EcoLincNZ

Category: biodiversity

  • Tricks of the underground trade: networking below the vines

    Life in the soil can be a tricky business for plants and microbes. Nutrients are a limited commodity for some, and competitors may swindle and cheat to gain the upper hand. Strategic partnerships are highly sought after enabling exchange of one commodity for another within elaborate networks.

    In a tough economy, well-connected networks promote resilience, sharing of ideas and opportunity to those participating in mutual exchange. However, an efficient network should be an intentional one. Making simple connections is one thing, but choosing the right friends and trade partners is another.

    Although it may not appear that obvious on the surface, most land plants are proficient networkers. Below ground, plants form selective partnerships with microorganisms in the soil to access nutrients, water, and protection from pathogens. Those with strong networks are favoured in times of scarcity and change.

    Fungal mycelium consisting of thread-like hyphae. Photo by Lex vB at Dutch Wikipedia, (CC0 1.0)

    Within soil communities, fungi known as mycorrhizae play a major role in the growth and survival of plants. It is estimated that more than 80% of vascular plants form partnerships with mycorrhizae, an ancient evolutionary network approximately 450 million years old.

    Mycorrhizae are of particular importance in the viticultural industry as grapevines are highly reliant on these partnerships for growth and nutrient uptake influencing grape composition, vine health and occurrence of disease. In fact, grapevines form associations with entire communities of mycorrhizae known as arbuscular mycorrhizal fungi (AMF).

    AMF form close associations within the root tissue of plant hosts through specialized tree-like structures called arbuscules. These allow exchange of mineral nutrients from the soil for carbon fixed by the plant host which is transferred through the extensive hyphal network in the soil. These hyphae form interconnected “superhighways” within the soil, linking neighbouring vines and nearby crops transferring nutrients, such as nitrogen, from one host to another.

    Arbuscule of Rhizophagus irregularis colonising a plant root. Photo by Hector Montero, Flickr (CC BY-SA 2.0)

    AMF are highly diverse and have different effects on nutrient uptake and growth on grapevines. Depending on the situation, AMF can have positive, neutral, or negative effects on plant growth and stress resistance. However, under field conditions, plants are selective in the networks they build. These communities perform a diverse range of functions which collectively contribute to plant health and characteristics. Therefore, investing in the right trade partners is crucial.

    Until recently, the effects of whole AMF communities on grapevines had been largely unexplored. A research project at Lincoln University lead by Dr. Romy Moukarzel sought to understand how AMF different communities influence nutrient uptake and growth of different grapevine rootstocks. 

    In other words, who are the trade partners behind the vines and what is the return from these communities?

    To answer these questions, AMF communities were recovered from the roots of three different grapevine rootstocks across three different vineyards. Each rootstock was inoculated with its own (“home”) community or communities from other rootstocks (“away”) within three different vineyards. Vine growth, nutrient uptake, and chlorophyll levels were measured to find out if different communities had positive or negative effects on the different rootstocks.

    Consistent with previous work, different vineyards and rootstocks had their own unique communities. Growth and nutrient uptake differed depending on the composition of the community and rootstocks responded differently to the same communities. While some species in these communities improved nutrient uptake, others improved growth. In particular, a diverse community with a large representation of AMF of the Glomeraceae family resulted in the greatest increase in grapevine growth.

    In one vineyard, home advantage was also evident with “home” communities having greater increase in vine growth compared to “away” communities. Interestingly, when the amount of each AMF inoculum was equalised, home advantage was no longer observed.

    By changing the community composition, the positive effects on plant growth were reduced.

    New Zealand vineyard. Photo by Jorge Royan (CC BY-SA 3.0)

    Moukarzel and colleagues suggested that altering the composition may have resulted in competition between AMF leading to reduced positive effects on the host. AMF are known to compete for host resources, soil nutrients and colonisation sites. As a result, cooperation, and rivalry between AMF within different communities may have major implications for vine productivity.

    So, what can grapevines teach us about networking?

    Basically, choose your trade partners wisely. Identify friends and adversaries within the network and invest in those relationships with the greatest return.

