Verlorenvlei

Site description

Verlorenvlei is a partially closed coastal estuarine lake and marsh system fed by an intermittent allogenic river. The estuary mouth lies along the Atlantic Ocean at the town of Elands Bay, which is located 25 km south of Lambert’s Bay. This is one of the largest natural wetlands along southern Africa’s west coast, and it is one of the few coastal freshwater lakes in South Africa. Its catchment covers some 1 890 km² and consists of four main tributaries: the Kruis, Bergvallei, Hol and Krom Antonies rivers, which have their sources in the Olifantsrivierberge and Swartberge in the east and the Piketberge in the south. Three of the four rivers drain the extensive flatlands of the sandy coastal plain, and the Krom Antonies River drains the Moutonshoek Valley. All four flow into the 30-km-long Verlorenvlei River.

Verlorenvlei can be regarded as an estuarine coastal lake and reed-swamp system due to its intermittent connection with the ocean. The main body of the lake is c. 13.5 km long and 1.4 km wide, and has an average depth of 3 m and a maximum depth of c. 4.5 m during the wet season. Extensive low-lying sand flats occur to the north and east of the lake, sloping up to a series of low hills that form the catchment boundary. On the southern side, the lake lies against the base of a continuous range of low sandstone hills averaging some 120 m a.s.l., with Muishoekberg (300 m a.s.l.) forming the only prominent peak. Towards the west and closer to the sea, the ridge becomes rugged, with high cliffs ending in the ocean at Baboon Point (200 m a.s.l.).

The system lies in a winter-rainfall area and given sufficient rain inland it fills and overflows into the sea at Eland’s Bay. In summer, however, it gradually desiccates, reaching its lowest levels at the end of the dry season. Generally the lake never dries up completely, although in very dry years the water level can become extremely low. The fluctuations in water level influence the distribution patterns of the flora and fauna, so the wetland’s variable nature is critical to the functioning of the system. A shallow, narrow, 2.5-km-long channel runs from Verlorenvlei to the sea, but a rocky sand-covered bar at the mouth and other artificial obstructions make it a virtually closed system. Usually, the mouth is blocked and the channel is reduced to a series of stagnant saline pools. During good rains, however, the lake spills into the channel and some tidal exchange takes place. The lake is regarded as oligotrophic, but the nutrient status varies, depending on the water level. Salinity levels can reach as high as 40 parts per thousand on the eastern side of the railway bridge (hypersaline conditions) to 0.5 parts per thousand at Redelinghuys.

The terrestrial vegetation surrounding the vlei is transitional between karroid and fynbos vegetation, resulting in a high diversity of ecotonal communities. The coastal dunes support strandveld, comprising clumps of succulent or evergreen shrubs interspersed with smaller shrubs and restios. Saline marshy areas with a dense cover of halophytic vegetation are found immediately inland of the seaward dunes and around the mouth of Verlorenvlei, whereas dry mountain fynbos grows on surrounding sandstone outcrops.

Birds

Verlorenvlei supports more than 189 bird species, of which 75 are waterbirds. The wetland occasionally hosts more than 4 000 birds; the highest number recorded in a single count was 11 891, according to the data from counts undertaken by CapeNature since 1990. At least 26% of the Western Cape’s Great White Pelican Pelecanus onocrotalus population congregates at this site at times. Greater Flamingo Phoenicopterus roseus and Lesser Flamingo Phoeniconaias minor also occur here occasionally, when conditions at Rocher Pan (35 km south) or Wadrifsoutpan (13 km north) are unsuitable or water levels in the lake are very low, as occurred in the 2004–2005 season. Relatively large numbers of Little Bittern Ixobrychus minutus and Caspian Tern Sterna caspia occur regularly in the wetland.

Historically an important moulting ground and summer refuge for Anatidae, the area supported large numbers of Yellow-billed Duck Anas undulata, Cape Shoveler A. smithii and South African Shelduck Tadorna cana. However, many of these species have declined over the past decades, as data from CapeNature illustrate. Large numbers of Great Crested Grebe Podiceps cristatus, Red-knobbed Coot Fulica cristata and White-breasted Cormorant Phalacrocorax lucidus can also be found at this wetland. There is a high density of African Marsh Harrier Circus ranivorus, which forages over the marsh and reedbed areas. Black Stork Ciconia nigra breeding in the Olifantsrivierberge and Swartberge to the east and Piketberge to the south very occasionally forages in the vlei. The site also holds 4–5 pairs of African Fish Eagle Haliaeetus vocifer, and Verreauxs’ Eagle Aquila verreauxii occurs on the cliffs around the vlei.

African Black Oystercatcher Haematopus moquini and Chestnut-banded Plover Charadrius pallidus are recorded at the estuary mouth from time to time. The palustrine habitats are diverse and rich and hold populations of secretive Rallidae such as African Rail Rallus caerulescens and Baillon’s Crake Porzana pusilla. Red-chested Flufftail Sarothrura rufa may occur, but has not been confirmed. Rallid species are particularly abundant between Matjiesgoeddrif and Redelinghuys, where the composition and structure of the palustrine vegetation are diverse and the area has extensive and excellent habitat for them and for waders. The diverse ecotonal terrestrial vegetation around Verlorenvlei’s fringes supports several biome-restricted assemblage species. In recent years, a pair of Goliath Herons seems to have been resident in the area and may be breeding.

