The Effect of the Allee Effect

Posted by Hester Williams @HesterW123

When a population is small, or at low density, the classical view of population dynamics used to be that the major ecological force at work is the release from intraspecific competition – the fewer we are, the more we all have, and the better each will fare…

Gold fishBut in the 1930s, an ecologist named Warder Clyde Allee used goldfish in tanks to demonstrate experimentally that conspecifics had a beneficial influence on each other and survived better in larger groups. This led him to conclude that a certain degree of aggregation (and consequently higher population density/size) can improve the survival rate of individuals, and that cooperation may be crucial in the overall survival of the population. This is basically because larger group sizes provide individuals with more opportunities to mate, defend themselves, feed themselves, and/or can work together to alter their environment in a beneficial manner to the whole group – too few and we might not fare so well!

Allee’s idea on the unsustainability of small populations is today known as the Allee effect and is formally defined as: ‘an increase in individual fitness and/or per capita growth rate, caused by an increase in population size or density’.

The Allee effect can be generated through several mechanisms in small populations including: difficulty in finding a mate, pollen limitation, inability to satiate predators, cooperative anti-predator behaviour, cooperative breeding, foraging efficiency, habitat fragmentation and habitat loss.


Cooperative living: The Southern African meerkat (Suricata suricatta) lives in groups of up to 40 individuals and is a prime example of how cooperation can improve survival. Responsibilities such as baby-sitting and raising the young, foraging, burrow maintenance and standing guard are shared. They also huddle together for warmth, and band together against rivals and predators. If group sizes fall too low, local population crashes can ensue.


ringlet butterflyHabitat fragmentation and loss: Small and more fragmented patches of woodland habitat decreased the resilience and survival of populations of the ringlet butterfly Aphantopus hyperantus by reducing successful dispersal between patches and build-up of sufficient population sizes.


Why does the Allee Effect matter?

The implications of the Allee effect are potentially very important in many areas of ecology and the practical management of population numbers, whether aiming to increase or reduce them, is strongly affected by this effect.

In Conservation the prevention of population collapses is a priority, and it is widely acknowledged that populations of small size are often at greater risk of extinction.

OLYMPUS DIGITAL CAMERAWith only around 100 individuals scattered in the wild (some experts believe only 30!), the Sumatran rhino, Dicerorhinus sumatrensis, is on the verge of extinction. This species is clearly in the grips of an extreme Allee effect – as numbers of individuals decline, factors associated with low numbers (e.g. narrow genetic base, skewed sex ratio, mate-finding, reproductive pathology associated with long non-reproductive periods) combine to drive numbers ever lower, even with adequate habitat and zero poaching. In a 2017 WWF Report experts urge that the days of “conserving” Sumatran rhinos are gone and that efforts to save this species should be in advanced crisis mode to prevent extinction.

Another area of ecological studies where the Allee effect plays an important role is in Invasion Biology. It can inhibit the establishment of newly arrived species or in other cases delay or prevent range expansion of established pest species. This is the case for the gypsy moth (Lymantria dispar) where some of the isolated low-density colonies founded by long-distance dispersal go extinct without any management interventions, simply because of the Allee effect.

The Allee effect also plays a critical role in Biological Control programmes (the introduction of a natural enemy species to control a pest species) where success often depends on releasing sufficient numbers of individuals to ensure establishment of the natural enemy species.


My Research:

The Allee effect is a key focus in my PhD studies. I am studying the establishment success of small, isolated populations of Neolema ogloblini, a beetle introduced as a biocontrol agent for Tradescantia fluminensis in NZ. The aim is to determine whether an Allee effect plays a role in the population dynamics of this beetle and to identify the mechanism driving the Allee effect. This project will generate a better understanding of the key factors that affect biocontrol agent establishment and also invasion success of pest species.

hester.jpgHester Williams is a PhD candidate in the School of Biological Sciences, University of Auckland and is stationed with the Landcare Research Biocontrol team in Lincoln, Canterbury. She is interested in invasion processes of both insect and plant species. Hester is supervised by Darren Ward (Landcare Research/University of Auckland) and Eckehard Brockerhoff (Scion), with Mandy Barron (Landcare Research) as advisor. Her studies are supported by a joint Ministry for Primary Industries – University of Auckland scholarship. The project is an integral part of an MBIE program “A Toolkit for the Urban Battlefield” led by Scion.