    As proposed by marketing expert, Porter Gale: the so-called ‘new model’ of networking should focus less on ‘handing out as many business cards as possible’ and more on making connections based on how you want to grow. In other words, efficient networking should focus on investing in specific needs and interests. A well connected network with diverse partners offers wide opportunity and stability if components are co-operative.

    Overall, the findings generated from the study will be an invaluable insight towards leveraging AMF communities to target specific growth and nutrient requirements of grapevines. This is of particular importance to the viticultural industry as the composition of these communities play an important role in determining vine health, yield, nutrition, grape composition, and wine characteristics.

    Featured image: vineyard inter-row by rawpixel.com (CC0 1.0)

    While this study has provided a step towards understanding the communities below the vines, soil is a complex system with a wide range of players and there is much to learn about the orchestration of these networks. There are likely many more tricks of the underground trade to uncover.

    Moukarzel, R., Ridgway, H. J., Waller, L., Guerin-Laguette, A., Cripps-Guazzone, N., & Jones, E. E. (2022). Soil Arbuscular Mycorrhizal Fungal Communities Differentially Affect Growth and Nutrient Uptake by Grapevine Rootstocks. Microbial Ecology. https://doi.org/10.1007/s00248-022-02160-z

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

  • Detecting eDNA: everything, everywhere all at once

    Let’s say you want to know what animal species are present in a forest. You could walk along line transects and record the species visually observed. You could set up trail cameras to take pictures of passing animals for as long as there is enough space in the memory card and battery life in the cameras. You can use the acoustic survey method to study bats, birds, frogs, and even some monkey species, as they can be distinguished based on their sounds and calls.

    Depending on the size of your study area, making a list of the animal species present might take a several hours to several months because you will need to carry out various methods to identify them, which may also require species experts.

    These are well-established conventional methods for biodiversity monitoring, but is there no single method to find all the species in a given area at once? A one-size-fits-all t-shirt?

    There is a rapidly developing method that can identify a good portion of species in a given study area, including those living on the ground, in the ground, in the water, and even those flying in the air.

    Every organism contains genetic material called deoxyribonucleic acid (DNA), passed down from parents to children. All organisms from the same species have very similar DNA.

    An illustration of the double-helix of the DNA molecule. Original public domain image from Wikimedia Commons

    This technology takes advantage of the traces that organisms leave of their DNA in their environment, whether feathers, skin, scales, urine, or faeces. These traces, known as environmental DNA (eDNA), can be found in soil, water, and air.

    This shiny new method is called DNA metabarcoding. Simply put, it identifies organisms by matching their DNA with reference DNA from the gene database or library. It is like matching the barcode of products when you check out at the supermarket.

    The process begins with collecting water or soil, or even air, samples from the study area. These samples typically contain genetic material from diverse organisms, including bacteria, plants, and animals.

    Once samples are collected from the field, they are brought to the laboratory. DNA is separated from the samples, amplified, and sequenced to generate vast amounts of genetic data that can be compared with existing DNA databases and reference libraries such as GenBank for species identification.

    Environmental DNA – An emerging tool in conservation for monitoring past and present biodiversity – Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/The-overall-workflow-for-environmental-DNA-eDNA-studies-with-examples-of-organisms-that_fig1_269724781 License: CC BY-NC-ND 4.0

    DNA metabarcoding can detect a broad range of organisms at once, providing a snapshot of the species diversity within the study area. That way, you can avoid performing various sampling methods. How convenient is that!

    Of course, no method is perfect, even DNA metabarcoding. Since it is still developing, there are limitations. The public gene library has the DNA references of many species but this is still a small fraction of all the species on earth, so far. There can be contamination in the samples, which could disrupt the results. Errors can occur not only during sample collection in the field but also in the laboratory.

    Compared to DNA metabarcoding, conventional methods have stronger standardised techniques for sampling and for interpreting the datasets. Besides, in the context of biodiversity monitoring, conventional methods can provide detailed information, such as abundance, age, sex ratios, and individual animals’ special characteristics, such as colours and conditions, which DNA metabarcoding cannot tell us.

    Conventional methods are like pictures with tiny pixels portraying good resolution, but their taxonomic scope is limited, whereas those of DNA metabarcoding cover a broad range of species, but the resolution is coarse.

    Is there the best of both worlds?

