EcoLincNZ

Category: ecosystem services

  • From stinky van adventures to restoration projects – the unseen potential of wastewater

    Picture this: you’re on a camping trip, enjoying the breathtaking view of one of the most beautiful lakes of Aotearoa New Zealand surrounded by snow-capped mountains, watching the incredible red colours of the sunrise, when suddenly a ghastly smell permeates the air. You quickly discover the source – a full wastewater tank in your camping van that urgently needs to be emptied.

    My friend Julia as she is emptying out the wastewater tanks of her van. Photo by Flora Brumen

    For those who have not experienced the dreadful smell of such a full wastewater tank, know that this is not easily forgotten. Standing in line at a dumping station, waiting to take your turn to get rid of your own disgusting fluids while someone is emptying their toilet container right in front of you, is a situation that brings shared discomfort to campers.

    Now, I may be exaggerating a little now, but you understand my point. Toilet tanks include so many chemicals, that it actually smells better than the tanks that collect just the wastewater from doing the dishes. However, it’s an experience that highlights the less glamorous side of camping but still unites people in their shared discomfort. It reminds us that wastewater is an unavoidable reality that affects us all, every day, not just while camping.

    The impact of wastewater goes beyond our noses. Uncontrolled discharge of wastewater poses a threat to human health, native freshwater species and ecosystems. In New Zealand, treated wastewater is often released into waterways or the ocean. Unfortunately, this can contaminate recreational surface waters with harmful bacteria and viruses.

    The consequences of this pollution are significant. Many popular swimming spots in Canterbury have been ranked unsuitable for swimming due to high levels of bacteria from human sewage found in the water. Last summer, heavy rainfall events worsened the situation, leading to increased runoff of faecal pathogens. Besides creating severe threats to human health and creating unsuitable recreational areas, the pollution also harms freshwater species and degrades aquatic ecosystems. In fact, a devastating 76% of the indigenous freshwater fish species are endangered or threatened, 46% of all lakes have poor water quality and 45% of New Zealand’s rivers are not suitable for swimming activities.

    What if we could turn the tables and use wastewater to actually help save our ecosystems? That’s exactly what a recent study under the direction of Alexandra Meister, a bio-waste scientist from ESR and the University of Canterbury, in collaboration with the Christchurch City Council and Lincoln University, suggests.

    The researchers carried out an experiment on Banks Peninsula, where they irrigated a site with native plant species with treated wastewater from the local treatment plant for three years. The research team made an exciting discovery: the native plants experienced significant growth with this wastewater regime. In fact, their plant height increased by an impressive 10% compared to plants not irrigated with treated wastewater.

    Site of the field experiment on Banks Peninsula, that was irrigated with treated wastewater. Photo by Meister, Gutierrez-Gines, Robinson (Kiwiscience)

    It doesn’t stop there. The soil at the experimental site showed no signs of an increase of potentially harmful elements – beyond what is normal in the soil – that could endanger humans or the environment. There may be exciting possibilities for combining restoration projects with wastewater application to land. By doing so, we could decrease the discharge of wastewater into our water bodies, but also promote the growth of native vegetation, leading to a potential recovery of native biodiversity.

    Of course, establishing native plants in these environments can be challenging if the species are not adapted to highly fertile soil conditions that are created by treated wastewater irrigation. One particular native plant, Mānuka (Leptospermum scoparium), was an obvious candidate for this experiment. This species has the ability to eliminate harmful soil pathogens and reduce the amount of nitrate leaking into water. Even though mānuka is not adapted to such nutrient-rich conditions, typically growing in low-fertility soils instead, the species responded well to irrigation and increased their growth.

    The success and safety of applying treated municipal wastewater to the land depend on two key factors: the quality of the wastewater and the characteristics of the local environment. Due to these unique considerations, it is crucial that each system is designed to specifically address these factors.

    Going forward, the researchers will continue their investigation by exploring various plants and soil types. They will continue to explore different plants and soil types, expanding our understanding of where and how wastewater irrigation can be utilised effectively.