What’s the point? Ethics and extinction

Posted by: Jessica Devitt @Colette_Keeha


Figure 1. We must protect endangered species (Yadav, 2016).

Robert Alexander Pyron’s Washington Post article (Pyron, 2017) titled: ‘We don’t need to save endangered species. Extinction is part of evolution’, caused somewhat of a stir in the natural sciences community. It was met with pushback and understandable outrage, especially from those who work to save endangered species and ecosystems. At first glance, I balked at what he was promoting too; my thoughts were that he is encouraging an anthropocentric world view, that the ability for humans to prosper is the only thing of real importance in this world, regardless of what they destroy in the process; and that it is not our moral obligation to save endangered species unless they provide something of practical importance for humanity.

All of that sounds pretty grim to me, yet I also think he has raised an interesting argument, and that he is probably not the only person that thinks this way: it should be noted that he later published a follow-up piece where he further clarifies his reasoning and thoughts with regard to what he wrote.


the end is nigh

Figure 2. Dinosaur extinction (Boblog, 2010).

Based on Pyron’s original article, I felt that the following were some of his main points:

  1. Extinction events are an evolutionary norm, and we should accept them.
  2. Humans are part of the natural world, therefore even if extinction is human-caused, it is no more inimical than ‘natural’ extinction events.
  3. Saving endangered species is a waste of time unless that species is of practical importance to humanity.
  4. Species extinction is not a moral issue for humanity if its loss does not negatively impact humanity.
  5. The animal kingdom is best left alone. For instance invasive species will naturally out compete less hardy native species, which could lead to native species extinction, which is just evolution at work.

Figure 3. Invasives must go (McMillan, 2012).

Like the Nature article by Antonelli and Perrigo (2018) in response Pyron’s piece, I too did not know whether to discuss my thoughts around his article from a scientific perspective or from an ethical perspective. The article also goes further with this issue asking if scientists should even enter into ethical arguments – is it not our job to merely present the facts? Antonelli and Perrigo (2018) note that half of their contingent felt that the rebuttal should be a purely scientific one, and half felt that it was most definitely an ethical argument. They conceded that it is most likely both, and urge fellow natural scientists to weigh in on topics such as this from both an ethical, and evidentiary standpoint.


Figure 4. The trolley problem (McGeddon, 2016).

For myself, I am more interested in exploring the ethical issues that Pyron’s article brings up, as not only am I not learned enough in the scientific mechanisms around his points, but I also think that one could probably find enough evidence to make a compelling argument either way, well at least to relative layperson such as myself. Pyron’s article made me think though, why is it important for me as an individual to conserve natural environments, and species? What’s the actual point in all this?


Figure 5.  Lepidoptera (Landcare Research, n.d.).

The point for me is that I personally think that the natural world, and the species within it, have intrinsic value in their own right.  Hence, that in and of itself is enough for me to try and protect it.  It brings me joy to know that, for instance, the Lord Howe Island stick insect (Dryococelus australis) exists, even though I will likely never see it in person. Further, this stick insect may not have any ‘practical’ benefit for humanity in existing, but I know I would be sad if it were to become extinct. Following this, how would we all reach agreement on what is an important species and what isn’t? Does an ‘impractical’ yet culturally important species get to be saved?


Figure 6. Lord Howe Island phasmid (Granitethighs, 2011).

Rightly or wrongly I also fall into a slippery slope argument where if humanity collectively is not willing to protect endangered species, if we are only interested in preserving what directly serves us, then where does that end? Does that then eventually extend to other humans? Would we later decide that some people are not worth helping because they are not ‘useful’? This reminds me of the medieval christian Great Chain of Being, where all living and non-living things are divided up hierarchically by importance or closeness to god, if you were lower on the chain then you were of less importance (Nee, 2005).  If you were a commoner for instance then you had less rights than say a noble person.


