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Location South Africa, Western Cape
Central coordinates 18o 29.00' East  33o 50.00' South
IBA criteria A1, A4i
Area 527 ha
Altitude 0 - 10m
Year of IBA assessment 2001

BirdLife South Africa



Summary This reserve lies between Tableview and Milnerton in the northern sector of the Greater Cape Town Metropolitan area. A range of natural and semi-natural habitats exists in this fluctuating wetland, which floods in winter, and dries out in summer when the estuary mouth closes. The high diversity of waterbirds is due to the wide range of wetland habitats present and the proximity of Rietvlei to the ocean, which allows both freshwater and coastal species to exploit the system.

Site description This reserve lies between Tableview and Milnerton in the northern sector of the Greater Cape Town Metropolitan Area, 10–15 km north-east of the city centre. A range of natural and semi-natural habitats exists in this fluctuating wetland, which floods in winter and dries out in summer when the estuary mouth closes. These habitats include shallow marine waters, estuarine waters, sand/shingle shores, tidal mudflats, saltmarshes, coastal brackish saline lagoons, rivers, streams and creeks, permanent freshwater lakes and permanent and seasonal freshwater marshes and pools.

Five distinctive wetland plant communities occur: perennial wetland, reed-marsh, sedge-marsh, open pans and sedge pans. The perennial wetland is characterized by scant aquatic vegetation, dominated by Ruppia, Potamogeton and Enteromorpha. The reed-marsh is dominated by Phragmites, invaded in places by Typha. The sedge-marsh is dominated by Bolboschoenus and Juncus. The open pans are sparsely covered in macrophytes, consisting mainly of Limosella and Salicornia, and the sedge pans are dominated by Bolboschoenus in summer and Aponogeton and Spiloxene in winter. Zooplankton multiply rapidly after winter flooding and disappear in summer as the water dries up. In the estuary there is a range of salinities, resulting in a diverse community of zooplankton. The invertebrate fauna is a vital food source for birds and fish, the most abundant fish in the wetland being Liza richardsoni.

Key Biodiversity See Box for key species. A total of 173 species have been recorded at Rietvlei, of which 102 are waterbirds and 76 are present regularly. Breeding has been confirmed for 23 waterbird species and is suspected for a further 13 species. The high diversity of waterbirds is due to the wide range of wetland habitats present and the proximity of Rietvlei to the ocean, which allows both freshwater and coastal species to exploit the system. Fluctuating water-levels are intrinsic to Rietvlei’s biological value. During peak floods, swimming birds of deep, open water abound. Birds of marshy habitats replace these as the water recedes, and waders exploiting shallow mudflats occur in great abundance just prior to the wetland drying up. Rietvlei has been ranked as the sixth most important coastal wetland in South Africa for waterbirds, and it supports an average of 5,550 birds in summer; during good years, however, numbers are boosted above 15,000. Phoenicopterus minor, a species of global conservation concern, occurs at the site, but not in globally significant numbers.

Non-bird biodiversity: Urban development and encroachment by non-native plants threaten the herptiles Cacosternum capense (LR/nt), Hyperolius horstockii, Bradypodion pumilum (CR) and B. occidentale, which all live on the wetland fringes.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Cape Shoveler Spatula smithii winter  337-506 individuals  A4i  Least Concern 
Great Crested Grebe Podiceps cristatus winter  54 individuals  A4i  Least Concern 
African Oystercatcher Haematopus moquini winter  present  A1  Near Threatened 
Pied Avocet Recurvirostra avosetta non-breeding  263-669 individuals  A4i  Least Concern 
Kelp Gull Larus dominicanus winter  665 individuals  A4i  Least Concern 
Hartlaub's Gull Larus hartlaubii breeding  150-375 breeding pairs  A4i  Least Concern 
Hartlaub's Gull Larus hartlaubii winter  543-1,102 individuals  A4i  Least Concern 

IBA Monitoring

2013 high not assessed high
unset
Medium - based upon reliable but incomplete / partially representative data