    It’s time to shift our perception of wastewater. Instead of viewing it as something unseemly to get rid of, we need to recognize it as a valuable resource that can be multi-purposes. By finding innovative applications for treated wastewater, we can decrease its careless discharge and contribute to saving our environment and ecosystems.

    The success of using treated municipal wastewater as a valuable resource shows us how even the unpleasant smelling wastewater from our camper van adventures something associated with an unpleasant smell can turn into the sweet scent of environmental protection and restoration efforts.

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

    Meister, A., Li, F., Gutierrez-Gines, M. J., Dickinson, N., Gaw, S., Bourke, M., & Robinson, B. (2022). Interactions of treated municipal wastewater with native plant species. Ecological Engineering, 183, 106741. https://doi.org/10.1016/j.ecoleng.2022.106741

  • Oh the horror! What should scare us at Halloween

    It’s Halloween today. Although ‘trick or treating’ has started to catch on over the last couple of decades, Halloween has never been that big a deal here in NZ. Perhaps it’s because it happens in spring when everything is greening up, new life abounds around us, and we are starting to appreciate the lengthening days and warmth. In the northern hemisphere it is the opposite and perhaps lends itself to the sinister, the thinning of the veil between worlds, the slide into the difficult time of the year.

    Halloween – a time for ghouls and ghosts.

    Most obviously, Halloween is a time for horror movies and themes. Scary images show up on our screens and theatres and aim to frighten us. I’ve often thought that horror does not capture Halloween that well. Halloween is more about fey magics, creatures of legend appearing to drive uncanny bargains, the sense of the other, and perhaps a sense of dread. Horror seems like a small part of this.

    To be fair, I am not a horror fan. I am certainly not a gore and blood person. I enjoyed the old Hammer Horror films, was scared by “The exorcist”, and scarred by “The fly” (the old black and white version – “Help me…”). But I have stayed clear of slasher films and probably haven’t seen a full-on horror for, well, for a long time.

    What are people horrified by at Halloween? Mostly it is ghouls, witches, zombies, vampires, English rugby referees, and ghosts. But it seems to me that there are plenty of other things to be horrified about.

    What’s down that path….? Opportunity or threat?

    Cate Macinnis-Ng and a host of authors, including Will Godsoe from Lincoln, have published a paper in the Journal of the Royal Society of New Zealand. In this they look at the potential threats and opportunities with the ongoing change in climate. The neat angle here is that they take perspectives from many different people and apply an ecological method, a horizon-scanning approach, to come up with ten for each.

    Most of the benefits revolve around the application of new technologies and the chance for major positive societal changes. The negatives are much more specific, more disease outbreaks, dealing with heat waves, increasing black swan events and so on. It is not difficult to read this and feel a real sense of alarm for the future.

    So, if you want some real dread this Halloween day, then this is an article to read. Perhaps under your bed covers with the torch. There are no bumps in the night, no jump cuts, no creepy faces in mirrors (although I guess NZ is a bit like a cabin in the woods).

    But there is plenty of dread and horror.

    Adrian Paterson is a lecturer at the Department of Pest-management and Conservation, Lincoln University.

  • Neighbourhood disputes, models, and a harmonious coexistence with elephants

    In my home country, Germany, we have cut down every bit of primeval forest. We hunted aurochs, brown bears, wolves, lynx and even beavers to extinction between the 17th and 19th centuries. After messing it all up like that, we now dare to tell other countries, that still hold on to their forests and wildlife, what to do with their nature.

    “Don’t hunt those animals you used to hunt sustainably for centuries; we think they are so charismatic”. Currently, wolves are slowly coming back to Germany, and immediately people (successfully) changed laws to permit their shooting if they prey on sheep because it is “not bearable” to live in close coexistence with wild animals like that. Apparently, wolves don’t belong to Germany anymore because…yeah, because what? Because humans live here?

