Celebrate fruit fly detections in New Zealand

Posted by Prof Jacqueline Beggs @JacquelineBeggs

About to bite into that luscious, juicy taste of summer, a tree-ripened nectarine? Be thankful you do not live anywhere with fruit fly.  This group of insects are infamous for the damage they do to a wide range of fruit and vegetables.

Apricot (left) and pear (right) are two of the many fruits affected by fruit fly. Images used by permission Plant Health Australia

As well as summerfruit, they attack citrus, apples, pears, berries, grapes, olives, persimmons, tomatoes, capsicum, eggplant, and avocado. We are not talking a bit of cosmetic damage to the skin – fruit can end up as a soft, mushy, inedible mess. Fruit fly females lay eggs into fruit and the developing maggots munch away, causing the fruit to rot and drop to the ground.

The extent of damage can be devastating. The island of Nauru ended up home to four species of pest fruit fly.  By 1998, about 95% of mango were infested and island-grown fresh fruit and vegetables were so scarce locals had to rely on more expensive imported produce. Fortunately, an intensive lure and poison programme eradicated three of the four species and mango and breadfruit were back on the menu.

Australia is not so lucky. They have two highly damaging fruit fly species, the Queensland fruit fly and Mediterranean fruit fly. Commercial growers spend hundreds of millions of dollars on various control measures and quarantine measures are in place to try to stop the spread into uninfested areas. With varying degrees of success.

A single Queensland fruit fly (Bactrocera tryoni) was recently detected in Devonport, New Zealand. A full scale response has been triggered as it is regarded as a serious pest [Image: James Niland, Wikimedia commons ].

It is no surprise then that detection of two different species of fruit fly in New Zealand in a week makes headline news and our dollar falls. Finding a second Queensland fruit fly near to the first is concerning. We certainly do not want them to establish. However, I think we should also celebrate. The detections are really New Zealand’s biosecurity system operating at its best. We have in place a world class fruit fly detection system; a nationwide surveillance network of 7737 traps baited with fruit fly specific lures that are checked seasonally.

Including the three latest finds, this network has detected 13 incursions of economically important fruit flies since 1989.  More importantly, early detection and effective control means fruit flies have not established in New Zealand. With such high stakes, it is critical that we keep going with research to improve surveillance, eradication and control tools. Recent PhD work at University of Auckland by Dr Lloyd Stringer is a good example; he developed a population model that helps to identify the most successful management and eradication options for Queensland fruit fly.

We cannot afford to take our foot off the pedal. Fruit fly will keep pushing at our border since there are around 80 pest species found in many countries we trade with and travel to. Furthermore, some regions have given up trying to achieve area wide fruit fly control, leading to higher density of these pests. That makes it easier for an individual fly to slip past all the measures we have in place to keep them out. So hats off to all the folk involved in keeping fruit fly at bay. That includes you – letting biosecurity officers onto your property to check for infestation, making sure you do not move fruit or veges from “controlled areas”, and encouraging everyone to never bring undeclared produce into New Zealand.

Prof Jacqueline Beggs is Director of the Centre for Biodiversity and Biosecurity, a member of the Biosecurity Ministerial Advisory Committee and co-supervised Dr Lloyd Stringer for his PhD research. And nectarines are probably her favourite fruit!

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Hello darkness, my old friend

Posted by Ellery McNaughton @EJ_McNaughton

Who’s afraid of the dark? Society in general it would seem. Some people have good reason to be, living in places where humans are not top of the food chain, and darkness provides cover for those that are. Yet even in places where predation is not a risk to contend with, darkness gets a bad rap. The Dark Side, the Dark Lord with his Dark Mark, dark magic, somehow we have conflated darkness with evil. Perhaps this is because in the dichotomy of light and dark, light outshines darkness in the PR department. Light is the stuff angels wear to look suitably holy. Light signifies safe places for lion kings to rule their lion kingdoms. Light is the symbol of enlightenment and civilisation, an indicator of human innovation, technology and progress. And in the immutable logic of opposing pairs, if light = good, then darkness must therefore = bad. It’s algebra, or something.

