EcoLincNZ

Category: ecosystem services

  • The legacy of Smaug: Exotic worms conquer New Zealand’s soils

    My armour is like tenfold shields, my teeth are swords, my claws spears, the shock of my tail is a thunderbolt, my wings a hurricane, and my breath death!” Smaug from The Hobbit, by JRR Tolkien.

    Wyrms or worms? It’s probably not the introduction you’d expect from your typical friendly neighbourhood earthworm, but as it turns out, they’re not as harmless as they may seem. Could it be that introduced specimens are actually taking over the home-soils of worms native to Aotearoa New Zealand?

    I am king under the mountain!
    Image by whadatobexy (CC)

    An invasion as ruthless as that of Smaug (you know, the “specially greedy, strong and wicked worm” described in JRR Tolkiens “The Hobbit”), when he drives the dwarves from their tunnels beneath the Lonely Mountain? Well, maybe.

    New Zealand is actually one of the countries with the highest number of endemic earthworms (“endemic” meaning they exist nowhere else in the world). It has over 200 different species, all of them in the Megascolescidae family.

    They thrive in soils of native vegetation but rarely survive in land used for agricultural purposes. For this reason, it’s fair to assume that the land-use-change, caused first by the Māori, then the Europeans, was not appreciated by the worms living in that ground. With the introduction of agriculture and pastures, it didn’t take long for native earthworms to disappear, only hanging on in areas that were still covered with the original vegetation.

    Twenty-three species of European earthworms (from the Lumbricidae family) were introduced. They quickly took over the changed habitats and ecological functions from their New Zealand worm-cousins, which themselves continued to live in exile, deep within the realms of untouched soils (this, and further information can be found here).

    Can we mingle?
    Image by Petr Kratochvil (CC0)

    As described here, European species have been moving from agricultural land into adjacent native vegetation. We know from other parts of the world, like the US, that the presence of invading exotic earthworms causes changes in the soil, such as nutrient levels. This has effects on the entire ecosystem as well as on the native worms living there.

    One of the first studies to look at the co-existence of the exotic and native earthworm species in New Zealand was done by researchers from Lincoln University in 2016. The study was called “Response of endemic and exotic earthworm communities to ecological restoration“. The goal of the project was to find out if endemic earthworm species would come back to recolonise areas where native vegetation has been restored. The study looked at  two sites, located on the east and on the west coasts of New Zealand’s South Island. On one of them, plant restoration had been happening for over 30 years, on the other for 8 years.

    The team of researchers excavated soil from each site and hand-sorted out all worms present. In the lab, they were carefully identified as either endemic or exotic. After the slimy work was done, the following conclusion was reached: the populations of endemic worms increases alongside the length of the restoration period. In the meantime, the population of exotics remained more or less stable.

    In restored sites exotic and endemic earthworms can co-exist in native soil. However, exotics may make life more difficult for New Zealand’s endemic worms, perhaps by making the soil less favourable for them, or just eating up the yummy leaf-debris. Further studies are urgently needed! However, despite these negative implications, are exotic earthworms just another invasive species in New Zealand, something we should get rid of to save the natives?

    Care for a handful?
    Image by Sippakorn Yamkasikorn (CC)

    The endemic worms are definitely not as feisty as JRR Tolkiens dwarves (I imagine them perhaps with more of a sedate and gentle character, more hobbit-like really, lots of second breakfasts and idling around the Shire). They most likely aren’t planning a revolt to reconquer their homeland that has been turned into pastures and cropland.

    Today, agriculture plays an immense role in New Zealand, and the European worms have become indispensable to the farmland areas, as as they provide many benefits in terms of waste recycling, soil fertility and crop productivity. This has encouraged efforts to continue increasing the dispersion of exotic earthworms in New Zealand’s agricultural land in recent years. It seems the exotic worms, like Smaug, are already hoarding the “gold” of the New Zealand’s fertile lowland agricultural soils and have begun expanding their sovereignty into the depths of the native land.

    Our native worms may need their own King Under the Mountain to come and save the day!

    This article was prepared by international exchange postgraduate student Nicola Wegmayr as part of the ECOL608 Research Methods in Ecology course.

    The study this blog is based on can be read here. It is the source of most of the factual knowledge that has been included.

    Boyer, S., Kim, Y.-N., Bowie, M., Lefort, M.-C., and Dickinson, N. (2016). Response of endemic and exotic earthworm communities to ecological restoration. Restoration Ecology, 24(6):717-721. https://dx.doi.org/10.1111/rec.12416

  • Making a splash: Protecting the manu with Mānuka and Kānuka

    The art and joy of bombing off a bridge. Photo: Gen Toop. Dec, 2022

    “Do a manu” “Do a bomb”. On a hot summers day these are the chants that ring out across Aotearoa as packs of kids and adults line up on bridges or climb atop rocks and get ready to jump into a lake or a river. A ‘bomb’ or a ‘manu’ is a very precise manoeuvre that involves jumping from somewhere high, curling into a ball and making the biggest splash you can when you hit the water. Some would argue that a manu involves more technical aerial acrobatics than a simple bomb. Either way, the bomb or the manu is a rite of passage for many New Zealand kids.

