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Wetlands: Assessing the effectiveness of restoration

An update from the Landcare Research Sustaining and restoring biodiversity programme funded by the Foundation for Research, Science and Technology.

New Zealand wetlands have declined significantly since European settlement and those that remain support a disproportionately high number of our threatened plants and animals.

The health or condition of these wetlands can easily decline. For example, changes in hydrology, water pollution, nutrient enrichment, and invasion by weeds and pests can lead to biodiversity loss and impaired wetland functioning.

Landcare Research aims to assist farmers and other landowners in protecting and restoring wetlands by providing guidelines to underpin management and restoration strategies.

The research is under the maintaining and restoring wetlands project which has synergies with the sustaining and restoring biodiversity programme.

Bev Clarkson, Plant Ecologist, says the research will benefit New Zealand by helping prevent further loss and degradation of wetlands.

‘As an example, nearly 80% of wetlands in the Waikato District have been lost since 1840.  The Sporadanthus Restiad vegetation class is completely destroyed and sedgeland is very poorly represented.'

Map: The loss of Waikato wetlands from 1840 to 1995 is shown in this map. The box indicates the Waikato District Council area.Waikato wetlands map

‘Our approach is to have a national wetland monitoring system including wetland classification and methods for monitoring wetland condition,' says Bev.

'By 2013, we are aiming for a 10% increase in the success rate of wetlands being restored as measured by the biodiversity condition index in the Handbook for Monitoring Wetland Condition.’

The handbook describes five ecological indicators based on threats that degrade wetlands. Compared against an assumed natural state, these provide a composite index of wetland condition.

Indicators are changes in:

  • Hydrological integrity (hydrology)
  • Physicochemical parameters (soil)
  • Ecosystem intactness (intactness)
  • Browsing, predation and harvesting (pest-free)
  • Dominance of native plants (weed-free).

The handbook describes each indicator and how to assign a value and tally scores to analyse the results. The indicators can be used to answer a range of monitoring questions.

Bev says those monitoring wetlands can design their own techniques for interpreting data and analysing change.

‘For example, to assess the effectiveness of fencing, use an indicator component “Damage by domestic or feral animals” or where willow is being controlled, use “Introduced plant canopy cover”.

‘Landcare Research has established a national wetland database to collect monitoring data which will be used to develop understanding of the essential properties of wetlands. We encourage those using the handbook monitoring methods to contribute to this database.’

Download the Handbook for Monitoring Wetland Condition

Cockayne Wetland: Monitoring condition

Cockayne Reserve is an isolated wetland fragment within Christchurch City, located on the Avon River. By 1982 the wetland had been degraded by altered hydrology, repeated fires and the spread of weeds such as tall fescue and yellow flag iris.

 Indicator Score - 1982   Score - 2000
 Intactness  0.50  0.50
 Hydrology  0.67  2.00
 Soils  0.50  2.00
 Weed-free  1.00  3.00
 Pest-free  3.67  4.00
 Total/25  6.34  11.50

Cockayne Wetland monitoring graph

Interventions including planting of native species and restoration of a water supply led to considerable recovery of the wetland by 2000.

However, weeds were still widespread and poor water exchange had allowed raupo to increase dramatically, leading to excessive sedimentation and in-filling.

The score therefore reflects an overall improvement but identifies issues still causing problems.

Protecting wetlands

Below: Protecting wetlands on private land with QEII covenants improves their condition.

Wetland covenant


Open Space
TM Magazine No. 70, July 2007 © QEII National Trust

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