Agriculture and aquaculture annual & perennial non-timber crops - small-holder farming happening now small area/few individuals (<10%) slow but significant deterioration low
Biological resource use fishing & harvesting aquatic resources - unintentional effects: subsistence/small scale happening now small area/few individuals (<10%) no or imperceptible deterioration low
Biological resource use gathering terrestrial plants - unintentional effects (species being assessed is not the target) happening now small area/few individuals (<10%) no or imperceptible deterioration low
Biological resource use hunting & collecting terrestrial animals - unintentional effects (species is not the target) happening now small area/few individuals (<10%) no or imperceptible deterioration low
Climate change and severe weather drought likely in long term (beyond 4 years) whole area/population (>90%) moderate to rapid deterioration high
Climate change and severe weather habitat shifting and alteration happening now majority/most of area/population (50-90%) slow but significant deterioration high
Climate change and severe weather storms and floods likely in short term (within 4 years) whole area/population (>90%) no or imperceptible deterioration low
Climate change and severe weather temperature extremes likely in long term (beyond 4 years) whole area/population (>90%) moderate to rapid deterioration high
Energy production and mining mining and quarrying happening now small area/few individuals (<10%) no or imperceptible deterioration low
Human intrusions and disturbance recreational activities happening now some of area/population (10-49%) slow but significant deterioration medium
Human intrusions and disturbance work and other activities happening now some of area/population (10-49%) slow but significant deterioration medium
Invasive & other problematic species, genes & diseases introduced genetic material happening now small area/few individuals (<10%) slow but significant deterioration low
Invasive & other problematic species, genes & diseases invasive non-native/alien species/diseases - named species happening now some of area/population (10-49%) moderate to rapid deterioration high
Invasive & other problematic species, genes & diseases problematic native species/diseases - named species happening now majority/most of area/population (50-90%) moderate to rapid deterioration high
Natural system modifications fire & fire suppression - increase in fire frequency/intensity happening now small area/few individuals (<10%) no or imperceptible deterioration low
Natural system modifications other ecosystem modifications happening now majority/most of area/population (50-90%) no or imperceptible deterioration low
Pollution agricultural & forestry effluents - nutrient loads happening now majority/most of area/population (50-90%) slow but significant deterioration high
Pollution agricultural & forestry effluents - soil erosion, sedimentation happening now small area/few individuals (<10%) slow but significant deterioration low
Pollution air-borne pollutants - smog happening now whole area/population (>90%) slow but significant deterioration high
Pollution domestic & urban waste water - run-off happening now majority/most of area/population (50-90%) slow but significant deterioration high
Pollution excess energy - light pollution happening now whole area/population (>90%) slow but significant deterioration high
Pollution excess energy - noise pollution happening now whole area/population (>90%) slow but significant deterioration high
Pollution garbage & solid waste happening now some of area/population (10-49%) moderate to rapid deterioration high
Pollution industrial & military effluents - type unknown/unrecorded happening now some of area/population (10-49%) moderate to rapid deterioration high
Residential and commercial development commercial and industrial development happening now some of area/population (10-49%) slow but significant deterioration medium
Residential and commercial development housing and urban areas happening now some of area/population (10-49%) slow but significant deterioration medium
Residential and commercial development tourism and recreation areas happening now some of area/population (10-49%) slow but significant deterioration medium
Transportation and service corridors flight paths happening now some of area/population (10-49%) slow but significant deterioration medium
Transportation and service corridors roads and railroads happening now some of area/population (10-49%) slow but significant deterioration medium
Transportation and service corridors utility & service lines happening now some of area/population (10-49%) slow but significant deterioration medium

Shrubland Shrubland - Cape (fynbos)  0 0 poor (40-69%) poor (40-69%) very unfavourable
Wetlands (inland)   0 0 moderate (70-90%) moderate (70-90%) unfavourable

Whole area of site (>90%) covered by appropriate conservation designation  A comprehensive and appropriate management plan exists that aims to maintain or improve the populations of qualifying bird species  The conservation measures needed for the site are being comprehensively and effectively implemented  high 

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Rietvlei Wetland Reserve Nature Reserve 527 is identical to site 527  

Habitats

IUCN habitat Habitat detail Extent (% of site)
Wetlands (inland) Coastal lagoons; Freshwater lakes and pools; Rivers & streams  -
Sea Shallow marine waters  -
Grassland   100%
Shrubland Shrubland - Cape (fynbos)  -

Land use

Land-use Extent (% of site)
tourism/recreation -
nature conservation and research 94%

References Allan (1993b, 1995c, 1996a), Allan et al. (1996b), Branch (1988), Cooper et al. (1976), CSIR (1994), Grindley and Dudley (1988), Kalejta and Allan (1993), Kalejta-Summers et al. (in press a), Rowlands (1983), Ryan et al. (1988), Scott (1954), Summers et al. (1976, 1977), Turpie (1995), Underhill and Cooper (1984), Winterbottom (1960, 1968b).

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Recommended citation  BirdLife International (2015) Important Bird Areas factsheet: Rietvlei Wetland: Table Bay Nature Reserve. Downloaded from http://www.birdlife.org on 04/07/2015

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