Wetlands are wet, swampy, sodden land, muddy land, or ground covered by shallow pools. The water does not easily drain away and the land seems like a big squishy sponge. Some wetlands are filled with fresh water and others with salty, brackish or briny water. Water either flows through them, drains into the ground or stagnates. Some are tidal. Wetlands can be permanently damp places or form seasonally, depending on sudden downpours or regular tidal movement to appear and then disappear as the water slowly drains away. They play an important role in protecting the land, preventing loss of soil and nutrients, filtering pollution, slowing runoff and storing moisture for drier months of the year.
Lakes are not generally classified as wetlands although they may be fed by water that has passed through a wetland, their edges may be shallow and form swampy margins or they may drain into a wetland. In NZ we also have wetlands forming in geothermal hotspots or bubbling out of the ground as fresh water springs.
Wetlands are often not photogenic. If you don’t know what to look for they look messy, wet and uninteresting but they hide an amazing variety of life (biodiversity). To learn about this habitat you could visit a wetlands on World Wetlands Day (February 2 or thereabouts) or take part in activities organised by DOC or your local council. Many plants are found only under these damp conditions. Home to a myriad of bugs and insects, which sustain a wide variety of fish and bird species, some found only in that one habitat. They are often best explored on specially created paths and boardwalks, which protect the fragile ecosystems from our weight and allow us to enter the heart of a wetland without damaging plants or sinking knee deep in mud. We can also often explore these secret spaces on the water by boat or kayak or from viewing platforms and behind hides getting closer views of any birds, eels or fish life without disturbing them.
Many swamps, marshes and bogs in New Zealand were drained by pioneer farmers. This destroyed eco-systems that people at that time did not value or understand. Gum diggers and mining for swamp kauri added to the destruction of wetlands. Farm runoff, septic tank runoff, weeds including imported plant, introduced animals, pollution caused by people and machinery, changing land use, forestry and housing developments all affect wetlands. Today some of these sites are being restored and local groups work together to protect their wetlands and educate people about the unique characteristics found there.
Understanding the special endemic species, which can be found in different wetlands and how to ensure they survive is a battle. We need to value these unique ecosystems and find ways to understand them better. In many places the value of wetlands is now recognised and people are working together to restore wetlands. Land owners, farmers, local groups, DOC, Forest and Bird, local and national government agencies are all involved in these projects.
Some wetland areas cover many hectares but they can also be small – like large muddy puddles, perhaps a low lying dip in the forest floor which holds water and supports its own distinct community of flora and fauna.
Some of the wetland birds you can look out for are –
- Kaki – black stilt
- Kuaka – bar-tailed godwit
- Kuruwhengi – NZ shoveler
- Makuku – Australasian bittern
- Mātātā – Fernbird
- Pāpango – NZ scaup
- Pāteke – Brown teal
- Poaka – Pied stilt
- Pūtangitangi – Paradise shelduck
- Pūweto – Spotless crake
- Tūturiwhatu – NZ dotterel
- Various species of shag
Some of the common wetland plants you might see are
- native sedges such as purei,
- swamp reeds like raupo
- native trees like kahikatea, tī kōuka (cabbage trees), swamp maire and coprosma.
Many trees, which grow in swampy conditions, have developed special root systems called pneumataphores. These enable them to access oxygen even when the rest of the roots are under water. Mangrove trees are the commonest example of this adaptation.
Different types of wetland have different names and recognising which is which can be tricky for the casual observer. Each had its own community of plants, insects, fish and birds. To complicate matters, our definitions do not always match those of other countries (like America or Britain).
- Swamps and marshes
- Bogs and fens
- Estuaries, tidal flats, salt marshes, dune lakes
- Mountain lakes, tarns, glacial pothole/kettleholes
- Geothermal and natural fresh water springs
- Manmade e.g. urban wetlands, storm water ponds, rain gardens bioswale gardens
Uncommon wetlands in NZ