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The Tristan da Cunha Archipelago in the South Atlantic Ocean comprises Gough Island, Tristan da Cunha, Nightingale Island, and Inaccessible Island. Gough Island, located about 350 km from the other islands, is approximately 2,700 km from Cape Town, South Africa, and 3,200 km from South America, making it one of the world’s most remote locations. This volcanic island, about 2–3 million years old and 65 km² in area, features steep, rugged cliffs and rises to a peak of 910 m above sea level. The island has a temperate oceanic climate with strong westerly winds, average temperatures ranging from 9 °C in winter to 14 °C in summer, and an annual rainfall of 3,154 mm. Since 1963, rainfall levels have remained fairly constant, though temperatures have risen slightly due to climate change.

Gough Island was first sighted by Portuguese sailors around 1505, with the first recorded landing in 1675 by the British. It was named after Charles Gough, who “rediscovered” it in 1732. Since then, visits have primarily been limited to scientific, cartographic, whaling, and sealing expeditions. In 1938, the United Kingdom declared Gough Island part of the Tristan da Cunha Dependency, and since 1956, South Africa has operated a permanent meteorological station there, staffed by approximately nine people who rotate annually. Human impact on the island has been minimal, though some species of animals and plants introduced since its discovery have been subtly altering its pristine environment.

The plant diversity on the island is relatively low, mainly comprising grasses, sedges, ferns, lichens, bryophytes, mosses, and liverworts. The tallest fern-bush reaches about four meters in height, with most other vegetation remaining low-growing. Gough Island is a vital bird sanctuary, hosting 22 breeding seabird species with over 8 million breeding pairs. Mammals are limited to three species: the sub-Antarctic fur seal and southern elephant seal, which use the island for molting and breeding, and the introduced and invasive house mouse, which has severely impacted local plants, birds, and invertebrates.

Although often overlooked, invertebrates play a crucial role in the ecosystem functioning and nutrient cycling. The island’s invertebrate fauna is relatively sparse by global standards, the low diversity is typical for isolated islands. The island’s indigenous invertebrate species bear similarities to the South American fauna, while many introduced species come from the Northern Hemisphere, suggesting human-mediated introductions. The first official invertebrate study took place during the Gough Island Scientific Survey (1955–1956), reporting 54 insect species (of which 32 were introduced) and other invertebrates such as arachnids, earthworms, mollusks, crustaceans and myriapods (16 indigenous, 11 introduced). The Gough Island Terrestrial Invertebrates Survey (1999–2001) identified 99 insect species (25 indigenous, 70 introduced), four introduced earthworm species and two marine mites (one introduced). Soil mites (Oribatida) collected during the 1999 survey have recently been donated to the National Museum, Bloemfontein. A preliminary analysis has identified nearly 20 soil mite species, six of which may be new to science, while five are introduced species.

One of the most striking features of Gough’s insects is the prevalence of winglessness in native moths, flies and beetles. This evolutionary adaptation helps insects avoid being blown out to sea in windy conditions. These flightless insects mainly inhabit the island’s windy upland areas.

Conservation concerns on Gough Island include the impacts of introduced species and climate warming. Fifteen introduced insect species have been found near the meteorological station, including cockroaches, booklice, wood-boring beetles and weevils, while others are now established across various habitats. The invasive animals can prey on indigenous arthropods (e.g., predatory beetles and mice feeding on local insects), compete for resources (e.g., an introduced isopod has displaced a native species at lower altitudes), alter nutrient cycling rates (e.g., introduced earthworms), and modify habitats. Climate warming could further stress indigenous insects by boosting introduced species’ populations. Of particular concern is the effect of warming on the mouse population, which preys on flightless moths, earthworms, plant material, and bird eggs and chicks, causing an estimated annual loss of over 1.3 million eggs and chicks. In a 2021 eradication attempt, rodenticide was spread across the island, but unfortunately, the operation was unsuccessful, with mice sightings reported soon after. However, the temporary decline in mouse numbers boosted the bird breeding success, providing hope that further intervention could make a difference, also for invertebrates.

Preserving Gough Island’s unique biodiversity requires prevention of further species introductions. Strict quarantine protocols are in place during staff rotations, with routine monitoring around the base to early detect potential new invaders. As the climate continues to change and human impact grows ever subtler yet significant, safeguarding Gough Island’s delicate ecosystem remains crucial for the survival of its extraordinary plant and animal life.

References

Caravaggi, A., Cuthbert, R.J., Ryan, P.G., Cooper, J. & Bond, A.L. 2019. The impacts of introduced House Mice on the breeding success of nesting birds on Gough Island. Ibis 161(3): 648-661. https://doi.org/10.1111/ibi.12664

Fisher, J. 2021. Heartbreak over ‘failed’ bid to remove Gough Island’s mice. BBC News, 15 December 2021. https://www.bbc.com/news/science-environment-59673823

Holdgate, M.W. 1965. The biological report of the Royal Society expedition to Tristan da Cunha, 1962, Part III. The fauna of the Tristan da Cunha Islands. Philosophical Transactions of the Royal Society of London, Series B 249: 361-402. https://doi.org/10.1098/rstb.1965.0015

Jones, A.G., Chown, S.L. & Gaston, K.J. 2002. Terrestrial invertebrates of Gough Island: an assemblage under threat? African Entomology 10(1): 84-91. https://hdl.handle.net/10520/EJC31892

Jones, A.G., Chown, S.L. & Gaston, K.J. 2003a. Introduced house mice as a conservation concern on Gough Island. Biodiversity and Conservation 12: 2107–2119. https://doi.org/10.1023/A:1024190331384

Jones, A.G., Chown, S.L., Ryan, P.G., Gremmen, N.J.M. & Gaston, K.J. 2003b. A review of conservation threats on Gough Island; a case study for terrestrial conservation in the Southern Oceans. Biological Conservation 113(1): 75–87. https://doi.org/10.1016/S0006-3207(02)00351-8

Jones, A.G., Chown, S.L., Webb, T.J. & Gaston, K.J. 2003c. The free-living pterygote insects of Gough Island, South Atlantic Ocean. Systematics and Biodiversity 1(2): 213–273. https://doi.org/10.1017/S1477200003001142

Marshall, D.J. & Chown, S.L. 2003. Marine hyadesiid mites from Gough Island. Hydrobiologia 495, 119–126. https://doi.org/10.1023/A:1025402522573

Reynolds, J.W., Jones, A.G., Gaston, K.J. & Chown, S.L. 2002. The earthworms (Oligochaeta: Lumbricidae) of Gough Island, South Atlantic Ocean. Megadrilogica 9(2): 5–15. https://www.researchgate.net/publication/313707942

Sæther, O.A. & Andersen, T. 2011. Chironomidae from Gough, Nightingale and Tristan da Cunha islands. Zootaxa, 2915, 1–19. https://doi.org/10.11646/zootaxa.2915.1.1

Figures

Figure 1: Two yellow-nosed albatrosses under a fern-bush tree on Gough Island. (With permission from The Royal Society for the Protection of Birds)
Figure 2: Location of Gough Island, with an insert of the island. (From Jones et al. 2003c)
Figure 3: Landscape of Gough Island with the base in the left bottom corner. (Photo with permission from Beneke de Wet)
Figure 4: Flightless insects of Gough Island: (A) crane fly, (B) moth. (From Jones et al. 2003c)
Figure 5: Oribatid mite from Gough Island. (Photo by Lizel Hugo-Coetzee)
Figure 6: House mouse Gough Island. (Photo with permission from Beneke de Wet)

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