The Olifants river estuary lies c.250 km north-west of Cape Town. The nearest towns are Lutzville and Vredendal, 23.5 km and 42 km east of the estuary respectively. The Olifants river rises in the Agterwitzenberg, a plateau lying between the Winterhoek and the Skurweberg mountains. The flanks of the estuary hold extensive saltmarsh; on both sides of the mouth, a steep rocky shoreline rises to form a gravel terrace.Marine algae grow on rocks near the river mouth, to the west of the island, and in the marshes, both at the mouth and farther upstream. The saltmarsh vegetation is well stratified. The flood-plain also holds numerous plant species with more terrestrial affinities. Reedbeds of Scirpus and Phragmites line the banks of the river upstream from Olifantsdrif. The terrestrial vegetation on higher ground is of considerable interest, as it is one of the few areas where karroid vegetation reaches the west coast. After spring rains the veld breaks out in mass flowering displays.
See Box and Table 3 for key species. Approximately 125 bird species have been recorded at the estuary and its environs, with at least 60 of these being waterbirds. The Olifants river estuary regularly supports over 15,000 waterbirds. Pelecanus onocrotalus, which breed at the nearby Dassen Island (IBA ZA088), use the estuary as a primary foraging and roosting area during the non-breeding season. Sterna balaenarum occasionally forage in the estuary. Large numbers of Tadorna cana, Calidris ferruginea and Larus hartlaubii use the estuary when conditions are suitable. Although waterbird numbers are not exceptional, this estuary acts as a vital staging point for both Palearctic migrants and flamingos between the Orange river mouth (IBA ZA023), and the important wetlands to the south and east, such as the Berg river wetlands (IBA ZA083), Langebaan Lagoon (IBA ZA084), Rietvlei (IBA ZA090) and the Wilderness-Sedgefield Lakes complex (IBA ZA093). The vegetation surrounding the estuary is suitable for many of the species restricted to the Namib–Karoo biome and for other arid-zone birds, including Eupodotis vigorsii, Parus afer, the recently recognized Certhilauda albescens, Cercomela tractrac, C. schlegelii, C. sinuata and Serinus alario. Phragmacia substriata occur in the Acacia thickets and reedbeds along the river margin. The recently described Certhilauda curvirostris, a restricted-range species (see account for IBA ZA023), also occurs here.
Non-bird biodiversity: The IBA lies in the centre of the ranges of many Namaqualand-endemic reptiles; most of them have been recorded in the vicinity and are probably present in the terrestrial succulent Karoo vegetation matrix surrounding the wetland, including Homopus signatus, Bitis schneideri (VU), B. cornuta, Acontias litoralis, Typhlosaurus caecus, Scelotes sexlineatus, Meroles knoxii, Cordylus macropholis, Gerrhosaurus typicus (LR/nt), Bradypodion occidentale and Pachydactylus austeni.
Pressure/threats to key biodiversity
The Cedarberg Divisional Council controls the estuary. Marine diamond-mining restricts general public access along the northern shore. The Olifants’ catchment is mostly rural, with farming being the most important activity. Most of the Olifants catchment is protected in the Groot Winterhoek (81,427 ha) and Koue Bokkeveld (96,348 ha) mountain catchment areas (both included in IBA ZA080), which are managed by the Department of Water Affairs and Forestry (DWAF). Although the mouth meets the criteria for recognition as a wetland of international importance, the site does not have Ramsar status. The expansive flood-plain is criss-crossed with vehicle tracks, and off-road vehicles have damaged the vegetation extensively. The terrestrial vegetation has also become drastically overgrazed in places. The passage of vehicles and pedestrians should be severely restricted, especially on the flood-plain and saltmarshes. Grazing by livestock should be controlled as the denudation of the vegetation is causing serious erosion.
BirdLife International (2022) Important Bird Areas factsheet: Olifants river estuary. Downloaded from
http://www.birdlife.org on 25/06/2022.