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Choose light or choose dark. Choose the hero or the villain. Somehow they’re always the same choice

However, darkness really is our friend, preserving our sleep patterns and physiological processes, keeping our biological clock running in an orderly manner. It’s an unappreciated and often abusive friendship on our part. Natural darkness is being eroded away as we increasingly choose to hang out with the cool new kid, light. Natural limiters of daily activity are for lesser species, and if we want to work late into the night, nothing can stop us (even if the numerous health problems should). Some people love light so much that when their streetlights are changed to have less light spill, they buy outdoor lights to make up for the lack of illumination. That’s not just enabling a later bedtime; it is actively avoiding the presence of darkness. Why are we afraid of the dark?

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Dumbledore promoting light pollution

While urban dwellers generally don’t have to deal with predation, in the dark we often feel at risk from other humans. Walking home at night becomes an exercise of fearful imagination, where every shadowy bush, alley or doorway becomes a hiding place for others up to no good. Light banishes the shadows and leaves no place for imagination to run riot; security lights are so named for a reason – they make us feel secure. This is in spite of the fact that light doesn’t appear to reliably banish the presence of the criminal element. Of course, even if light doesn’t actually make us safe, it is important for people to feel safe in their cities. And until we as a society stop viewing darkness as a villain to be conquered, light is a necessary evil.

 

Ellery McNaughton is a PhD student in the Centre of Biodiversity and Biosecurity, School of

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Ellery

Biological Sciences, University of Auckland. Her project investigates the effects of a city-wide changeover in streetlight technology on urban bird behaviour and ecosystem function. She is supervised by Margaret StanleyJacqueline BeggsKevin Gaston (University of Exeter, UK) and Darryl Jones (Griffith University, Australia).

Missed opportunities in the SPCA controversy

Posted by: Jessica Devitt @Colette_Keeha

Last month I was closely following the news and debates that were sparked by the RSCPA of New Zealand’s (herein SPCA) official stance on the use of 1080 in pest control.

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Figure 1. Ban 1080 protesters speak to Newshub (Newshub, 2018).

The SPCA wants the toxin 1080 (aka sodium monofluoroacetate) banned because it considers the toxin an inhumane way of reducing pest animal populations.  The SPCA further notes that it does not regard one type of animal as more deserving of life than another, arguing there is no justification to control pest animals in the first place, and that ways to allow conflicting species to ‘co-exist’ should be encouraged.

I am pro the use of 1080 based on the positive outcomes it has for native species. I am in agreement with the Parliamentary Commissioner for the Environment that 1080 is the most effective invasive species management tool that we have at this point in time.

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Figure 2. A large male L. barbicornis guards a female drilling an egg-laying hole (Painting, 2013).

I was a financial supporter of the SPCA for several years with monthly, albeit small, contributions. I decided to withdraw my support for them post their 1080 statement, and instead I promptly spent my money on joining Forest and Bird, whom I had never financially supported but always wanted to.

I did actually think quite a bit about this before doing it – I am not a big fan of ‘cancel culture’, so I did not want to boycott the SPCA over one disagreement, and part of me felt like I was doing that. However, realistically I had to look at the bigger picture and I realised that their statement and some of the attitudes expressed within it do not align with me.

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In fact, the ongoing debate made me realise that although the thought of native species loss filled me with genuine sadness, it did not always spark the same kind of outrage that I got from seeing domestic animals harmed or neglected by humans. I never really looked at the loss of native species as an animal welfare issue, when actually it is. I academically understood the issue of native species loss, but it is not something that I am reminded about regularly with visually disturbing pictures; like what is often seen with domestic animal abuse.

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Figure 3. Possum and rat both preying on a thrush nest (Nga Manu Images, n.d.)

