Lake Heron, Ashburton Lakes, Ō Tū Wharekai

Image: Jack Mace | ©

Introduction

A key focus of the programme is research to improve our understanding of the three sites, and to develop best-practice management and monitoring tools to share with others.

Highlights

We do this by working with a range of organisations including regional councils, universities, research institutes and consultants.

Some of the main successes of our science projects so far are summarised in our report cards

Other achivements in the programme include:

  • Vegetation mapping at all three sites
  • Determining the effects of flood inundation at Whangamarino wetland
  • Tracking the recovery of wetland vegetation after large-scale willow control at Ō Tū Wharekai
  • Better understanding of how macrophytes respond to lagoon openings in Waituna Lagoon.

Find out about the projects and findings taking place at each site.

Ō Tū Wharekai (Canterbury)

Ō Tū Wharekai (Ashburton Lakes Upper Rangitata River) is a mosaic of diverse wetland habitats nestled amongst high-country tussock.

It is one of the best examples of an intact, intermontane wetland system remaining in New Zealand.

The habitats include reaches of braided river, high country lakes, ephemeral turf, streams, swamps and bogs. It is home to wrybil, crested grebe, upland long jaw galaxiids, and the strange tadpole shrimp.

What we've learnt

Key finding: Using sediment cores and pollen records, we have found that early vegetation in the basin was a mix of podocarp forest on high ground, with Coprosma shrub land in the valleys.

We've also learnt that natural fires may have been a controlling factor – unusual for New Zealand.

Implication: Challenges our perceptions of what the natural vegetation was in the basin, helping to guide re-vegetation efforts.

Projects on the go

Wetland Resilience to Nutrients: Investigating how much added nutrient is too much. By adding known amounts of different fertilizer (nitrogen, ammonium, and phosphate) to the wetland and recording changes we hope to work out how resilient the wetland is to land use change.

This is a MBIE funded program (C09 X1002) with NIWA and Landcare Research.

Lambies Stream willow control: Investigating the recovery of wetland plants following spraying to kill off willow along 2 km of stream. We are finding that the native understory is coming back well once it is given a chance.

This is a DOC research and development project with NIWA.

Whangamarino Wetland (Waikato)

Whangamarino is a Ramsar site, and at 7,000 ha the second largest bog and swamp complex in the North Island.

It supports threatened wetland ecosystems and recreation and is part of a substantial flood-control scheme on the lower Waikato River. It is home to Australasian bittern, black mudfish, and the tiny helmet orchid (Corybas carso).

What we've learnt

Key finding: At Whangamarino sediment accumulation rates were assesed. We found that sediment accumulation rates are now 3 times greater than they were in the 1970s, degrading the wetland.

Implication: Wetlands are naturally good at accumulating sediment, but this has consequences for wetland vegetation.

At Whangamarino the extra sediment is changing plant communities and manuka is spreading further into the wetlands. We may need to develop ways to remove the extra sediment.

Projects on the go

Predators in wetlands: DOC is well known for predator control work, but there is little understanding of mammalian predators in wetlands. We have been tracking, trapping and developing targeted control methods to help managers tackle this problem.

This is a DOC research and development project.

Monitoring wetland birds: Some wetland birds are very good at hiding. This project's been trialling different methods of counting and monitoring these birds to see if our management is working.

This is a DOC research and development project.

Awarua–Waituna Wetlands (Southland)

Awarua–Waituna Wetland was New Zealand's first Ramsar site and one of the largest remaining coastal wetlands in New Zealand. The wetlands include extensive peat bog, swamp, coastal lagoon, estuary and stream habitats.

Intensification of land use and the conversion of wetlands to pasture are still major threats to the wetlands and water quality entering the lagoon. The wetlands are home to threatened giant kokopu, Australasian bittern and the rare Asaphodes moth.

What we've learnt

Key finding: Collecting cores from Waituna Lagoon confirmed that macrophyte beds have always been present and that the naturally the lagoon was open less frequently and often for shorter periods.

Implication: Macrophytes (aquatic plants) are a natural and intrinsic part of the lagoon and we need to manage water quality to protect them.

Projects on the go

Limits to wetland vegetation regeneration in Awarua–Waituna Wetlands: PhD student investigating what is preventing the natural regeneration of forest species in the wetlands. Early findings indicate that rats and possums graze on seedlings, making them a new priority for control. Working with University of Canterbury.

Nutrient limitation in the lagoon: This investigation is trying to determine which nutrients stimulate the growth of algae and phytoplankton in the lagoon, and how artificial lagoon openings may affect this. Improved understanding will help us better protect the sensitive macrophyte beds in the lagoon. Working with University of Otago.

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