Benguela Current Marine Ecosystem Sites
Namibia National Commission for UNESCO
Karas and Erongo Regions
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The Benguela Current Marine Ecosystem Sites represent a western boundary large marine ecosystem along the coast of south-western Africa, between 34°S and 15°S, from the South African coast equatorwards towards the Namibia-Angola geopolitical boundary. The ecosystem is characterized by high productivity and defined by the Benguela upwelling associated with the eastern boundary current (Benguela Current) of the South Atlantic subtropical gyre. The Benguela Current is driven by the prevailing South Easterly trade winds of the South Atlantic Ocean. Inshore of the Benguela Current proper, the south easterly winds cause coastal upwelling, forming the Benguela Upwelling System. The principal upwelling center is situated offshore the Lüderitz area in southern Namibia. A marine protected area in Namibia along the southern Namibian coast and adjacent islands is associated with this upwelling area. The upwelling of cold, nutrient rich waters from around 200–300 m depth results in high rates of phytoplankton growth that sustains the Benguela ecosystem.
The intensity of upwelling events is determined by wind strength. Variations in wind strength cause pulses of upwelling, which propagate to the south along the coast with speeds of 5 to 8 m/s. Pulses of upwelling induce biological production. Phytoplankton growth in the Benguela system requires a period of upwelling followed by a period of stratification and relatively calm waters. It is estimated that the annual new production in the Benguela system is 4.7 × 1013 gC/y, making the Benguela system 30 to 65 times more productive per unit area than the global ocean average. Mean annual primary productivity of 1.25 grams of carbon per square metre per year (gC/m2-yr), with primary productivity estimates in some upwelling areas of the Benguela system of >300 gC/m2-yr, have been suggested to be the highest in the world.
The Benguela Upwelling System is one of five wind-driven coastal upwelling systems in the global oceans. The Benguela Marine Ecosystem is an important center of marine biodiversity and is one of the most productive ocean areas in the world due to its distinctive bathymetry, hydrography, chemistry and trophodynamics. The system supports rich fish stocks of sardines, anchovies, horse mackerel, other small pelagic fish as well as zooplankton and crustaceans. The most abundant fishes in the Benguela system are pilchards (Sardinops ocelata), which has been intensely overfished by foreign fishing fleets during the 1950s to 1970s, and anchovies (Engraulis capensis). These species in turn supports a large biomass of larger fish, sea birds and marine mammals.
Small islands immediately offshore the Namibian coast, principally Mercury Island, Ichaboe Island, Halifax Island and Possession Island, support the entire Namibian breeding population of Cape Gannets (Morus capensis), 96% of the Namibian population of the endangered African Penguin (Spheniscus demersus), and nearly one quarter of the global breeding population of Crowned Cormorants (Phalacrocorax coronatus). Approximately 80% of the global population of the endangered Bank Cormorant (Phalacrocorax neglectus) breeds on Mercury and Ichaboe Islands. These various seabirds breed on the islands from where they range tens of kilometres out to sea before returning. Mercury Island alone, which is ca. 3 hectares in size, is home to an estimated 16,000 penguins, 1,200 Cape Gannets and 5,000 cormorants. The endemic Haviside’s Dolphin (Cephalorhynchus heavisidii) and a considerable number of whale species are regularly encountered at sea while vast colonies of Cape Fur Seal (Arctocephalus pusillus pusillus) occur near upwelling centres along the coast, e.g. near Lüderitz, Cape Cross and Cape Frio. Almost 70% of the global population of Cape Fur Seals occur in these Namibian colonies.
The bird guano deposits on these islands attracted thousands of ships during the 1870’s to collect the guano as fertilizer. Early in the 20th century annual harvesting of the bird guano accumulating at nesting sites on the offshore islands started that continue to this day, currently managed to ensure sustainability and to prevent disturbing the sea birds during their breeding seasons. At that time a novel and globally unique guano harvesting industry was pioneered by building wooden platforms at suitable locations near Swakopmund and Cape Cross in Namibia. These platforms provide protected breeding areas for thousands of seabirds, principally cormorants, which are inaccessible to land-based predators such as jackals, brown hyenas and seals. The thick accumulations of bird guano are harvested after the end of the breeding season and marketed world-wide as organic fertilizer.
The Benguela Current also plays a significant role in global ocean and climate processes through heat transfer from the Southern Hemisphere to the Northern Hemisphere. In the regional context the upwelling area imposes extreme aridity over the adjacent continental areas. The Benguela Current developed around 11 million years ago with the expansion of Antarctic ice sheets and changes in global circulation caused by tectonic processes such as the emergence of the Panama Isthmus and rise of the Himalayas and Tibetan Plateau. The upwelling system was fully established around 4-3 million years ago, imposing the atmospheric conditions that resulted in the Namib Desert, the Karoo arid shrublands and the Succulent Karoo Ecosystem.
Justification de la Valeur Universelle Exceptionelle
The Benguela Marine ecosystem is one of the most productive coastal upwelling zones in the global oceans, of which an area offshore southern Namibia is known as the most concentrated and intense upwelling regime in the world. The high levels of primary productivity of this ecosystem support an important global reservoir of biodiversity and biomass of zooplankton, fish, sea birds and marine mammals. Bird guano produced by the large numbers of sea birds resulted in the globally unique guano platforms of Namibia, built at suitable localities on the coast that allows sustainable industrial harvesting of organic fertilizer. Small islands immediately offshore the Namibian coast support the entire Namibian breeding population of Cape Gannets, 96% of the Namibian population of the endangered African Penguin, nearly 25% of the global breeding population of Crowned Cormorants, and approximately 80% of the global population of the endangered Bank Cormorant. Marine mammals include whales, the endemic Haviside’s dolphin and almost 70% of the global population of South African Fur Seals.
