Wetlands and Streams

Wetlands are places where the ground is permanently or temporarily wet, and can be found from the coast to the mountains. They support a natural ecosystem of plants and animals that are adapted to wet conditions. Southland’s wetlands are widespread and diverse; however our intact wetlands have been reduced by 37% since European settlement. Find out more about Southland’s wetlands and the special plant communities found within them.

Types of wetlands

Southland wetlands can be grouped into four main types:

  1. Coastal
  2. Swamps
  3. Peatlands
  4. Alpine

Wetlands are very complex systems and often a single wetland type will often be found in association with another type.

1. Coastal wetlands

There are two main types of coastal wetland in Southland: salt marshes and dune slacks. Visit the following to see a diversity of coastal wetland communities:

  • New River Estuary
  • Awarua Bay
  • Waikawa Harbour
  • Jacobs River
  • Toetoes Harbour
  • Waiau River Mouth
  • Waituna Lagoon.
Salt marshes

Salt marshes are a type of coastal wetland that form in estuaries or lagoons where they are regularly exposed to sea water. Here you’ll see a zonation pattern where plants with the most salt tolerance grow where they are exposed to the tide. Less salt tolerant plants grow where they are only occasionally reached by salt water or spray. Salt marsh plants grow in four main zones:

  • Lowest zones – such as eel grass beds.
  • Low-mid zones – for example, succulents, such as glassworts, which are adapted to high salt levels.
  • Mid zones – such as ‘salt meadow’ communities.
  • Upper zones – for example, tall sedges, rushes and some shrubs, which have their bases submerged when the tide is in.

Salt marshes can sometimes be found on headlands above the sea, forming where there is wave splash and sea spray. These are called ‘coastal turfs’.

Dune slacks

Dune slacks are a type of mini-wetland that forms in the hollows between sand dunes. They form where the wind has eroded sand down to the level of the water table. Here you’ll find patches of rushes or sedges, creeping plants or solid turf.

Check out examples of dune slacks at Oreti Beach in Invercargill, Waipapa Beach and Masons Bay on Stewart Island.

2. Swamps

Swamps can be found on the edges of lakes, rivers and ponds, as well as wet pasture. They have been more extensively modified by land development than any other wetland type. Valley floors with swampy areas were once common through Southland. However, only small patches can still be found on today, mainly on farmland.

The Redcliff Reserve below Manapouri is a good example of an extensive area of shallow water with swampy vegetation. This wetland has an open water area of about 50 hectares and is home to a great range of waterfowl and other wetland species. It also has high numbers of long-finned eels.

Swamp forest of kahikatea was once widespread on the flood plains of Southland. However, only a few remnants remain. You can visit these at Thomsons Bush along the Waihopai River and Turnbull Bush, Tussock Creek.

Swamp vegetation includes purei and other sedges, flax, manuka, red tussock, toetoe and cabbage trees.

3. Peatlands

Peatlands differ from freshwater swamps because their soil substrate is made up of peat. Peat has low fertility, is usually saturated with water and is anaerobic (lack of oxygen).

Peatlands support a range communities, including manuka shrublands, wire-rush tangle, fern-swamp inaka-manuka, red tussock-flaxland, rushland, sphagnum hollows and pools. The most extensive community association in Southland is the wirerush-tangle.

Some of Southland’s largest and most important wetlands are nationally or even internationally important, such as the Waituna Wetland. Waituna peatland is one of the most significant wetland habitats in New Zealand. It is home to specialized plants, fernbirds, the Australasian bittern and a range of other fauna, such as skinks, the giant kokopu (native fish of the Galaxias genus), as well as moths, grasshoppers and beetles.

4. Alpine wetlands

You’ll find alpine wetlands in mountain environments with high rainfall, cloud cover and colder temperatures. They are usually found in snow tussock landscapes and have a high diversity of plants and animals.

Alpine wetlands are relatively untouched by human development. As a result, they function naturally and often have a direct influence on maintaining water flows in the headwaters of river catchments.

Visit Key Summit off the Milford Road or the Garvie Mountains in Northern Southland to see significant examples of alpine wetlands. There are herbfields, cushion bogs, sedgeland-mossfields, sometimes with patterned pond systems, or adjacent to lakes or tarns.

Streams

An important part of wetland restoration is the fencing and planting of stream edges. Native plants growing along stream edges benefit the whole stream environment. By fencing and planting stream edges you’ll find improvements in stream bank stability, habitat for wildlife and better water quality.

See our recommended planting list of wetland species for Southland. Find out more about them and check out the photos to help you identify them.

Restoring Wetlands

Natural wetland habitats are very diverse and complex. It is difficult to reproduce nature, so the best we can do is protect what is existing and speed up the process of recovery from damage.

Your wetland restoration project may involve restoring a drained wetland, one affected by grazing, or creating a new wetland habitat from scratch (for example, a pond from a grass paddock).

When undertaking a restoration project, remember to:

  • Protect what is already there – people cannot re-create it in our lifetimes.
  • Fence off wetlands – no matter how small or damaged, native vegetation will repair itself given time and the removal of browsing animals.
  • Undertake weed and animal pest control to assist repair.
  • Re-establish the high water table if that has been damaged.

Remember that planting is only done when a wetland is so badly damaged that it cannot repair itself or you want to create a new wetland from scratch.

What to plant

Restoring the range of wetlands illustrated above is very difficult. However, here are a number of native wetland plants that do well in Southland.

See our recommended planting list of wetland species for Southland. Find out more about them and check out the photos to help you identify them. Check out our information about creating a pond.

Find out more

Find out more about Southland’s wetlands in the following booklet:

  • Wetlands of Southland – A Guide for Maintaining and Enhancing the Values of our Wetland Areas

Booklets are available from the Invercargill City Council.