Wetlands and estuaries

Otago's wetlands and estuaries are some of the most valuable ecosystems in our region, and are recognised for their ecological, cultural and socio-economic values.

   

What is a wetland?

Wetlands are permanently or intermittently wet areas that support natural ecosystems of plants and animals. They can include bogs, swamps, fens, shallow water and salt marshes, and are found from the  coast to the high country.

90% of New Zealand’s wetlands have been cleared and drained in the last 150 years, however an increasing number of land owners are now seeing the value in restoring these unique landscape features. 

   

What’s so special about wetlands?

Wetlands are important environmental filters, often described as the kidneys of the landscape. They are also important for biodiversity by supporting a variety of native birds, fish, invertebrates, and plants.

   

Wetlands can improve water quality by:

  • Filtering sediment and nutrients
  • Removing soluble nitrogen from runoff and resurfacing groundwater. In some soils, managed wetlands are the most effective solution to reducing the amount of nitrogen reaching waterways. Too much nitrogen in the water can cause nuisance plant/algae growth, which affects ecosystems and water quality.

Wetlands are also valuable for Otago’s environment because they:

  • Improve local biodiversity by providing a habitat for fish, birds and insects
  • Reduce flood peaks by slowing the water flow
  • Retain summer water flows by releasing water slowly
  • Have both recreational and educational value.

Downlaod the Wetlands in Otago brochure

 

Regionally Significant Wetlands

A Regionally Significant Wetland is:

Any wetland that has one or more of the following values:

  • Habitat for nationally or internationally rare or threatened species or communities
  • Critical habitat for the life cycles of indigenous fauna which are dependent on wetlands
  • High diversity of wetland habitat types
  • High degree of naturalness
  • Wetland scarce in Otago in terms of its ecological or physical character
  • Wetland which is highly valued by Kai Tahu for cultural and spiritual beliefs, values and uses, including waahi taoka and mahika kai
  • High diversity of indigenous flora and fauna
  • Regionally significant wetland habitat of waterfowl
  • Significant hydrological values including maintaining water quality or low flows, or reducing flood flows
  • Any wetland over 800 metres above sea level (alpine wetlands).

To protect the ecology, habitat and cultural values of Regionally Significant Wetlands, you must:

  • Not dig any new drains without resource consent. You can maintain existing drains, but there are conditions around this so give us a call before you start any work
  • Not dig any ponds without a resource consent
  • Not allow stock to damage the area - ORC recommends stock is excluded from wetlands
  • Not harm any native flora or fauna through over-spray or drift from weed spraying
  • Not introduce any exotic plant species without resource consent. A list of permitted plants can be found below
  • Not dam, divert or take water from a Regionally Significant Wetland, or alter the bed of a Regionally Significant Wetland, without resource consent
  • Make sure that any water discharged to a Regionally Significant Wetland is clear and colour-free, and does not change the water level range or flow of the wetland.

To find out the rules for Regionally Significant Wetlands, including plants you can and cannot plant in a wetland, click here.

Where are Otago's wetlands?

We encourage the establishment of new wetlands

Wetlands can improve water quality and provide additional habitat for birds, animals and insects. If you are planning to construct a wetland on your property, give us a call first and we can talk you through the process, resource consents, and other relevant issues. 

If you’re interested in protecting your wetland for future generations find out about covenants by contacting QEII National Trust on 04 472 6626 or www.openspace.org.nz

   

Estuaries

Estuaries are partially enclosed coastal bodies of water that are saltier than freshwater but not as salty as sea water. Usually they have one or more rivers or streams flowing into them and have a free connection to the open ocean.

Estuaries provide a transition from the river environments to the sea, and are dynamic, tidal environments that provides a unique and rich environment for plants and animals.

 

Estuary issues in Otago

The state of an estuary is a reflection of land use practices throughout the river catchment, and can be impacted by intensive agricultural practices, urbanisation and water discharge practices.

During heavy rainfall and flood events, sediment from the land is readily flushed into rivers where it is carried to and deposited within estuaries and near coastal areas. Fine sediments are among the most widespread contaminants of New Zealand rivers and estuaries, and sediment particles carry other contaminants, such as microbes, heavy metals and nutrients. These sediments reduce light levels in coastal waters and smother sea grass and animals in and on the seabed.

Excessive nutrient input (eutrophication) threatens many Otago estuaries causing ecological problems, such as algal blooms and poor physical and chemical conditions for estuarine life. The problems arise because the nutrients affect the trophic condition of the estuary, essentially overfeeding algae, causing very high growth and then poor oxygen and other conditions as the algae respire and decay. Until recently, guidance on how to assess the extent of eutrophication was limited.

Potential climate change effects, such as sea level rise and more frequent storm events, could also have an impact on our estuarine environment.

 

What is ORC doing to monitor estuaries?

From 1 April 2020, the Otago water plan will include limits for the amounts of nitrogen, phosphorus and E. coli that can leave rural landowner’s properties. These limits are designed to protect our waterways, including estuaries. 

In order to assess ongoing long-term trends in the condition of estuaries, it is common practice to establish a strong baseline against which future trends can be compared. This typically includes comprehensive broad scale habitat mapping on a 5-10 yearly cycle, targeted monitoring where specific issues are identified (e.g. opportunistic nuisance macroalgal growth), and fine scale monitoring comprising 3-4 consecutive years of baseline monitoring, followed by 5 yearly impact monitoring.

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