My issue with the SPCA’s statement, was in retrospect, more to do with how they went about stating their position rather than me expecting them to be pro 1080 or agree with its use.  Their statement was very one-sided, completely failing to grasp the complexities of the situation. It briefly notes reproductive control of pest species as an alternative option. However, this is not a straight forward fix. Reproductive control is not an option for most of New Zealand’s mammalian pests as there is no way currently this can be applied at a scale that would lead to significant reduction in pest numbers. Furthermore, applying reproductive control has its own set of problems – adding reproductive hormones to the environment has many downstream impacts on non-target wildlife, and surgically sterilising then releasing animals still leaves them hunting and killing native wildlife for the rest of their lifetime.

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Figure 4. Gene editing (Luecke & Steadman, n.d.).

The SPCA firmly stands on the side of ‘ban 1080’ by supplying links to ways in which you can support a ban, but fails to give other options, such as supporting your local environmental group or donating funds to Predator Free NZ or Forest and Bird for their continued research on predator control. Both of these organisations are interested in finding alternatives to 1080.

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Figure 5. Predator Free NZ logo (Hill, 2018).

The press release reads more as an individual’s viewpoint and something that would have been more fitting in a blog (such as this) than a press statement by a large well-established organisation.  The release appears out-of-place in comparison to the other press releases on the website. Looking over the past year of press releases I could not see any big statements taking a side on other topical animal welfare issues such as the horrors of the dairy industry, horse racing, rodeo, releasing pets into the wild, trapping, and other poisons besides 1080.

I am not surprised that the SPCA does not endorse the use of toxins for pest control; I think this would be expected from any animal welfare group. I also think it’s pretty clear from the subsequent debate that everybody would like a more humane method of pest control. I think that the SPCA really missed an opportunity here to offer up other ways in which people can support pest free New Zealand without necessarily jumping straight to ‘ban 1080’.

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Figure 6. Community conservation groups. (Department of Conservation, n.d.)

 

Addendum: Forest and Bird met with the SPCA on January 22nd to discuss their position on 1080. The SPCA clarified that their position is to encourage more research and development into alternative non-toxic pest control methods.  Forest and Bird also stated that the SPCA will amend it’s statement to reflect this (@Forest_and_Bird, 23rd January 2019, https://twitter.com/Forest_and_Bird/status/1088258572612333568).

Here is a list of some of the organisations that are currently working to find alternative means of pest control:

Biological Heritage National Science Challenge

Predator Free New Zealand

Genomics Aotearoa

Forest and Bird

The Royal Society of New Zealand

Manaaki Whenua – Landcare Research

Department of Conservation

Here is are a couple of links that connect people to local conservation efforts:

Department of Conservation

Conservation Volunteers New Zealand

 

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Jessica Devitt is a PhD student at the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland and Plant and Food Research. She is researching the respiratory responses of the golden-haired bark beetle to advance fumigation techniques. She is supervised by Jacqueline Beggs from the University of Auckland, Adriana Najar-Rodriguez and Matthew Hall from Plant and Food Research.

 

References

Department of Conservation. (n.d.). Community conservation groups. Retrieved https://www.doc.govt.nz/get-involved/volunteer/groups/

Hill, C. (2018). Predator Free NZ logo. Retrieved from https://predatorfreenz.org/about-us/pfnz-logo-332-by-222/

Luecke, J. & Steadman. (n.d.). Gene editing. University of Texas at Austin. Retrieved from https://www.labroots.com/trending/genetics-and-genomics/8655/crispr-edit-genes-outside-cell

Newshub. (2018) Ban 1080 protesters speak to Newshub.  Retrieved from https://www.newshub.co.nz/home/new-zealand/2018/09/ban-1080-protesters-descend-upon-parliament.html

Nga Manu Images. (n.d.) Possum and rat both preying on a thrush nest. Retrieved from http://www.ngamanuimages.org.nz/image.php?image_id=459