Figure 7. Great Chain of Being (Valdes, 1579).

I realise that this might be somewhat of a stretch to say that not saving endangered species will end up with humanity disregarding those people that are deemed not useful or of ‘less importance’. However, it seems to me that we have been, for the most part, progressively moving away from categorising beings on importance and usefulness, and instead moving in a direction that identifies all living things as important in their own right. Whether I am wasting my time or not I want to stay on this path of protecting what cannot protect itself, because I think at the very least this is a mind-set that will benefit all humanity in the long run.

jessJessica 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.


Antonelli, A., & Perrigo, A. (2018). The science and ethics of extinction. Nature Ecology & Evolution, 1.

Boblog. (2010) Dinosaur extinction.  Retrieved from

Granitethighs. (2011). Lord Howe Island phasmid.  Retrieved from

Landcare Research (n.d.) Lepidoptera. Retrieved from

McGeddon. (2016). The trolley problem: should you pull the lever to divert the runaway trolley onto the side track? Retrieved from

McMillan, S. (2012). Invasives must go.  Retrieved from

Nee, S. (2005). The great chain of being. Nature435(7041), 429.

Yadav, P. (2015). We must protect endangered species. Retrieved from

Pyron, R. A. (2017). We don’t need to save endangered species. Extinction is part of evolution. The Washington Post (22 November 2017).

Valdes, D. (1579). Great Chain of Being.  Retrieved from




Hedgehog hunting: A glimpse into the hunt, the stomachs and the cool things you see in between

Posted by Cathy Nottingham @cathy28495357 

As I’m sure everyone knows, hedgehogs are out there in New Zealand ecosystems wreaking havoc every night munching their way through large volumes of invertebrates, with some lizards and birds thrown in for good measure. But what damage could they really be doing in cities? To get a clearer idea on what hedgehogs are eating in urban bush fragments, I have spent many hours over the last six months stumbling around at night hunting for them so that I can find out.

Hedgehog in hand

Let me tell you, hunting for hedgehogs is hard! They are small and cryptically coloured, making them difficult to spot amongst the vegetation and leaf litter on the forest floor. Fortunately, I have been lucky enough to have access to a thermal scope which shows anything warm as a bright white glow that is hard to miss.  With the scope I have seen many rats, mice, possums, cats (which often seem to be stalking us…) an elephant*, and many, many sleeping birds.  I have also managed to locate and pick up a number of hedgehogs.  Thank goodness for the scope! Many hedgehogs were seen glowing brightly through it, for me to only peer confused into the darkness, with my torch, wondering where on earth the hedgehog could be.  It sometimes took a second look to realise that the hedgehog was under the log in the bushes.  The great thing about hedgehog hunting is that once you have found them you can just walk up and pick them up (although using gloves is definitely required).

The thermal scope I used and a picture of a swan that I saw with it – you can see how brightly the swan glows

Hedghog under log

Hedgehog hiding under a log – I’m sure you will have no difficulty seeing it

So what have I found in all of my hedgehog stomachs**?  Lots of interesting things.  Hedgehogs seem to be hoovering up whatever they come across, including birds, lizards and invertebrates.  Some of the more interesting things I have found include bird feathers (with tissue attached) in three of my stomachs, another stomach with two lizard feet as well as a number of stomachs with weta in them.  I have also found some giant centipedes with some very pretty blue legs.  The more common things in the stomachs have been beetles, slugs and worms.

A foot of a skink and a giant centipede

There is so much cool stuff out there in our urban bush patches, and with hedgehogs around, anything at ground level is getting hoovered up pretty quickly.


Hedgehog hoovering up some delicious invertebrates

Giant centipede

Giant centipede I saw while I was hunting for hedgehogs – it was about the length of my hand


Some more cool stuff that is in our bush when I was out at night hunting – a spider, puriri moth and a couple of weta


*Sadly not wandering, wildly in the bush.  Apparently, Western Springs has a great view into the elephant enclosure.  Disappointingly I only saw it once, although I went back to Western Springs a number of times to hunt for hedgehogs…

**Collected under UOA animal ethics approval 001896


cathyCathy is a MSc student in the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland. She is investigating the impact of hedgehogs in urban forest fragmentsShe is supervised by Margaret Stanley and Al Glen.


