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Site description (2001 baseline):
Site location and context
De Hoop Nature Reserve is situated near the southern tip of the African continent, c.56 km east of Bredasdorp. This reserve comprises a unique diversity of natural habitats and it is situated in the heartland of a mosaic of grainfields and wheat pastures. The reserve holds the Ramsar-designated De Hoop Vlei, a coastal lake, which formed when the mouth of the Sout river was blocked by the emergence of estuarine sandbars, creating a landlocked, brackish expanse of water, separated from the ocean by 2.5 km of mobile sand-dunes, and fed by the Sout and Potteberg rivers and by several springs.
The lake is c.15 km × 500 m in extent and its depth varies considerably, reaching a maximum of 8 m during periods of flooding, which may persist for several years. During floods, large areas of adjacent land, mainly to the south-west, are inundated. On the other hand, the lake has dried up completely during drought periods. Salinity can vary considerably, with fluctuations of between 3 and 49 being recorded over a three-year period. The dominant aquatic plants are
Ruppia and
Potamogeton. Marginal vegetation includes small reedbeds
Phragmites and patches of sedge-marsh
Scirpus.
Surrounding the lake are localized forest patches of
Sideroxylon,
Celtis and
Euclea. The coastal plain supports dune fynbos, with proteoid fynbos farther inland. The Potberg mountain range, which rises abruptly in the north-eastern part of the reserve, is an inselberg of sandstone and quartzite. The isolated and unique nature of this mountain has resulted in the evolution of an unusual dry mesic heath, holding many species endemic to the mountain.The reserve’s astonishing terrestrial diversity is coupled with a rugged coastline, which is gently concave and faces the broadest part of the Agulhas Bank. The meeting of the icy Benguela and warm subtropical Agulhas currents offshore contributes to the variety of habitats, both terrestrial and marine, found within the reserve. The marine system is dominated by various marine algae such as kelp
Ecklonia,
Macrocystis,
Ulva and
Laminaria. There is an area of shifting dunes at Koppie Alleen which covers some 1,000 ha; some dunes are up to 100 m high. The dunes hold few plant species, but the unique dune fynbos is adapted to this unstable environment.
See Box and Tables 2 and 3 for key species. At least 260 bird species have been recorded at the reserve, of which 97 are waterbirds, primarily dependent on the Ramsar-designated De Hoop Vlei. The vlei, on average, supports over 8,000 birds. However, the system is highly variable, and numbers of waterbirds visiting and breeding vary considerably, depending on water-levels and salinity. In good years, the vlei has supported over 30,000 birds, but during drought years it may be dry. This is the only locality in South Africa where
Phoenicopterus ruber has bred successfully (in 1960 and 1963); they still occur regularly at the vlei. Other species supported by the vlei include
Sterna caspia and
Charadrius pallidus. The vlei also sometimes has extremely large numbers of
Anas undulata,
A. smithii,
Fulica cristata and
Alopochen aegyptiacus.
Sterna balaenarum, which breed at the nearby Heuningnes estuary (IBA ZA100), are occasionally seen within De Hoop. The beaches hold breeding pairs of
Haematopus moquini.A cliff on Potberg has the only remaining breeding colony of
Gyps coprotheres in the Western Cape. Unfortunately, the total number of vultures had been showing a general and progressive decrease. However, thanks to vulture-friendly agricultural methods implemented by the local farming community, this trend has been reversed. The short restioid fynbos on the slopes of Potberg is known to hold both
Sarothrura affinis and
Turnix hottentotta.
Grus paradisea,
Neotis denhami and
Circus maurus have large populations in the modified agricultural matrix of the Overberg Wheatbelt (IBA ZA094) surrounding the reserve; the open plains in the reserve also support important numbers of these species. Some typically karroid birds are also found here, including
Eupodotis vigorsii and
Parus afer, and the recently described
Certhilauda brevirostris also occurs.
Campethera notata occurs scarcely in forested gorges.
Non-bird biodiversity: The reserve is thought to contain more than 1,500 plant species, representing one of the highest diversities within the Cape Floristic Kingdom. At least 108 fynbos plants are threatened and/or endemic to De Hoop and its immediate vicinity. There are at least 50 endemic species; 12 occur only on Potberg, the remainder on the limestone outcrops. Fourteen plant species were recently discovered and remain undescribed, of which eight are not known to occur outside De Hoop Nature Reserve. Among mammals, the reserve holds a healthy population of the South African endemic Equus zebra zebra (VU) and the world’s largest population of Damaliscus dorcas dorcas; the latter subspecies is endemic to the Cape Floristic Kingdom. The marine reserve off the coast protects a wide diversity of organisms, notably the whale Eubalaena australis (LR/cd), which mates and calves here annually between June and December.
Pressure/threats to key biodiversity
The De Hoop Nature Reserve was established in 1956 for the purpose of breeding game; it is currently administered and managed by Cape Nature Conservation. Since establishment, several farms have been bought and incorporated into the reserve. De Hoop Vlei was designated a Ramsar Site in 1975 and expanded in 1986 to include all of the vlei between the causeway at Apolsfontein in the north and De Mond in the south. The marine reserve, which extends three nautical miles off the coast, was also included in 1986. The development of the Overberg Test Range, adjacent to the reserve, by the South African Armaments Corporation (ARMSCOR) in 1983, resulted in increased activity, vehicular use, construction, noise pollution and vegetation burning, all of which have impacted on the neighbouring reserve.
Gyps coprotheres forages widely outside the reserve and it is vulnerable to indiscriminate use of poison by small-stock farmers targeting mammalian predators such as jackals, caracals and dogs. Although farmers surrounding De Hoop are highly responsible and very eager to contribute to conservation programmes, it must be emphasized that a single poisoned carcass could decimate the entire colony. In the nearby Albertina District, concerned farmers have activated a vulture restaurant of their own accord, and the increase in vulture numbers in the district has been ascribed to the active cooperation of enlightened role-model farmers in this area.
In the past, patches of veld were burnt frequently in order to improve grazing, often at an undesirable frequency, intensity and season. This resulted in many Proteaceae being destroyed before they had time to produce seeds. The Bredasdorp coastal strip supports a large variety of natural floral communities, with many endemics occurring in small localized populations. These plants are extremely vulnerable to extinction as a result of habitat loss and physical disturbance to their environment. Renosterbosveld occurring farther inland is critically threatened; more than 90% of it has been ploughed up for agriculture.
Infestation by non-native plants, such as
Acacia saligna and
A. cyclops, is a major threat to the indigenous vegetation within the reserve, and its removal is a conservation priority. In terms of recreational and aesthetic value, the reserve offers a unique spectrum of ecotourism activities, making it economically valuable.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: De Hoop Nature Reserve (South Africa). Downloaded from
https://datazone.birdlife.org/site/factsheet/de-hoop-nature-reserve-iba-south-africa on 23/12/2024.