    But increasingly this treasured national pastime is under threat. The Ministry for the Environment painted a grim picture of waterway health in its recent Our Freshwater report. Nearly half of New Zealand’s lakes are in poor or very poor health. Only two in every hundred lakes are in good or very good health. Many rivers have become so polluted that they are now unsafe for swimming at times. And it is not only humans who can no longer safely swim in some of the country’s rivers. Native freshwater fish are struggling to survive. More than three-quarters of them are threatened with extinction.

    The native freshwater birds that depend on rivers, lakes and estuaries, are also in peril. More than two thirds of them are threatened with extinction or at risk of becoming threatened. Introduced predators, like trout and stoats, are one of the main culprits behind the decline in native freshwater fish and bird populations. The degradation of freshwater habitat by pollution is another driver that is pushing these precious species closer to extinction. Cleaning up waterways is important not only for protecting the long-held tradition of doing a ‘manu’, it’s also critical to the protection ngā manu (the birds) of Aotearoa.

    Algal Bloom in the Waikirikiri, Selwyn River. Photo Credit: Gen Toop. Jan 2021

    Nitrogen pollution is one of the leading causes of the degradation of New Zealand’s freshwater ecosystems. When excess nitrogen on the land seeps down through the soil past the rootzone of plants it can get into the groundwater. From there it can move into the aquifers that many communities and cities get their drinking water from, or it can re-emerge in springs and get into lakes and rivers. Once in those lakes and rivers nitrogen can cause algal blooms, which can suck oxygen out of the water making it difficult for freshwater fish to survive. These algal blooms also make rivers a lot less appealing for jumping into on a hot summers day. Some algae are even toxic and can cause human health issues as well as kill sensitive animals like dogs.

    There are lots of different forms of nitrogen, but one of the main forms that leaches in this way is nitrate. The vast bulk of nitrate pollution getting into New Zealand’s freshwater comes from agriculture. That’s mainly because New Zealand’s pastures are loaded up with synthetic nitrogen fertiliser and the urine of the livestock feeding on these pastures has huge amounts of nitrogen in it. When livestock, particularly dairy cows, urinate the plants can’t always use all the nitrogen for their growth and so the excess nitrate can leach into waterways.

    Mānuka (Leptospernum scoparium) flowers. Photo Credit: Vil Sandi, Flickr, licensed under CC-BY-ND 2.0

    A promising new solution to this nitrate leaching problem has been explored by researchers from Lincoln University, Canterbury University and Plant and Food Research. In 2017, the scientists simulated a dairy cow urinating (not something many of us do in our day jobs) and compared the nitrate leaching rates under three tree species that could be planted into dairy pastures; radiata pine (an exotic species), mānuka (native) and kānuka (native). They found that mānuka and kānuka leached far lower amounts of nitrogen (2 kg/ha) than pine (53 kg/ha).

    Speaking about the project Dr Juergen Esperschuetz, the lead researcher from Lincoln university said, “These results show mānuka and kānuka could be even more effective at protecting water systems than anyone expected.”

    Intentionally planting trees into pasture where animals continue to graze is a farming system called silvopasture. Silvo is derived from the latin word for forest and pasture, well we all know what that is. Silvopasture is not just about shelterbelts, windbreaks, and riparian buffers, systems which relegate trees to the margins of a farm. Instead, silvopasture systems often plant trees into the paddock itself. It has been said that silvopasture, and other agroforestry systems like it, represent a shift away from monocultural production and towards an agricultural system that more closely mimics natural forest ecosystems. Mānuka and kānuka are native trees to Aotearoa so incorporating them into dairy pastures also provides a way to bring more native biodiversity back into farming landscapes.

    The researchers also found that soils under the mānuka and kānuka emit far less nitrous oxide, with the mānuka soils emitting the least of the three. Nitrous oxide is an extremely potent greenhouse gas, it is long lived and in Aotearoa, the vast bulk of nitrous oxide emissions come from livestock farming. So planting mānuka and kānuka into dairy pastures could also help in the fight against climate change. On top of that, both trees produce high-value products in the form of oils and honey and that could be used to supplement farm income.

