CAPE WHALE COAST IMPORTANT BIRD AND BIODIVERSITY AREAPosted on the 25th November 2015
(We have received our copies of the IMPORTANT BIRD AND BIODIVERSITY AREAS OF SOUTH AFRICA DIRECTORY and it is really an impressive volume of work. Congratulations to everyone at BirdLife South Africa who contributed to it and particularly Dale Wright who had drafted the text for the Western Cape Province. Interesting that the Overberg now has six IBAs – certainly the district with the highest proportionate coverage. Read what conservation issues the birds in the Cape Whale Coast IBA are facing. - Ed.)
CAPE WHALE COAST IMPORTANT BIRD AND BIODIVERSITY AREA
Status: Global IBA (A1, A2, A3, A4i, ii, iii)
Province: Western Cape
Protection: Partially Protected
Size: 35 240 ha
This IBA extends from the Stony Point seabird colony at Betty's Bay eastward for c. 35 km to the Klein River estuary adjacent to CapeNature's Walker Bay Nature Reserve. This stretch of coastline is known locally as the Cape Whale Coast, due to the large number of southern right whales Eubalaena australis that visit its bays each year to breed and calve. The predominantly coastal IBA also encompasses, from west to east, the Palmiet estuary, the Bot River–Kleinmond estuarine system (including the Lamloch swamp and CapeNature's Rooisand Nature Reserve), the smaller Onrus River estuary and Vermont salt pans, and Fernkloof Nature Reserve inland of Hermanus. It therefore incorporates estuarine systems, a seabird breeding colony and small patches of montane fynbos within a semi-urban matrix of small coastal towns that include Betty's Bay, Kleinmond, Fisherhaven, Hawston, Vermont, Onrus and Hermanus.
|The Onrus estuary|
|Onrus coastline - Images by Anton|
The Bot River–Kleinmond estuarine system covers about 1 400 ha between Kleinmond and Hawston. The 42-km-long Bot River and its main tributary, the 48-km Swart River, drain the Houwhoek, Groenland, Swart, Shaw's and Babilonstoring mountains in a catchment area of c. 1 000 km2. Part of this catchment also feeds the Klein River. Although its catchment is relatively small, the Bot River forms one of the largest open-water lagoons on the Western Cape coast. It flows into the Botrivier Vlei, a shallow, triangular lagoon in a broad valley flanked by mountains. The lagoon is separated from the sea by a dune belt that is 100–200 m wide and 3–6 m high, and is partially vegetated with coastal grasses and shrubs. This belt is broken by two narrow berms, at Meerensee and Kleinmond, which are occasionally breached either naturally or artificially.
The water level across the system varies considerably. The main lagoon can be up to 7 km long and 2 km wide, and at its seaward western end is a shallow side-arm, Rooisand, which is connected to it by an 80-m-wide bottleneck called Die Keel. When the water level in the main lagoon is low, Rooisand is dry; when the water level rises sufficiently, the lagoon floods across this area and into the Kleinmond estuary, or vice versa.
|Wild horses & pelicans along the Bot - Carin Malan|
|View over Walker Bay - Image by Anton|
Since the mid-1800s there has been a tendency for the Bot River–Kleinmond estuarine system to alternate between an open estuary and a coastal freshwater lagoon that has no more than a tentative link to the sea via the Lamloch swamp. The Botrivier Vlei is thus described as an open/closed system, with the overflow channel into the Kleinmond estuary providing the only contact with the sea. The disadvantage of the system being closed is that the lagoon cannot discharge its suspended mud load or obtain sea water by means of tidal exchange. The recruitment of marine fish is also impeded by this limited connection. The overflow system acts as a one-way safety valve that allows excess floodwaters to escape via the Kleinmond estuary, but prevents the lagoon from breaking open to the sea by natural means. Under certain conditions, however, such as when the catchments of the Isaaks and Lamloch rivers receive rain earlier than usual and fill Lamloch swamp, the swamp's water level rises above that of the Bot River and its water effectively flows through Die Keel into the main Bot River estuary.
Algae, such as Chara species, seem to be present throughout the Bot River–Kleinmond estuarine system but are particularly dense near its head and in the Lamloch swamp. The aquatic vegetation is dominated by Ruppia maritima, which occurs throughout the vlei in water shallower than 2.9 m. Dense stands of Phragmites australis and Scirpus littoralis occur in marginally waterlogged areas near the head of Botrivier Vlei and in the Lamloch swamp.
|Fernkloof fynbos - Images by Anton|
|View from Fernkloof Nature Reserve|
The Klein River estuary is a micro-tidal system fed by the Klein River and its tributaries, the Hartebees and Steenbok rivers. Rising in the Kleinrivier Mountains, which lie only 5 km in a straight line from the estuary, the Klein River follows an approximately 80-km course to the sea. The open water and tidal mudflats section of it are known locally as the Klein River lagoon, which is c. 10 km long and about 2 km across at its widest point. The Klein River estuary covers c. 1 280 ha, with an open water area of about 920 ha making up the bulk of the estuarine habitat. Although it is fed mainly by the Klein River, which also provides for the agricultural needs in this area, up to 30% of the estuary's flow comes from the mountains on its northern shore. This surface flow recharge of high-quality water near its exit to the sea is essential to the ecological functioning of the estuary.
