At approximately 574 ha in extent, Robben Island is South Africa's largest coastal island. It lies 11 km from Table Bay harbour in Cape Town and 7 km from Bloubergstrand, its closest point on the mainland. This oval 5 x 2-km island rises 30 m a.s.l. at its highest point. The base rock is Malmesbury Shale and it appears to be a mainland fragment exposed through recent uplifting of the subcontinent. The island was one of the first areas in South Africa to be colonised by European settlers and it has been extensively altered through a long history of human habitation and use. The terrestrial vegetation is dominated by exotic Acacia cyclops, A. saligna and Myoporum serratum, as well as plantations of Pinus pinaster and various Eucalyptus species, which grow in dense stands over large areas. These alien trees, in combination with exotic forbs, create a landscape that is almost completely transformed from its natural state.
African Penguin Spheniscus demersus re-colonised Robben Island in 1983 after an absence of about 180 years. Penguin numbers have increased from nine breeding pairs in 1983 to 2 000 pairs in 1992 and more than 8 000 pairs in 2004, with a decline in recent years to a population of c. 1 600 pairs. The breeding area was only a few square metres in 1983, but by 1996 it had extended to more than 55 ha. The birds nest mainly under trees or bushes in the north and east of the island.
Robben Island also holds the largest colony of breeding Bank Cormorant Phalacrocorax neglectus in South Africa and significant populations of Cape Cormorant P. capensis, Crowned Cormorant P. coronatus, African Black Oystercatcher Haematopus moquini, Hartlaub's Gull Chroicocephalus hartlaubii and Swift Tern Sterna bergii. The Swift Tern and Hartlaub's Gull colonies are the most important along the South African coastline (B Dyer pers. comm.). Swift Tern numbers in particular have increased dramatically at this colony over the past decade. This is in stark contrast to many other breeding seabird species in South Africa. Research projects are under way to ascertain the reasons behind the success of this species. A significant number of Kelp Gull Larus dominicanus breeds on the island, but it is not high enough for this gull to meet the threshold for an IBA congregatory species.
In some years, a large heronry forms in the north-eastern section of the island. The alien thickets support Cape Spurfowl Pternistis capensis and the only 'naturalised' population of Chukar Partridge Alectoris chukar in South Africa. The island also hosts a breeding population of feral Indian Peafowl Pavo cristatus.
The globally threatened species are African Penguin (1 669 breeding pairs), Crowned Cormorant (74 breeding pairs), Bank Cormorant (93 breeding pairs), Cape Cormorant (2 166 breeding pairs) and African Black Oystercatcher (266 individuals). The IBA also hosts 1% or more of the population of African Penguin, Cape Cormorant, African Black Oystercatcher, Hartlaub's Gull (average 1 695 and maximum 3 243 individuals) and Swift Tern (average 9 311 and maximum 12 986 individuals). (Data taken from Makhado et al. 2013 and Sherley et al. 2011.)
A small population of the threatened bontebok Damaliscus pygargus pygargus was introduced to the island, but had been extirpated by 2008. Cape golden mole Chrysochloris asiatica, sand rain frog Breviceps rosei, Cape dwarf chameleon Bradypodion pumilum and the west coast endemic Gronovi's burrowing skink Scelotes gronovii also occur here.
Historically, Robben Island supported huge numbers of seabirds. However, as is the case on all islands off the west coast of southern Africa, piscivorus bird species are under pressure due to a dramatic decrease in the pelagic fish stocks. This is a serious threat to many of the trigger species on Robben Island. Competition with commercial fisheries, especially purse-seining for surface-shoaling fish such as sardine Sardinops sagax, has been identified as one of the most significant factors causing the global population decline of African Penguin. Recent research has indicated that the localised protection of its food resources may result in improved breeding success and survival (R Sherley pers. comm.). However, the African Penguin population on Robben Island has been in steady decline since 2004, decreasing c. 10% per annum.
The high level of human-induced disturbance and activity on Robben Island has resulted in several species ceasing to breed. Human disturbance in the form of uncontrolled tourism activities and high volumes of tourists and associated tourism services is considered to be the major threat affecting birds on the island. There are also approximately 50 people resident on the island who cause disturbance, particularly over weekends when there is little to no law enforcement. This threat can be addressed by establishing specific 'no-go' areas that restrict access and disturbance to breeding birds and by putting up signage that alerts the public, both tourists and residents, to the needs of the bird colonies and the biodiversity of the island. Visitor numbers are expected to increase in the coming years and it is imperative that management actions be put in place to reduce the threat associated with increased human traffic.
Vehicular traffic on Robben Island has been known to disturb and kill penguins. Although road-kills caused by tourist buses as well as residents do lead to bird mortalities, they do not impact on the trigger species in high numbers (estimated at 5–10 adult African Penguins per year (R Sherley pers. comm.). However, the low adult penguin survival rate makes it essential to address every threat affecting the species. Potential mitigation measures such as speed bumps or enforceable speed limits should be investigated.
Many introduced species occur on Robben Island, including 38 exotic plant species that have considerably modified the landscape and occupy a large proportion of it. Introduced mammals have also been present, including black rat Rattus rattus and domestic cat Felis catus, which feed on birds' eggs and young fledglings. Between 1950 and 1975 several ungulate species were intentionally introduced, including eland Taurotragus oryx, springbok Antidorcas marsupialis and steenbok Raphicerus campestris, as well as Ostrich Struthio camelus and European fallow deer Cervus dama. Dedicated programmes to eradicate invasive species have had some degree of success. However, there is still a small population of feral cats on the island and attempts to control them are sporadic.
A threat that is both unpredictable and difficult to control is chronic pollution by crude oil or other pollutants that spill into the ocean when tankers break up. African Penguin is particularly susceptible to such events and a single oil disaster can severely affect the population.
Robben Island is protected as a National Historical Monument and it received World Heritage Site status in 1998. This level of protection, however, is primarily for the historical and cultural value of the site, which is famous as the location where Nelson Mandela and other political freedom fighters were imprisoned during the years of apartheid. A comprehensive Integrated Conservation Management Plan has been drafted for the period 2013–2018 and guides all environmental management activities on the island.
Conservation actions include the control of invasive alien fauna and flora and putting in place artificial nests for African Penguins to replace nest sites in the alien vegetation that is removed when fire-breaks are created. Fire-breaks are being cut in certain areas to reduce the risk of fire to the infrastructure and breeding bird colonies.
In 2012 signage indicating a number of no-go areas was put up to limit disturbance to breeding birds. The signs were sponsored by BirdLife South Africa and SANCCOB, and their procurement and placement was led by a research team from UCT and DEA.
Ongoing research and monitoring projects on the seabird colonies and African Penguin breeding colony include: studying survival rates by means of transponder tags implanted in the penguins, which are read when they pass through an automated reader or are scanned at a nest by researchers; testing the effect of fishing on penguin foraging behaviour and breeding success (the sea around the island was closed to fishing from 2011 to 2013); and monitoring breeding success and chick condition, carried out by the ADU and the Earthwatch programme.
Injured and oiled seabirds found on the island are collected and sent for rehabilitation to SANCCOB.
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