EcoLincNZ

Category: biodiversity

  • Every pyromaniacs dream… the science plant BBQ

    In recent decades, climate change has been a cause for social and environmental transformation. For example, the inclusion of words such as ‘eco-anxiety’ to the Oxford English Dictionary shows the growing apprehension we have about the future of our climate. Next time you are feeling overwhelmed as a result of the environment, you’ll have the perfect word to describe it! The reasoning behind part of this social shift is due to ecological impacts caused by events such as rising sea levels, ocean acidification and wildfire. 

    When I was growing up, we lived on the outskirts of Rangiora. I was 7 years old when I experienced uncontrolled fire for the first time; the boundary trees of a farm I could see from my bedroom window went up in flames. After a couple of hours, and a team of fire fighters, the blaze was put out. This event was minuscule compared to the damage caused by the Port Hills fire in 2017, which burnt 1,660 hectares of land, or 1,646 rugby fields, over a worryingly 66 days.

    The Sugarloaf transmission tower is threatened by multiple fires burning out-of-control in the Port Hills south of Christchurch, New Zealand (Left), Image by Ross Younger from Flicker.
    Orroral Valley Fire viewed from Tuggeranong, Australia (Right), Image by Nick D from Wikimedia Commons.

    More recently, our neighbours across the ditch experienced one of the worst fire events in history. The Australian Bushfires of 2019/20 burnt a whopping 18.626 million hectares of land; equivalent to too many rugby fields to count!

    The impacts of wildfire go beyond immediate destruction. Long term effects include challenges for biodiversity and human health. Additionally, the economic toll of wildfires can be extremely pressing. The Port Hills fire alone cost $7.9 million NZD to suppress; I would hate to think of the cost imposed by the Australian Bushfires. Throughout these events, astounding acts of courage were witnessed, whilst land, infrastructure and, regrettably, lives were lost; but could these events have been prevented or the severity of damage lessened? 

    Though recent fires in New Zealand may not be as severe as those witnessed overseas, further destructive fire events are looming. Future conditions likely to be more common in much of New Zealand are hotter temperatures, lower rainfall and windier conditions: a recipe for a fiery landscape. One of the key factors that impacts the scale and intensity of fires is vegetation and their corresponding fuel loads. For example, a plant with a low moisture content and high dead material percentage will, in theory, pose a higher risk if fire were present. However, little research in New Zealand, or worldwide, has put this to the test empirically. 

    Sarah Wyse from the University of Canterbury and her team of scientists acknowledged this knowledge gap and took it as an opportunity. “A quantitative assessment of shoot flammability for 60 tree and shrub species supports rankings based on expert opinion” was published in the Journal of Wildland Fire in 2016. The aim of this paper was to quantify the shoot-level flammability of 60 native and exotic plant species found in New Zealand and compare these results with rankings derived from previous studies. 

    Plant barbeque in action! Image by Georgina Woods

    One of the key pieces of equipment required for this study was a plant barbeque; yes you heard me right. Built out of a 44-gallon drum, the plant barbeque is every pyromaniacs dream. Rather than just burning components of a plant, this study burnt whole shoots (maximum 70 cm long) which preserved much of the plant’s structure. Each sample was left on the grill for 2 minutes to create the same environment as if an approaching wildfire. Once the sample had heated, it received direct flame from a blow torch for 10 seconds. Following this, measurements, such as ignition time, burning time and maximum temperature, were recorded. Overall, this approach creates more realistic wildfire conditions and much more ecologically significant data.

    The study found species such as gorse, manna gum and kūmarahou to be high in flammability whereas species such as whauwhaupaku, hangehange and kotukutuku were low in flammability. These findings have contributed to paving the way for the development of mitigation tools, such as green firebreaks. Green firebreaks are strips of vegetation comprised of plant species that are low in flammability. This reduces the spread of fire, making our landscapes more resilient. As well as this, they contribute to encouraging native biodiversity to flourish.  

    This is only the beginning for plant flammability, which has scope for future research. One of the co-authors of this project, Tim Curran from Lincoln University, has a goal to make this data set and future research known worldwide. Further investigation is going to continually contribute to the existing valuable pool of knowledge, tackling the challenges that continue to threaten humankind.