Uncovering hidden gems

Posted by Cate Macinnis-Ng @LoraxCate

If you missed Ed Yong’s piece on his efforts to improve gender representation in his reporting in The Atlantic, you should check it out. In short, in late 2016, Ed analysed the proportion of quotes used in his stories from women for that year. At only 24%, he decided to do something about it and he’s since been spending more time seeking out women to interview. The good news is, Ed reports that it has only taken a little extra time to improve the balance and now he’s looking at seeking out other underrepresented groups. My favourite quote from the story is, ‘I assumed that my passive concern would be enough. Passive concern never is.’


I was reminded of this when I was assigned my first paper to handle as an associate editor for the American Journal of Botany. It’s easiest to send papers to the big names but they are often too busy to review and that means less established researchers miss out on valuable learning opportunities. Positive responses to review requests are often more likely from PhD students and in my experience, quality of review if often as good, if not better than more senior researchers. Since finding suitable candidates can be a challenge, I put out a call on twitter.

I’ve had a great response with heaps of retweets and about a dozen self-nominated volunteers. I’d love to add more people to this list so get in touch if you are keen.

It got me thinking that there are a number of simple things we can all do to avoid ‘passive concern’. Here are some ideas –

Early careeer researchers and PhD students

  • Be active on Twitter – bulid a following and a voice so people start to notice you. You never know when an opportunity may arise.
  • Contribute to blogs and other forms of more accessible communication. Rapid Ecology looks like an exciting new platform to do this. The Conversation and The Spinoff are other examples of places to have pieces published online.
  • Do media training so that you feel prepared when the time comes. Formal training will help you learn how to refine your message, improve your on-air performance, reduce use of jargon and be strategic about using media in career development and advancement. If you can’t find formal training, a local community or student radio station is a good place to practice being interviewed.
  • Add your name to databases like 500 Women Scientists’ Request a Scientist and Diversify EEB. You might not hear anything for a while but these lists do work – that’s how I got the invitation to be AE for AmJBot.
  • Don’t be afraid to remind more senior colleagues about being inclusive. For instance, if you are helping organise a symposium, suggest diversity is considered when invitations to speak and attend are sent out.

Established researchers

  • Consider diversity when appointing reviewers, inviting people to speak, suggesting people for committees, collaborators on projects – we need a diversity of voices in all scientific activities. Use Diversity EEB, request a scientist or other resources. If what you need doesn’t exist, consider building the resource.
  • Don’t be a broadcaster on Twitter. Broadcasters tweet about their own work but rarely engage with others. They are often high profile senior researchers. If your follower to followed ratio is high, you are not really listening to what people are saying on twitter.
  • Follow diverse voices on Twitter – seek out ECRs, women, POC, LBGTQ researchers to follow. I’ve learnt so much from twitter. If someone makes a good point, amplyfing it with a retweet is a good way to help diverse voices be heard.
  • If you are involved in a professional society, check out their equity and diversity statement. If they don’t have one, you could volunteer to help put one together.
  • Join the #KindnessInScience movement by improving the research culture in your institution by being more welcoming, respectful and responsible.

With a little bit of effort, we can all do our part to build a more equitable system. Do you have other simple ways to uncover hidden gems? Feel free to add other ideas in the comments below.

Dr Cate Macinnis-Ng is a Senior Lecturer and Rutherford Discovery Fellow, School of Biological Sciences, University of Auckland she is also President of the New Zealand Ecological Society and PI in Te Pūnaha Matatini.  She is a plant ecophysiologist and ecohydrologist working on plant-climate interactions.

Ratting on Rakitu

Posted by James Russell @IsldJames

Last week I had the pleasure to finally visit an island I had long wanted to survey. My perverse reward was finding not one but two species of rats inhabiting the island. Rakitu lies off the east coast of Aotea (Great Barrier Island) – a remote island off the coast of a remote island. Its inverted shape; a valley in the centre surrounded by towering cliffs and tors, lends it English name of Arid Island. With delays to our expedition I was left wondering if the island ever wanted me to visit, but eventually we arrived and I had the pleasure of meeting the descendants of the previous owners also staying out there.

