Climate change driven redistribution of key commercial tuna species will deliver an economic blow to the small island states of the Western and Central Pacific and threaten the sustainability of the world’s largest tuna fishery, a major international study has found.
UC Santa Cruz Assistant Professor of Environmental Studies Katherine Seto is a coauthor on the new paper, alongside researchers from a consortium of institutions and organizations across the Pacific, North America, and Europe, including the University of Wollongong (UOW), Conservation International, the Pacific Community, the Pacific Islands Forum Fisheries Agency, and the Parties to the Nauru Agreement Office.
The study, published in Nature Sustainability, combines climate science, ecological modeling, and economic data to provide a comprehensive analysis of the impact of climate change on Pacific tuna stocks and on the small island states that depend on them.
The 10 island states of the Western and Central Pacific—Cook Islands, Federated States of Micronesia, Kiribati, Marshall Islands, Nauru, Palau, Papua New Guinea, Solomon Islands, Tokelau, and Tuvalu—are so reliant on their tuna fisheries for economic development and food security that they are considered “tuna dependent”.
The management of most of the islands’ tuna fisheries through a cooperative agreement has been a sustainable development success story over several decades, providing reliable and much-needed revenue for development while preventing the depletion of fish stocks through overfishing. But as the climate changes, key species like skipjack, yellowfin, and bigeye tuna that are currently found largely within the waters of Pacific Island states are projected to shift eastward, out of sovereign waters and into the high seas.
UC Santa Cruz Assistant Professor Katherine Seto noted that, as more tuna move into the high seas, beyond areas of national jurisdiction, they become vulnerable to overfishing.
“Preventing overfishing, and ensuring compliance with fisheries management measures, is more difficult outside the exclusive economic zones of the island states because the sole responsibility for compliance rests with the states that flag the fishing vessels, often resulting in self-regulation,” she said.
Beyond overfishing concerns, the large-scale movement of fish away from sovereign waters could be devastating to local economies on its own.
Around half of the world’s tuna catch comes from the waters of the Western and Central Pacific, and for those 10 small island states, fishing fees from industrial fishing fleets to gain access to their waters accounts for an average of 37 percent of all government revenue (ranging from 4 percent of government revenue for the relatively large economy of Papua New Guinea to 84 percent for Tokelau).
Under a continued high greenhouse gas emissions scenario, as more fish move into the high seas, the total biomass of skipjack, yellowfin, and bigeye tuna in the waters of the 10 Pacific Island states could decline by an average of 13 percent by 2050, said study lead author Johann Bell, the Senior Director for Pacific Tuna Fisheries at the Conservation International Center for Oceans and a Visiting Professorial Fellow at UOW’s Australian National Centre for Ocean Resources and Security.
The potential implications for Pacific Island economies in 2050 include an average decline in purse-seine catch of 20 percent, a loss in regional tuna-fishing access fees of up to $140 million, and reductions in government revenue of up to 17 percent for individual Pacific Island states.
“The greenhouse gas emissions of these small island states are negligible, and yet they are among the most vulnerable to the impacts of climate change,” Bell said. “Many of the island states have very few opportunities to earn income other than from their tuna resources, which are expected to move from their jurisdictions due to ocean warming. This is a climate justice issue that should be raised at the United Nations Climate Change Conference in Glasgow later this year.”
The future for the Pacific Island states looks more promising under lower greenhouse gas emission scenarios, which would lead to smaller losses. Reductions in greenhouse gas emissions in line with the Paris Agreement would provide a pathway to sustainability for tuna-dependent Pacific Island economies. Regional fisheries management organizations can also play a role in helping Pacific Island states negotiate agreements to maximize the economic benefits of tuna, even as the future distribution of fish may change.