    Now close your eyes and imagine you are a subsistence farmer. Oops, don’t close them, rather, continue reading! You can still imagine, though! Every day you’re working hard taking care of all the veggies and crops you planted to feed your family. One day you look up, and what you see is a massive giant, almost as tall as your house. That giant has destroyed everything you ever planted.

    African elephant (Loxodonta africana) drinking. Picture © Severin Racky (used with permission).

    Happily munching on the last corn cob, the elephant greets you with an intimidating “HEI!”. Sounds absurd? Well, this scenario is much more realistic than our Western culture’s perception of African savannas as a vast untouched wilderness with Simba and all his large mammal friends living their best lives, without humans in the picture and without “HEI”, Human-Elephant-Interactions.

    This perception of wild Africa has influenced our approach to mitigating HEI. A common attempt is to build physical barriers, such as fences, to separate humans and elephants, believing they could protect both parties. However, elephants are unbelievably strong and intelligent creatures, and they easily overcome these obstacles, leaving farmers caught in a perpetual battle to safeguard their livelihoods.

    I have personally witnessed elephants knocking over trees onto “elephant-proof” electric fences to get to the other side. No fence can hold back a herd of determined elephants. Fences, therefore, cannot be the only solution when both humans and elephants need to get their food from the same land. It doesn’t stop with crop and infrastructure damage, though; Humans and elephants die through HEI. Elephants are killing around 500 humans per year and humans return the favour.

    After bothering you with way too much bad news, at least I can tell you that science offers a glimmer of hope! Picture a team of brilliant minds huddled around computer screens, armed with data and determination. With powerful tools with mystical names like Agent-based modelling (ABM) and Geographic Information Systems (GIS), ecologists are unravelling the complexities of HEI to help us understand human-elephant interactions better. With these tools, the researchers can simulate scenarios and explore the factors determining conflict incidents, to develop effective measures to reduce the conflicts and to mitigate poaching. The models are needed because, due to plenty of ethical problems, these kinds of experiments could not be conducted in real life.

    In their study from 2021, Abel Mamboleo, Crile Doscher, and Adrian Paterson, from Lincoln University, simulated 18 scenarios, considering things like human population, elephant population, rivers, conservation corridors, and protected areas. They evaluated their impact on different HEI incidents, such as crop damage, human deaths, elephant deaths, and hidden impacts. The term “hidden impacts” refers to indirect consequences of HEI and includes fear restricting movements, missing school, or resulting health issues. For example, their “elephant-effects scenario (ES)” evaluated the effects of varying elephant populations on HEI, the “human-effects scenario (HES)” evaluated the effects of varying human populations on HEI, and the “environment-effects scenario” evaluated the effect of varying environmental parameters (distances to rivers, protected areas and corridors) on HEI.

    Using their models, the scientists identified hidden impacts of HEI (e.g. fear and resulting health issues or restricted movements depending on elephants) as the most challenging incidents to mitigate. Interestingly, maintaining a greater distance from rivers seemed to effectively reduce those hidden impacts. Now who would have thought that?

    Their model also indicated that most incidents of elephant crop damage occur within 1 km from rivers. Therefore, according to the model, it is possible to lower the risk of your crops being eaten and trampled by a grey giant by planting them further away from rivers (Yeah, good news!). Among the incidents studied, human deaths were found to be the easiest to reduce (more good news!). Fifteen out of the 18 scenarios lead to significantly fewer human deaths.

    African elephants drinking and playing at a waterhole. Picture © Severin Racky (used with permission).

    Distancing human activities from rivers, and creating conservation corridors and protected areas, seem to be an effective mitigation strategy. However, challenges remain. Reducing the deaths of elephants seems to be one of the most difficult tasks, with only six out of the 18 scenarios showing significantly fewer dead elephants. The number of elephant deaths was reduced in some scenarios, such as a so-called “ENS-River-Protect-Corridor”, in which the scientists modelled farms to be 7000 m away from rivers, protected areas and wildlife corridors.