    As we experience the consequences of climate change, it is normal to feel that creeping sense of eco-anxiety, but this research may help you ease those nerves. Knowing more about a problem is always helpful. So, whilst Sarah, Tim and other keen researchers help expand what we know about plant flammability, I’d save your marshmallows for another day; perhaps we won’t end up as a ball of flames after all. 

    This article was prepared by Bachelor of Science (Honours) student Georgina Woods as part of the ECOL608 Research Methods in Ecology course.

    Citation: Wyse, S. V., Perry, G. L. W., O’Connell, D. M., Holland, P. S., Wright, M. J., Hosted, C. L., Whitelock, S. L., Geary, I. J., Maurin, K. J. L., & Curran, T. J. (2016). A quantitative assessment of shoot flammability for 60 tree and shrub species supports rankings based on expert opinion. International Journal of Wildland Fire, 25(4), 466–477. https://doi.org/10.1071/WF15047

  • The superpowers of NZ moss: Dry shrubland and its moss ground cover

    I love moss.

    I have always loved mosses. They are so cute!

    Moss is green, all kinds of green, every nuance.

    Some of them are leafy, some of them flat, and some look like cushions.

    They make the forest floor look like a fairyland.

    Moss between bricks in front of Ivy Hall, Lincoln University. (Image from Eva Saison)
    Moss surrounded by render, Lincoln University. (Image from Eva Saison)
    Moss growing on Ivy Hall facade, Lincoln University. (Image from Eva Saison)

    Even better than simply being aesthetically pleasing, mosses have superpowers.

    Like Spider-Man, they stick to vertical flat surfaces, decorating walls with adorable green spots. Moss also has another power. I remember walking through the dunes in my hometown of Calais (France), the sound of waves in the background. Suddenly, between the European beachgrass (Ammophilia arenaria) that keeps the sand and dunes in place, I spot a brown patch of dead moss. Dead? Not really. With just a few drops of water on it, the moss revives in a few seconds, turning the brownish-dead area into a bright green patch of life. Just amazing. Tiny dune zombies are coming back to life through water.

    Moss shows off its Spider-man skills on Ivy Hall, Lincoln University. (Image from Eva Saison)
    Dead looking (but not dead at all) moss on a tree. (Image from Eva Saison)

    Consequently, moss brings joy to people, or at least to me. However, what role is moss playing in nature?

    The study conducted by Rebecca Dollery, Mike Bowie, and Nicholas Dickinson in 2022 helps to answer this question. They were particularly focused on the importance of moss ground cover in a dry shrubland area of New Zealand. They found that moss could be represented as a collector that loves to hoard various things.

    First into the hoard is water. Moss absorbs rainwater or humidity from the air. Moss is almost always wet when touched. The water is then used by the moss. The soil benefits from the waterlogged moss cover: in summer, soil is wetter under the moss carpet. The moss acts as a protective layer for the soil against the summer heat, allowing retention of water in the soil. The water is later used by the surrounding plants. In a dry shrubland environment, moss can have a positive effect on other native plants populating the area.

    Second into the hoard are soil nutrients. All plants need them to grow. One of the most important nutrients is nitrogen (N). It can be found in soil and absorbed by the plants in two forms: nitrate (NO3–) and ammonium (NH4+) molecules. With the ground covered by a moss carpet, the quantity of nitrate and ammonium in the soil decreased, up to 75% for the latter. In addition, the thicker the moss, the lower the amount of nitrate. Therefore, moss not only absorbs water but also sequesters essential nutrients. The nitrogen is trapped within the moss.

    This sounds alarming: moss is taking away the necessary food source of all other plants. However, this is not a tragedy for the dry shrubland environment. Indeed, their soil is low in nutrients under normal circumstances. Consequently, the plants growing there are adapted to these conditions. On the contrary and surprisingly, they might even suffer from a large increase in soil nutrients. The moss carpet thus preserves the original composition of the soil, which is also the optimum growing condition for plants native to dry shrublands.

    Third into the hoard are the seeds that fall and are stored within the moss layer. The researchers tested the impact of moss ground cover on the ability of some native species to germinate. Generally, moss cover prevents germination: fewer seeds germinate than on bare ground. The scientists supposed that the seeds did not germinate because they were in the dark, after falling into the depth of the moss layer. This was mostly observed with tauhinu (Pomaderris amoena) and kānuka (Kunzea serotina) (the species name was revised back to Kunzea ericoides in 2023). Both suffered a 60% reduction of their germination capacity.

