Pacific islands ocean acidification vulnerability assessment

The Pacific island region covers an area of more than 27 million km2 and is dominated by ocean. The 22 Pacific island countries and territories are mostly small island states with significant geological, biological, and social diversity. Unsurprisingly, Pacific island people have a high dependence on their ocean resources for food security, livelihoods, and economic revenue, as well as cultural connections to marine environments and animals.

Throughout the tropical Pacific, fisheries and aquaculture make vital contributions to economic development, government revenue, food security, and livelihoods. Climate change, and ocean
acidification, are expected to have profound effects on the status and distribution of coastal and oceanic habitats, the fish and invertebrates they support and, as a result, the productivity of fisheries and aquaculture.

Anthropogenic activities have caused a significant increase in greenhouse gas emissions into the Earth’s atmosphere, with 24–33% of the excess carbon dioxide being absorbed by oceans globally,
changing the chemical composition of seawater. Average ocean pH is now 8.1 and varies seasonally and spatially by 0.3 units. Increased emissions of greenhouse gases have decreased the pH of the tropical Pacific Ocean by 0.06 pH units since the beginning of the industrial era (in the early 19th Century), and the current rate of decrease is ~0.02 units per decade. Ultimately, the pH of the tropical Pacific Ocean is projected to decrease by a further 0.15 units from the historical 1986–2005 period by 2050.

Declining ocean pH will cause dramatic changes in aragonite (calcium carbonate) saturation, with implications for calcifying organisms, such as corals, some plankton, and shellfish. The best available modelling suggests that by 2050, only about 15% of coral reefs around the world will be in areas where aragonite levels are ‘adequate’ for sustainable coral growth. The Pacific island region will experience similar changes and, as a result, oceanic and coastal reef habitats are expected to be modified. Subsequent declines in fisheries productivity of some target species (e.g. reef fish and sea cucumbers) and impacts on calcareous aquaculture commodities (e.g. pearl oysters and marine ornamentals) are anticipated. (…)

Johnson J., Bell J. & Gupta A. S., 2016. Pacific islands ocean acidification vulnerability assessment. Secretariat of the Pacific Regional Environment Programme (SPREP), Apia, Samoa, 40 p. Report.

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