Ailing estuary harbour gets a health check-up

The health of the Kaipara Harbour, the largest in the Southern Hemisphere, will be in the spotlight next month. Photo / Michael Cunningham

The health of New Zealand's largest estuarine ecosystem will be in the spotlight when the Integrated Kaipara Harbour Management Group holds a two-day seminar at Te Hana.

The Integrated Kaipara Harbour Management Group (IKHMG) event will showcase the taonga that is the Kaipara Harbour and also celebrate a 10-year partnership. The IKHMG was established in 2005 to promote management and inter-agency co-ordination of the Kaipara Harbour and its catchment, using traditional Maori philosophy and western science.

The harbour - the largest in the Southern Hemisphere - covers 94,700ha and soaks up run-off from a river network of more than 9000km, in a 6400sq km catchment. More than half of that catchment supports productive pasture.

Te Iwi o Ngati Whatua hapu hold mana whenua status over the harbour; Te Roroa, Te Parawhau, Ngapuhi and Ngati Hin in the northern parts and Te Kawerau a Maki over part of the south-western catchment.

The IKHMG connects with Auckland, Northland Regional, Kaipara District and Whangarei District Councils, Rodney Local Board, Northland Conservancy, Department of Conservation, Auckland Conservancy Department of Conservation and the Ministry of Fisheries (MFish).

The harbour contains five broad ecosystems including forest, freshwater, scrublands, dunelands and estuaries. It is well known as a fish and shark nursery, and reputedly provides most of the coastal snapper populations on the West Coast of the North Island.

But it suffers from the stress of sedimentation and eutrophication, or harm caused by artificial or natural substances.

And it is not just a modern problem. Most of the natural world of the Kaipara was exhausted by the 1920s. Since pre-European times levels of contaminants entering catchment waterways, such as phosphorous, nitrogen and E. coli, have risen.

A long history of deforestation has caused land management issues throughout the catchment, such as soil erosion, silted-up waterways, poor water quality and a loss of biodiversity and productive land. The Northern Wairoa River system delivers the greatest sediment and nutrient loads to the harbour.

Kaipara Moana Looking Back Thinking Forward is the name of the first seminar, which will be held at Te Hana Te Ao Marama on November 15-16.