    The seeds of the common broom (Carmichaelia australis) can germinate in the dark. For this species, the high humidity within the moss could be the reason why seeds germinated up to 88% less often with moss ground cover. Nevertheless, some seeds germinated and became seedlings. Their next step was to have their roots access the soil to absorb nutrients. The scientists observed that more common broom seedlings survived on the bare ground than with ground moss cover. The moss layer probably acted as a barrier between the roots and the soil. Despite that, the seedlings of common broom and tauhinu that germinated with moss were up to 3 times heavier than the ones from bare soil. This indicates that the conditions provided by the moss cover have had a positive impact on their growth.

    Rebecca and the team identified the moss as a plant that loves to stockpile things: first water, then nitrogen, and finally seeds. The various impacts of the collecting moss were in some ways beneficial for the native plants of the dry shrubland ecosystem. They were, however, detrimental towards exotic and invasive weeds. These invasive species suffer from the low nutrients in the soil and the difficulties of germinating within the moss layer. Moss, therefore, participates in the conservation of native plants in the dry shrubland ecosystem.

    A very interesting name can be added to the “things collected by moss” list: carbon (C). Sphagnum moss are one of the main components of peatlands. In these ecosystems more vegetation is growing than is decomposing, thus vegetation, including moss, is gradually accumulated as layers of peat. Furthermore, when plants are growing, they absorb CO2 from the atmosphere, they keep the carbon to form sugar and release oxygen (O2). Therefore, peatlands are trapping carbon in their vegetation, in their moss. Larmola and colleagues (2014) calculated that one-third of the total amount of carbon stocked on land is trapped in peatlands!

    Zoom in on Sphagnum moss. (Kirill Ignatyev, CC BY-NC 2.0, Flickr)

    After all those discoveries, I continue to love and admire moss. I will carry on watching the moss turn green again in the dunes and taking naps on forest moss. Those tiny superheroes decorate my city pavement and walls, promote native plant species in New Zealand’s dry shrublands and trap carbon from the atmosphere, as little fighters against global warming.

    This article was prepared by Master of International Nature Conservation student Eva Saison as part of the ECOL608 Research Methods in Ecology course.

    Dollery, R., Bowie, M. H., & Dickinson, N. M. (2022). The ecological importance of moss ground cover in dry shrubland restoration within an irrigated agricultural landscape matrix. Ecology and Evolution, 12(4). https://doi.org/10.1002/ece3.8843

    Heenan, P. B., McGlone, M. S., Mitchell, C. M., McCarthy, J. K., & Houliston, G. J. (2023). Genotypic variation, phylogeography, unified species concept, and the ‘grey zone’ of taxonomic uncertainty in kānuka: Recognition of Kunzea ericoides (A.Rich.) Joy Thomps. sens. lat. (Myrtaceae). New Zealand Journal of Botany, 0(0), 1–30. https://doi.org/10.1080/0028825X.2022.2162427

    Larmola, T., Leppänen, S. M., Tuittila, E.-S., Aarva, M., Merilä, P., Fritze, H., & Tiirola, M. (2014). Methanotrophy induces nitrogen fixation during peatland development. Proceedings of the National Academy of Sciences, 111(2), 734–739. https://doi.org/10.1073/pnas.1314284111

  • A foreign threat: New Zealand’s Invasive insects

    One of the many great fascinations of New Zealand is the absurd number of bugs found here that are found no where else on Earth. What’s a bug, you might ask? They’re the six-legged creepy crawlies you find everywhere. They are a part of your life, from the obnoxious house fly in your room to the big, bold beetle in the garden! Well, technically, I mislead you with the name bug. Bugs are a single group of piercing-sucking insects; the correct term to describe errant creepy crawlies is insects.

    Aside from being a nuisance in the home, what do New Zealand’s insects do? They provide excellent services to our ecosystem, whether churning up dirt, pollinating flowers, or controlling noxious weeds. They also serve as an essential part of the food web and are a key to the survival of many birds and lizards.

    A friendly, Robust grasshopper says hello! This photo I took in the Mackenzie district shows one of our largest grasshoppers. They’re excellent grazers of lichens and mosses. Historically they provided great nutrition for many birds and lizards.