Rakitu as seen looking eastwards from Aotea
Rakitu as seen looking eastwards from Aotea (Source: NZ Herald)

The 328 hectare island was a major centre of Māori activity, and in colonial times was farmed through its central valley and slopes. In 1993 the island was purchased to be managed by the New Zealand Department of Conservation where today it is an open access scenic reserve. Black rats (Rattus rattus) were long known to be present, and our team wanted to assess their abundance, and their impacts on the abundance of native birds, reptiles and invertebrates.

Rakitu cove provides a sheltered and welcoming anchorage
Rakitu cove provides a sheltered and welcoming anchorage (Source: James Russell)

Using an intensive 25 metre trapping grid in the remaining rich native forest in Bush creek, we studied the rat population. Checking only 37 live traps took the entire day, every day. To our surprise, on the first day, we caught a small number of Pacific rats (Rattus exulans) in the forest. This species would have been introduced during Māori occupation, and so it was a surprise that it had never been recorded when its presence was likely, but the abundance of the much larger black rats masked the presence of Pacific rats (locally known as kiore) for a long time, as known from elsewhere. Indeed, the black rats on Rakitu are among the largest ever recorded in New Zealand, averaging over 200 grams weight, and the most dense, at over 20 per hectare. The Department of Conservation intends to eradicate the rats from the island this winter, which is urgent given the declines in bird species and reptiles we were also observing on the island.

Kereru (native wood pigeons) are one of the few bird species still thriving on Rakitu, due to their large body size
Kereru (native wood pigeons) are one of the few bird species still thriving on Rakitu, due to their large body size (Photo: James Russell)

Given the extremely challenging terrain (with locations inaccessible to humans where rats could evade trapping) and size of the island (over 4,000 traps would be required if it was even possible), the only way rat eradication (every last rat removed) can be guaranteed would be by aerial distribution of brodifacoum. Some of the local community on Aotea are fundamentally against poison, which as a principle is laudable (poisoning an environment or species is never good). However, evidence from over 100 rat species eradications on islands around New Zealand for over 50 years shows no long-term effects of one-off brodifacoum use for rat eradications. The evidence does show, however, many, many long-term benefits to the resident native species on all those islands. The dilemma is thus not poison or not poison, but poison or rats?

Pāteke (native brown teal) struggle to breed on Rakitu in the presence of rats, with only one pair present
Pāteke (native brown teal) struggle to breed on Rakitu in the presence of rats, with only one pair present (Photo: James Russell)

Originally posted on National Geographic Voices

Decent proposal: Science engaging GIA

Posted by Lloyd Stringer @lloydstringer2

The biosecurity landscape in NZ is undergoing change. It is shifting from government-led surveillance and responses to a shared response with industry. The Government Industry Agreement (GIA) enables partnerships between industry and government to manage pests allowing for agreement on, for example, decision-making and cost-sharing of responses to new pests and diseases before an incursion has occurred.

This coming together of government, industry and science was exemplified in a recent trip to investigate, share knowledge and trial new surveillance tools for Halyomorpha halys, the Brown Marmorated Stink Bug in Santiago, Chile.BMSB Setting trap Santiago

Decent proposal- science engaging GIA: Lloyd Stringer (University of Auckland/ Plant & Food Research) kneeling with Matt Dyck (from Kiwi Fruit Vine Health, a GIA signatory) putting up a surveillance trap for the Brown Marmorated Stink Bug.

The delegation comprising members from the Ministry for Primary Industries, Kiwifruit Vine Health, New Zealand Wine, Horticulture New Zealand and Plant & Food Research shared their combined knowledge with the Chilean SAG (equivalent to MPI in NZ) and vice versa.

So far populations of Brown Marmorated Stink Bug have not been detected in New Zealand, but it is knocking on the door so the risk of incursion is great. Biosecurity is a shared responsibility, and it is great to see different organisations domestically and internationally sharing information so that all parties benefit from collaborative science and operational research.

