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NRRP - Chapter 7 (Wetlands)

Waihora Ellesmere Trust

What are wetlands?

Wetlands are permanently or temporarily wet areas of land or shallow water, with fluctuating land-water margins, that support plants and animals specially adapted to wet conditions.

Wetlands bring life to land

People generally think of wetlands as areas of waterlogged ground and shallow waters with emergent vegetation, such as are often found at land-water margins, and describe these as bogs or swamps. Technically, however, the term ‘wetland’ can also include shallow lakes and ponds, tidal estuaries, and lagoons, as well as bogs (fed by rainwater alone) and swamps (fed by streams, groundwater or run-off).

Canterbury has a great variety of wetlands, large and small, from the coastal to alpine zones. Wetland water may be fresh, brackish or saline. The types of plants and animals found in wetlands depends on the water - its amount, depth, permanence, temperature, the chemicals found in it, and its source - ground water, surface water, rainwater or seawater.

Examples of the range of wetlands in Canterbury include:

  • Estuaries such as the Avon-Heathcote and Ashley River mouth
  • Coastal lagoons such as Wainono Lagoon
  • Margins of the shallow, brackish Lake Ellesmere
  • Freshwater swamps such as Travis wetland in Christchurch City
  • Margins of the Ashburton lakes
  • Ephemeral “kettlehole tarns” in the glacial moraines of the high country

No two wetlands are exactly alike. The look of a wetland and its mix of plants and animals vary with local conditions (for example, climate, water flow, altitude and substrate). Several different types of plant and animal communities may be present in larger wetlands, and all wetlands may change over time as environmental conditions alter.



Why wetlands are important

Wetlands once covered large areas of New Zealand. Now they are some of our rarest and most at-risk ecosystems. Wetlands provide habitat for a diverse range of plants and animals and are home to many rare and threatened species, such as the Australasian bittern and Canterbury mudfish. Wetlands are essential breeding areas for whitebait species and valuable habitat for eels. Although wetlands now cover less than 2% of New Zealand’s land area, they are still home to an astounding 22% of all native bird species.

Single wetlands should not be considered as isolated wildlife habitats but rather part of a network. Migratory bird species are very dependent on a chain of suitable wetlands on their flyways for resting and feeding.

Find out more about New Zealand bird life Leaving Environment Canterbury

The conservation and restoration of wetland habitats can make a real difference for wetland species and also benefit the wider environment (including ourselves!).

Wetlands are important storage areas for floodwaters. Think of a wetland as a giant sponge. Wetland plants slow the flow of water off the land, soaking up excess floodwater, and then slowly releasing it to maintain summer water flows.

Wetland plants trap sediment suspended in water, improving water quality. In riparian areas, their roots hold riverbank soil together, reducing erosion. Nitrogen and phosphorus enter waterways through groundwater, surface runoff and disposal of effluent. Wetland vegetation uses some of these nutrients for growth. Bacteria living in wetland soils absorb and break down nitrogen from farm run-off and leaching, also improving water quality.

Wetlands are highly valued by tangata whenua and local communities for their educational, scientific, aesthetic, spiritual and cultural values. They form part of our natural landscape and offer many opportunities for recreation such as fishing, hunting, canoeing and bird watching.



Where have all the wetlands gone?

Approximately 90% of New Zealand’s freshwater wetlands have been lost in the last 150 years. Most of these wetlands were in areas very desirable for the development of farmland. Draining, burning and clearing of vegetation for farmland, together with the reclamation of wetlands for urban and industrial uses, have been the principal agents of wetland destruction.

Within Canterbury, for example, in 1840 a massive complex of freshwater and saline wetlands extended across the low plains from the Waipara River to the Rakaia River. These have mostly been reduced to small, scattered fragments, surrounded by urban areas and farmland.

 

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