Physical Environment
The coastline from Berghan Point to Takou Bay is predominantly steep and rocky, interspersed in places by sandy beaches. The rocky terrain is composed of andesite and greywacke, with a deposit of manganese visible in the headland separating Tauranga and Marble Bays. Small estuaries occur at Tauranga Bay, Mahinepua Bay, and Takou Bay. Road access to the northern part of this area is poor, but from Matauri Bay to Wainui Bay a road runs close to the coast. South of this, the area is again relatively inaccessible by road, with the only road to the coast being that to Takou Bay. The coastline has been extensively modified by the removal of indigenous forest for timber and agricultural use, and has been locally modified for residential use, especially the estuarine areas at Tauranga Bay and Mahinepua.
The coast north of Whangaroa Harbour entrance to Berghan Point is nationally important for its coastal forest remnants, dotterel nesting sites, and archaeological sites. South of Whangaroa Harbour heads, habitats used as breeding areas by brown teal are internationally important, with other wetland areas and archaeological sites having national importance.
Offshore from the coast are the Stephenson and Cavalli Islands. Stephenson Island (an island of 112.5 ha.) is situated approximately 10 km north of the entrance to the Whangaroa Harbour. Off the northwestern tip of Stephenson Island lies Cone Island (2 ha.) and the Kawhiti Reef. 23 km further down the southward coast lie the Cavalli Islands, situated approximately 1 km off Matauri Bay on the east coast. The Cavalli Islands consist of 28 islands, with 82 associated rocks, plus 25 stacks, within an area of approximately 29 km 2 . Motukawanui and Motukawaiti are the largest of the islands (350 ha. and 47 ha. respectively). Both of these islands have been highly modified through clearing for agriculture, but most of the other islands have retained their natural state. Cavalli and Stephenson Islands are nationally important habitats for threatened flora and fauna, and are nationally important as archaeological sites (DOC, 1990).
Except where sheltered by the islands mentioned above, the coast is exposed to the Pacific Ocean, although indentations in the coastline provide some locally less exposed areas. The ecology of the area is influenced by the sub-tropical East Auckland current.
Flora & Fauna
The exposed rock coastline is dominated by broad zones of barnacles Chamaesipho brunnea and Elminius plicatus , and algae species such as Porphyra columbina, Gelidium pusillum, Codium adherens, Xiphophora chondrophylla var. minor , and Carpophyllum angustifolium . Species of mollusc commonly found include the gastropods Nerita melanotragus, Neothais scalaris , and limpets Cellana ornata, C. radians , and Notoacmea parviconoidea . Paua, kina and crayfish are also abundant, and scallops are found inshore of the Cavalli Islands.
The many small rivers and streams along this coastline provide an important habitat for fernbird, and lesser numbers of brown teal. The estuarine areas at Tauranga Bay, Mahinepua Bay and Takou River include areas of mangrove and saltmarsh. Further up, the Takou River estuary is one of the largest mainland brown teal roosts. Banded rail and spotless crake are also present in some wetland areas. Nesting and feeding areas for NZ dotterel occur at Motukahakaha Bay, Tauranga Bay and the area between Tamauri and Taronui Bays. Variable oystercatchers nest on the sandy beach at Takou Bay.
The Stephenson and Cavalli Islands contain areas of high natural value. Motukawanui was farmed until 1974, but regeneration is now occurring. Stephenson Island was also farmed. Many of the small islands are rat and mustellid (e.g. stoat and weasel)-free, thus promoting a greater diversity of birds and reptiles. The lizard fauna of individual Cavalli Islands is diverse - for example, seven species of lizard are found on Motuharakeke, including the rare Cyclodina macgregori . Many seabirds use Stephenson Island for roosting and breeding, including Pycrofts petrel ( Pterodroma pycrofti ) (DOC, 1990).
References:
Department of Conservation. 1990. Coastal Resource Inventory - First order survey: Northland Conservancy. Compiled by Tim Shaw & Joan Maingay.
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