A lack of long-term monitoring data on coral cover and fish biomass means trends are limited, which reduces confidence in detecting trends due to climate change. However, increasing average sea surface temperature since the 1970s has not yet resulted in a definitive trend in primary production over the same period, which represents the base of the food web supporting fisheries.
El Niño Southern Oscillation (ENSO) strongly influences the oceanography of the Pacific Ocean and the distribution of tuna fisheries. However, the Pitcairn Islands EEZ is located in an area where ENSO has little to no impact on tuna oceanic habitats. Consequently, the Pitcairn Islands do not experience redistribution of tuna into its waters associated with ENSO cycles.
Low evidence, medium agreement
In general, the confidence is low due to a lack of long-term monitoring. This differs slightly when looking at the impacts of climate change on tuna where confidence is medium.
Increasing ocean temperatures and acidification are expected to affect the health of coral reefs that support coastal fisheries in the Pitcairn Islands. A 20-50% reduction is projected in productivity for demersal fisheries and 5% reduction in productivity of intertidal and subtidal invertebrates in the Pitcairn Islands. This is due to both the direct effects (e.g. impacts of increased SST on fish behaviour) and indirect effects (e.g. declines in fish habitats) of climate change. These effects are not expected to have a noticeable impact on the fish availability per person for food security due to the small population.
Projections do not indicate substantial redistribution of albacore, bigeye, skipjack or yellowfin tuna into the waters of the Pitcairn Islands. Several climate models predict decreases in dissolved oxygen by 2050. The high sensitivity of albacore tuna to oxygen availability may result in albacore decreases in the waters around the Pitcairn Islands. Therefore, the predicted eastward movement of tuna stocks under future climate change is unlikely to deliver significant benefits for the Pitcairn Islands.
Low evidence, medium agreement
Low due to low evidence, but with medium agreement among scientists. This differs slightly when looking at the impacts of climate change on tuna where confidence is medium due to wider regional studies.