Kauri die-back survey almost complete
An operation aimed at identifying kauri trees showing signs of disease is nearing completion, with more than three million hectares aerially surveyed over the last three years by the Kauri Dieback Programme.
Some 450 sites across Northland, Auckland and the Waikato, excluding sites in Waipoua Forest and parts of the Auckland region — the Hunua and Waitakere ranges — have been identified for possible investigation.
Surveying of the remaining areas — Aupouri and Kaitaia — may be completed within the next few weeks, depending on weather and aircraft availability, but few, if any, additional sites are expected to be found there.
The next step will involve the Ministry for Primary Industries, Department of Conservation and regional councils prioritising sites and potentially undertaking ‘ground-truthing’ visits.
“One of the symptoms of kauri dieback is a yellowing and thinning canopy. This may also be caused by other things, such as drought, poor soil conditions, high winds, cattle and other animal movement under the tree,” MPI manager recovery and pest management John Sanson said.
“In cases where kauri dieback disease is suspected, sites may be ground-truthed and soil samples potentially collected for laboratory testing.” Ground-truthing was time-consuming and costly, but was currently the best way to verify whether kauri dieback disease was present, he said. Surveillance included low-level flying, taking almost a million photographs and covering an equivalent distance to one circuit of the Earth.
Around three-quarters of the 450 sites identified for possible further investigation were individual trees, most in Whangarei/southern Northland, southern Kaipara and Rodney. About 50 were in the Waikato.
Further aerial surveys would be carried out as part of ongoing efforts to manage kauri dieback disease.
Mr Sanson said pinpointing potentially affected trees took time. Up to $180,000 had been spent each year since July 2015 on surveillance, including flying time, GIS mapping and data input, and laboratory analysis of samples. Each photograph was also assessed to identify trees and their health.
Research was under way to find a faster survey tool. Remote sensing techniques using highresolution satellite imagery, Lidar and hyper-spectral imagery were being trialled.
Meanwhile in Northland the regional council had a huge task with the ground-truthing programme. It planned to work with joint agency partners to look at the options for accelerating a ground-truthing programme and prioritising ground-truthing efforts.
The council would also continue to work closely with land owners. The Northland Regional Pest Management Plan legally obliged them to report any suspected kauri dieback.
“Council has been providing advice and assistance to many private Northland land owners who have reported trees with kauri dieback symptoms in recent years,” NRC group manager environmental services Bruce Howse said.
“We’ve been working with them to develop personalised kauri dieback disease management plans to try to reduce the risk of the disease spreading from private land and district council reserves, and will continue to do so.”