    Yes! Robert Holdaway and colleagues, including Ian Dickie working at Lincoln University, suggested that combining DNA metabarcoding with conventional monitoring methods will benefit scientists in many ways.

    Using them together will enable scientists to test and improve the reliability and accuracy of our still-developing DNA metabarcoding method. Moreover, combining them will result in a higher chance of detecting species from the same lineage.

    Robert and colleagues provided three case studies in New Zealand that can benefit from the dynamic duo.

    First, the duo can be of advantage to the nationwide measurements of New Zealand’s biodiversity. They can provide greater taxonomic coverage and more thorough information on the relations among biodiversity, ecosystem functions, and services.

    Second, integrating DNA metabarcoding with Māori biodiversity monitoring approaches will bring more understanding to the Māori worldview of interconnections among living and non-living beings. Metabarcoding can enhance biodiversity inventories, identifying species important and relevant to Māori which are rare or hard to find using conventional methods.

    Third, combining DNA metabarcoding with traditional surveillance in detecting pest species at the early stage will secure native species and landscapes from harmful biosecurity threats, such as harmful pests and diseases.

    In addition, DNA results shared from various surveys using the dynamic duo will be added to the reference libraries making them more resourceful and convenient for future research. Having more reference DNA sequences of species in the reference libraries, like GenBank, will make biodiversity monitoring much easier by identifying species with just a few clicks.

    DNA metabarcoding is a rapidly developing and powerful tool for monitoring biodiversity. Integrating it into conventional methods will lead to a stronger method to get plausible results. Overall, as Robert and colleagues indicated, not only will they add value to New Zealand’s biodiversity and Māori culture, but they will also protect the native natural environment and species through early detection of pests.

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

    Together, they will indeed make the best of both worlds for conservation.

  • Toxins help rare birds

    As a birder, there is a unique and somewhat pure excitement to seeing a bird you’ve never seen before – at least that’s my experience. Spotting a “lifer” (a.k.a. a species ‘new to you’ in birding lingo) comes with a feeling of accomplishment, especially if the bird turns out to be rare. For example, I could still tell you when and where I saw my first California condor, Great bustard, or Rock wren/tuke. Some birders, or “twitchers” to separate them from more casual birdwatchers, even make somewhat of a sport out of seeing as many rare species as possible. I recommend watching “The Big Year” if you want to learn more about this and have a good laugh while you’re at it.

    As a conservation biologist, spotting a rare bird often brings about feelings other than excitement. After the initial high, it leaves a little bit of a bitter taste behind because, more often than not, there is a not-so-great reason why a bird is rare.

    I feel this particularly strongly when birdwatching in New Zealand, where introduced predators have wreaked havoc on the unique and vulnerable bird life and caused many species to disappear from large parts of their natural ranges. Many native birds now survive in wildlife sanctuaries and are difficult to spot in the wild.

    “Since the arrival of humans, [59 species of bird] have been recorded as lost to extinction as a result of changes to the landscape and the introduction of predatory mammals.”

    Te Mana o Te Taiao – Aotearoa New Zealand Biodiversity Strategy 2020

    While New Zealand’s charismatic rarities certainly are a great addition to any twitcher’s life list, I find it hard to forget that some of these species are on the brink of extinction. The birdwatcher and conservation biologist in me are at odds when I go birdwatching here, and I never know how to feel when spotting a rare bird. When I saw my first yellowheads/mohua near the Blue Pools by Haast Pass, I felt ecstatic and sombre at the same time – it’s quite the dilemma.

    Rock wren in Fiordland. © Antonia Ulle

    The upside is that New Zealanders know the value of their native wildlife and are committed to conserving it. Native birds, along with other indigenous species, are considered taonga and, as such, an important part of the country’s national identity – why else would a kiwi shooting laser beams have been such a popular design for New Zealand’s alternative flag back in 2015?

    Naturally, making rare species not as rare is one of the cornerstones of New Zealand’s Biodiversity Strategy, and protecting native birds is a national priority. This goal goes hand in hand with eliminating the mammals that threaten their existence.

