Key climate change effects on the coastal and marine environment around the Pacific UK Overseas Territories

• Climate-driven changes in the central south Pacific Ocean will cause widespread warming of ocean waters, altered circulation, increased stratification of the water column and limited nutrient supply to the surface, decreasing dissolved oxygen, ocean acidification and rising sea levels. These changes will impact marine and terrestrial ecosystems and the communities they support.

• Ultimately, important sectors, such as fisheries and tourism, will be affected by these changes, as will food and water security and essential services, such as energy, transport of goods and coastal protection.

• Coral reefs are unlikely to experience significant heat stress, but should they be impacted by changes in sea temperature, including cold water intrusion, their recovery appears challenging due to the islands’ isolation and therefore the low supply of healthy coral larvae from other reef systems. By the end of the century, even under lowemissions scenarios, acidification conditions in the seawater around the Pitcairn Islands are likely to become marginal for coral calcification.

• Increasing Sea Surface Temperature (SST), ocean acidification and related changes to oxygen concentrations and stratification are expected to affect the health of coral reefs that support coastal fisheries in the Pitcairn Islands, and reduce productivity. Pelagic tuna fisheries are also expected to be affected by climate change with a slight increase in biomass for all tuna species projected for this part of the central south Pacific Ocean.

• Rising sea levels, storm surges, severe storm events and heavy rains will impact infrastructure networks on Pitcairn Island and the safe transport of goods via shipping to the island. Integrating climate change considerations into existing and new infrastructure is essential for building resilience to future climate change impacts.

• Downscaled projections for the Pitcairn Islands (at a relevant scale) will be particularly important for SST, since it is postulated that coral reefs and marine species may be buffered from regional increasing SST due to circulation patterns. This dynamic needs to be examined further to determine if it is in fact occurring or likely to occur, and therefore improve understanding on the potential impacts of increasing SST on marine ecosystems.

Johnson J. E., Dutra L., Starling G., Lehodey P., Loubster D. & Nicol S., 2021. Key climate change effects on the coastal and marine environment around the Pacific UK Overseas Territories. MCCIP Science Review 2021. Report.

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