The estuary is described as temporarily closed, and the large floodplains on its southern shore suggest that there have been periods of regular inundation when water levels were high. There are now human settlements around the estuary, however, and the water level is kept low, with artificial breaching sometimes used to reduce the risk of flooding. If not carried out at the correct time, artificial breaching can reduce the scouring effect and lead to the accumulation of sediments in the estuary. In addition to the open water, the major habitat types at the estuary mouth include salt marsh above the tide line, sandbanks and submerged vegetation, all of which provide essential habitat to a diverse array of waterbirds.
Approximately 1 800 ha in extent, Fernkloof Nature Reserve is situated in the Kleinrivier Mountains, adjacent to the town of Hermanus. It conserves primarily fynbos vegetation, with more than 1 400 plant species documented so far, as well as small pockets of indigenous forest. Sections of the coast within Hermanus, including the Cliff Path Nature Area and Vogelgat River, as well as parts of the Klein River estuary have now been incorporated into this reserve, thus providing a link from the mountains to the sea and conserving additional habitats. Some of the vegetation types present are Overberg and Kogelberg Sandstone Fynbos, Elim Ferricrete Fynbos and Hangklip Sand Fynbos. The Kleinrivier Mountains are also the catchment for a number of smaller streams and tributaries in the area.
|Caspian Tern - Images by MC Botha|
The Whale Coast from the penguin colony at Stony Point through the Bot River–Kleinmond estuarine system to the Klein River estuary supports more than 233 bird species, at least 86 of which are waterbirds. The wetlands across this IBA have historically held up to 25 000 birds and on occasion even more than 40 000. The Bot River–Kleinmond system and the Klein River estuary are important summer refuges for waterfowl when ephemeral waters dry up and birds are forced to seek permanent water.
At the Bot River estuary, the different ecological conditions that result when the berms are breached and when they are closed favour different species guilds. When the mouth is open, species that feed on fish and invertebrates are present; when it is closed, herbivorous waterfowl move in after a certain period. The densities of different bird species utilising the estuary are therefore likely to change on a cyclical basis as they respond to ecological alterations driven by the estuary's hydrological dynamics.
The IBA regularly supports large numbers of Anatidae, including Yellow-billed Duck Anas undulata and Southern Pochard Netta erythrophthalma. Red-knobbed Coot Fulica cristata is the dominant waterbird in the Bot River–Kleinmond system, where as many as 15 000 birds may be present when conditions are favourable. The estuarine systems also hold important numbers of Cape Shoveler Anas smithii, Black-necked Grebe Podiceps nigricollis and Great Crested Grebe P. cristatus, which breed here. The waterbodies are considered to be of vital importance for Great White Pelican Pelecanus onocrotalus, as most of its regional population depends on them for long periods when conditions elsewhere are unfavourable. Important numbers of Greater Flamingo Phoenicopterus roseus, Hartlaub's Gull Chroicocephalus hartlaubii and Caspian Tern Sterna caspia occur regularly. African Marsh Harrier Circus ranivorus is occasionally present in small numbers.
|African Black Oystercatcher|
|Preening penguins - Images by Anton|
In summer, the estuaries have historically supported more than 4 000 waders of at least 11 different species, of which Curlew Sandpiper Calidris ferruginea is dominant. Terns, which are at times very abundant, use the estuaries largely as a roosting area, from which they move to marine environments to feed. African Black Oystercatcher Haematopus moquini occurs near the estuary mouths and along sandy beaches on the seaward side of the coastal dune fields, where it has been recorded breeding.
Growing numbers of the critically endangered African Penguin Spheniscus demersus are found at Stony Point, Betty's Bay. Important populations of Cape Cormorant Phalacrocorax capensis, Bank CormorantP. neglectus, Crowned Cormorant P. coronatus and Cape Gannet Morus capensis also occur here.