Criterion (iv): It was realized during the late 19th century that fertilizers significantly increase crop yields. That resulted in a so-called ‘guano rush’ at islands in the Humboldt Current in the South Pacific and Benguela Current in the South Atlantic to harvest vast accumulations of sea bird guano that accumulated at breeding areas. The limited availability and rapid depletion of natural sources of fertilizer led to the establishment of the global fertilizer industry. Entrepreneurs in Namibia built globally unique platforms of wood at the beginning of the 20th century to encourage bird breeding in order to harvest the bird guano that accumulates at such breeding sites. Industrial-scale sustainable harvesting of organic fertilizer as a result of birds feeding on the rich fish stocks of the Benguela Current continues to this day due to the global demand for fertilizer to enhance agricultural production.
Criterion (ix): The Benguela Current Marine Ecosystem is one of five wind-driven coastal upwelling systems in the global oceans and contains the most productive ocean upwelling centre on Earth. Primary productivity resulting from high rates of phytoplankton growth sustains a globally important center of marine biodiversity and rich stocks of pelagic fish and crustaceans. This in turn supports a large biomass of larger fish, sea birds and marine mammals.
Criterion (x): Many of the marine mammal, sea bird, fish and crustacean species associated with the Benguela Current Marine Ecosystem are endemic to the system or rare elsewhere. For example, Namibian sites associated with the Benguela Current Marine Ecosystem support the entire Namibian breeding populations of Cape Gannets, African Penguins, and Cape Fur seals, while nearly 25% of the global breeding population of Crowned Cormorants and approximately 80% of the global population of the endangered Bank Cormorant occur at these sites.
Déclarations d’authenticité et/ou d’intégrité
The area includes within its proposed boundary all the elements necessary to express its Outstanding Universal Value. Breeding populations of fish, seabirds and marine mammals are strictly controlled through appropriate Namibian legislation. Harvesting of appropriate species are determined through annual monitoring missions that determines Total Allowable Catch (TAC) that are allocated to operators through a quota system.
The Benguela Current Marine Ecosystem, as is the case for all the very productive marine ecosystems of the world, suffer from overfishing, marine pollution, introduced species, and issues related to global commerce. Aspects related to global climate change may also impact on the Benguela Large Marine Ecosystem in future. However, the sites selected to represent the Benguela Current Marine Ecosystem are far removed from major shipping lanes or fishing areas, thus the direct impacts of these global problems is less severe than elsewhere in the Benguela system. Fish stocks in Namibian waters have been severely impacted prior to 1989 by foreign fishing fleets due to the inapplicability of international laws regulating such activities. The Namibian government has implemented strict controls since the country’s independence to ensure recovery of the fish stocks, ensure sustainable harvesting, regulate fisheries and encourage the emergence of a national fishing industry. Interannual variations in the strength of the upwelling system and marine production hamper the degree to which the effectiveness of these measures can be evaluated.
The sites considered to represent the proposed area are part of a Marine Protected Area in Namibia, are coastal conservation areas or are private property that have been managed for almost 100 years on a sustainable basis. All these sites harbour globally significant populations of species, provide protected breeding areas through national legislation, and adequately express the values for which the area will be nominated.
There is no offshore mining or petroleum exploration in the sites that will represent the Benguela Current Marine Ecosystem. The annual harvesting of bird guano from the islands and bird platforms are part of the outstanding values of the sites.
The wooden guano platforms are still in their original form as constructed early in the 20th century. Annual maintenance of the platforms is carried out after guano harvesting or damage by storms. The technology for harvesting guano has changed very little since the early part of the 20th century and still involves scraping, shovelling and bagging the guano that has been produced.
Comparaison avec d’autres biens similaires
There are five coastal currents worldwide associated with significant upwelling areas in the global oceans, of which four eastern boundary currents comprise the most important upwelling zones globally. These are the Benguela Current (offshore western southern Africa), the Canary Current (offshore Northwest Africa), the California Current (offshore California and Oregon) and the Humboldt Current (offshore Peru and Chile). A minor upwelling area is associated with the Somali Current (offshore Somalia and Oman). Within this context, the area of permanent upwelling offshore Lüderitz in Namibia is the strongest upwelling zone in the world. Although all these upwelling areas support major fisheries, the Benguela Current Marine Ecosystem is recognized as one of the most productive areas in the global oceans.
Various reports from the World Heritage Marine Programme identified the Benguela Current ecosystem (Hillary et al. 2002; IUCN 2004; Spalding 2012) as a priority area for future action.
There no global comparison to the annual guano harvesting for fertilizer from constructed bird nesting areas. Harvesting of organic fertilizer such as bat guano from caves or animal faeces from stockyards is unlike the purpose built bird platforms of Namibia that entices wild species to utilize a specific location by providing a protected environment. Contemporary harvesting of other avian resources such as the nests of cliff-breeding swallows for food also does not involve man-made provision of a suitable habitat.