    While no single scenario that the scientists played through was able to completely eliminate all incidents, their modelling provided valuable insights and recommendations for potential strategies to reduce HEI. With their models, the researchers showed that HEI is influenced by many different factors beyond the pure numbers of humans and elephants. Geographical and environmental features, such as rivers, protected areas, and corridors, and socioeconomic activities, also play crucial roles. With the approach of creating safe distances between human activities and critical areas, the researchers found practical strategies to minimize the deaths of both humans and elephants.

    The study’s findings, therefore, highlight the need to address the spatial relationship between humans and elephants and promote responsible settlement planning. Successful strategies for mitigating HEI require a holistic approach that balances the needs of both humans and elephants and prioritizes a healthy elephant population as well as the well-being of affected human communities.

    It is important to emphasize that models are just a tool, implementing solutions still needs to be done by our big, juicy human brains. For example, in all scenarios, the model suggested to just lower the population size of humans and/or elephants to mitigate HEI. Fewer humans, fewer elephants: fewer human-elephant interactions. Of course, both options are far away from an ethical or recommendable solution. If the elephant density is extremely high, relocating them to other areas could be a (very complicated and expensive) option.

    Wait a minute! Hey, German politicians, how come you haven’t thought about reducing the population size of humans in areas where the wolves are coming back? I heard many of us would love to live in New Zealand anyway. What about providing a free one-way ticket to New Zealand for every revengeful German sheep farmer who wants to kill wolves as a compensation measure?

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

    Mamboleo, A. A., Doscher, C., & Paterson, A. (2021). A computational modelling approach to human-elephant interactions in the Bunda District, Tanzania. Ecological Modelling, 443, 109449. (https://doi.org/10.1016/j.ecolmodel.2021.109449)

  • The secret life of elephants: ecological engineers and agricultural pests

    As a Kiwi, when I hear the word ‘pest’ my mind instantly goes to possums, stoats, rats and cats. These are some of the invasive mammals which are killing so many of our native species, most of which cannot be found anywhere else in the world. These lethal pests have turned us into killers as well; we promote and stand by numerous lethal methods for pest management, without batting an eyelid. Whilst some are made uneasy by the thought of trapping, poisoning or hunting these creatures, we still employ these measures as second nature.

    When talking about pest management in the past, I never quite understood the shock or disapproval from visitors from overseas. They get a certain look on their faces when they hear what we do to these mammals, many of which they are trying to protect at home. It seems to them that we have become somewhat apathetic to the lives of these creatures and accustomed to having blood on our hands in the name of pest management.

    Dead stoat, trapped in Fiordland National Park/ Avenue

    The way that I look at it, along with many other New Zealanders, is that I feel a strong sense of responsibility for protecting our native birds, lizards and plants. I do accept that these pests are simply trying to survive, on an island archipelago that they didn’t choose to live on.

    Some parts of the world, have a much larger agricultural pest issue: elephants. Hearing this, helped me to understand what others feel when we talk about pests in New Zealand. How can an elephant, such a majestic creature, be considered a pest?

    Of course, an agricultural pest differs in definition to the introduced conservation pests that we have in New Zealand, although reactions to these pests seem to be the same. In retaliation to the damage caused to local livelihoods or personal safety, some people have been reported to purposefully remove native elephant habitats or even employ lethal methods to control the “problem elephants”. I am now the one in shock, although in the grand scheme of things it’s not so dissimilar to our pest control strategies.

    Abel Mamboleo, as part of his PhD research at Lincoln University, asked the question, published in the Journal of Biodiversity & Endangered Species, of whether elephants were really the most disastrous agricultural pest animals or are they actually the agents of ecological restoration. He reviewed multiple studies and publications to obtain crucial information about elephants, agricultural pests and ecological restoration. All of this helped guide him towards the answer to this big question: are elephants a pest or an ecological blessing? He also wanted to summarise the existing knowledge to help both conservationists and local people create appropriate plans for sustainable management.

    Indian elephant bull in musth in Bandipur National Park/ CC-BY-SA 3.0 Yathin S Krishnappa.