Painting, C.J. (2013). A large male L. barbicornis guards a female drilling an egg-laying hole, demonstrating the extreme sexual dimorphism in this species. Retrieved from https://en.wikipedia.org/wiki/New_Zealand_giraffe_weevil#/media/File:Lasiorhynchus_barbicornis_male_and_female.png

Te Ara – the Encyclopedia of New Zealand. (2007). Rat attacking bird’s nest. Retrieved from https://teara.govt.nz/en/introduced-animal-pests

 

New Zealand Ecological Society 2018: Great Talks and the Great Outdoors

Posted by Simon Connolly

Wellington is bloody windy. This is perhaps not the most original observation, but it certainly seems to be a correct one, particularly when your trip coincides with a severe weather warning. However, it was not the prospect of gale force winds that had me travelling south at the end of November. Ecologists from the length and breadth of the country, and beyond, were gathering for the New Zealand Ecological Society Conference, hosted at Victoria University.

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The view from my accommodation (Yes, I did pick the worst day for dramatic effect)

The talks kicked off on Sunday at the conference’s student day, which was followed by three days of talks at the main conference. It would be folly to try and list all the amazing and interesting talks that were given (especially as there were over 100), but here are just a few of the highlights: the use of drones in sampling New Zealand’s epiphyte diversity; the history of the extinction of a native fish that smelled of cucumber; tadpoles that interact with the microbiome to regenerate their lost tails; mysterious fungivorous beetles; tracking New Zealand’s biodiversity with place names; the role of New Zealand’s flightless birds in seed dispersal; a myriad of talks and posters about orchids and their sexually deceived pollinators; why the straw breaking the camel’s back is more than an idiom in ecology; the drivers of social wasp abundance on New Zealand’s offshore islands; and the question of whether Kauri are thirsty at night (long time readers will note that the last three topics have been discussed on this very blog).

In amongst all this were my talks on my Master’s research (the subject of which has also been discussed on this blog). Like I said, I have not been active in the research space for very long and consequently this was my first time speaking at a major conference. The concept was a little overwhelming at first, but I soon warmed to the idea. I was most taken aback by the positive and informed response I received. Intelligent questions are one thing, but I was incredibly grateful to those who suggested improvements to my methods or offered advice from their own research and experiences.

However, a man cannot live on talks alone. Also included in my time at Wellington were two trips into the field. The first was a highly atmospheric night trip to Zealandia, an enclosed pest-free reserve near the heart of Wellington. Whilst this was blighted by the same foul weather as before, I could spend almost an entire post talking about this trip alone. Suffice to say that seeing creatures like Tuatara and Weta thriving in their natural habitat gives me some hope that all is not in vain. The second trip was to Manaaki Whenua Landcare Research’s Field Station, or at least to the far side of the swelled Orongorongo river from the field station. This trip taught me that a “short 1-hour hike” does not reckon with botanists’ ability to stop and discuss every plant.

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A tuatara, inspecting the tourists from his burrow – Photo Credit: Mark Herse

All in all, my trip to Wellington was an enjoyable one, and I hope to revisit the NZES Conference in the future. Now enjoy a couple more wildlife photos.

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Weta and a ‘gherkin’ slug (obligatory entomological photo) – Photo Credit: Kaavya Benjamin

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A cryptic Stick Insect, found near the banks of the Orongorongo river (obligatory entomological photo 2)

jgs head and shoulders Simon is a Masters Student at the School of Biological Sciences, University of Auckland. His research is focused on threatened insects and he is supervised by Darren Ward.
scon870@aucklanduni.ac.nz

Nocturnal water loss and why it matters for kauri

Posted by Tynan Burkhardt @TynanBurkhardt

Nocturnal transpiration is often ignored when studying the water relations of plants, with the assumption that stomata (small pores on the bottom of leaves) close at night, leading to negligible water loss. Although transpiration is far lesser at night than during the day, it can contribute a considerable component of daily water loss. For kauri, I have found nocturnal water loss to make up around 15 % of yearly canopy transpiration. However, for other species, nocturnal transpiration can contribute up to 30 % of daily water loss!

