What is a defined "Wetland"?

We are often asked by clients and Councils whether there are any wetlands on properties proposed for development, or wetlands that could be restored for other reasons. This requires an ecological assessment.

The Resource Management Act defines a wetland as: "Wetland includes permanently or intermittently wet areas, shallow water, and land water margins that support a natural ecosystem of plants and animals that are adapted to wet conditions."

(Most district and regional plans adopt the RMA definition, although the Draft National Policy Statement on Indigenous Biodiversity seeks to clarify the definition in the Act with "wetlands requiring protection must retain ecological integrity and the NPS definition of ecological integrity specifically anchors the wetland’s composition to indigenous species, habitats and communities.").

The test to answering the question of “is this a wetland” in any particular case is:

  • Does it include permanently or intermittently wet areas, or shallow water?
  • Does it support a natural ecosystem of plants and animals that are adapted to wet conditions?;
  • Does it support have ecological integrity and indigenous species, habitats and communities?

We set out some scenarios below to provide some initial guidance, but a site assessment is really necessary to be certain in a specific case.

Scenario 1:

A landowner fences a wet area along a stream course to exclude any farm stock and over time wetland vegetation (including indigenous rushes, sedges and trees and shrubs) establish in the damp ground and intermittent and permanent stream courses.

Is this a wetland?
  • It includes permanently or intermittently wet areas, or shallow water and land/water margins. This usually excludes ephemeral streams or overland flowpaths in the upper catchment, as they are not permanently or intermittently wet.
  • It supports a natural ecosystem of plants and animals that are adapted to wet conditions, that have regenerated under natural processes.
  • It supports indigenous species, habitats and communities and may have ecological integrity.

Yes, it is a wetland.

Scenario 2:

There are rushes and sedges growing along the ephemeral, intermittent and permanent stream courses on a property.

Are they wetlands?
  • The wetland are includes permanently or intermittently wet areas, or shallow water and land/water margins. This may exclude ephemeral streams or overland flowpaths in the upper catchment, as they are not permanently or intermittently wet.
  • It supports a natural ecosystem of plants and animals that are adapted to wet conditions, that have regenerated under natural processes.
  • It supports indigenous species, habitats and communities and may have ecological integrity.

Partly; the intermittent and permanent stream margins are wetlands, but this usually excludes ephemeral streams or overland that are not permanently or intermittently wet. The wetland area will need to have a predominance of indigenous vegetation and fauna (including fish and wetland birds).

Scenario 3:

On rural properties owners often have cattle and other stock grazing time and cattle in particular pug up wet areas in paddocks and graze out the more palatable wetland plants that come up in these (now) boggy sites. Stock also pug the margins of streams, so the wet margins may be 10-15m wide, rather than 1-2m wide. The wetland vegetation is predominantly exotic wetland plants.

Is it a wetland?

  • The permanently or intermittently wet areas, or shallow water along streams and land/water margins may be wetlands. But this would exclude ephemeral streams or overland flowpaths and wet pugged areas where the wet area has been induced by stock trampling
  • It supports an induced ecosystem of plants and animals that are adapted to wet conditions, but they have not come about under natural processes
  • There are few indigenous species, habitats and communities and it is predominantly exotic wetland species

No, it is not a wetland.

(These may occur on ridges and hill slopes where wetlands do not naturally form. The rush and sedge vegetation on these sites have few indigenous plants and generally lack wetland fauna species.)

If you are unsure about your property, call Terra Nova’s ecologists to arrange a site assessment.