    On a landscape scale, predator control often requires dropping 1080 (a biodegradable poison) from helicopters and planes in the rugged backcountry to target mammals in areas that are otherwise hard to reach. Experts say that for birds with a remote and inaccessible range, such as rock wrens, kiwi, blue ducks/whio, yellow-crowned parakeets or mohua, that this is currently the only practical management tool. Despite research showing that the aerial application of 1080 helps the recovery of native bird populations, this strategy is often criticised by members of the public for being indiscriminate and endangering the very species it is supposed to protect.

    So, how does DOC make sure native birds aren’t dropping dead left, right and centre when they use 1080 for predator control? The answer is research, research and … more research! Preliminary research, follow-up research, and intensive monitoring of bird populations during pest control operations, all help the people in charge understand how 1080 affects native birds with the aim of reducing their poisoning risk is as low as possible during any 1080 drop.

    Some of this important research was done here at Lincoln University when Jakob Katzenberger and James Ross investigated how mohua were affected by a pest control operation using aerial 1080 in the Catlins State Forest Park back in 1999. Intensive monitoring before and after the 1080 drop showed that the control operation didn’t have unwanted non-target effects for mohua. More specifically, the researchers concluded that mohua numbers didn’t differ significantly before and immediately after the control operation.

    While this might not seem like the most exciting result, it tells an important story – that 1080 worked and only killed what it needed to kill. Now, in case you’re wondering if these results still hold true since the research for this study was carried out over 20 years ago – rest assured, they do. Studies conducted in the Landsborough, Dart and Routeburn valleys since then have shown that both mohua numbers and nesting success increased following predator control using 1080. In 2006 and 2009, nesting success of mohua was on average twice as high after 1080 than without it in the Dart and Routeburn valleys, and in the summer of 2015 89% of mohua nests in the area were successful.

    Another key takeaway from the study by Katzenberger and Ross is that the timing of 1080 control operations is critical to maximise the benefits for native species. While the 1080 drop in 1999 did not affect mohua in the Catlins negatively, it could have provided more benefits had it been timed better. Monitoring showed that a predator boom caused by beech masting in the summer after the 1080 drop caused drastic declines in the resident mohua population. Applying 1080 after this masting event could have reduced predator numbers and, therefore, protected mohua more effectively by providing a “predator free” window for them to breed.

    Benefits of aerial 1080 for mohua from the 2014 “Battle for Our Birds” pest control operations in the Dart valley.
    © Department of Conservation 2016

    In 2014, DOC managed to protect mohua and other natives in a year of heavy beech masting with the “Battle for Our Birds” campaign by applying aerial 1080 just before predator numbers skyrocketed. Without predator control, that beech mast and the resulting high predator numbers would have been detrimental for the populations of native animals. This is an excellent example of how protecting native species is a learning process, and how research helps us learn, and improve conservation practices.

    What we can take from this is that 1080 works and that native birds do better where it is used. Researchers don’t just leave it at that though. A lot is still being done to make aerial 1080 baiting as “bird proof” as possible and ensure that birds gain the maximum benefit from it. Baits are improved continuously, sowing rates are reduced, and bird populations are carefully monitored. Overall, 1080 baiting has come a long way since it was first done, and now is an effective tool to protect native species. Some people may always oppose the use of 1080 no matter how loud the science talks, but, to use the words of Dr Nick Smith, New Zealand’s 6th Minister of Conservation, “reason must trump prejudice about poisons when the very species that define our country are at stake”.

    I consider myself lucky to have seen many of New Zealand’s birds, rare or not. Some of the encounters I’ve had here have been quite magical and, to be honest, almost cheesy. Like the time I was hiking Gertrude saddle in Fiordland, wondering if I would get to see a rock wren – only to have one poke its head around a rock to check me out while I was having lunch. Or when a family of mohua landed in the trees right next to me in Hawdon valley and I got to watch them for a good half an hour.

    Mohua in Hawdon Valley. © Antonia Ulle

    With research continuously improving how introduced predators are controlled, I hope that, in the future, encounters like this will once again become the rule rather than the exception.

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

    Katzenberger, J.K. & Ross, J.G. (2017). Mohoua ochrocephala abundance in the Catlins following aerial 1080 control. New Zealand Natural Science, 42, 1-8.