For many plants, night-time is a period of replenishment, where the stem water storage is refilled, after being depleted during the day. However, the importance of night time in the refilling process differs between species. In South American rain forests, where water is readily available year-round, water storage is small and very little refilling occurs at night, with most occurring in the evening. In comparison, kauri have extensive water stores, which are held within their iconic large stems and branches. Refilling of these stems and branches extends almost all the way to sunrise (Figure 1), demonstrating the importance of the nocturnal replenishment period for kauri.

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Figure 1 – Daily pattern of withdrawal and refilling for kauri water storage, showing diurnal withdrawal followed by evening and night-time refilling.

Kauri rely heavily on night-time refilling in their water use strategy, with water storage buffering trees from the high evaporative demand and temperatures of summer. Night-time water loss limits a plant’s ability to refill water stores and increases in drought summers. For example, most nights of the 2012/13 drought summer had a considerable amount of transpiration, compared to last summer (2017/18), where most nights had very little transpiration (Figure 2). Worryingly, drought is expected to increase in frequency and severity for many regions where kauri is present.

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Figure 2 – Frequency of nights at different levels of nocturnal transpiration (En) for kauri canopies in a ‘normal’ summer (2017/18) and a drought summer (2012/13).

But what does this mean for kauri if drought does become a common summer condition? Clearly, they will be less able to refill their water stores, perhaps leading to a water deficit as the drought progresses. However, water storage is not the only defense kauri have against drying soils. They have also been observed to drop leaves in drier summers and close their stomata when under even mild water stress. Therefore, the reduced ability to refill water storage does not necessarily mean there will be large scale kauri die offs when drought does occur, but it is one of the pathways in which kauri stands may become more water stressed.

IMG_7437Tynan is a Masters student at the University of Auckland’s Ecology Ngatahi lab group. He is studying Nocturnal Transpiration in kauri trees and is supervised by Cate Macinnis-Ng.
email: 
tbur187@aucklanduni.ac.nz

No “global” trend: utilising taxonomic collections for assessing the global pollination crisis

Posted by Darren Ward @nzhymenoptera

There is increasing concern about the decline of pollinators worldwide. However, despite reports that pollinator declines are widespread, data are scarce and often geographically and taxonomically biased. These biases limit conclusions about any potential pollinator crisis.

Natural history museums have the potential to transform the field of global change biology. However, museum specimens are underused and could be better utilised to reveal patterns that are not observable from other data sources. Specimens historically collected and preserved in museums provide information on where, and when, species were collected, but also contain other ecological information such as species interactions and morphological traits.

In a recent paper we provide a global synthesis of how researchers have used historical data to identify long-term changes in pollination services. We show that scientific information on the status and trends of most pollinators is poor, if not absent. For example, although a wide variety of countries have recent records of pollinators, they lack historical data. Thus, greater emphasis should be placed on the digitisation of specimens already held in natural history museums.

Furthermore, changes in pollinator communities are context specific, and ‘global trends’ need to be assessed with caution, especially when most of the globe is not assessed!

In Spain, a hot-spot for bee diversity, data analyses showed there were a reduced number of bee species, however, this trend was highly site-specific. Declines in species were clustered around certain types of bees, such as the ground-nesting bees (especially Andrenidae), suggesting a pattern of winners and losers, where some groups of bees are more sensitive to disturbance than other groups.

In New Zealand there are relatively few native bee species, however, they are well studied, and therefore museum records can be used to identify trends in pollinator communities. In contrast to Spain, we found that 11 out of 27 bee species increased in relative occurrence over time, 13 species were stable, and only three bee species declined in relative occurrence.

A greater number of long-term datasets from different countries are needed in order to provide a robust and truly global assessment of trends in pollinator communities. Natural history museums play a central role in assessing the extent of the global pollination crisis, because they are the source which can serve as a baseline.

 

Bartomeus I, Stavert JR, Ward D, Aguado, O. 2019. Historic collections as a tool for assessing the global pollination crisis. Philosophical Transactions of the Royal Society B. 374, issue 1763.

