Biological Environment of the West Coast Coastal Marine Area: an outline of Marine and Coastal Ecosystems and Habitats
3.7 Ecosystems on the Margins of the West Coast Coastal Marine Area
Some ecosystems and habitats on dry land and in freshwater on the margin of the West Coast coastal marine area are briefly discussed below because they can have a physical and biological influence on the coastal and marine environment. Some of the main types include:
- islands and rock stacks;
- dune lands; and
- freshwater waterways and wetlands
3.7.1 Islands and Rock Stacks
Above the wash of the tide, islands and stacks often have a cap of vegetation
with the amount of soil development depending mostly on the height and area
of the island’s surface. These off-shore sites provide resting and breeding
places, free of predators and other types of disturbance, for wildlife which
otherwise live in the marine zone, such as fur seals and burrowing seabirds.
Islands also provide refuges for threatened plants (e.g. seal cress nau) and
add greatly to the diversity of habitats and marine life along open coasts.
For example, they can be surrounded by rocky reef areas that sometimes extend
to considerable depths, and are less affected by wave action compared to the
mainland coastlines.
The main island groups off the West Coast are mapped in Figure 3.3. Of the
70 vegetated rock stacks and islets in the West Coast Tai Poutini Conservancy,
Taumaka me Popotai (the Open Bay Islands) makes up most of the total area.
Taumaka me Popotai (Open Bay Islands), a group of islands 4 km off the mouth
of the Okuru River in South Westland (see map12, Haast, in Chapter 5), are
regarded as the most important islands on the West Coast because of their
habitat and wildlife features.
| Islands and rock stacks rise above the surrounding coastal marine area. | |
 |
 |
| Open Bay Islands Photo: P Ryan, DOC collection |
Motikiekie Rocks Photo: D Neale, DOC |
The cluster of islands at Motukiekie81 support burrowing
seabirds (which are not common on the West Coast) and threatened plants. Some
islands such as Wall, Hanata, and Cascade Islands are places for such species
as fur seals, threatened plants and reef invertebrates. Other island and stack
clusters at Wekakura, Punakaiki, Moeraki and Jackson Head have not yet been
well studied.
Taumaka me Popotai is private (Maori-owned) land, and is also a gazetted wildlife
refuge and a Coastal Protection Area in the Regional Coastal Plan. Seal Island
is a scenic reserve and, along with several other islands and stacks, is among
the Outstanding Natural Features and Landscapes listed in the West Coast Regional
Coastal Plan. A biosecurity plan produced by DOC82 aims to protect the natural features of Taumaka me Popotai from weeds and
animal pests.
3.7.2 Dune Lands
The best development of dune landscapes on the West Coast is north and south
of the mouths of the Haast and Okuru Rivers, where shore-parallel dune ridges
extend inland for 2–3 km. This section of coastline is extending seawards
as sand continues to accumulate. These Haast-Okuru dunes also carry impressive
sequences of undisturbed indigenous vegetation, from pioneer sand-binding
plants to mature forest (with intervening swamp vegetation).
ohnson (1992) surveyed the sand dune and beach vegetation of the West Coast as part of a national inventory carried out by DSIR Land Resources. The DSIR inventory showed that the relatively inaccessible coastline (backed by bush-clad hills) from Kahurangi Point to about Karamea has a predominantly rocky coast interspersed with dune systems which are botanically significant83. Here, “Small beaches contain lenses of unmodified native vegetation and the larger dune systems have excellent mosaics of sand dune communities, including pingao, dune herbs and grassland, coastal broad-leaved forest, nikau forest, hard beech and northern rata forests, and some lagoon vegetation locally”.
 |
 |
| Burmeister Morass: forested sand dune and wetland complex. Arawhata River mouth in distance. Photo: DL Homer |
Nikau palms on the coastline, south of the Heaphy River. Photo: L.F. Molloy |
The coastline from Hunts Beach to Sandy Beach (Makawhio River) and on to Maori
Beach (Bruce Bay) consists of a wave-worked beach practically without vegetation
and abuts a low scarp cut by storms into the alluvial deposits of the hinterland.
Here, “....there is almost no transition between the bare sand and gravel
of the beach, and salt-damaged podocarp forest behind”.....”Very
different beaches occur between Tititira Head and Ship Creek where there is
an indented coast backed by steep hills of Tertiary sedimentary and volcanic
rocks. Here numerous sandy beaches (such as Monro, Moeraki, and Murphy Beaches)
line small coves”.
Overall, Johnson rated the beaches at three sites – Saltwater Lagoon,
Okarito Beach, and Ohinemaka – as having the best unmodified indigenous
duneland vegetation in Westland. “Despite modifications by grazing,
fire and weeds, these sites are valuable biologically, the more so because
of their settings within a diversity of adjacent landforms and vegetation”.
Two other beaches in South Westland – Cole Creek and Ship Creek to Waita
River – “are of interest partly because of their dune-to-forest
sequences, but also because they have examples of native coastal vegetation
easy of access from the highway north of Haast”84.
Cascade River and Barn Bay (which Johnson included as part of a ‘Fiordland’
area) were rated very highly as “very important for their diversity
of dune communities and associated wetlands, in good condition.”
Pingao (golden sand sedge) is the main dune-forming endemic coastal plant
on the West Coast. Previously widespread throughout New Zealand, it has suffered
from competition with weeds such as marram grass and gorse, as well as grazing
by stock and other browsing mammals. It remains relatively common in some
parts of the West Coast, especially to the north of the Heaphy River and south
of Cascade Point. Ship Creek and Pahautane Beach are two very accessible sites
where this plant still thrives.
.jpg) |
Pingao on sand dunes at Ship Creek. |
3.7.3 Freshwater Waterways and Wetlands
Other wetland types also occur upstream of the coastal marine area, e.g. freshwater
swamps, lakes and rivers.85 These are often connected directly to the coastal
marine area by a flowing channel that provides important physical linkages
(e.g. the movement of fresh water, sediments and nutrients into the coastal
marine area) and biological linkages (e.g. the migration of freshwater fish
and their use of wetlands for spawning) between the land and sea environments.
81 [as shown in Chapter 5, Segment 5 of this report]
82 Newton 2005
83 Johnson 1992
84 Johnson 1992, p216