BMSB-poster-zealand 2

Science helps to underpin surveillance, eradication and pest management programmes. Recent work done by Ecology Ngātahi members have helped to show how to speed up the confirmation that a species has been eradicated and estimate the probable effectiveness of eradication tools. As NZ becomes more familiar with GIA, I expect there to be many opportunities for science to take what we have learnt and apply it so that it can be more readily used to inform decision making to keep NZ relatively pest free.

So remember if you see something odd, catch it and call the MPI exotic pest and disease hotline 0800 80 99 66.



Lloyd Stringer is a BMSB-plagued PhD student at the School of Biological Sciences at the University of Auckland, and scientist in the Biosecurity Group and Plant & Food Research, Lincoln. He is trying to understand how populations and management tools interact for pest surveillance and eradication. He is supervised by Max SucklingJacqueline Beggs, and John Kean


2017 highlights for Ecology Ngātahi

Post by Anna Frances Probert @AFProbert

It’s almost the end of the year, so I thought I’d take the opportunity to reflect on the achievements of the Ecology Ngātahi research group for 2017. However, please note that the following post merely highlights some of the achievements of Ecology Ngātahi – there is simply not enough space or time to cover everything!


Dr Garvey and Dr Galbraith at graduation earlier this year

We said haere mai to six new students this year: Kshama Awasthi (MSc), Andre Bellve (MSc), Zach Carter (PhD), Ben Cranston (PhD), Kathy Crewther (PhD) and Cathy Nottingham (MSc) who added to our diverse array of research interests, involving everything from remote sensing to impacts of hedgehogs! On the flip side, we had five students graduate: the wonderful Patrick Garvey and Josie Galbraith were awarded their PhDs earlier this year and Sam Heggie-Gracie, Sam Lincoln and Tom Saunders were awarded their Masters degrees. Congratulations!


More recently, we congratulated a number of our academic team who were promoted to Associate Professor. Congratulations to the new Assoc. Prof. Bruce Burns, Assoc. Prof. Margaret Stanley and Assoc. Prof. James Russell. Further congratulations must also be extended to the newly appointed Professor Jacqueline Beggs. I think a lab party is in order!

Earlier this year, we were very fortunate to have two visiting PhD students from Brazil for several months thanks to their collaboration with James Russell. Vinícius Peron de Oliveira Gasparotto and Carlos Robberto Abrahão, conduct their field research at Fernando de Noronha, an archipelago 545km of the coast of Brazil in the Atlantic. Viní’s work focuses on the endemic Noronha skink (Trachylepis atlantica), with his research investigating the biology of this poorly studied species, as well as assessing the potential risk posed to the skink population from invasive species. Carlos, on the other hand, researches the biology and impacts of a large, ferocious, invasive lizard occurring on the islands, the Tegu (Tupinambis merianae). We wish Viní and Carlos all the best in finishing their PhDs and hope they come visit again (or even better, we go and visit them).

Vini and Carlos.jpg

Carlos and Viní having some car issues, but remaining in good spirits as they travel NZ



Carolina and Margaret in Sevilla (with Lucy and Jamie)

Travelling was a theme of the year, with many members of our groups going to far-flung places as a result of conferences and collaborations. James Russell had the fortune of visiting Brazil to work on island invasives, taking the opportunity to capture what I’m awarding the “Cutest critter cuddle” for his picture with a tapir. Several members of our group, including Carolina, Margaret, Jamie and Jacqueline, spent time sipping sangria (or at least I hope they did) in Sevilla, due to their international collaborations. Carolina took advantage of the European visit to attend and present a poster at the Ecological Networks Symposium in Uppsala, Sweden. Julia Schmack and James attended the Islands Invasive Conference in Dundee, Scotland and Julia Kaplick attended the 10th International Sap Flow workshop in California in May. Later in the year Ecotas lured Bruce, Cate Jamie and Ben to the Hunter Valley in NSW, Australia, where Cate was elected President of the New Zealand Ecological Society.

