservation of all ecosystems in the monument. Since the reserve expanded, yellowfin tuna catch rates have increased by 54% and bigeye by 12%. Ahi, referring to both yellowfin and bigeye tuna, is seen as a focal point in local Hawaiian weddings, family gatherings, birthdays, and graduations. When data showed a decrease in tuna numbers during the decades leading up to Papahānaumokuākea’s expansion, researchers knew fishing without restricted areas could lead to the collapse of these culturally important species. Data collected on fishing boats displays quantifiable impacts for efforts located nearby the reserve by comparing catch rates both near and far from the boundaries of Papahānaumokuākea before and after the 2016 expansion. For a species previously in decline, these numbers provide hope of sustainable harvesting in the long run.
Environmental economists working at the University of Hawai’i also evaluated catch increases at the level of individual fish, finding that the reserve still supports a higher yield. This proves that what was observed is not due to more hooks being in the waters around the protected area, because fishing effort was accounted for within the model researchers used. Exactly what experts expected, average yield per effort, increased along the edges of the no-fishing zone. The study also accounted for the possibility of an ocean-wide increase in tuna and found that catch size closest to the reserve increased regardless of larger population fluctuations.
Spillover benefits from marine protected areas had not been demonstrated in detail previously, but now there is evidence that reserves are effective not only from an ecological standpoint, but also from an economic one. The global tuna industry generates $40 billion in revenue annually.
The fish provide employment and food all over the world. They also present ecological importance: tuna species are both a predator and important food source for ocean systems, working to maintain balance amidst a time where environments are rapidly changing.
Unfortunately, as the authors of the study suggest, these results are only a starting point for further analysis into MPAs. Currently, less than 10% of the ocean is covered by MPAs. Of this figure, 72% is concentrated within thirty-six established reserves. Papahānaumokuākea happens to be the largest reserve. Because research was done dealing with such a large MPA, it may be too soon to generalize spillover benefits to smaller MPAs in other areas of the world. At the same time, many MPAs prove less effective because of their location. What scientists have discovered over the past thirty years is that tuna do not venture far from home; their spawning grounds are where they spend a large portion of their lives. Establishing a reserve in the known nursery grounds of the Hawaiian Islands provides a good chance the conservation efforts will have lasting impacts.
Despite the uncertainty that lies ahead in MPA research, spillover effects in Papahānaumokuākea suggest that there is hope. MPAs that have been established with goals of similar benefits should not be easily dismissed as ineffective. There are over 11,000 smaller MPAs worldwide that lack the data for proper economic and ecological analysis. While this is just the beginning of quantifying MPA success, research on Papahānaumokuākea demonstrates that these 11,000 sanctuaries stand a chance at being impactful now and in the future for species and ecosystems in need of recovery.
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Sarah, Medoff, et al. “Spillover benefits from the world’s largest fully protected MPA.” Science, vol. 378, no. 6617, 2022, pp. 313-316. Science, https://www.science.org/doi/10.1126/science.abn0098.
“Study shows benefits of protection in Papahānaumokuākea ʻAhi recovery up, more fish caught thanks to no-fishing zones.” Papahānaumokuākea Marine National Monument, 21 October 2022, https://www.papahanaumokuakea.gov/new-news/2022/10/21/ahi-recovery/. Accessed 2 December 2022.
Vernimmen, Tim. “The world’s biggest marine reserve seems to be doing its job.” National Geographic, 20 October 2022, https://www.nationalgeographic.com/environment/article/the-worlds-biggest-marine-reserve-see ms-to-be-doing-its-job? Accessed 2 December 2022.