Threats to the Waitakere Ranges

The Auckland region derives much of its unique character from the magnificent forest-clad ranges to the west - the Waitakere Ranges. This expansive area of native forest has been occupied for more than a thousand years. The impact of people has been greatest in the last one hundred and fifty years when the kauri giants were felled.

Much of the land has been protected and is regenerating. However forest recovery is now severely jeopardised by weeds and pests which kill mature bush and prevent regrowth. On privately owned land, continuing subdivision and bush clearance not only damage the immediate environment but also place the larger region at risk of further degradation both visually and ecologically.

The Waitakere Ranges has a significant coastline, nature at its most powerful and poignant, but is stressed though the increasing number of visitors, intensive recreation, and excessive fishing and shellfish gathering.

The Te Henga wetland is the region's most important swamp, a vital habitat for fifteen species of native birds. Yet here too land clearance and weed invasion insidiously threaten its ecological viability. The cumulative effect of all this is irreparable damage to the region's outstanding natural landscape. Continuing vigilance is needed to protect the Ranges from such an outcome.

The authorities which administer the Waitakere Ranges and West Coast are all required to prepare management plans. These plans collectively determine the future of the Ranges. It is vital that clear and compelling submissions are presented to all of these plans. Where necessary, these are followed through with appeals. This requires a huge volunteer effort and funding. Conservation is achieved only after a great deal of hard, persistent effort - which is where the Waitakere Ranges Protection Society comes in.

The Ranges are a place of high value, for its ecosystems, for the beauty of its rugged landscape, its ocean and harbour shore and for its native plant and animal life.

We owe them an inheritance that is not debased and ruined because of short-term thinking and inappropriate development.

It is important that places like this are protected for their own sake and also for their value to people. We have a duty, to think about the generations yet to come as well. We owe them an inheritance that is not debased and ruined because of short-term thinking and inappropriate development.

Kauri Dieback Disease

Kauri dieback lesionKauri dieback lesion

What is Kauri Dieback Disease?

Kauri Dieback Disease is an incurable disease affecting only New Zealand kauri trees. It is caused by a microscopic (invisible) water mould called Phytophthora taxon agathis (PTA). There are many species of Phytophthora in the world (one caused the potato blight and famine in Ireland) but this one affecting kauri is completely new to science & it is not known where it has come from.

The mould spreads via soil disturbance and in water. High risk activities include disturbing the ground around kauri roots by digging or even walking on them. Kauri roots are very sensitive to compaction and spread out well beyond the dripline of the tree. Any damage to the roots can enable the PTA pathogen to enter the tree.

How does it kill the tree?

Once inside the roots the PTA pathogen moves up the tree in the cambium tissue (food vessels) just below the bark. In an attempt to stop the pathogen the kauri tree bleeds gum to seal off the infected issue. However the pathogen moves sideways around the tree's girth to avoid the gum and eventually the tree ringbarks itself and dies.

Tree death can take many years depending on the size of the tree. As the bleeding continues the tree gradually cuts off its own food supply and the crown starts to yellow and die back - hence the name "dieback disease". No resistance has yet been found and every tree with kauri dieback symptoms eventually dies.

How does it spread?

Kauri dieback disease is spread by soil movement and in water. So tramping along tracks with infected kauri spreads the disease in the soil on people's and animals' feet. Vehicles, especially earth moving equipment, are a huge risk. Landscaping and moving soil or mulch around that has been in contact with infected trees is likely to be spreading the disease far and wide. Nurseries may also be inadvertently spreading the disease in the soil around young trees. The PTA pathogen can hide in other host plants without showing any symptoms, so without testing it's impossible to know if your soil is clean or infected.

What can I do?

Always SCRUB and SPRAY your footwear (and your dog's feet) when entering or leaving kauri forest. The Auckland Council have cleaning stations on main tracks, please use them and encourage others to do so. If there isn't a station then scrub your boots with water when you get home. You can pick up a bottle of trigene disinfectant from the Arataki Visitor Centre to take tramping with you.

Keep dogs on a lead in the bush and keep to the tracks at all times. Clean any equipment that you take into the forest when you get home. Do not take your bike into kauri forest.

If you have kauri on your land you need to keep them healthy, as stressed trees are more susceptible to infection. See the Care for Kauri guide from kauridieback.co.nz and learn how to keep your kauri healthy. Keep people and animals away from your kauri trees and minimise movement around their roots.

If you think your kauri may be sick, report them to the Auckland Council's Kauri Dieback Management Team on 0800 NZ KAURI (69 52874) for help and advice.

