Page 583 - Atlas Sea Birds Ver1

Guano platforms in Cape Cross Lagoon (photo RJ Braby)

2,000 t in 1990 to nearly 6,000 t in 1923 and then decreased Around the Benguela ecosystem, guano harvests off
to < 800 t in 1975 and 1976 following the collapse of southwest South Africa (from Cape Point to Cape Agulhas)
Namibia’s sardine. Cape Gannet colonies at Mercury, peaked in the 1910s and then decreased, whereas those
Ichaboe and Possession islands contributed substantially in central and south Namibia and west South Africa (from
to the guano harvests at the Namibian islands but numbers Walvis Bay to Cape Town) peaked in the 1920s and
breeding at all three colonies decreased (Sherley et al. then decreased. By contrast yields off the south coast of
2019). The last harvest at Namibian islands was at Ichaboe South Africa (Algoa Bay) peaked between the 1920s and
in 2016.The total recorded collection of guano at Namibian 1980s and guano production off north Namibia peaked in
islands between 1896 and 2016 was c. 292,000 t (Table 2). the 1980s. The trends after the 1920s accorded with the
Guano harvests from 1896–1992 at 18 islands around provision of nesting platforms for cormorants in the north,
South Africa are given in Table 3. The overall collections and with decreases of Cape Cormorants in central and
southern Namibia after the 1970s and in western South
increased from 1,490 t in 2000 to a maximum of nearly Africa after the 1980s. They also matched decreases of
4,300 t in 1926. They then decreased in fluctuating manner Cape Gannets at colonies in Namibia after the 1950s and in
to a final harvest of just 2 t from the harbour breakwater western South Africa after the 1990s, but a recent increase
at Robben Island in 1992. As at platforms and islands in in the Cape Gannet colony at Bird Island, Algoa Bay
Namibia, guano production at South African localities (Makhado et al. 2021). The cessation of guano collections
was influenced by food availability (Crawford and Shelton at Namibian and South African islands was prompted by
1978). The total recorded collection of guano at South both decreasing yields and concern about detrimental
African islands between 1896 and 2000 was c. 166,000 t effects of harvests on dwindling seabird populations (e.g.
(Table 3). Frost et al. 1976, Crawford and Cochrane 1990).

An aerial view of buildings and guano harvested at Ichaboe Island, Namibia. The bagged harvest is outside the settlement’s perimeter
wall (photo RJ Braby)

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