IBA trigger species:
Globally threatened species are African Black Oystercatcher, African Penguin (948 breeding pairs; Crawford et al. 2012), Cape Cormorant, Bank Cormorant, Crowned Cormorant and Cape Gannet. Regionally threatened species are African Marsh Harrier, Caspian Tern, Greater Flamingo and Great White Pelican. Restricted-range and biome-restricted species that are common in the IBA include Cape Spurfowl Pternistis capensis, Cape Bulbul Pycnonotus capensis, Cape Sugarbird Promerops cafer and Orange-breasted Sunbird Anthobaphes violacea.
|Cape Sugarbird at Rooiels - Images by Carin Malan|
|Cape Spurfowl - Image by Anton|
Species that meet the 1% or more congregatory population threshold are Caspian Tern (maximum 88 individuals; this and the following figures are from Harebottle 2012), Greater Flamingo (maximum 2 884 individuals), Great Crested Grebe (maximum 356 individuals), Black-necked Grebe (maximum 199 individuals), Swift Tern Thalasseus bergii (maximum 704 individuals), Sandwich Tern T. sandvicensis (maximum 2 059 individuals), White-breasted Cormorant Phalacrocorax lucidus (maximum 247 individuals), Cape Shoveler (maximum 1 111 individuals), Yellow-billed Duck (maximum 2 500 individuals), Red-knobbed Coot (maximum 15 352 individuals), Kelp Gull Larus dominicanus (maximum 867 individuals), Hartlaub's Gull (maximum 954 individuals) and Great White Pelican (maximum 524 individuals). Species that meet the 0.5% congregatory threshold are Black-winged Stilt Himantopus himantopus (maximum 125 individuals), Southern Pochard (maximum 390 individuals), White-backed Duck Thalassornis leuconotus (maximum 134 individuals) and White-fronted Plover Charadrius marginatus (maximum 106 individuals).
|Bank Cormorant - Images by Carin Malan|
Arum lily frog Hyperolius horstockii, the endangered micro frog Microbatrachella capensis, Cape platanna Xenopus gilli and Cape dwarf chameleon Bradypodion pumilum are threatened species that occur in the IBA. The South African endemic sand toad Bufo angusticeps, sand rain frog Breviceps rosei and Cape sand frog Tomopterna delalandii have been found nearby and may well be present in the IBA. Silvery dwarf burrowing skink Scelotes bipes occurs in the nearby strandveld. Leopard Panthera pardus, caracal Caracal caracal and aardwolf Proteles cristatus have been recorded in the greater catchment area.
Changes in the quantity and quality of water entering the Bot River–Kleinmond estuarine system and the Klein River and Onrus River estuaries represent the major impact on these waterbodies. The changes are primarily due to the abstraction of water for agricultural and other development activities; water use by invasive alien vegetation; and pollution by the run-off from agricultural areas and the discharge of treated sewage effluent. Ultimately the volume, flow regime and quality of water moving through an estuary are the most important factors for maintaining its ecological functioning.
About 60% of the drainage basin is used for agriculture, primarily wheat; much of the remainder of the farmland is sheep pasture, although the number of hectares under vineyards is increasing. Soil in the catchment is poor and fertilisers are used extensively, with run-off into rivers posing a major problem as nutrient levels in the estuarine systems increase and disrupt their ecological functioning. The abstraction and storage (damming) of water to support agricultural activities alter the flow regime of rivers and the estuary. Encroachment into the riparian zone of streams in the estuary catchment may increase erosion, further disturbing the system's functioning.
Siltation of the estuaries is linked to agricultural activities and alterations to flow regimes and has become a major issue. Caused by the excessive run-off of surface soil from nearby agricultural lands, it builds up in an estuary, particularly at its head. At the same time, marine sediments may wash over the berm and be deposited at the estuary's mouth. It is essential that the berm is breached so that accumulated sediments can be flushed naturally out of the estuary. Changes to the sediment levels not only reduce the water level, but also alter the biotic communities in the estuary, which in turn impacts on other trophic levels, for example by changing the composition of the bird community.
|Southern Double-collared Sunbird - Anton|
Controversy has arisen concerning the management of the system, specifically with regard to the artificial breaching of the dune barrier at the Bot River estuary, which allows estuarine conditions to develop in the Bot River–Kleinmond system. If the dune barrier is breached every 3–5 years, juvenile fish enter the vlei and angling is good in subsequent years. Conversely, angling is poor when the dune barrier is not breached. Both the Bot River–Kleinmond and Klein River estuaries function as important nurseries for fish stocks along the coast as far afield as Cape Agulhas in one direction and Cape Point in the other. This nursery capacity is also severely compromised by illegal gill-netting in the Bot River–Kleinmond estuarine system and, to a lesser degree, in the Klein River estuary. Although good for fish stocks, artificial breaching has been shown to have detrimental ecological consequences. When management options area being considered, a range of values should be taken into account. The ecological integrity of the system is especially important, but the interests of the local community and tourism as well as the general aesthetic value should also be weighed up. When the water level drops the vlei bottom is exposed, resulting in massive macrophyte dieback, eutrophication and the destruction of much of the aquatic flora and fauna. The recreational potential of the area is also reduced for a considerable period. The breaching cycles need to account for the requirements of all biodiversity and, in particular, they should allow the estuary to maintain its capacity as a fish nursery. Artificial breaching should be carried out only after consultation with scientists from CapeNature and other concerned biologists.
