An operation to identify kauri trees showing signs of disease is nearing completion, with more than 3 million hectares of countryside surveyed over the past 3 years.
As a result of the comprehensive aerial survey carried out by the Kauri Dieback Programme, 450 kauri sites across Northland, Auckland and the Waikato have been identified for possible investigation. These 450 sites exclude sites in Waipoua Forest as well as sites in parts of Auckland region (for example, in Hunua and Waitakere Ranges).
The remaining areas to be surveyed – Aupouri and Kaitaia – may be completed within the next few weeks (dependant on weather and aircraft availability). However, the Programme expects few (if any) additional sites will be found there.
The next step will involve the Ministry for Primary Industries (MPI), 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. In cases where kauri dieback disease is suspected, sites may be ground-truthed and soil samples potentially collected for laboratory testing," says John Sanson, MPI's manager recovery and pest management.
Ground-truthing is a time-consuming and costly process but at present is the best way to verify whether kauri dieback disease is actually present, says Mr Sanson.
Surveillance has involved flying at low level across the countryside, taking nearly a million photographs and covering an equivalent distance to one circuit of the Earth.
It's estimated around three-quarters of the 450 sites identified for possible further investigation are individual trees within bush areas. The majority of these sites are in Whangarei/southern Northland, southern Kaipara and Rodney. While about 50 of these sites are in the Waikato region.
Further aerial surveys will be carried out in the future as part of the ongoing efforts to manage kauri dieback disease.
Mr Sanson says pinpointing kauri trees or stands that may be affected by kauri dieback disease takes time. Up to $180,000 has been spent by the national programme each year since July 2015 on surveillance – this includes flying time, GIS mapping and data input, and laboratory analysis of samples. Each photograph is also assessed to identify kauri trees and their health. In addition to this is the expenditure by programme partners on site visits, soil sampling, and on their own aerial and other surveillance activities.
"Research is taking place to find a faster survey tool," says Mr Sanson.
Remote sensing techniques are being trialled to detect kauri trees, as well as those kauri trees that may be infected with kauri dieback disease – using high resolution satellite imagery, Lidar and hyper-spectral imagery.
"By the end of this year we hope to know how feasible this might be and, if it is, how we can put this into operation." says Mr Sanson.
Northland Regional Council (NRC) has a "huge task" ahead with the ground-truthing programme. NRC intends to work with joint agency partners to look at what options are available to accelerate a ground-truthing programme and prioritise ground-truthing efforts. In Northland, NRC will continue to work closely with landowners and reminds landowners that legally – under the Northland Regional Pest Management Plan – any suspected kauri dieback must be reported to an appropriate management agency.
"Council has been providing advice and assistance to many private Northland landowners who have reported trees with kauri dieback symptoms in recent years," says Northland Regional Council's group manager, environmental services, Bruce Howse. "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."
Auckland Council funds a great deal of the kauri aerial surveying and ground-truthing across the Auckland region, and has carried out further work in Rodney since the aerial survey identified the need for further investigation there. This includes obtaining high resolution aerial photographs of high biodiversity value areas and the collection of soil samples near potentially infected kauri to determine if kauri dieback disease is the cause of poor health.
"It is really important that we understand the scale of the problem and the impact on our kauri forests. That's why we have prioritised extensive monitoring of kauri across the region, as we know this will add to our understanding about the spread of the disease. That means we can focus our resources on tackling the spread in affected areas and in keeping kauri healthy in those areas that are still disease free" says Auckland Council biosecurity manager, Phil Brown.
In Waikato and Bay of Plenty
Kauri dieback was first found in the Waikato region in 2014. It has been confirmed at 3 locations on the Coromandel Peninsula in Hukarahi and Whangapoua.
Waikato Regional Council has been working closely with private landowners to protect kauri on their properties and to prevent the spread of the disease. This has involved activities such as fencing off stands of kauri, feral animal management, and promoting on farm biosecurity practices such as the use of cleaning stations for footwear and vehicles.
Aerial surveillance has also been completed in the Bay of Plenty region's kauri lands.
Department of Conservation
The Department of Conservation (DOC) surveyed its entire 735km network of tracks through kauri forest it manages. A plan was then developed to combat the spread of kauri dieback. DOC is in the third year of this work-plan. It involves a range of work to prevent kauri dieback from spreading:
- upgrading tracks to eliminate muddy sections and protect kauri roots
- re-routing tracks to avoid kauri to keep trees safe
- closing some tracks to stop kauri dieback spreading from infected trees or to keep forest without kauri dieback safe from the disease
- installing footwear cleaning stations at track entrances
- working to get more people to use footwear cleaning stations.
DOC will be reviewing the results of the aerial surveillance across kauri forest managed by the Department.
"We'll be looking to see if the results show that kauri dieback could be present at sites where the disease had not been previously detected," says DOC northern North Island operations director Sue Reed-Thomas.
"We'll also continue working with other agencies in the Kauri Dieback Programme in progressing the development of tools that will enable us to know more about kauri dieback and how it spreads."
The Kauri Dieback Programme
Kauri dieback disease is found in the upper North Island and can kill kauri of all ages. It is a disease caused by a microscopic fungus-like organism called Phytophthora agathidicida. It lives in the soil and infects kauri roots, damaging the tissues that carry nutrients and water within the tree, effectively starving it to death. Soil disturbance from human activity like people using unofficial tracks or not cleaning footwear is one of the main ways spores can be spread.
The Kauri Dieback Programme was launched in 2009. The programme is a collaborative partnership between MPI, which coordinates the programme, and the kaitiaki of those areas where kauri are found – tangata whenua (via the Tangata Whenua Roopu), Department of Conservation, Waikato Regional Council, Northland Regional Council, Bay of Plenty Regional Council and Auckland Council.
For further information contact:
Matt Johnson – Northland Regional Council – Phone 027 452 2151
Michael Smith – Auckland Council – Phone 021 538 940
Waikato Regional Council – Phone 021 369 815
MPI media line – Phone 029 894 0328