IBA trigger species

Globally threatened species are African Black Oystercatcher, Black Harrier Circus maurus and Lesser Flamingo. Regionally threatened species are African Marsh Harrier, Caspian Tern, Great White Pelican, Greater Flamingo, Lanner Falcon Falco biarmicus and Verreauxs’ Eagle. Biome-restricted species are Cape Spurfowl Pternistis capensis and Cape Bulbul Pycnonotus capensis, which are common; Karoo Lark Calendulauda albescens, which is locally common; and Karoo Chat Cercomela schlegelii and Layard’s Tit-Babbler Sylvia layardi, which are uncommon.

The IBA hosts more than 1% of the biogeographic population of Great Crested Grebe (maximum 140 individuals), South African Shelduck (maximum 489 individuals), Pied Avocet Recurvirostra avosetta (maximum 1 256 individuals), Hartlaub’s Gull Chroicocephalus hartlaubii (maximum 377 individuals), Caspian Tern (maximum 34 individuals), Great White Pelican (maximum 478 individuals), White-breasted Cormorant (population regularly exceeds 130 individuals), Kelp Gull Larus dominicanus (population exceeded 700 individuals on two counts), Greater Flamingo (population exceeded 750 individuals on one count) and Whiskered Tern Chlidonias hybrida (population exceeded 85 individuals on one count). The site also supports more than 0.5% of the population of Lesser Flamingo (maximum 320 individuals), Egyptian Goose Alopochen aegyptiaca (maximum 2 041 individuals) and Red-knobbed Coot (maximum 3 104 individuals).

Other biodiversity

Verlorenvlei occurs at the transition between fynbos and Karoo vegetation types and, as is typical of ecotonal areas, it holds a high diversity of plant species. Rare plants include Ferraria foliosa, F. densepunctulata, Cerycium venoum (presumed extinct) and Cullumia floccosa.

Three indigenous freshwater fish, Cape kurper Sandelia capensis, Cape galaxias Galaxias zebratus and Berg River redfin Pseudobarbus burgi, occur in the Verlorenvlei area. A redfin previously regarded as a subspecies of Berg River redfin has recently been upgraded to full species status: Verlorenvlei redfin P. verloreni. Taxonomic studies are been carried out on the Cape kurper and Cape galaxis and it is possible that new species will emerge from these studies.

Endangered mammal species that occur in the area are Grant’s golden mole Eremitalpa granti, De Winton’s golden mole Cryptochloris wintoni, Van Zyl’s golden mole C. zyli, Cape gerbil Tatera afra, aardvark Orycteropus afer, Cape spiny mouse Acomys subspinosus, spectacled dormouse Graphiurus ocularis, honey badger Mellivora capensis and aardwolf Proteles cristatus. Other mammals include leopard Panthera pardus, caracal Caracal caracal, African wild cat Felis lybica and striped polecat Ictonyx striatus.

The IBA lies in the centre of the ranges of several reptiles endemic to Namaqualand, most of which have been recorded in the vicinity and may be present in the Succulent Karoo terrestrial vegetation matrix surrounding the wetland. These are speckled padloper Homopus signatus, Namaqua dwarf adder Bitis schneideri, many-horned adder B. cornuta, coastal legless skink Acontias litoralis, Cuvier’s blind legless skink Typhlosaurus caecus, striped dwarf burrowing skink Scelotes sexlineatus, Knox’s desert lizard Meroles knoxii, armadillo girdled lizard Cordylus cataphractus, large-scaled girdled lizard C. macropholis, Namaqua plated lizard Gerrhosaurus typicus, Namaqua dwarf chameleon Bradypodion occidentale and Austen’s thick-toed gecko Pachydactylus austeni.

Southern African endemics that have also been recorded in the vicinity and may be present at the site are Karoo toad Bufo gariepensis, angulate tortoise Chersina angulata, tent tortoise Psammobates tentorius, Cape cobra Naja nivea, striped legless skink Acontias lineatus, spotted sand lizard Pedioplanis lineoocellata, Karoo girdled lizard Cordylus polyzonus, southern rock agama Agama atra, southern spiny agama A. hispida, giant ground gecko Chondrodactylus angulifer, Western Cape thick-toed gecko Pachydactylus labialis, Weber’s thick-toed gecko P. weberi and Marico thick-toed gecko P. mariquensis.