  • Small animals show us the value of old natural forests

    Hambach. You are in Germany right now, halfway between Cologne and the Belgian border. I’d like to warmly welcome you to the Hambach forest – an ancient forest that is dominated by oak and hornbeam, representing a rare forest type in modern Germany. The Hambach forest is the last remnant of a forest that ranged over wide flat plains since the end of the last ice age around 12,000 years ago. Regrettably, it has become famous for being gradually absorbed by a vast hole!

    Tree house in the Hambach forest.
    CC BY-NC 2.0 by Tim Wagner, Flickr

    The Hambach forest used to range over an area of around 5 500 ha. During the past four decades, around 90 percent has already vanished. What remains today is not a normal forest anymore – idyllic, undisturbed, and peaceful. The forest is not only threatened by further sliding into the hole. In 2018, the Hambach forest also became the stage for one of the largest major police operations, owing to another curiosity about the Hambach forest: it is inhabited by people, living in tree houses. Occupying the forest, they want to protect what is left of it and demonstrate against the further expansion of the hole. However, since the forest is privately owned by the company that sacrifices it for the hole, activists were forced out of the forest with the help of police power – before occupying it again.

    So what is the gigantic hole? It is the result of four decades of open-cast coal mining in the Hambach region. However, its further growth will eventually take an end. For the year 2038, Germany has committed itself to complete the coal phase-out, a critical step for Germany’s energy transition. Until then, coal power stations in Germany can be fuelled by coal – extracted from German coal mines (“holes”), with a spectacularly bad impact on the climate. Still, based on the coal-phase out, the remaining part of the Hambach forest can be saved.

    Hambach open-cast coal mining hole.
    CC BY-SA 2.0 by Traveling Tourist, Flickr

    Growing up close to the Hambach forest, that received international attention in the environmental and climate movement, I’ve been concerned about one question for a very long time: How can we replace an ancient forest that is destroyed for mining purposes?

    “If we are moving several villages, people, and a motorway for the open-cast coal mining, why don’t we also move the forest?” That is how people in my region would have addressed this question in the past. Believe me or not, that’s exactly what has been done. At one end of the gigantic hole, the largest artifical hill worldwide was created and recultivated with trees. It serves the region now as a recreation area, comprising an about 70km network of hiking trails. “Forest is forest. There is no difference”, people say in my region. So why be concerned?

    But is it really that easy? Are humans really able to shape a new forest within a few years as a replacement for a destroyed ancient forest, that has the same value for biodiversity and people? And will the planted trees provide an appropriate habitat for all mammals, birds, insects, spiders, herbs, lichens and other important life forms that used to inhabit the lost forest?

    In many countries around the world, there are nowadays regulations regarding compensation and restoration measures that mining and other companies have to fulfil when their activities destroy land. However, in reality, is it always possible to restore an ecosystem that has undergone complete degradation from a natural forest to a mining site, back to its original state and biodiversity value? Otherwise, it is possible to shape a new ecosystem with the same values at another site – like it was aimed with the planted artifical hill as a compensation for the destruction of the Hambach forest? Fortunately, there are ecologists who have learned the answers to these questions. Closely monitoring the process of ecosystem restoration they can tell how successful undertaken restoration efforts are for biodiversity.

    So, now that we’ve already practiced thinking in great dimensions, let’s undertake a great jump to another mined forest – we’re jumping off Germany, over Italy and the Mediterranean Sea, crossing the Arabian Peninsula and the Indian Ocean, passing Australia and are finally landing in… Auckland! Well done! We’re standing here at the Hunua Quarry site, near Papakura in South Auckland. It is part of the Hunua ranges that consist of over 20 000 ha of native forest, comprising tawa, podocarp, kauri–hard beech, and taraire forest as main vegetation types.

    The Hunua Ranges.
    CC BY-NC 2.0 by Neil Hunt, Flickr

    The Hunua Quarry is managed by Winston Aggregates, New Zealand’s largest aggregates provider. As a restoration measure, in six years over 140 000 plants have been planted in this highly modified habitat after quarrying. The aim is to provide a new forest as a replacement of the forest area destroyed. Next to the restoration area, you can still recognize unrestored areas of exotic grassland that have established after quarrying, as well as undisturbed mature native forest.