Developments, both residential and commercial, are present across the entire IBA and on land adjacent to watercourses or within the estuaries. These threaten sensitive vegetation types in the landscape surrounding the estuaries, resulting in loss of habitat, and may also increase water abstraction from rivers and waterbodies in the IBA (groundwater and De Bos Dam on the Onrus River supply most of the water to this area). Polluted storm-water run-off from hard surfaces and fertilised golf courses is also a concern.
Recreational activities, including boating, kite-boarding, flying (gyrocopters), horse-riding, dog-walking and birding, occur on estuary shores and can disturb birds. These activities need to be managed and the existing zonation of activities enforced by CapeNature or the relevant municipal officials at the Bot River and Klein River estuaries so that disturbance is reduced without affecting the recreational potential of the site.
Alien vegetation (mainly Australian Acacia and Eucalyptus species) grows in the river catchments and along river courses that empty into the estuaries, and there are stands of alien vegetation on the shores of certain sections of the Bot River and Klein River estuaries. Onrus River is also heavily infested. Although projects to clear alien vegetation are under way, they need to be intensified in order to increase water flow into the estuaries, reduce erosion and hence sedimentation, and allow indigenous vegetation to recover. The fynbos that once surrounded Botrivier Vlei was extremely rich in endemics and what is left is of great conservation value. The exotic plants also transpire excessively and are inefficient users of water, which may disrupt the flow of ground and surface water and the distribution of nutrients, upsetting delicate hydrological conditions.
Poaching, especially illegal gill-netting, affects IBA trigger species indirectly, as diving birds get caught in the net. This practice also impacts severely on the estuary's ability to act as a fish nursery, one of its primary ecological functions.
|Cape Rock-jumper at Rooiels - Anton|
|Greater Flamingos over the Bot - Riaan Jacobs|
There are formal protected areas (nature reserves) on the shores of the Bot River and Klein River estuaries, where conservation action focuses mainly on the removal of invasive alien vegetation. However, there are no protected areas in the estuaries themselves, other than bird sanctuaries that depend on voluntary compliance. Management plans have been developed for the Bot River–Kleinmond estuarine system and the Klein River estuary as part of the C.A.P.E. Estuaries Programme, and management forums have been established in compliance with the Integrated Coastal Management Act and National Estuary Management Protocol. The forums have been tasked with implementing the management plans.
The formal protected areas in the IBA are CapeNature's Rooisand Nature Reserve on the western shore of the Bot River–Kleinmond estuarine system; Kleinmond Nature Reserve, surrounding the Palmiet estuary; Fernkloof Nature Reserve on the northern shore of Klein River estuary and around Hermanus; and sections of CapeNature's Walker Bay Nature Reserve on the southern shore of the Klein River estuary. The Stony Point penguin colony at Betty's Bay is a controlled area that provides a degree of protection for the penguins and other seabirds breeding there. CapeNature is now the formal management authority for this site.
Conservancies also exist in some of the farmland around the estuaries, but they are not very active and require rejuvenation. As well as developing a Ramsar application for the Bot River–Kleinmond estuarine system, CapeNature is investigating the possibility of conservancy or other Biodiversity Stewardship options for local landowners.
Additional conservation actions include the monitoring of water quality (faecal bacteria) in the estuaries every three weeks; summer and winter fish surveys and bird counts; and quarterly monitoring of the physical and chemical properties (salinity, temperature, dissolved oxygen, pH, turbidity and inorganic nutrients) at the estuaries of the Bot and Klein rivers. Management plans for the artificial breaching of the Bot River and Klein River estuaries have been approved by the provincial environmental authority and they are implemented as required (to compensate for reductions in flow). Projects to clear alien vegetation are carried out in the catchments and riparian areas of the estuaries. Some wine farms in the Bot River catchment and the Hemel en Aarde valley in the Onrus catchment are members of the Biodiversity & Wine Initiative, which assists with environmental management interventions for these areas. Activities that require authorisation from the provincial authorities, following a process prescribed in the Environmental Impact Assessment regulations, have been identified under NEM:PAA. They help to protect biodiversity and ecological functioning and prevent pollution, the destruction of estuarine and riparian habitat and the disruption of natural coastal processes.
(All images by members of BirdLife Overberg).