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Wetlands in our region

Wetlands in our region

Updated 21 September 2021 10:46am

In the Wellington region, we have a number of different types of wetlands which are home to different ecosystems. The species you might find in a wetland depends on many factors. These include whether it is coastal or inland freshwater, water flow, how long the water stays in the area, the depth, temperature, and what sediments and nutrients are in it.

Wetlands in the Wellington Region

There are only around 3 percent of wetlands remaining in the Greater Wellington Region. Many of our remaining wetlands continue to be under pressure from the impacts of land use and plant and animal pests.

Wetland species are adapted to cope with change. Periods of high wind, dry summers, and the constant ebb and flow of water are conditions that must be endured by all species that live there. However, plant and animal pests, clearing of plants, and the drainage of wetlands for land use are changes that these species cannot cope with. The few wetlands that remain are now isolated and fragmented, and many wetland plants and animals are now threatened with extinction.

In 2020, Wairarapa Moana was recognised as an area of international significance under the Ramsar convention. The Wairarapa Moana Wetlands Project is a joint initiative between Greater Wellington Regional Council, the Department of Conservation, South Wairarapa District Council, Kahungunu ki Wairarapa and Rangitāne o Wairarapa Inc. 

Check out the Wairarapa Moana Wetlands website for information on visiting, and what makes this place so special.

Threats to wetlands

Wetlands, and the species that exist within them, face many pressures. Careful management of wetlands can decrease the effects of certain threats, including

Drainage: Drainage and cultivation of land has caused significant loss of our region’s wetlands. Changes further upstream, such as damming and channelling, can also affect the amount of water that reaches a wetlands.

Plant and animal pests: A range of introduced species have become established in some wetlands, and pose a threat to the native plants and animals present by:

  • Preying on native animals and eggs
  • Stirring up sediment and grazing on aquatic vegetation
  • Competing for light, nutrients and space.

Pest animal species include rats, possums, stoats, deer, rabbits, hares, pigs, and koi carp. Pest plants can be just as threatening as pest animals. Some species can grow quickly in wetlands, competing against native species for light, nutrients and space. 

Our Regional Pest Management Plan (RPMP) sets out programmes for managing pest plants and animals in our region. Find out more about pests in the Wellington Region. 

Hunting and harvesting: Hunting, eeling and whitebaiting are important traditions for many New Zealanders. This can put pressure on the fragile populations in wetlands, but does also encourage people to protect them for these practises. 

Grazing - Stock with uncontrolled access to wetland areas can increase nutrient levels through their urine and dung, disturb the wildlife and plants, spread weeds and erode the soil. Allowing stock to access wetlands can also be dangerous to them, as they can become bogged down and trapped.

Pollution - Fertiliser applied to farmland can affect nearby wetlands through run-off, leaching and spray drift. Nutrients can also enter wetlands during storms or floods, when eroded soil washes down into wetlands.

While some wetlands are associated with naturally filtering sediments and nutrients, excess nutrients in wetlands can change the delicate balance of the ecosystems that exist there.

Types of wetland

Types of wetlands that can be found in our region include:

Bogs: Bogs are rare and precious in the Wellington region. Fed only by rainfall, they are low in fertility and are acidic. They are home to a variety of specialist plant life, with the wettest dominated by sphagnum moss. Drier bogs support a variety of plants including sedges, rushes, umbrella ferns and mānuka.

Coastal wetlands: Estuaries (including salt marshes) are the most productive of all wetlands, and especially rich in animal life. Many coastal fisheries depend on estuaries as fish spawning grounds.

Swamps: Most wetlands on private land are swamps. They are more fertile than bogs because the water flowing through them brings silt and organic matter. Swamp water levels fluctuate seasonally.

Typical swamp plants include raupō (bullrush), pūrei and harakeke (flax). The organic matter these plants produce encourages large populations of aquatic invertebrates including insects, watersnails, crustaceans and worms, and vertebrates like frogs and birds.

Lakes and ponds: Lakes are permanent areas of fresh water. Open water areas with shallow margins surrounded by swamp vegetation provide important water fowl habitat. Of the significant number of lakes in the Wellington Region, the largest is Lake Wairarapa.