James tapir

James Russell wins the annual “Cutest critter cuddle” award 2017 for his picture with this tapir

Some noteworthy research highlights from students include Josie publishing two new papers on her urban bird research, Jamie publishing on functional redundancy across agricultural intensification gradients and Lloyd Stringer with his paper on the


Jamie enjoying a well deserved beer immediately post-thesis hand in

management and eradication options for the Queensland fruit fly. A special mention of congratulations Alice, who handed in and successfully defended her thesis this year, and to Jamie, who handed in his PhD in September, and is due to defend in January 2018.


Several students including the illuminating Ellery, Carolina and myself wrapped up field work for our PhDs and are now to be contained to the lab (at least in my case) or office for the foreseeable future. On the opposite side of the PhD, Ben established his kauri drought experiment Huapai and we look forward to hearing about these forest giants deal with the stress of water shortage.

And on one final note, our group had a really fantastic year for science communication. School visits, guest writing spots, radio interviews, policy opinion panels – there was a lot going on!

We wish everyone a jolly good festive season, and happy New Year. Don’t forget to spread the word and Respect the Rahui!


Merry Christmas and a Happy New Year from us!


MeblogAnna Probert is a PhD student in the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland. She is using ants as a model to assess the risk posed by exotic invertebrates to native ecosystemsShe is supervised by Margaret StanleyJacqueline Beggs, and Darren Ward.



Rāhui to protect kauri in the Waitākere Ranges

Posted by Julia Kaplick @julekap

New Zealand kauri is one of the country’s most iconic species and of great natural and cultural importance, but this forest giant is under threat by a deadly pathogen. Kauri dieback is caused by the seemingly invisible organism Phytophthora agathidicida. The first symptoms are wilting leaves and lesions at the base of trees. Underground the fine feeding roots as well as the anchoring tap roots are rotting. Over time the infection kills the trees leaving only ghostly wooden skeletons standing.


Dead kauri tree at Waipoua forest

A recent report published by Auckland Council found that a fifth of kauri in the Waitākere Ranges Regional Park show symptoms of dieback and the picture looks especially grim along the many walking tracks. The spread of the deadly pathogen more than doubled in the last five years showing that whatever measures were taken in the past had unfortunately little effect.

Phythosanitary stations have been in place since 2008. They mostly consist of Trigene or Sterigene solution filled spray bottles and brushes to clean soil from footwear. The disinfectant kills the active zoospores of Phytopthora agathadicida, but not the dormant spores which is why it is so important to remove all soil from shoes. The Council report does however show, that the stations are not effective enough, mainly due to people ignoring them or not using them properly.


As people are the main reason why the disease spreads so quickly through the forest local iwi Te Kawerau a Maki placed a rāhui over the Waitakere Ranges. Their hope is to stop any further spread and to give the forest time to heal and recover. Auckland Council on the other hand decided to not officially close regional park. To some this might be surprising, but track closures in the past have shown, that many people just ignore them. The regional park is simply too big to enforce a complete closure. This way the cleaning station will be maintained for people deciding to go for a walk despite the rāhui. The Council does support the rāhui and several individual tracks throughout the Waitakere Ranges are closed due to dieback.

Personally, I will respect the rāhui and stay away from kauri in the Waitākere ranges and I hope many will do the same. It is for now the only way to protect kauri and preserve this iconic tree for future generations.

photo_juliaJulia Kaplick is a PhD student in the Centre of Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland. She is researching the response of native trees to seasonal variation in climatic conditions using measurements of sap flow, water relations and carbon allocation. Julia is supervised by Cate Macinnis-Ng (University of Auckland) and Mike Clearwater (Waikato University). Julia is supported by funding from the Marsden Fund.  

