Types of Environments within the coastal environment

The environment provided by the land-sea interface supports a large number of animal, insect and plant species that are not found further inland. The coast also sustains an unusually wide range of birdlife, with birds acting as important ecological engineers through carrying material across ecosystems. The coast has, however, seen much change in the last thousand years through human activities.

When Māori first arrived in New Zealand, over 800 years ago, most of the coast was covered with forest to the water’s edge. Much of this coastal forest was destroyed within 200 years of human settlement, primarily through burning. ³⁰⁹²  When European settlers arrived over 500 years later, the  destruction of vegetation in the coastal environment accelerated dramatically. In addition to clearing large tracts of coastline, these settlers introduced numerous invasive plant and animal species.

Duneland systems

Dunelands have developed along the coastal margin where sediment has collected and been trapped by vegetation. Between the dunes, where the water table is high, swamps, wetlands and even large coastal lakes can form. The wet sand gives these systems more stability than the surrounding dunes and extensive plant and wildlife communities can become established. Where the hollow between the dunes is free of water, extensive sandy plains can form. The front face of  the foredune is usually the most dynamic part of any dune system, and it is here where most sand is initially trapped, by sand-binding plants. These plants are particularly hardy, as they need to survive the forces of wind, waves and salt spray.

Two important sand-binding plants are the endemic primitive sedges pingao and kōwhangatara.  Backdunes are typically more stable, and if left undisturbed, these dunes can become covered with woody and herbaceous species. In northern areas toetoe grows in damp dune hollows. Eventually these dunes become stabilised and covered with woody shrub and tree species, forming coastal forest.

One of the largest unmodified dune systems can be seen at Mason Bay, on the west coast of Stewart Island, where the dunes back the nineteen kilometre long beach. ³⁰⁹³  Nearly complete dune systems  also occur on Great Barrier Island and these are associated with intact wetland ecosystems.

Estuaries

Estuaries commonly form when rivers meet the sea. Along sheltered coastlines, estuarine areas provide very ecologically productive environments, where fertile sediment washed from the land is trapped in shallow tidal inlets. New Zealand has around 300 estuarine systems, covering over 100,000 hectares. ³⁰⁹⁴

Estuaries are important habitats and feeding grounds for a range of migratory and wading birds,  including the eastern bar-tailed godwit. About 60,000 of these birds visit New Zealand each summer, with large numbers feeding in the Kaipara and Manukau harbours and at Farewell Spit. Oystercatchers, godwits, wrybills, pied stilts, herons and Caspian terns all spend hours searching the mud for invertebrates. The mangrove and saltmarsh habitats in estuaries are commonly inhabited by a range of swamp birds, such as bittern and banded rail.

Estuaries are important spawning and nursery areas for a wide range of fish and shellfish species. Fish such as sand flounder, kahawai and yellow-eyed mullet use estuaries every day. Other fish, such as snapper, red cod and gurnard, enter estuaries seasonally, coming in as juveniles to feed in the rich, sheltered waters and heading back out to sea as adults. ³⁰⁹⁵  Estuaries are also important for a number of native fish that migrate between freshwater systems and salt water, such as adult whitebait or īnanga. ³⁰⁹⁶

Estuaries are dominated by salt-tolerant plant species. In northern frost-free areas, large mangrove forests can be seen growing in the intertidal zone of shallow muddy inlets. Mangroves are common in the north, but where they are affected by frost, sea rushes tend to replace them in marshy coastal areas. Saltmarsh ribbonwood can form a dense mat just above the high tide mark.

Wetlands

Wetlands are very diverse; they vary in wetness, fertility, acidity and salinity. They are influenced by a range of factors including different landforms, substrates, hydrology and vegetation ³⁰⁹⁷  and cross both coastal and terrestrial environments. The major types of wetlands found in New Zealand’s coastal environment include bogs, fens and swamps. Each supports a different community of fauna and flora.

Swamps are much richer in nutrients than bogs and fens, so they can be highly fertile. They benefit from both ground and surface water inflow, carrying nutrients and sediments from adjacent land. A wide variety of plants can be found in swamps including sedges, rushes, reeds, bullrush (raupō), flax and mānuka. A number of coastal forest trees live in swamps including kahikatea, pukatea and cabbage trees. Swamps tend to be found in low lying areas such as coastal plains.

Rocky coasts

New Zealand’s rugged and rocky coastline is exposed to energy from ocean swells and salt-laden winds. The shrublands and forests which survive in this harsh environment are made up of a range of species which can tolerate salt and wind like the pōhutukawa. Pōhutukawa only naturally grow in upper parts of the North Island, north of a line stretching from Gisborne on the east coast to just north of New Plymouth on the west.

In southern areas where the climate is cooler and more inhospitable, the southern rātā occupies a similar niche. Closer to the shoreline smaller species are found, including taupata, karo, pūriri and karaka. Rocky coasts support threatened and rare plants including the nationally critical coastal peppercress and nationally endangered Cook’s scurvy grass and New Zealand water cress. ³⁰⁹⁸

Seabirds

New Zealand has been called the ‘seabird capital of the world’, with eighty-four species of seabirds breeding in the country, a quarter of the world’s total. The rocky coastline provides a critical breeding environment for many of these seabirds. One of the rarest penguins in the world, the yellow-eyed penguin, is found only in New Zealand along the southern east coast of the South Island. The little penguin (also known as the blue penguin), is the smallest penguin species in the world and is far more abundant around New Zealand’s coastline, particularly along the east coast.

Marine mammals

The New Zealand fur seal population, once abundant and now recovering after harvesting by both Māori and European settlers, is estimated to be between 50,000 and 100,000. Seals can be seen along the coastline of the South Island and in some southern North Island areas. Seal ‘haul outs’, important spots for marine mammals to rest between feeding, include those around the coast of Wellington. The New Zealand sea lion and the southern elephant seal can also be seen around the southern coasts, mainly hauling out on sandy beaches, although the main populations are on the subantarctic islands.

Last updated at 3:58PM on February 2, 2018