    Researchers from Lincoln University (Mike Bowie and colleagues) studied the invertebrate communities at Hunua Quarry, including wetas, beetles, cockroaches, crickets, spiders, centipedes, earthworms, ants, flies, mites, moths, slugs and snails, amongst many others. Although rather small animals, invertebrates are essential for the functioning and health of ecosystems, thereby making an important contribution to biodiversity. The objective of their study was to develop a better technique for the assessment of restoration success after mining, using invertebrates as bioindicators. Bioindicators are species that react sensitively to changes in their environment so that they can be used to assess the quality of an ecosystem.

    The researchers collected invertebrates in the undisturbed mature forest, in restored areas, as well as in the unrestored exotic grassland. They compared how many and which invertebrates were living in the respective areas. Interestingly, the undisturbed mature forest, the restored areas, and the unrestored exotic grassland were characterized by very different invertebrate communities. The invertebrates found in the six-year-old restored areas were mostly still very unlike those found in the undisturbed mature forest. For instance, the researchers were able to collect eight times more cave weta in their pitfall traps in the undisturbed mature forest than in the restored areas. In addition to cave wetas, the mature forest also harboured many spiders and beetles. Hence, if the forest restoration process is successful, it is expected that more cave weta, spiders and beetles typical for mature forest will inhabit the restored sites in the next years. At the same time, fewer exotic snails, slugs and earthworms that were found to be characteristic for the unrestored exotic grasslands are expected.

    This beetle,
    Holcaspis mucronata,
    was found most abundant in the mature forest.
    CC BY 4.0 by Birgit E. Rhode, Wikimedia Commons

    The study identified several invertebrate species as bioindicators. These can be used in future studies to assess the success of forest restoration at mine or quarrying sites. The study findings have been recognized in several other invertebrate studies of different parts of the world, for example, in a global synthesis on how good forestry plantations are at providing habitats to native beetles in comparison to natural forests. In that study, restoration sites were considered as forestry plantations, being planted by humans for conservation purposes and therefore different from natural forests. Another study dealt with the effect of removing an invasive plant as a restoration measure on an Mediterranean island. It referred to the study at Hunua Quarry for the use of beetles as bioindicators to observe the effects of restoration.

    All in all, the study showed that invertebrates might tell us more about the quality of a forest than you would easily see yourself. Hence, studying invertebrates as bioindicators has great potential for making better decisions in ecosystem management and for restoration projects. I hope that research about restoration will also raise public awareness for the complexity of biodiversity and the needs for appropriate habitats. Perhaps, I will hear many people around the Hambach forest region in Germany say: “Forest is not like forest. We need to consider old natural forests as valuable habitats and save them from vanishing, not only for the sake of spiders and beetles.”

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

    Link to the research article:

    Bowie M, Stokvis E, Barber K, Marris J, Hodge S. 2018. Identification of potential invertebrate bioindicators of restoration trajectory at a quarry site in Hunua, Auckland, New Zealand. New Zealand Journal of Ecology 43.

    Read more:

    Donahue, Michelle Z. 2018. Is Germany’s Hambach Forest Doomed by Coal? National Geographic, April 13. https://web.archive.org/web/20190914181247/https:/www.nationalgeographic.com/news/2018/04/hambach-forest-germany-logging-coal-conservation-science/

    Coal exit will save Hambach Forest: activists. Deutsche Welle, January 27, 2019. https://www.dw.com/en/german-coal-exit-plan-will-save-hambach-forest-activists-say/a-47251256

  • Defend the buffer!

    “Hold the line! The invasives are coming!”

    “Captain, we’re losing ground! The phosphate is encroaching.”

    “Retreat to higher ground! It’s safer up there.”

    “Send in the spiders and beetles! Earthworms, you stay here.”

    “Defend the Buffer!!!” [insert battle cry]

    If the plants and insects at Bankside Scientific Reserve could talk, they would probably sound something like that. While this 2.6 ha protected area is home to important communities of native species, it is under threat of phosphate intrusion and the breaking-up of the local habitat. Humans have greatly altered the lowland Canterbury Plains of Aotearoa/New Zealand. With the recent switch to irrigated dairy farming, very few patches of undisturbed native dryland vegetation are left in the region. This change in land-use has led to a higher reliance on fertilizers as well as water for irrigation, which has come with its own set of challenges.

