The Bushland Trust
PO Box 123
Awanui 0451
New Zealand



Sweetwater Lakes Walkway

This path which goes around Lake Ngatu and down to Sandhills Road via Lake Heather and Lake Rotoroa is run by The Bushland Trust as a local environmental initiative. The walk is approximately 10 km in length and takes approx. 2 hours to walk.

View map.

Grass carp to the rescue

From The Northland Age - Thursday June 17, 2010

Four hundred grass carp are to be released into Lake Heather - one of the dune lakes inland from 90 Mile Beach west of Kaitaia - in a bid to wipe out two invasive weeds threatening some of the country's most precious dune lakes. The Northland Regional Council is working closely with the Bushland Trust in Kaitaia, and the Department of Conservation, to eradicate the aquatic weeds hornwort and egeria (an oxygen weed) from the eight-hectare lake.

Peter Wiessing, the NRC's Kaitaia area manager, said the two species had formed large, dense mats in the 5.6-metre-deep lake.

"These weeds are smothering native plants and affecting an important habitat for fish, plants, birds and other species," he said. "The release of these 400 fish will cost the council about $17,000, but is the most cost-effective and environmentally-sustainable option to eradicate these weeds."

The 25-centimetre carp, which, all going well, will be trucked north from a Warkworth supplier and released into the lake on Tuesday, June 29, were unable to breed in New Zealand waters, ate only plants and had a good track record in terms of aquatic pest plant control in Northland. The releasing of grass carp in Lake Swan, on the North Kaipara Head, about 12 months ago had accounted for most of the egeria and about 40 per cent of the hornwort there.

Mr Wiessing said lakes such as Heather and Swan were important habitats for a wide variety of fish, plant, bird and invertebrate species, and Northland had some the best examples of those ecosystems in New Zealand.

"The regional council, the Bushland Trust and the local community have become increasingly concerned about the risk of hornwort and egeria spreading from Lake Heather to other lakes in the area," he added however.

Aside from that threat, the council was also concerned that, left unchecked, the hornwort and egeria problem in Lake Heather could lead to the eventual collapse of other plants living in the lake. That in turn could provide ideal growth conditions for algae, which could relatively quickly dominate the lake, affecting water quality for both recreational and stock use as well as adversely affecting other aquatic life.

Representatives from the Bushland Trust, the local iwi, community and school were all expected to witness the release, along with staff from the regional council and DOC.

"If the eradication of hornwort and egeria is successful, we intend to remove the fish from the lake in several years' time, allowing native plants to re-establish," he said.
Mr Wiessing warned that Northland had a large number of lakes that were vulnerable to invasive aquatic pests, which could establish themselves and spread rapidly. Weeds would grow from small plant fragments, people and activities like boating and fishing providing the most common means of spreading.

"We encourage all users of freshwater areas to check, clean and dry all their gear to help stop the spread of aquatic pests," he said. "It's important to be alert for aquatic life that looks different and report it to the regional council or MAF Biosecurity NZ."

Future Projects

  • Filtration zones to improve water quality of Lake Ngatu.
  • Removing invasive weeds such as gorse, woolly nightshade, lantana and pampas.
  • Completing the Lake Ngatu planting.
  • Completion of signage and walkways.
  • Maintaining the existing planted areas.

Lake Ngatu – a treasure to preserve

How do we in the North maintain the water quality of our local lakes?

This is a question that affects all of us: local residents, recreational users of the lake, visitors and our descendents. Already a gradual deterioration in the water clarity and amount of sludge underfoot can be noticed from year to year.

Lake Omapere and Lake Mimiha at Ahipara are examples where the deterioration has reached the point of no return. There are probably more.

Many of us have individual opinions on how we can best improve the Lake edge – be it grassed and landscaped to afford private views, low trees, beaches and jetties dotted around, or whatever. But the underlying premise for any development is – how do we best preserve the lake? For If Lake Ngatu dies, we will all suffer.

The views and lifestyle we enjoy as residents will be worthless. Those who have water rights to use lake water will find it totally useless. Property values will fall. The heritage we leave to our children and our children’s children is gone.

Nutrients and pollution entering the lake water create an imbalance in the mineral proportions that sustain optimum quality. Oxygen depletes, phosphorus and nitrogen increase and produce enzymes that fertilise and increase growth. The die-off of this increased vegetation growth can't be absorbed by the depleted oxygen level. Rotting vegetation forms a sludgy mat on the bottom, then continues the cycle of providing nutrient for regrowth, further depleting oxygen levels and deteriorating the water quality.


The Bushland Trust would like to express its appreciation and thanks to its sponsors and supporters, both past and present:

  • Sir John Logan Campbell Residuary Trust
  • World Wildlife Habitat Protection Fund
  • Pacific Development & Conservation Trust
  • ASB Trust
  • Northland Regional Council
  • Department of Conservation
  • Far North Community Forests Trust
  • Waipapakauri Community Trust
  • Cornwall Park Nursery (seed raising)
  • R Greenwood Environmental Trust
  • Robert C Bruce Trust
  • C.O.G.S