Regional Impacts - South Atlantic

Increase in sea temperature.

Sea level rise will adversely affect nesting beaches and could cause a drop in sea turtle nesting success to nest inundation.

Changes in regional seasonal rainfall patterns could advance the spread of invasive plant species and increase erosion.

St. Helena

Fish stocks and the fishing industry are at the highest risk from climate change.

Changes in air and sea temperatures could influence weather patterns and cause disruption to established wind and rainfall patterns, leading to floods, drought, and/or soil erosion.

Research points to a strong warming trend in air temperature (2°C over 60 years) and a slight decrease in rainfall. Over time, the latter could have implications for local water supplies.

Altitudinal shifts in vegetation zones.

Currently identifiable ecological imbalances could become even more marked

Cooler, less saline water may affect distribution and abundance of the main inshore fauna and flora.

There has been little monitoring of climate-linked changes on Tristan da Cunha and Gough Island, so the full extent of impacts is unknown. However, anecdotal evidence and observation of certain trends point to the several likely changes.

The greatest potential threat is increased invasiveness of introduced species due to warmer temperatures that allow them to thrive and displace more vulnerable native species. Species introduced from South Africa, especially invertebrates and plants, that at one time would not survive, may establish themselves.

The introduction of rats and mice to Tristan de Cunha and Gough Island has already affected the environment and islanders’ way of life. Warmer temperatures could lead to an increase in the mouse population. Species like the Tristan Albatross (Diomedea dabbenena), which is already considered ‘critically endangered’ by mouse predation, would be further threatened by any growth in the mouse population.

There may be a potential risk to the five Seamounts in the islands’ exclusive economic zone.

Costal areas are likely to be affected if there is a rise in seawater, as it could encroach on the native habitat forcing species that breed in the coastal zone, such as the Northern Rockhopper Penguins and Sub- Antarctic Fur Seals, to move further inland.

Although there has been no evidence of a change in rainfall at Gough Island over the last 40 years, older islanders are commenting that there is a seasonal change, and this is also being noticed by other residents.  Instead of the four seasons, winter appears to go straight into summer and the summers seem drier and winters wetter.

Some of the natural ponds/bogs are becoming smaller (either drying up or being taken over by Scirpus and Sphagnum bog grass).

Changes in oceanic circulation patterns due to warming sea temperatures could affect some fish species and could have implications for some of the marine predators (seabirds and seals) that rely on the islands as breeding sites. The islands are the only breeding site in the middle of the South Atlantic for several species; other breeding areas are 2,000 km away.

Tristan da Cunha relies almost entirely on the revenue from fishing, so any negative climate-induced impact on fisheries, such as changes in fish stocks, would be a severe blow to the local economy.