From a themed issue, ‘Biological collections for understanding biodiversity in the Anthropocene’. http://rstb.royalsocietypublishing.org/content/374/1763

 

New Zealand bee collection records were gathered from multiple sources, including university, research institute, museum and private collections. Collection records from the New Zealand Arthropod Collection (NZAC) and are freely available online (https://scd.landcareresearch.co.nz/).

Darren Ward is an entomologist, Head Curator at the New Zealand Arthropod Collection at Landcare Research, and a senior lecturer at the School of Biological Sciences, University of Auckland.

What drives social wasp abundances on NZ’s offshore islands?

Watch my first stop motion video on the drivers of social wasp abundances on New Zealand’s offshore islands below:

 

Julia Schmack is a PhD student at the Centre for Biodiversity & Biosecurity, School of Biological Scinyences, University of Auckland. She is researching the ecology and control of social wasps, supervised by Jacqueline Beggs, Darren Ward and Mandy Barron (Landcare Research). Her PhD is funded by the Biological Heritage National Science Challenge.

twitter_pixabay.com @julia_schmack     email_commons.wikipedia.org j.schmack@auckland.ac.nz

The point of collapse

Posted by Ellen Hume

Imagine a clear winding stream flowing from the hills above into a small yet pristine lake. Birdlife is abundant, and the water is teeming with fish including freshwater eels known as native tuna, while macrophytes, aquatic plants, provide habitat and food to the aquatic species. Over time, as people move into the area, the surrounding lush native forest makes way for paddocks of farmland. The local whānau use the waterways for gathering mahinga kai to feed their families and enjoy being connected to the beauty of nature. Eventually the landscape is one of commercial productivity, with a mosaic of cropping and grassland feeding livestock and only small pockets of fenced forest remaining. It is harder to catch fish and tuna but children still splash around in the water in warmer months. Agriculture in the area continues to intensify with further use of fertiliser and irrigation water and more animals on the land. Then one summer the stream dries down to a trickle. The lake is murky and native fish are far and few between. Aquatic plants along the once clear stream and lake beds have been replaced by masses of slimy green growth. No-one goes near the water anymore. The connection with the land, the balance, the kaitiakitanga have been lost.

So what has happened here?

Well, the situation can be explained by the concept of tipping points. A tipping point is the point at which a system changes from one state to another, sometimes quite unexpectedly. In this case, the previously healthy pristine waterway system has reached a tipping point, collapsing into a degraded unhealthy state. This is due to the gradual accumulation of small changes to the local landscape and greater human inputs increasing the nutrient levels in the water to a critical point where a significant change to the whole aquatic community occurs. This process is called eutrophication and can be very difficult to reverse due to the system being stable and resistant to change. In today’s world of change, if we could identify which systems are likely to experience tipping points then we could use management actions and policy to avoid these occurring. Knowledge of how tipping points affect a system is also invaluable when trying to shift a system purposely into another state, for example restoration of the degraded waterway and modified landscape.

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Image credit: Troy Baisden

In the case of the waterway system described above, the local community rallied together to take action in claiming back their kaitiakitanga. It is a long journey but through concerted effort and connection to the land they have a strong vision to tip the system back into the healthy, functioning waterway it once was.

 

Ellen Hume is a PhD student funded by Te Pūnaha Matatini Centre of Research Excellence. Her project is looking at detecting temporal and spatial regime shifts to enable better risk-based decision making, with supervision from Dr Cate Macinnis-Ng and Professor Troy Baisden.

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Which tree to plant where? Do we know enough to plant 1 billion trees?

Posted by Cate Ryan, @cate_ryan

Aotearoa was once cloaked in lush temperate rainforests and beech forests. They ensured the land was well looked after by providing ecosystem functions such as habitat, soil protection, carbon storage, fuel, localised shading and cooling effects, and filtration of water.

