Harvesting of Guano
In the 1840s, after the value of guano as an agricultural fertiliser became known, accumulated deposits of seabird guano were stripped from many southern African islands. Then, from the late 1800s until the mid-1980s or early 1990s, fresh deposits of seabird guano were regularly collected at a number of islands off Namibia and South Africa. At Ichaboe Island in central Namibia sporadic guano extraction persisted until 2016. From 1896, annual records of quantities removed from different islands were maintained. Most of the guano extracted from the islands was produced by Cape Gannets Morus capensis and Cape Cormorants Phalacrocorax capensis. Phosphatic sand was at times removed from African Penguin breeding areas at Dassen Island to mix with guano or to spread over breeding areas of Cape Gannets, which build their nests from guano. In southern Africa, the African Penguin, Cape Gannet and Cape Cormorant became known as the ‘guano-producing’ seabirds, although other cormorants and Great White Pelicans Pelecanus onocrotalus would have contributed small amounts to guano depositions at some localities.
Between 1930 and 1971 platforms were constructed by private entrepreneurs to collect guano at Bird Rock, Swakopmund and Cape Cross on the northern Namibian coast, which was mainly produced by Cape Cormorants. Annual records of quantities taken from each platform were maintained. Between 1900 and 1999, an average of c. 5,700 t of seabird guano (after subtraction of additions of phosphatic sand) was extracted annually in the BCLME, with a maximum of c. 9,600 t and a minimum of c. 1,500 t.
Guano extraction sometimes displaced or caused disturbance to seabirds, reducing breeding success. It also created hollows on some islands, allowing rain to accumulate, which on occasion flooded nests of some seabird species and also reduced breeding success.
From: B. Makhado A, Braby R, M. Dyer B, Kemper J, M. McInnes A, Tom D, et al. Seabirds of the Benguela Ecosystem: Utilisation, Long-Term Changes and Challenges. Birds - Challenges and Opportunities for Business, Conservation and Research [Internet]. 2021 Jul 21; Available from: http://dx.doi.org/10.5772/intechopen.96326
Namibia's islands first attracted interest in the early nineteenth century. Merchants, recognising the value of their vast guano reserves, soon stripped the islands of guano and shipped it to Europe where it was used for manufacturing fertiliser and gunpowder.
Although the heyday of guano mining was between the 1840s to 1860s, it continued well into the twentieth century. On Halifax Island, the removal of the guano in the 1930s was devastating to African Penguins that had nested in burrows in the thick guano. In recent years there has been a small recovery with several thousand birds living on the island, however, they were again severely impacted in 2018/19 by an outbreak of bird flu.
From: Atlas of Namibia (https://atlasofnamibia.online/chapter-2/namibias-marine-world)
Harvesting of African Penguin eggs
From the late 1400s, African Penguins Spheniscus demersus and other seabirds in the Benguela Current Large Marine Ecosystem (BCLME) were caught as food by early explorers, as fuel to supply ship boilers and to be rendered down for their fat. However, the primary attraction of African Penguins was their eggs. Collection of these on a large scale may have begun as early as 1652. Details of numbers of eggs collected at different breeding localities are available for each year from 1871–1967 (after which collections ceased) with gaps from 1879–1890, 1894–1896 and in 1904 and 1914.
Annual collections averaged c. 192,000 eggs from 1871–1878, c. 537,000 eggs from 1891–1931 and c. 76,000 eggs from 1935–1967 (see figure below). The overall harvest for the 80 years between 1871 and 1967 for which records were kept was c. 23.4 million eggs, with a maximum of 801,500 eggs in 1899. About 99% of the eggs were taken off western South Africa (84% from Dassen Island), with small proportions coming from southern Namibia (< 1%) and southwestern South Africa (c. 1%). Although ease of access to colonies and of gathering eggs would have influenced localities selected for collections, their geographical distribution approximated that of African Penguins at the time. In the early 1900s, Dassen Island off western South Africa was the largest colony holding an estimated 0.57–0.93 million breeding pairs between 1910 and 1930. In 1956, no African Penguins bred in Angola or northern Namibia. The proportions then breeding in central and southern Namibia and in western, southwestern and southern South Africa were 5%, 25%, 62%, 3% and 5%, respectively.
Trends in total collections of African Penguin eggs and seabird guano in the BCLME, 1871–1999.
At Dassen Island, c. 48% of penguin eggs produced in the early 20th century were collected; this was unsustainable and led to an estimated decrease in the number of penguins there aged two years or older, from c. 1.45 million in 2010 to c. 0.22 million in 1956 and 0.14 million in 1967.
