kauri dieback – Sciblogs https://sciblogs.co.nz Sciblogs Mon, 11 Jan 2021 02:36:38 +0000 en-US hourly 1 https://wordpress.org/?v=5.6.2 https://sciblogs.co.nz/app/uploads/2019/04/cropped-SciBlogsFBProfile-32x32.jpg kauri dieback – Sciblogs https://sciblogs.co.nz 32 32 Seeds of Doubt https://sciblogs.co.nz/tuhia-ki-te-rangi/2021/01/11/seeds-of-doubt/ Mon, 11 Jan 2021 02:36:38 +0000 https://sciblogs.co.nz/?p=274714 NOTE: This is an excerpt from a digital story – read the full story here.

Tess Tuxford

Ko te Kauri Ko Au, Ko te Au ko Kauri
I am the kauri, the kauri is me

Te Roroa proverb

In Waipoua Forest, at the top of the North Island, New Zealand’s largest kauri tree stands at over 50 metres tall. According to indigenous Māori culture, its namesake Tāne Mahuta was ‘The God of the Forest’.

As the story is told, at the beginning of the universe there was only darkness. Ranginui (the sky father) and Papatūānuku (the earth mother) lived together in a never-ending embrace, their children nestled between them away from the light.

One day, tired of the perpetual darkness, Tāne decided to free himself and his siblings. Using his great strength he pushed his parents apart, forcing his father high into the heavens. Their separation allowed light to flood into the world and gave Tāne dominion over the forests.

Many iwi consider the tall and ancient kauri to be the legs of Tāne keeping his parents apart. Kauri are taonga and considered ancestors. They serve as sources of inspiration in songs, dances and proverbs.

For Māori the health of the forest is intrinsically linked with the health of the people. Failure to protect kauri is a failure to ensure the wellbeing of future generations.

“This is timber country”

The first threat to the survival of kauri was the settlement of Europeans in New Zealand and the start of the timber industry. In 1840, two-thirds of the country was covered in native bush. Kauri forest accounted for one million hectares of this land. As a species it has existed for twenty million years.

For many decades the kauri bushman has existed in the lore of New Zealand history as an icon of mateship and endurance. The gargantuan and long-lasting kauri trees stood as a worthy adversary to test the tenacity and ingenuity of these European settlers.

Kauri are believed to live as long as 1500 years, possibly even longer. The kauri felled during this time are said to have had a circumference of up to twenty-six metres – almost twice that of Tāne Mahuta. In familiar black and white photos logging gangs stand together atop the felled trees, like hunters displaying their biggest trophies yet.

But while native forestry may have built the country we know today, only seven thousand hectares of kauri forest remain. The exploitation of native trees disseminated the forest ecosystems and have left kauri extremely vulnerable.

While the trees are now technically protected by the Department of Conservation, their longevity is at risk once again. This time the impending threat is proving much harder to stop than the swing of an axe.


Phytophthora are species of Oomycota, fungus-like microorganisms which are responsible for infecting a variety of different plants. One of the most well-known is Phytophthora infestans, better known as potato blight, which caused the Irish Potato Famine in the 1840s.

In New Zealand, the species threatening kauri is named Phytophthora agathidicida. It is the cause of the root rot disease known as kauri dieback. Initially discovered in 1972, the number of infected trees has increased over the last ten years. There is currently no known cure for infected trees and the disease is ultimately fatal for kauri.

In the initial stages of infection there are almost no visible symptoms of disease. This period can last for several years before the tree enters the chronic phase. At this point, excessive gum bleeding and the loss of the tree’s crown cover are an indication that the tree is close to death. The time from infection to death is variable and can be anywhere from one to ten years, with larger trees lasting longer than their smaller, younger counterparts.

The lack of visible symptoms is perhaps the most dangerous aspect of the disease. Humans are the primary distributors of the kauri dieback. Unable to detect infected trees, any tramper or hunter who has wandered off the track has no way of knowing if any deadly microbes may have hitched a ride on their boots.

Once relocated to new soil, tiny spores are dispersed and are able to sense kauri roots and swim towards them. Moving contaminated soil to different areas can create entire new sites of infection. But it is not just individual kauri that will face elimination, P. agathidicida has the capability to destroy many other species who rely on kauri as the heart of the forest.

Read the rest of the digital story here.

Tess Tuxford is completing a Master of Science in Society at Victoria University of Wellington. This article was written as part of SCIS 410 – Science Communication and is presented within Shorthand, courtesy of the Shorthand for Education programme.

