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Site description (2001 baseline):
Site location and context
Possession Island is located 1.6 km from the Diamond Coast of south-western Namibia, just south of Elizabeth Bay, c.40 km south of Lüderitz. This rectangular island is the largest of Namibia’s guano islands. It extends 4 km from north to south and is at most 1 km wide. Low rainfall (less than 10 mm per year) and frequent storms inhibit vegetation growth, and isolated bushes are scattered around otherwise barren and somewhat sandy ground. Old diamond diggings have broken much of the sandy surface. The island still holds a main jetty and the remains of a small village. Like the other guano islands it was stripped of its guano cap in the 1840s and has never regained it. It is permanently manned to keep seals from settling on the island.
See Box for key species. As Possession Island is the largest of the Namibian coastal islands, it has the potential to hold the most seabirds. This honour, however, goes to Ichaboe (IBA NA016) which is 14 times smaller than Possession. Despite the relatively low seabird densities, Possession Island is a vitally important coastal seabird breeding island, supporting over 20,000 seabirds in total. Important species include decreasing numbers of
Spheniscus demersus,
Morus capensis,
Phalacrocorax capensis,
P. coronatus and
P. neglectus (10 pairs). Some of these breeding seabirds have been in decline since the island was first surveyed in 1956. Numbers of
Spheniscus demersus decreased by 92% and numbers of
Morus capensis by 68% over the next 40 years. While some colonies have disappeared altogether, others remain at much-reduced densities. Single pairs are unusual, scattered haphazardly over barren portions of the island. Large areas which were once occupied by breeding birds, now stand unused. This is the only island breeding site of the normally mainland-breeding
Sterna balaenarum. Small colonies of
Sterna balaenarum, that once bred between dunes on the adjacent mainland, have largely disappeared since the early 1970s.
Sterna bergii are said to have nested on the island, but now no longer do.
Haematopus moquini are common on the island.
Non-bird biodiversity: Of great significance was the birth of a calf of Eubalaena australis (LR/cd) in Elizabeth Bay in 1996, the first breeding record of this whale on the Namibian coast for over 100 years.
Pressure/threats to key biodiversity
Like the other 18 islands off Namibia’s desolate Diamond Coast, the 1994 Walvis Bay and Offshore Islands Act brought Possession Island back from South African to Namibian jurisdiction. It now falls under the auspices of the Ministry of Fisheries and Marine Resources, who have a post (unfilled) for a full-time marine ornithologist and have permanent staff on the island. The main purpose is to prevent seals from invading the island and displacing the seabirds, with a view to re-exploiting the guano deposits that may then accumulate. Onshore disturbance is higher than on other islands, as a large diamond mine was established in Elizabeth Bay in 1991. The most important seabird species on this island are
Spheniscus demersus,
Morus capensis and
Phalacrocorax capensis, all of which have suffered serious population declines in the last 100 years, mostly because of overfishing of their main food source. This island has suffered particularly from guano-scraping, as it is relatively featureless and guano was easy to remove. The lack of guano has reduced penguin-nesting habitat to a few peripheral shoreline areas.
Spheniscus demersus populations plummeted from 35,000 birds in 1956 to less than 3,000 birds in 1997. Little guano is currently harvested owing to the severely reduced numbers of birds on the island. Research conducted by the Ministry of Fisheries and Marine Resources includes assessing breeding success of colonial and solitary penguins, and the effect of the numerous parasites on brood-size and growth-rates. Whether guano harvesting will prove viable remains to be seen. Unauthorized landing by fishermen still occurs on the island but disturbance is minimized by Fisheries personnel.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Possession Island (Namibia). Downloaded from
https://datazone.birdlife.org/site/factsheet/possession-island-iba-namibia on 23/11/2024.