Waitakere wasps

Reference: ”Wasps, the Invaders” by Dr Jo Berry of Landcare Research in “Waitakere Ranges”. The following note is largely based on this chapter.

University of Florida Dept of Entomology and Nematology Vespid waspUniversity of Florida Dept of Entomology and Nematology Vespid wasp

The invasion of New Zealand by vespid wasps is a biological disaster for the New Zealand ecosystem. These insects fill an ecological niche that was vacant in our natural ecosystem and the consequences are far reaching and extremely severe in some situations possibly paralleling the impact of stoats and ferrets on our native birds as far as insects and other invertebrates are concerned.

Four of the species in the Waitakeres are social while the fifth is a solitary species. The first is the German wasp (Vespula germanica) which was first noticed in New Zealand in 1945 in the Waikato region and is thought to have been transported here during the war in crates of aircraft parts at Hobsonville. The second is the Common wasp (Vespula vulgaris) which established around Wellington in the late 1970s. It is superficially identical with the German wasp and has a similar biology. The third species is the Australian or Tasmanian paper wasp (Polistes humilis) which was already abundant in Northland when it was first noticed in the 1880s. It is a paper wasp as is the fourth species, the Asian paper wasp (Polistes chinensis) which was first found in the Auckland region in 1979. The fifth species is the European tube wasp (Ancistrocerus gazella). This beautiful little wasp is a recent and very successful immigrant. It was first recorded here in 1988 and is now widely distributed in both the North and South Islands. It is not a social species and makes solitary nests in all sorts of small holes – hollow plant stems, nail, bolt or drill holes in timber or concrete, holes in basalt rock, old tunnels made by wood boring beetles and so on.

The two Vespula wasps – the German and Common wasps – develop large populations and occur throughout New Zealand. Of the two Polistes wasps, the Australian or Tasmanian species is established only in the warmer parts of the North Island. The Asian paper wasp on the other hand is still expanding its area of occupation which will probably become New Zealand-wide. Its natural area of distribution includes parts of Asia subject to very severe winters so cooler temperatures will be no barrier to it.

All five species are present in the Waitakere Ranges and will certainly be having a serious detrimental impact on some elements of the insect and other invertebrate faunas. The two Vespula wasps are native to the temperate parts of the Northern Hemisphere. They are voracious scavengers and predators and feed on fruits, flower nectar and tree sap as well as live insects and other invertebrates and fresh carrion. The paper wasps on the other hand are primarily predators and get all of their protein from live insects especially caterpillars. The European tube wasp feeds almost exclusively on caterpillars.

In the Northern hemisphere Vespula nests collapse during severe winters and only fertilized queens survive. This does not happen in the milder winters of the more northern regions of New Zealand and perennial nests become established which increase to enormous sizes. Each may contain hundreds of thousands of wasps. Fortunately this did not happen to a large nest in Green Bay from which abundant wasps survived the winter but rather suddenly disappeared during July. However, the first large surviving queen was seen flying already in September. The nests are built in urban areas, mostly underground or in walls or roofs of dwellings. If swimming pools lie under the flight path of wasps excavating their nest they may be muddied. In the bush, the nests are mostly underground but occasionally they are created in trees. The nests themselves are completely encased in a layer of “paper” and have a small opening at the base. The “paper” comprises wood fibres scraped from wooden surfaces, chewed and mixed with saliva to form a paper-mache-like material. The presence of wasps can be detected by the distinctive patterns their scraping makes on exposed wooden surfaces – wooden walls, decks, posts and so on. Polistes wasp nests are very much smaller and lack any paper covering so that the honey comb cells are exposed.

The Vespula and Polistes wasps pose a grave threat to our native biodiversity and can create “biological deserts” in the region of their nest. Although their impact is severe it cannot be precisely assessed because there is little base-line data available with which to make a comparison. A wasp-free biological island like our predator-free mainland islands (in which wasps can be reduced but not entirely eliminated) would probably show some fascinating and unexpected results. Wasps can be watched hawking trees and shrubs in gardens hunting their prey and are possibly important in limiting the numbers of monarch butterflies. Their predation probably has a detrimental effect on birds and other animals dependent on caterpillars as a mainstay of their food. In the South island beech forests, they compete for nectar and honeydew which are important food sources for native birds, bats, reptiles and insects. The recognition of their conservation threat to the native biodiversity has resulted in huge efforts being made to control them. The introduction of a tiny parasitic wasp as a biological control agent has not been successful because although released throughout New Zealand, it is only known to have established at a few sites in the South Island. Poison bait trials have been carried out in the Waitakeres with promising results. One dreams of the existence of a wasp Varroa mite that could do to wasps what the Varroa mite is doing to our honey bees.