    Despite their abundance, insects are massively understudied both globally and in New Zealand. We must understand how our insects contribute to our ecosystems and what might happen when new insect species arrive in our country. Species not previously found in New Zealand (nonindigenous creatures) have been a massive threat to New Zealand’s native biodiversity over the past 200 years.

    Of the non-indigenous species in New Zealand, much of the focus has been on mammals, like stoats, and plants, like wilding pines. This work is essential because these sorts of species have huge impacts on our environment and our economy. But what effects do the over 2000 introduced insect species have on New Zealand? A study by Brockerhoff (in 2009) featuring Lincoln University’s Dr Cor Vink, attempts to determine the threat of new insects to New Zealand’s ecosystems.

    The threat of introduced insects was recognised soon after European arrival. From what we know few of these species are capable of affecting native ecosystems aside from the well-studied Vespula wasp.

    The currently accepted view is that new insects do not generally hurt our ecosystems. However, as New Zealand’s ecosystems are often so understudied there is little way for us to measure the effects of new insects on the environment. Across most of the world, the arrival of new insects can be a catastrophe with substantial environmental and economic impacts.

    A photo by Will Frost of a typical Mackenzie Basin floodplain grassland. A habitat type threatened by new species of weevils and the expansion of dairy farming.

    So far New Zealand has avoided such a catastrophic invasion. Brockerhoff (2009) suggests that perhaps our intact native ecosystems repel insect invasions well compared to other parts of the world. While our forests have repelled invaders so far, the threat of climate change may alter the balance in the war of plants and insects.

    Brockerhoff (2009) aimed to investigate the effects of insect invaders across a range of New Zealand’s habitats. It was found that over 200 insects capable of damaging forests have been found in New Zealand but have had minimal impact on our native ecosystems. Several generalist moth species and a passion vine hopper have had minor effects without significant damage. In grasslands, several weevil species have been found all over New Zealand, even as high as 2800 metres, but their impact on the surrounding environment so far seems to be minor. These results suggest that all is well for New Zealand’s ecosystems. However, with rising temperatures creating more optimal conditions for invaders there could be an increase in foreign insect invaders.

    When species reach more significant numbers, their effects can start to worsen. Vespula wasps are well documented for their disruptive effects in beech forests. They feed on honey sap and compete with native birds for this resource. Worse still, these wasps predate on many native insects, some requiring a 90% reduction in Vespula wasps to survive.

    The Argentine ant spreading through New Zealand and is also of grave concern. In large numbers this ant has the ability to displace native ants and often eradicate many other native insects in the soil ecosystem.

    A photo by Will Frost showing a honey-dew beech forest from Craigieburn Forest Park which is threatened by Vespula wasps.

    So far many of the more harmful insect species are isolated to human-altered habitats. And insects which make it to intact ecosystems fail to make an impact. As these insect’s populations build over time and more begin to enter the country as temperatures warm the threat of invasion into native forests may increase.

    Many insects are selective of the plants they consume due to plant defences and palatability. This is true even for generalist insects that specialise on many plants. This likely explains why so far our plants have provided protection from so many would-be insect invaders.

    Honey dew being produced by scale insects. A rich food source for wasps. Photo from Adrian Paterson

    Brockerhoff (2009) suggests that for these reasons the greatest risks to our ecosystems now are from generalist insects, especially those which don’t rely upon plants. Generalist predators, like Vespula wasps, threaten the whole ecosystem’s natural processes. Due to their ability to consume the sugar produced by scale insects. These wasps prey on the majority of native fauna in beech forests to provide food for their young. When in huge abundances the composition of insects in the forest and availability of sugar sap is hugely reduced. If more generalist insect species with no natural predators were to arrive within New Zealand the impacts would be even greater.

    To reduce the threats to our ecosystems in future, introduction of more insects for biocontrol should not be taken lightly. We are fortunate that few exotic insects have been established in New Zealand’s native habitats. However, many of the subtle effects caused by invasive insects are not yet known, more study is needed to grasp how these effects are impacting the ecosystem.

    In the future, climate change and habitat disturbance could allow new insects to arrive and threaten our native ecosystems. We know enough now to say our environment is safe from hugely adverse effects; however, the future is uncertain. Developing a greater understanding of how these creepy crawlies subtly affect our ecosystems is paramount.