    Human-elephant conflicts arise through any interactions between our two species that have negative impacts on social, economic or cultural life, on elephants, or on the environment. The most common feature of these interactions is crop-raiding. As human populations increase, our demand for land, water and food also increases. Consequently, historical elephant habitat is being infiltrated by human activities through agricultural development, limiting elephant habitats to small “ecological islands”. This means their usual dispersal routes are restricted and the competition for resources with humans increases.

    So, what happens when the natural habitat and resources of elephants are taken away? They search for food elsewhere, with the most abundant source being crops on surrounding farms. Elephants actually prefer agricultural crops to wild plants because they are more palatable, nutritious and readily available. For this reason, local people have labelled elephants as the most disastrous agricultural pests, because of the damage from elephants that they sustain. But is this a fair statement?

    Elephants were compared to the criteria an animal must fit to be considered a pest. These criteria include any animal that feeds on crops, damages buildings or stored food, injures people and kills livestock. When looking at it this way, yes, elephants by definition are pests. They damage stored and field crops, which ultimately affects human food security during drought seasons. However, to be labelled the most disastrous agricultural pest seems a bit extreme. In fact, for this to be the reality they must be causing massive economic damage to crops and property; more than other pests.

    While they do cause some local damage, Mamboleo found that they only cause moderate damage when compared to other pests. The damage inflicted by wild pigs actually far outweighs that of elephants and puts them in first place for the most disastrous agricultural pests. Elephants even sit behind rodents, European starlings, red billed quelea and desert locusts when looking at the line-up for the worst pest offenders in these areas. While it is true that elephants can inflict extensive damage, it is still significantly less than other pests. For local people, it is hard to see it this way as they have entire fields of crops decimated by these giants.

    People are seeing persistent crop damage and associating this with pest behaviour. Because their farms often closely border protected elephant habitats, it means people are seeing more severe crop-raiding and they’re seeing it more frequently. While on the other hand, the elephants just see more food. Naturally, the elephants are getting the blame and inheriting this new title; from a local perspective it is an obvious response.

    On the other hand, elephants are considered as agents of ecological restoration. Much like secret agents, they work inconspicuously to repair and re-establish ecosystem services that may have been damaged by human activities. A successful act of ecological restoration must be effective, efficient and engaging. This is otherwise known as the “triple E” principle, which serves as the guidelines for evaluating environmental restoration processes.

    Elephant in India/ CC-BY 4.0 Sanghavisrini

    Elephants are effective because their natural and physical abilities provide all sorts of environmental benefits to humans and other wildlife. They also have the ability to restructure their environments, sometimes opening up thick vegetation and helping their herbivore neighbours in the process.

    Elephants are also efficient because of their high level of intelligence and behaviours; they are able to perform productive ecosystem rehabilitation activities in a consistent and timely manner. Usually this is without the support of human intervention. Elephants have been branded “ecosystem engineers” or “mega-gardeners” because of their role in dispersing seeds, helping both wildlife and humans. Through ecological restoration, these elephants are replenishing cultural resources and socioeconomic conditions for humans and allowing re-connection with nature. Some would call that engaging. This ecosystem restoration allows humans and other wildlife to reuse otherwise damaged ecosystems.

    So what is the answer to whether elephants are the most disastrous agricultural pests or actually the agents of ecological restoration? This needs to be looked at from two separate viewpoints. Yes, they are pests, but they are not the most disastrous. And, yes, they are agents of ecological restoration. But they are both occurring simultaneously, depending on the perspective you view it. Can’t they be both?

    This article was prepared by Master of International Nature Conservation student Quinn O’Halloran as part of the ECOL608 Research Methods in Ecology course.

    Mamboleo, A.A., Doscher, C., & Paterson, A. (2017). Are elephants the most disastrous agricultural pests or the agents of ecological restorations? Journal of Biodiversity & Endangered Species, 5(185). doi:10.4172/2332-2543.1000185 .

  • 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.