Today only 43% of Aotearoa is in native vegetation compared to c.80% before human settlement (Norton and Pannell, 2018). Ecosystem functions have degraded, especially water quality and soil protection (erosion) and we must also increase carbon sinks to play our part in tackling climate change.

The current NZ government seeks to significantly increase the number of trees in NZ with the 1 billion trees policy. Species that will be planted include radiata pine, redwood, eucalyptus, Douglas fir, totara and mānuka and these will be planted on private, public and Māori owned land (MPI , 2018). However, which species we plant has a big impact on ecosystem function. Plants trade-off water and carbon during the gas exchange process so that the quicker a tree grows, sinking carbon in the process, the more water it uses, and vice versa. Introduced species like eucalypts grow quickly so are great from a carbon perspective but they use a lot of water. Natives grow more slowly so they don’t accumulate carbon as quickly but they often use less water. We don’t yet have the numbers to properly quantify this in the field so we can’t currently make good decisions on prioritising carbon over water. Moreover, we need to plan ahead for climate change – which is expected to increase dryness and water scarcity.

My PhD research will determine the water use of a range of native compared to plantation exotic tree species in Northland and Canterbury farms, from the leaf to the landscape level – to help inform decisions about what trees to plant where. This is in collaboration with a wider Biological Heritage National Science Challenge programme around ‘Enhancing the ecological function of native biodiversity in agroecosystems’.

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Cate Ryan is a PhD student in Biological Sciences at the University of Auckland, supervised by Dr. Cate Macinnis-Ng

Exotic Insect Invaders – can taxonomic collections help us learn from the past?

By Kaavya Benjamin @kaavyabenjamin95

Globalisation has ensured the prompt arrival of our Amazon purchases, direct flights to Hawaii and ability to share the best of what NZ has to offer with the world. However, the increase in global trade and transport has also intensified the establishment and spread of exotic insect species. These are insect species who invade areas they aren’t native. A recent study also showed that these hitchhiking invaders aren’t planning on stopping any time soon.

Exotic insect invaders can do a lot of harm to native ecosystems. For example, in NZ Vespula wasp invaders have been known to reduce honeydew by 70% and compete with the endangered Kaka. Argentine ants are one of the most problematic invaders of the insect world. Like Genghis Khan’s hordes, the abundance and aggressive nature of this species cause major problems for native birds, lizards and insects. These issues have driven numerous studies to understand the negative impacts of these invaders on native ecosystems. However, very little is known about the dynamics of their spread once established

Image 1 Kaka and wasp image

More than 1,400 exotic insect species have established in NZ, that we know of. Of these over 500 are herbivores who attack numerous plant species. However, other than a few well-known examples, comparatively, there aren’t many instances of exotic insect herbivores spreading into native NZ ecosystems. This is thought to be due to the resistance of the native ecosystems to invaders because of phylogenetic differences between NZ and overseas plants.

However, the more alarming fact is that exotic insect species in NZ have not yet reached equilibrium, meaning their spread will likely continue in the future. A study in 2012 showed the vulnerability of habitats to invasion was dependent upon rates of spread of exotic species. Thus, taxonomic collections, which house specimens collected over a wide range of time and space, could help identify key drivers of population dynamics for the spread of exotic insects. This could point to management options to control/limit widespread invasion. Taxonomic collections can also come in handy when informing conservation managers where control efforts can best be targeted. I am using the New Zealand Arthropod Collection to assess the spread of herbivorous insects into native NZ ecosystems as a part of my Masters’ project. This could help DOC and MPI come up with better pest risk-assessments and provide information for invasive species research.  

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Understanding the dynamics and patterns of past invaders could also result in better-informed predictions for future exotic invasions. While taxonomic collections are far from perfect, they are still a robust source of information which can aid conservation management.

Kaavya is a Masters student in the School of Biological Sciences, University of Auckland. Her project aims to assess spread, over time, of all exotic herbivorous insects into native New Zealand ecosystems. She is supervised by Darren Ward.