    Aggressive introduced weeds, pasture grasses and forbs, have also begun to dramatically alter the functioning of native plant communities. Remnant areas are both vulnerable and essential to maintaining native ecosystems (hence the need to defend the buffer). Mike Bowie and his team investigated one of these remnant areas, looking at soil chemistry, plant distribution, and soil invertebrates along transects at the Bankside Scientific Reserve. Their study identified the current conservation value of the reserve, assessed how persistence of native biodiversity changed along the pasture-reserve gradient, and evaluated the effects of the likely infringement of irrigation water and nutrients from adjacent farmland.

    The vegetation of Bankside Scientific Reserve had been studied previously by Malloy (1970), who provided a detailed catalogue of the flora, listing 66 native vascular plant species. Jenson & Shanks (2005 – unpublished DOC Report) also completed a one-day reassessment of the site, but recorded only 14 native species. Today, the vegetation at the reserve can be described as a patchwork of native woody shrubs, made up mainly of makahikatoa, matagouri, and dry grassland. As Mike and his team point out, the modified soil conditions seem to have made the reserve not as well suited for native species, and better for the invasion by exotic plants. Compared with detailed surveys prior to the dairy conversion, only 31% of the original 65 native vascular plant species were found in the current study, and 27 new exotic species had arrived since the original survey.

    As for the underground conditions, soil nutrient concentrations and pH were lower in the reserve than in the surrounding farmland, with peaks of nitrate and ammonium being recorded at the boundary. Meanwhile, soil phosphate was higher in lower-lying areas within the reserve. Four species of endemic (Megasolecidae) earthworms were found in the reserve, but not in the neighbouring pasture.

    Other cool finds included ground wētā (Hemiandrus sp.) and trap door spider (Cantuaria dendyi). A 2011 survey by Emberson et al. (2011) also found the large rare rove beetle, Hadrotes wakefieldi, and several species of long-horn beetles. As opposed to the earthworms, the diversity and abundance of beetles and spiders in the reserve was similar to that recorded at least 10 m into surrounding farmland.

    Another interesting take-away from this research, is the importance of areas of higher elevation. Although elevational differences between highest and lowest contours were <5 m in the study, the higher areas were very important in avoiding environmental change from agricultural drainage and effluents. They helped to maintain environmental conditions that were closest to the original habitat, providing the best-suited habitat for native plants and animals.

    Image created by Catherine Priemer

    The work of Mike Bowie and his team, along with previous studies, points out the significance of small remnant reserves for the conservation of indigenous invertebrates found in these rare dryland ecosystems. Their findings also suggest that lime and phosphate fertilisers may represent the main threats to dryland nature reserves in irrigated dairy landscapes. Above all, their research underlines the importance of the soil environment in sustaining the variety of plant, animal, and insect life in this unique environment.

    Taking the team’s findings into consideration, the maintenance of a buffer zone – a protected zone established around sensitive or critical areas – could be beneficial in lessening the impacts of human activity and land disturbance around remnants, such as Bankside Scientific Reserve. To do this, native species can be planted between agricultural and conservation areas, to help protect sensitive habitat. The key take-away: Defend the Buffer!

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

  • Island life, saviour of the wrybill

    I’ve never been so pleased to see the braids of a river than when I finally escaped the jaws of the Waimakariri Gorge in my kayak, as part of the Coast to Coast race. A braided river brings not just relief from roaring bluff corners, and the threat of capsizing my kayak, but a peaceful place that unusual birds decide to call home.

    Rakaia River, NZ (Geoff Leeming, 2006, CC BY-NC 2.0, via flickr)

    One such creature is the Wrybill or Ngutu parore. It’s the only bird in the world with a laterally curved beak (bending to the side)! Sadly, this little bird faces many threats. In 2008 some optimism was found in the research of Duncan, Hughey, Cochrane and Bind (River Modelling to better manage mammalian predator access to islands in braided rivers). The paper explained how particular characteristics of braided rivers could be used to support successful breeding of braided river birds, including our wee friend, the Wrybill.

