Isolated in the middle of the ocean, Pacific islands rely closely on fishing for their economy and food security. But global warming could considerably reduce their accessible fish resources over the coming decades. This is what has been revealed in the journal Nature Climate Change, a study by the IRD, the Secretariat of the Pacific Community (SPC) and their French, Australian and American partners. According to IPCC climate forecasts, the quantity of coral reef fish, essential for the inhabitants' food, could drop by 20% by 2050.
Tuna fleeing eastwards
The scientists studied the response of the fish biomass to climate change in the Pacific, according to the forecasts of the intergovernmental panel on climate change (IPCC). Fishing for skipjack in particular, a fish in the tuna family making up 90% of catches, will be seriously affected. According to the models, the rise in surface water temperature, greater in the western ocean, will lead to the migration of tuna towards eastern Polynesia. Thus, catchment areas will move away from the Melanesian coast, the Salomon islands or Papua New Guinea. The exodus of tuna from the territorial waters of these countries will be a significant economic loss. Fishing rights paid by major international fisheries are an important source of revenue for these small insular Nations.
Coral ecosystems threatened
Along the coasts, the availability of coral fish is also under threat. Forecast ocean warming will increase coral bleaching leading to the death of numerous reefs. Population growth in these territories, preserved up to now, will also exert strong pressure on coral ecosystems -- exploitation, damage, pollution, etc. The recovery rate of coral reefs should fall from 40% throughout the Pacific today, to 10 or 20% in 2050. According to the study, this loss will reduce by 20 % the quantity of coral fish, an essential resource for local populations.
Sectors to develop
Some Pacific islands could however turn to aquaculture and fresh-water fisheries. On land, it's a whole different scenario. The expected rise in rainfall, increasing the surface of lakes, rivers, etc. by 10% by 2050, could be beneficial to these activities. In their study therefore, the scientists are encouraging the development of these sectors. To make up for expected losses, they are inviting governments to facilitate access of local fishermen to tuna resources -- for example by installing fish aggregation devices, sorts of floating pontoons that attract them, along the coast. Finally, other fish resources still unexploited, could be drawn upon, such as mackerel, anchovy, sardine, etc.
Minimising the risks by preserving reefs and maximising opportunities: a challenge that the public authorities of these small Pacific Nations will have to face in the coming decades to cope with climate change and the increasing need of their growing population for fish.
- Johann D. Bell, Alexandre Ganachaud, Peter C. Gehrke, Shane P. Griffiths, Alistair J. Hobday, Ove Hoegh-Guldberg, Johanna E. Johnson, Robert Le Borgne, Patrick Lehodey, Janice M. Lough, Richard J. Matear, Timothy D. Pickering, Morgan S. Pratchett, Alex Sen Gupta, Inna Senina, Michelle Waycott. Mixed responses of tropical Pacific fisheries and aquaculture to climate change. Nature Climate Change, 2013; DOI: 10.1038/nclimate1838
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