    Cows grazing in a silvopasture. Photo Credit: Gayle Weaver,pixabay.com, licensed under CCO

    Since the publication of this study, other researchers have gone on to use parts of its methodology and draw on its findings in their research. In the Wairarapa, a study done in the field found much lower nitrate levels under manuka than under pasture, corroborating the findings from this glasshouse study done by Dr Esperchuetz and his team. In Spain, researchers also drew on the study when they investigated nitrate leaching risk under walnut silvopasture.

    This study has added to the toolkit of options available to help reduce the environmental impact of pastoral farming in Aotearoa. Incorporating mānuka and kānuka trees into pastures will not only bring biodiversity into farming landscapes. Thanks to this research, we now know it will likely help clean up our lakes and rivers too, protecting both ngā manu and the manu now and into the future.

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

    You can read the full article here: Esperschuetz, J., Balaine, N., Clough, T., Bulman, S., Dickinson, N. M., Horswell, J., & Robinson, B. H. (2017). The potential of L. scoparium, K. robusta and P. radiata to mitigate N-losses in silvopastural systems. Environmental pollution, 225, 12-19.

  • 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

  • Can mushrooms save our planet from burping cows?

    Ever since I was a small child, I have listened to people talk about global warming and climate change. Back then I had no idea what it meant. Was our planet going to catch on fire? Were we all going to die? And why did no one seem to agree if it was fact or fiction?

    I come from a family of old school sheep and beef farmers that believed it to be a myth, or at least an over-exaggerations by scientists. As I grew up, I became increasingly more inquisitive, always asking how could something as large as our planet be warming? And what could be the cause?

    Burning earth globe west hemisphere. By Boris Ryaposov. © Adobe Stock #45170848, used with license

    Many of my questions were left unanswered until I started high school and discovered science. Straight away I fell in love with its explanations for how everything functioned. Everything from the stars in the sky right down to the soil beneath our feet (and even further down to the centre of the earth).

    Global warming quickly became a topic that piqued my interest. The more I learnt, the more obvious it became that it was a very real, very serious problem. What exactly is global warming? Thankfully, the planet isn’t going to literally catch on fire like I once thought (although fires will be more likely). The temperature of our planet is slowly increasing each year due to ‘dirty industries‘ pumping pollutants, called greenhouse gases (GHGs), into the atmosphere.

    These gasses end up trapping heat from the sun, rather than it being reflected back into space. This heat warms the atmosphere, resulting in extreme weather events becoming more frequent . This means more forest fires, droughts, floods and heatwaves, which combined have disastrous effects on the environment and negatively affect many peoples’ lives.

    Methane emissions! 牛のゲップ、メタンガス排出のイラスト. By MAYUK0. © Adobe Stock #488498751, used with license.

    Studying environmental science at university has taught me all of the main contributors to this problem. A major issue for New Zealand (NZ) is the gas methane. Methane makes up the majority of NZ’s agricultural GHG emissions, and it often comes from farm animals, such as sheep and cows. These animals produce methane during their digestive process and release it into the air by burping! Scientists have estimated that 40% of the total warming effect generated by human activities is due to methane.

    Under the Climate Change Act, NZ must reduce methane emissions from agriculture by 10% by 2030, and within the range of 24-47% reduction by 2050 (NIWA). Hence finding methods to reduce the amount of methane produced by animals is particularly important.

    The paper by K.T. Rangubhet and colleagues in the Journal Animal Feed Science and Technology found that by adding spent mushroom substrate (SMS) to cow food, that their methane emissions were significantly reduced.

    Mushroom substrate refers to the waste generated from mushroom production and is usually found in abundance after a mushroom harvesting period. The chemical composition of the mushrooms affects an animal’s fermentation and ecology. A useful byproduct of this is reduced amounts of methane burped into the atmosphere. Applying SMS to the feed of dairy cows could reduce the amount of emissions that animals contribute to greenhouse gases.

    Fungi – an image by Adrian Paterson

    Adding spent mushroom substrate uses diet and nutrition as a method to reduce GHG emissions throughout NZ. It is an approach that could allow our country to achieve the reduction goal set by the climate change act. Since this is in the next 8 years, SMS may be able to help NZ achieve these goals, especially as it is cost-effective and easy to apply. Other approaches are herd management, where animal breeds are selected that can utilise food more efficiently, and emit less methane. The strategy also includes reducing the number of unproductive animals in a herd to improve profitability.

    If these methods continue to show promise by substantially reducing methane emissions from dairy cows, this could be applied to farms throughout NZ. SMS could make a real difference to this country’s effort to prevent climate change due to GHG. This could then be part of a global solution to help to mitigate climate change and slow down our planet’s increasing temperature.

    The author Polly Cavanagh is a postgraduate student in the Master of Science -Environmental Science taught at Lincoln University. This article was written as an assessment for ECOL 608 Research Methods in Ecology.