Conservation issues

Threats

Despite being one of the most important estuarine/lacustrine systems in South Africa, Verlorenvlei does not have any formal protection status, and neither statutory control nor any form of management is currently in place. The lack of formal protection exacerbates the threats that influence the estuary from further upstream. Cultivation in the catchment is widespread, and more than 90% of the Malmesbury-derived soils have been ploughed, mainly for potato and wheat production, which is totally reliant on water derived from the Verlorenvlei system. Growing crops around the estuary and in its catchment has a major impact on its ecology, particularly as a result of the abstraction of ground and surface water that not only reduces the water levels, but also impacts on water quality. These agricultural activities can also lead to increased soil erosion, which in turn leads to increased sedimentation in the estuary, as well as nitrification as the run-off carries excess nutrients into the river mouth. The combined higher sediment load and increased nutrients stimulate the growth of Phragmites australis reeds, contributing to a loss of open water habitat and further altering the ecology of the estuary.

Infrastructure and developments on the estuary floodplain include several man-made obstructions that disrupt the system. A rubble causeway at the railway bridge and earth berms just east of it, as well as road causeways 1 km and 2.6 km upstream of the mouth, stop the natural flow and disturb the sensitive ecological functioning of the system. These obstructions disrupt hydrological fluctuations in the wetland, causing flooding upstream, extensive siltation and reduced freshwater flow into the estuary. They also prevent fish migration. Other inappropriate infrastructure includes low-lying properties, fences across the floodplain, power lines across some sections of open water and jetties and pump houses in the waterbody itself. They all have localised impacts on habitat and the estuarine ecology and should be removed or mitigated as a matter of urgency in order to restore natural hydrological functioning and reduce bird mortalities.

Invasive alien flora, including Acacia cyclops, in the catchment and floodplain of the estuary reduces the extent of indigenous habitat and the water volume flowing into the estuary. There is also increased top-soil run-off in alien-infested areas, which adds to the sediment load affecting the estuary.

Uncontrolled recreational activities in the estuary can lead to the disturbance of wildlife, especially birds. Recreational activities should be kept to a minimum and limited to certain zones to reduce disturbance.

Illegal gill-netting and the presence of invasive alien fish species such as carp Cyprinus carpio and Mozambique tilapia Oreochromis mossambicus are affecting other components of the estuarine biodiversity. The exotic fish compete with indigenous freshwater species and alter the vegetation structure, potentially changing system dynamics. Gill-netting can also lead to indirect mortality of trigger species due to diving birds getting caught in the nets.

If not properly managed, livestock grazing in the riparian zone floodplain can also lead to increased soil erosion and eutrophication. Goats from the nearby Elands Bay communities may degrade the habitat around the edge of the wetland and have a detrimental effect on wetland plants. This impact is mainly localised to the area between the railway bridge and the main Elands Bay road bridge. The effect of potential poaching and trapping of waterfowl, mainly prevalent in the lower parts of the estuary close to town, is unknown but may lead to a decline in the populations of target species.

Conservation action

Although the Ramsar-designated land is State-owned, there is currently neither a designated management authority nor formal protection status. The lack of a management authority means that no conservation action – or very little – has taken place at this site. However, the recently formed Verlorenvlei Estuary Management Forum is the first step towards improving its status. Launched in 2009, it facilitates the coordinated management of the estuary by a body that represents all the relevant stakeholders: local farmers and home-owners, various conservation organisations and government officials from all the departments concerned.

BirdLife South Africa is working closely with WESSA and other partners to develop a conservancy and utilise Biodiversity Stewardship to proclaim a Protected Environment in the buffer zone around the estuary. CapeNature is seeking to have the land that includes the waterbody transferred to its jurisdiction so it can be properly managed alongside other nature reserves in the area. To this end BirdLife South Africa has employed a Verlorenvlei Protected Areas project manager who is leading the stewardship work at the vlei and its primary catchment, the Moutonshoek Valley. Much of the southern shore of the Verlorenvlei waterbody forms the border of the Vleikraal Private Nature Reserve and it is essential that this reserve is properly managed in order to reduce negative impacts and promote the conservation of Verlorenvlei.

An Estuary Management Plan for the area has been developed by the CSIR as part of the C.A.P.E Estuaries Programme and the forum is assisting with its implementation wherever possible. Working for Wetlands has been operating at the site since 2006, in partnership with CapeNature and SANBI, specifically to conduct alien clearing programmes (1 100 ha has been cleared), but also to construct a bird hide (which unfortunately burnt down in 2012), build two gabion structures to reduce erosion, and develop and distribute wetland management guidelines to farmers in the estuary. Regular bird counts are undertaken by CapeNature and regular water-quality monitoring is now being undertaken by the West Coast District municipality.

CapeNature, through its Greater Cederberg Biodiversity Corridor Landscape Initiative, has also highlighted the Sandveld Core Corridor for conservation action. Verlorenvlei and the surrounding farmlands form part of this corridor and several conservation initiatives have been implemented, including awareness, coordination, stewardship and the development of best-practice guidelines for the potato and rooibos industries. Soil conservation committees have been established in the Department of Agriculture’s Landcare Division recently, and these aim to improve the management of this critical resource in the farmlands surrounding the IBA.

Related webpages

None.

Contact

If you have any information about the IBA, such as a new threat that could impact on it, please send an e-mail to iba@birdlife.org.za or call BirdLife South Africa +27 (11) 789 1122.

Page last updated

Thursday, 26 February 2015