About 27km of popular walking tracks in the Waitakere Ranges will be closed in a bid to halt the spread of a kauri tree-killing disease.

Formation of protection zones around unaffected kauri in the dense forest west of Auckland City was called for yesterday by Auckland Council's parks, recreation and heritage forum.

Officials had reported a higher incidence of the kauri dieback disease in areas more often visited by walkers and survey work showed the need for more extensive measures to protect healthy kauri than the present boot disinfection stations.

It is estimated about 8 per cent of the ranges' dense kauri areas are already infected and another 3 per cent probably infected.


"The disease may have long-term ecosystem impacts if it continues to spread unabated and uncontrolled," said a biosecurity team report.

In some cases where it was not practicable to close a track, there would have to be upgrading and rerouting.

Forum chairman Sandra Coney said it was a precautionary approach that still allowed enjoyment of most of the Waitakere Ranges Regional Park, which had 256km of tracks.

Protection zones were proposed for the Cascade Kauri, Anawhata, Waiatarua, Piha, Karekare, Huia and Parau areas, to be reviewed in a year while scientists learned more about the disease and whether a vaccine or cure could be found.

The forum expects a report in May on the need to close tracks in the Hunua Ranges to the city's southeast, where there's no sign of the disease.

The Department of Conservation has restricted access and closed tracks at Mataitai Reserve, near the Hunuas, for five years to protect healthy trees and monitors for kauri dieback.

The biosecurity report said more work was needed to identify protection zones in the Hunua Ranges.

"Kauri is not as widespread in the Hunua Ranges as in the Waitakere Ranges, so presents a slightly different challenge that requires further work to confirm a sustainable approach."