    This article was prepared by Master of Science postgraduate student Will Frost as part of the ECOL608 Research Methods in Ecology course.

    Brockerhoff, E. G., Barratt, B. I. P., Beggs, J. R., Fagan, L. L., (Nod) Kay, M.,K., Phillips, C. B., & Vink, C. J. (2010). Impacts of exotic invertebrates on new zealand’s indigenous species and ecosystems. New Zealand Journal of Ecology, Suppl.Special Issue: Feathers to Fur, 34(1), 158-174. https://newzealandecology.org/nzje/2916

  • Fantastic mantids and where to find them 

    This past year I have been reading a lot of papers about mantids because I will be doing my Masters thesis on the New Zealand mantis. They are very interesting animals that fill the niche of a top predator in many habitats.

    New Zealand only has one native species of mantid which is called te whē/rō in te reo Māori. Te whē/rō is a name shared with the stick insect. This relates to a tradition that Māori have where, depending on which of these insect species lands on you, this will indicate which gender your child will be. Maybe New Zealanders could bring it back for some niche (and traditional) gender reveals?

    Image from Ken Vernon

    The New Zealand mantis isn’t the only mantid species in New Zealand though. Since the 1970s we have had a second species in our country. Spreading from Auckland and across the North Island, the South African mantis quickly established itself in New Zealand. This South African invader is also well established in Nelson on the South Island.

    These invasive mantids have caused the decline of our native mantis on the North Island. This impact is likely driven by the female South African mantis that eat our native mantis males. These males follow their noses to the exotic female only to find out that it is a dinner date, and they are on the menu.  

    NZ ootheca (Jon Sullivan)

    The native mantis is more of a gentle species, where the females are unlikely to try and eat their mate. They don’t live for very long, perhaps six months in the wild. Mantids need a way to survive the winter and ootheca (little mantid egg cartons) protect their eggs while they develop. Both mantid species in NZ have ootheca, though they can easily be told apart. The South African mantis has a puffy white ootheca, which looks like a small meringue, while the New Zealand mantis has a brown ootheca that is smaller and more geometric.

    Mike Bowie, and his son Matthew Bowie, looked at where the New Zealand mantis laid their ootheca. Mike recently retired after over 40 years at Lincoln University, working on many native species, including the habits of New Zealand mantids.  

    The Bowies found that the New Zealand mantis preferred kowhai, native broom, lancewood, and cabbage tree, which together had 78% of the oothecae. Over half of the ootheca were found on smaller branches, predominantly non-shaded. They found that these spots were warmer and brighter than other parts of the trees and this would help with development.

    Oothecae were also centred on true north, which works with most New Zealand houses and fences since most properties are also facing true north. Ootheca are attached to houses and fences that face north, maximising their sunlight. This allows developing mantids to grow quickly. 

    The Bowies also found that there was a size difference between ootheca in Lincoln compared to those in Palmerston North. The Lincoln oothecae were significantly larger than the egg cases up north. There could be a few reasons for this and one of them is that a larger size helps them handle the colder temperatures down here. This size difference also allowed the southern population to fit a few more eggs in their ootheca giving them a bit of an advantage.  

    South African ootheca (Jon Sullivan).

    The study shows that our mantis has various adaptions that allow them to survive the New Zealand winters, especially by using the modified habitat we have created in New Zealand. Despite this, the New Zealand mantis is in decline. The South African mantis lay their ootheca in more sheltered spaces and produce oothecae that are larger than the locals, giving them advantages. They can even lay an ootheca without mating and it will hatch successfully.

    Just like those male mantids, we’ll be praying for a happy ending!

    This article was prepared by Master of Science postgraduate student George Gibbs as part of the ECOL608 Research Methods in Ecology course.

    Bowie, M. K.; Bowie, Michael H. 2003. Where does the New Zealand praying mantis, Orthodera novaezealandiae (Colenso) (Mantodea: Mantidae), deposit its oothecae? New Zealand Entomologist 26(1): 3–5. (https://doi.org/10.1080/00779962.2003.9722103)

    Further reading:

    https://academic.oup.com/beheco/article/27/3/851/2365697

    https://traviswetland.org.nz/about-travis/scientific-papers/praying-mantis-in-new-zealand/