Ultrabasic sea cliffs
Coastal cliffs are very steep rock faces near the sea that are greater than 5 m in height. They may ascend in steps and have ledges, crevices and overhangs. Coastal cliffs may rise directly from the sea or be separated from it by a narrow shore. Ultrabasic (also known as ultramafic) rocks contain very little quartz or feldspar and are composed essentially of ferromagnesium silicates, metal oxides, and native metals (Anon 1962) that weather to soils with low concentrations of major nutrients and high concentrations of toxic metals such as nickel, chromium, and cobalt. Cliffs and outcrops provide many varied habitats: from bare rock that can only be colonised by mosses and lichens to deeper soils supporting woody vegetation; from highly exposed situations to heavily shaded and sheltered habitats; and from very dry to permanently wet surfaces. Coastal cliffs are influenced by salt spray, particularly near their bases, with halophytes often characteristic. Vegetation often consists of matted small-leaved shrubs such as wire-netting bush (Corokia cotoneaster), naturally uncommon Cassinia amoena, and Mingimingi (Leptecophylla juniperina). Native species that have been lost from neighbouring habitats may find refuge on cliffs and scarps.
Coastal cliffs of ultramafic rocks, coastal cliffs of serpentine rocks
Where do they occur?
Ultrabasic sea cliffs occur on the Surville Cliffs, North Cape, and further south at Taipare Bay, D’Urville Island.
Notable flora and fauna
Threatened plants include the nationally critical Surville Cliffs hook grass (Uncinia perplexa), the nationally endangered Surville Cliffs kohuhu (Pittosporum serpentinum), the nationally uncommon North Cape sedge (Carex ophiolithica),Coprosma distantia,Coprosma spathulata subsp. hikuruana,Geniostoma ligustrifolium var. crassum, Surville Cliffs haloragis (Haloragis erecta subsp. cartilaginea),Hebe brevifolia Surville Cliffs mingimingi (Leucopogon xerampelinus), North Cape native jasmine (Parsonsia praeruptis),Pittosporum pimeleoides subssp. majus,Pomaderris paniculosa subsp. novae-zelandiae, Pimelea aff. tomentosa (b) (AK 130893;Surville Cliffs), and Pseudopanax aff. lessonii (AK 46066; Surville Cliffs).
Threat statusEndangered (Holdaway et al. 2012)
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