Featured image: Bush scene, 1919, Auckland, by Charles Blomfield. Purchased 1972. Te Papa (1972-0024-6)

Forest health in a changing climate https://sciblogs.co.nz/guestwork/2017/01/27/forest-health-climate-change/ Fri, 27 Jan 2017 02:30:21 +0000 https://sciblogs.co.nz/?p=238236 By Dr Cate Macinnis-Ng, Senior Lecturer and Rutherford Discovery Fellow, School of Biological Sciences, University of Auckland

There’s still so much to learn about forests ecosystems, especially threatening processes in a changing world.

We know forests are essential for human health and well-being. They supply food and building materials for people across the globe and forests also store carbon, regulate the water cycle and provide habitat for biodiversity.

At least 45% of forests have been lost due to human activities like land clearing for farming and logging but natural processes like severe storms and droughts also contribute to forest decline.

Extreme climatic events are becoming more frequent and more severe because of human-induced climate change. As forests disappear, the carbon and water cycles are further modified, making climate change worse. While forest clearing has slowed in recent years, climate change is one of the biggest threats to forest.

New Zealand’s unique forests

Severe storms will increase under climate change, making damage to forests more frequent and widespread.

Here in Aotearoa, our forests are particularly special because we have a high proportion of species that are found nowhere else in the world. Around 80% of our plants are endemic and these ecosystems support unique biodiversity including birds, reptiles, invertebrates, fungi and a range of microorganisms. Many of these living things are central to our identity as a nation and are natural treasures (taonga) for Māori and European New Zealanders alike.

Introduced pests including mammals, invertebrates, weeds and diseases pose the greatest risk to our rare and endangered animals but when it comes to forest conservation, the impact of climate change is often overlooked.

A changing climate

Our island nation is surrounded by ocean so our climate is reasonably mild but it is also highly changeable. Our ecosystems have evolved to deal with fluctuations in wind, temperature and rainfall. We know these temperatures are increasing but more concerning is the increased incidence of extreme events. More frequent storms and more intense droughts have a greater impact on forest health than slowly increasing temperatures. Drought-induced forest mortality is a global problem that is increasingly widespread and while windthrow is a natural forest process, if severe storms are too frequent, the forest may be unable to recover properly between storm events, leading to ecosystem decline. Dry conditions are also more favourable for fire and ongoing research suggests many native plants are not well-equipped to recover from fire events.

The good news is that during the most severe and widespread drought in 70 years in early 2013, native vegetation survived. At my field site in west Auckland, we saw leaves of kauri trees brown and the clay soil cracked and shrank as it dried. But the trees also showed they had adaptations to help them save water and survive the dry period. Leaves dropped to reduce plant water loss, remaining leaves closed their leaf pores to retain water and we found evidence that the trees were accessing water stores deep within the ground.

Left: Ongoing research at the University of Auckland’s Huapai Scientific reserve is exploring responses of kauri to climatic conditions. Right: We are measuring how much water the trees are using and how that changes from day-to-day and from season-to-season.

Kauri dieback

For kauri, it seems the biggest threat remains kauri dieback disease. Newly funded innovative research harnessing people-power is exploring treatment options using a variety of approaches for fighting the nasty pathogen, Phytophthora agathidicida. However, interactions between climatic conditions and kauri dieback remain unknown. For instance, P. agathidicida requires water to spread so lower rainfall in Northland under a future climate may be a good thing for kauri. However, when rain does come after a dry spell, already stressed trees may be more susceptible to infection through their roots.

Unanswered questions

Across the country, increasingly frequent extreme events and longer-lasting droughts also pose serious research questions. We all know that if we withhold water from plants for long enough, they will eventually die. We don’t know what that threshold is for our native forests. We also don’t know what the effects of subsequent droughts over successive summers will be. Droughts often have legacy effects that take years of recovery. We don’t know how frequently these severe droughts will be tolerated.

Also, because a forest remains standing, that doesn’t mean it is OK. Droughts can thin vegetation and reduce growth rates, reducing the rate of carbon uptake and the amount of carbon stored in a forest. Hydrological and other processes can also suffer in this way.

Finally, interactive effects between invasive species and climatic conditions need to be explored. Certain invasive weeds may be favoured by more regular droughts and fires and we need to find ways to identify and control these weeds.

The better we understand our forests, the better chance we have of preserving them for future generations.


The Sciblogs Horizon Scan

This post is part of the Sciblogs Horizon Scan summer series, featuring posts from New Zealand researchers exploring what the future holds across a range of fields.

All images provided by Dr Cate Macinnis-Ng, University of Auckland.