    Braided rivers are made up of multiple threads of flowing water, with islands found between the threads. The researchers knew that these islands provided a safe place for endangered breeding birds, with the water flowing around them providing a partial barrier to a major threat –

    Wrybill
    (57Andrew, 2007, CC BY-NC-ND 2.0, via flickr)

    introduced mammalian predators, such as hedgehogs, rats, mice, stoats, weasels, ferrets and cats.

    It was already known that water extraction, narrowing and stop-banking of rivers impacted the flow of water in the braids, but little was known about the optimal flow of water or the required characteristics of the islands to support breeding birds. Models were used to determine the number and area of islands needed for successful breeding. The researchers found that certain levels of water flow preserve islands large enough for nesting (larger than 2 hectares) and protect the area from mammalian predators or weed invasion. This information was used to recommend abstraction rates on braided rivers during peak breeding season. They did conclude that using photos in the research would increase understanding of how islands change in different flows.

    One of the authors, Ken Hughey, was from Lincoln University and his PhD, back in 1985, looked at factors impacting the breeding of braided river birds in Canterbury. He studied five different birds: Wrybill, Banded dotterel, Black-fronted tern, Pied stilt, and the South Island pied oystercatcher. Among other things, Ken found that higher levels of predation on birds occur where there were lower flows of water and lower numbers of channels or threads in the river. He recommended that minimum flow levels should be higher during the breeding season to protect the nesting birds. The 2008 study builds on this understanding and provides information not just about the flow of water needed, but also the size of the islands required to protect the nesting birds.

    This study has been used in subsequent research in New Zealand around maintaining river flows in braided rivers. This is unsurprising given braided rivers are rare around the world and Canterbury is known as New Zealand’s braided river hotspot. The themes within the research were around maintaining river flow levels, predator and weed control, maintaining river islands, and water abstraction. Advances since this work seems to be focussed on weed control and the impacts of hydropower to braided river systems.

    It appears that the messages about the importance of minimum flows and island size in braided rivers for breeding birds are getting through. The Regional Council in Canterbury (ECAN) refers to the importance of flows in preserving the ecology of the river for breeding river birds in the Canterbury Water Management Strategy and the Canterbury Land and Water Regional plan. The knowledge that came from the research by Duncan, Hughey, Cochrane and Bind, and subsequent research, has clearly shown how local communities think about braided rivers and informed how they care for them. This is demonstrated by the Ashley Rakahuri River Care Group in 2022, when they made a submission to the ECAN to raise concerns about gravel extraction on the Ashley Rakahuri River and how this will impact the islands needed by birds to breed safely.

    This approach also appears to complement work by the Predator Free 2050 campaign regarding pest control within braided river environments. I was intrigued as to how the authors felt the research was received and asked one of them, Ken Hughey, about the impact. He said it ultimately led to high flows being recommended and resourcing for predator control on the islands. Sounds like a great result!

    New Zealand Map (mhx, 2010, CC BY-NC-ND 2.0, via Flickr)

    Undertaking research consumes your life while you are doing it. It is fascinating to see the journey from conception to the completed work and then how it informs environmental work moving forward.

    The Wrybill is still classed as vulnerable and there is work to be done, but this research has added valuable insight into flow regimes for braided rivers. It has highlighted the importance not just preserving islands for breeding birds, but ensuring they are above a certain size. It has prompted further research, and informed councils and charitable groups on how to best support endangered braided river birds, like our wee friend the Wrybill. I’m sure there shall be some grateful kayakers out there too! I shall sign off this blog with an image of the Wrybill making the most of his unique laterally curved beak.

    This article was prepared by Master of Environmental Policy and Management student Katherine Manning as part of the ECOL608 Research Methods in Ecology course.

    Wrybill/Ngutuparore (Shellie, 2016, CC BY-NC-ND 2.0, via Flickr)

    Here is a full citation for the article:

    Duncan, M.J., Hughey, K.F.D., Cochrane, C.H., Bind, J. (2008) River modelling to better manage mammalian predator access to islands in braided rivers. Exeter, UK: British Hydrological Society 10th National Hydrology Symposium: Sustainable Hydrology for the 21st Century, 15-17 Sep 2008. 487-492

  • 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

  • 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