Berg River Estuary

Site description (2001 baseline):

Site location and context
The Berg river wetlands are located 140 km north of Cape Town. The town of Laaiplek lies directly north of the river mouth; 6 km upstream of the mouth lies the town of Velddrif. The Berg river forms one of only four perennial estuaries on the arid west coast of southern Africa. The IBA includes only the lower Berg river, but this system is reliant on the management of its catchment, which extends c.160 km upstream from the river mouth to its source in the Franschhoek and Drakenstein mountains.

In addition to the river channel, the flood-plain encompasses eight major wetland types: ephemeral pans, commercial saltpans, reed-marsh, sedge-marsh, saltmarsh, halophytic flood-plain, xeric flood-plain and intertidal mudflats. The ephemeral pans comprise monospecific stands of Juncus during summer. After winter rains, abundant Aponogeton develops, along with other aquatic plants. Reed-marsh is found mainly on inner riverine beds, and is dominated by Phragmites, Scirpus or Cyperus. Sedge-marshes are dominated by Juncus, with smaller sedge species occurring in a varied mosaic. The saltmarsh experiences tidal flooding by saline water twice a day and is dominated by fleshy-leaved salt-tolerant species. Halophytic flood-plain vegetation consists primarily of Sarcocornia, which may be interspersed with open patches, which are colonized by ephemeral growth during spring. The xeric flood-plain vegetation is highly diverse. Succulents include Mesembryanthemaceae and Asparagaceae. Rhus and Lycium bushes also occur. The flood-plain can be inundated for up to two weeks at a time when the Berg river floods.

Key biodiversity
See Box for key species. An analysis of the importance of South Africa’s estuaries for wetland birds consistently showed the Berg river wetlands to be in the top three and, along with Lake St Lucia (IBA ZA044) and Langebaan Lagoon (IBA ZA084), it was considered to be an indispensable site for waterbird conservation in South Africa. Since 1975, approximately 250 bird species have been recorded on and adjacent to the lower Berg river; 127 of which are waterbirds.The most important habitats for foraging birds are the estuarine mudflats and ephemeral flood-plain pans. The most important breeding sites are riparian marshes and the commercial saltpans. On average, more than 12,000 non-passerine waterbirds occur at the estuary during summer and 6,000 non-passerine waterbirds during winter. A count of both the estuary and the flood-plain yielded 46,234 waterbirds in December 1992, and in combination, the estuary and flood-plain regularly support over 20,000 birds.

Waterbird numbers are strongly influenced by the influx of Palearctic migrants, and more than 8,000 migrant waders are regularly present in summer, especially Calidris ferruginea and C. minuta. The commercial saltpans support many breeding species, including very large numbers of Sterna caspia, incorporating up to 13% of the South African breeding population. Charadrius pallidus breed here regularly. Larus dominicanus and L. hartlaubii are resident at the Berg river and occur in large numbers, breeding in midsummer and early winter respectively. Sterna bergii breed sporadically. Large numbers of Pelecanus onocrotalus occur regularly on the lower Berg river, which is a key foraging and roosting area for the Dassen Island (IBA ZA088) breeding population during the non-breeding season.Podiceps cristatus and P. nigricollis breed occasionally. Tadorna cana use the estuary in large numbers as a moulting site and they also breed regularly. Anas undulata, A. capensis, A. smithii and Fulica cristata breed in the inundated saltmarshes in the upper estuary. There is a large heronry c.1 km west of the Kersefontein farmhouse. The heronry, which is known to have existed for the past 300 years, holds 13 breeding species, including substantial numbers of Mesophoyx intermedia, Platalea alba and Plegadis falcinellus (which appears to be increasing).

Non-bird biodiversity: Three endemic, highly localized and threatened reptiles occur on the xeric flood-plain of the Berg river: the west-coast endemic Scelotes gronovii (LR/nt), S. kasneri (VU) and Cordylus macropholis all occur here. A fourth threatened reptile, Psammophis leightoni, is also found on the flood-plain.

Pressure/threats to key biodiversity
The permanent water-body and intertidal mudflats are State-owned and controlled by Cape Nature Conservation. The saltmarshes, saltworks and most of the flood-plain and catchment area are all privately owned. The Berg river supports both high numbers as well as a great diversity of waterbirds, and is of sufficient importance for waterbirds to satisfy the criteria for registration with the Ramsar Convention. However, the South African national committee has repeatedly refused registration because the site receives no legislative protection and it does not have a management plan. Whereas registration is desirable, attention should be focused on affording the estuary protection at a national level.Existing developments in the Berg river basin, including water supply to the Greater Cape Town Metropolitan Area, have reduced Mean Annual Run-off (MAR) by 23%. These alterations have not yet affected the seasonal pattern of water flow in the Berg river. The largest threat to this wetland is the further reduction of MAR, which would significantly affect seasonal water-flow patterns and volumes. The MAR may be reduced by a proposed impoundment upstream of the estuary and water volumes will almost certainly be reduced by the construction of the Corex steel smelter (Saldanha Steel) and the associated industries near Saldanha Bay, which will require considerable quantities of water for operation. It has been proposed that water be abstracted from the Berg river for these purposes.

Winter inundation of the flood-plain, either naturally or through controlled releases, is essential for the continued ecological functioning of the flood-plain and estuary. Lack of winter flooding may result in the development of hyper-saline conditions and consequent biological sterility on the flood-plain. Other threats to the Berg river include the dredging of the mouth to allow access to boats. Dredging increases the velocity of the tidal flow, the turbidity of the water and the penetration of salt water upstream, and also increases erosion within the system. Nutrient pollution of catchment waters from intense farming activities upstream, including excessive fertilizer run-off, impacts estuarine functioning further.

The Lower Berg river is currently the most important wetland in South Africa that does not enjoy legislative protection. The rich birdlife offers substantial tourism potential if managed appropriately. Furthermore, the lower flood-plain is vital as a nursery area for juvenile fish, many species of which form the basis of employment for hundreds of families who live on the west coast. Any deleterious impacts that affect commercially valuable fish species—and many are already in decline—will lead to a decline in the well-being of many human communities in the area. Protection of the lower estuary, and the waters that inundate its flood-plain, is imperative.

Recommended citation
BirdLife International (2023) Important Bird Area factsheet: Berg River Estuary. Downloaded from on 04/10/2023.