The Beautiful Sea Creatures

Posted by Carolina Lara @carislaris

In the process of becoming half New Zealander, I have invariably found myself spending a lot of time at the beach. I grew up in a semi-deserted area of Mexico so the marine environment was unknown to me, particularly the vast seabird community. From this I’ve learnt two things, not all birds live in the forest and not all seabirds are seagulls. In New Zealand/Aotearoa, around a third of the ca. 80 species of seabirds are endemic. Among the most amazing ones we find the largest albatross in the world, the magnificent toroa; the tiny and unfortunately endangered dotterel/tūturiwhatu; the Chatham Island oystercatcher/tōrea; the Westland petrel/tāiko, and the fascinating  New Zealand storm petrel (believed extinct and re-discovered in 2003), to mention a few.


New Zealand storm Petrel

Why are seabirds important? Well as explained by Moller et al (2000), seabirds often breed in dense colonies and their abundance, high guano loads and soil burrowing makes them a “keystone species”, species that play a large role in the prevalence and population levels of other species within their environment.  Any change in seabirds abundance would likely affect important soil processes (nitrification, plant regeneration) and therefore abundance of other animal species. Most importantly, seabirds shape the ecology of terrestrial communities by acting as a link between the sea and the land because they import marine-derived nutrients into terrestrial communities.

Despite the great value of seabirds in maintaining of ecosystems, their abundance has dramatically decrease worldwide, with an estimated 70% decline over the last 60 years, representing the deaths of 230 million birds. Some of the threats seabirds face are: plastic pollution (plastic rubbish is found in 90% of birds guts), overfishing, toxic pollution, nest predation by invasive species (e.g. rats) and the effects of rising sea temperatures on their food supply. New Zealand hasn’t escaped this trend with the dotterel/tūturiwhatu and yellow-eyed penguin/hoiho making it to the news recently, not many individuals of each species are left in the wild.


Dotterel/tūturiwhatu at Martin’s Bay

Is there still hope for our seabirds? Yes, with adequate management programs to get rid of invasive species in seabird colonies, regulating fishing to avoid birds getting caught in fish nets, reducing our plastic consumption and the establishment of conservation areas we can expect a recovery in seabird abundance in the long run. For now, let’s go out and appreciate these beautiful sea creatures.


CalisCarolina Lara M. is a PhD Candidate within the Centre for Biodiversity and Biosecurity, School of Biological Sciences, University of Auckland. Her research interests focus on seed dispersal networks within fragmented landscapes. She is supervised by Margaret StanleyJason Tylianakis, Karine David, and Anna Santure.

Detecting drought with remote sensing – some preliminary results

Posted by Kshama Awasthi

Green vegetation growth is a useful indicator of drought events and vegetation indices such normalised difference vegetation index (NDVI) and enhanced vegetation index (EVI) are often used for the assessment of agricultural drought. I have been evaluating the sensitivity of these indices to detect the impact of drought on forest areas in various parts of Aotearoa New Zealand. In general, a higher NDVI or EVI value represents more healthy vegetation so I expected to see a decline in the vegetation indices during drought.

Picture1Right: NDVI values for the Hunua Ranges for the month of March

There was a slight decline in NDVI in 2013 during the drought. To confirm the role of drought in the decline in NDVI, I am using soil moisture deficit (SMD) data from NIWA. SMD is calculated using incoming daily rainfall (mm), outgoing daily potential evapotranspiration (mm) and fixed available water capacity that is the amount of water in the soil reservoir that plants can use.

picture 2 v 4

Above: Soil moisture deficit and vegetation health indices for summer months at Hunua Ranges.

As expected, the NDVI (r2=55%) and EVI (r2=65%) both show a strong relationships with SMD which indicates NDVI and EVI values are responsive to drought.


Above: Relationships between soil moisture deficit and NDVI and EVI vegetation indices for summertime at Hunua Ranges, 2006-2017.

EVI values decreased more in response to drought conditions as compared to NDVI, indicating that EVI is more sensitive then NDVI on the onset of drought conditions.

Since the relationship between EVI and SMD is stronger than the correlation between NDVI and SMD, EVI can be the better indicator of drought detection in forest as compared to the NDVI as EVI provides improved sensitivity in high biomass regions while minimizing soil and atmosphere influences.

This is the result for the Hunua Ranges and calculations for other sites are still ongoing.

kshama Kshama Awasthi is an MSc student supervised by Cate Macinnis-Ng and Jay Gao