• Summary
• Text account
• Data table and detailed info
• Map
• Reference and further resources

Site description
The Wilderness–Sedgefield Lakes complex (WSLC) incorporates the Wilderness National Park and the Goukamma Nature Reserve along the coastal belt east of Wilderness. The entire lakes complex lies below the 5 m contour line on the flat Touw river flood-plain. Three discrete lake systems comprise the Wilderness–Sedgefield Lakes complex. The first, to the west, is the Wilderness lakes system, which consists of a natural channel, the Serpentine, which links the Touw river to its estuary and flood-plain. The channel also runs between Eilandvlei to two other lakes, Langvlei and Rondevlei. The central system is known as Swartvlei, and it consists of a large lake, Swartvlei, which is connected to the sea via the Swartvlei estuary. The last system, which lies to the east, is a single landlocked lake known as Groenvlei. Collectively, they are the only warm-temperate coastal lakes with a marine connection in South Africa.

Whenever a lake’s connection to the estuary is periodically closed by longshore drift, a lagoon, dominated by freshwater, forms. When the connection to the estuary opens, it becomes flooded with seawater. When water-levels are low, exposed sand/mudflats appear on the periphery of most of the water-body. Submerged plants that grow in the lakes, channels and estuaries include Chara, Lamprothamnium, Potamogeton, Najas, Zostera and Ruppia. The fluctuations in salinity and water transparency can sometimes cause total dieback of such plants. The surface waters are clear and open in the central areas. Beds of fringing vegetation, such as Phragmites, Scirpus, Juncus, Typha, Cladium and Bolboschoenus, occur in the littoral zone. The lakes support a diverse community of estuarine macroinvertebrates and fish.

Forests dominated by Podocarpus, Diospyros, Gonioma, Olea, Cassine, Pterocelastrus, Trichocladus and Rapanea border the lakes and comprise most of the terrestrial vegetation within the Wilderness National Park. A 38-km stretch of coastline, including a series of high undulating coastal sand-dunes, is protected within the park and the neighbouring Goukamma Nature Reserve. The Nature Reserve holds dune fynbos.

Key biodiversity
See Box and Tables 2 and 3 for key species. The site supports an average of 10,868 non-passerine waterbirds every month, and the monthly total has ranged between 4,841 and 24,427 waterbirds between 1980 and 1984. The system is important for Palearctic migrant waders and southern African waterbirds, especially ducks (Anatidae), which moult and breed here. The lakes support 72 waterbird species, including good numbers of Thalassornis leuconotus and Anas undulata.The marsh and reedbeds surrounding the lakes hold Circus ranivorus, Rostratula benghalensis, Ixobrychus minutus, Porzana pusilla, Sarothrura rufa, Rallus caerulescens and small numbers of Tyto capensis. The coastline holds notable numbers of Haematopus moquini. Although not present in very significant numbers, up to 6,000 Palearctic waders, consisting primarily of Calidris ferruginea, C. minuta and Philomachus pugnax, can be found within the system during the austral summer. The well-wooded backwaters on Swartvlei and Groenvlei hold small numbers of Podica senegalensis and Alcedo semitorquata.

Non-bird biodiversity: The forests hold several endemic plant species including Gladiolus vaginatus and Satyrium princeps. The endemic and threatened fish Hippocampus capensis (EN) occurs in the Swartvlei estuary. The terrestrial vegetation surrounding the wetland system supports the endemic vertebrates Myosorex longicaudatus (VU), Myosorex varius and Breviceps fuscus.

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Recommended citation
BirdLife International (2021) Important Bird Areas factsheet: Wilderness - Sedgefield Lakes Complex. Downloaded from http://www.birdlife.org on 25/02/2021.