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Site description
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.

Key biodiversity
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.

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Recommended citation
BirdLife International (2021) Important Bird Areas factsheet: De Hoop Nature Reserve. Downloaded from http://www.birdlife.org on 13/04/2021.