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 Aquatic plants along the once clear stream and lake beds have been replaced by masses of slimy green growth.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.

Tuning in to smallness

Posted by Yen Yi Loo @looyenyi 

How do you survive by being small? The soundscape in a New Zealand bush is filled with splendour. But among the powerful song and majestic plumage, there is a niche for all things small and sweet. In Boundary Stream Mainland Island, a forest reserve in the Hawkes Bay region, a group of tiny birds constantly flick and flutter in the trees; Tomtits, Grey warblers, Silvereyes, Robins…and the smallest of them all is the Rifleman. They are so small that a wing flap of a butterfly could be mistaken as a Rifleman. Not only that. They are also very difficult to hear. Rumour has it that people after about 50 years of age can’t hear them. And because of that, many don’t notice them among the Tūī, Bellbirds, and Kākā. I spent the first week of my PhD fieldwork tuning in to the high pitch calls of the Rifleman, tilting my head this way and that, like an owl, to pick up subtle wisps of conversation between foraging pairs. After some practice, I could finally tease apart the calls between Rifleman, Grey warblers and Tomtits, by their small differences in pitch and length.

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Spotting a rifleman takes a little patience and a good sense of auditory localization,
and also ways to watch from different perspectives!
© Ines Moran

I am a first year PhD student looking at the vocal learning abilities of the Rifleman. Could they be learners? Well, we know that they are not songbirds, because they don’t sing to defend their territory or to attract mates – or do they…? But findings in the past decade have also plucked them from the suboscine group and placed them as a link between the passerines and the parrots. So here we are, trying to decipher their potential hidden skill of vocal learning. The more I spend time with them, the more I learn about their interesting behaviours. For instance, they constantly open and close their wings while hopping on branches and trunks of trees in an incredible speed of about 0.05 seconds for each ‘flick’, maybe to maintain balance due to their short of tail? And I saw a male hover for one second in the air!

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“Whoa, didn’t see that branch there!”
© Yen Yi Loo

I can relate to the Rifleman in many ways. For one, I am small, even for Asian standards. For another, I speak softly – well, because I wouldn’t want to disturb the birds! And most relatable of all, I can’t sit still. Although the Rifleman don’t migrate or have large territories, they are busy little birds constantly communicating and working on staying alive. It is difficult to follow them because they move so quickly. I, too, am constantly moving; I travel the world from one side to the other, chasing little birds and learning their behaviour and language. Truth be told, there is a lot to learn wherever we go. And it led me here to this beautiful land of unique bird life. Being surrounded by the soundscape of this forest and the wonderful team that I’m working with, I am glad this is where I will spend all the summers of my PhD doing fieldwork!

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The Cain Lab on the first week at Boundary Stream Mainland Island.
From left, Me: cold and numb from the NZ spring rain,
Daria Erastova: looking to expand her incredible bird list,
Sarah Withers: the pioneer of Rifleman research in the North Island,
Ines Moran: my PhD team mate – the best I could ask for,
and Kristal Cain herself!

YenYen Yi Loo is a PhD student in the School of Biological Sciences, University of Auckland. Her study aims to determine whether the rifleman (Acanthisitta chloris) are vocal learners by investigating the ontogeny and temporal changes in their vocal parameters, and its implication on the evolutionary origins of vocal learning in the avian phylogenetic tree. She is supervised by Kristal Cain and Margaret Stanley.

 

10 Reasons to Love ‘Bird of the Year’

…and why we should have ‘Critter of the Year”

Posted by @mc_stanley1

When you’re completely swamped and just trying to get through the day hour by hour, hoping to find Hermione Granger’s time-turner, how do you get through the massive stress of being overloaded*?

The answer for me this week has been NZ ‘Bird of The Year’.

Bird of the Year voting has filled Twitter with the most amazing positive energy and opportunities to smile.

Here’s why I think ‘Bird of the Year’ is awesome:

  1. It’s a stress-relieving reward: “If I just finish marking this assignment, I can have a sneaky peek at the hilarious memes” (healthier for mind & body than food rewards!)
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Two of the of many awesome memes – check out whio & weka memes too!

2. Breaks down stereotypes – it’s a brilliant opportunity to showcase that scientists are creative, and funny. Scientists such as Stephanie Galla and Josie Galbraith show us that science and art go hand-in-hand (I’m jealous).

 

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Art by Josie Galbraith, Auckland War Memorial Museum (Left) and Stephanie Galla, University of Canterbury (Right)

3. #Scicomm (science communication) is increasingly important in an age where there is a distrust in science among some groups. Ecologists throughout NZ are developing their fledgling #scicomm wings this week and communicating the incredible reasons why these birds are important. While some are old hands at this.

Here’s a couple:

Josie Galbraith on the numbers of Kakī left in the wild: “There are probably more cats on your street than that, more cocopops in your bowl, more lone socks in your drawers.”

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Stephanie Galla’s  genius scicomm – explaining the kakī captive breeding programme by putting kakī on Tinder.

4. What biodiversity in Aotearoa-New Zealand needs is for people to care. And people to care enough to do something about it. We need people other than us biodiversity nerds to care and that means engaging people other than our own peer groups. The Bird of Year has seen some high profile supporters, including the Prime Minister (Black Petrel – ‘the bogan bird’), raise the profile of their chosen species – reaching more New Zealanders we could ever do alone.

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While Bill Bailey and Stephen Fry are onboard, #TeamKakī tries desperately to attract Sam Neil @TwoPaddocks attention, while #TeamHihi are trying to win over Hilary Barry @Hilary_Barry. Come on Sam!

5. Talking to people about why they are voting for a particular species is fascinating and tells us something about nature connection. Some examples:

  • ‘I’m not voting for something I’ve never seen’
  • ‘That bird doesn’t need a profile, not voting for that’
  • ‘It’s won before, it [kakapo] should be deleted’
  • ‘It’s not even endangered’
  • ‘I like an underdog’
  • ‘A robin almost stood on my shoe – it was so cool’
  • ‘But it’s got a tiny head and beady red eyes’
  • ‘They shouldn’t lump all the shags together, no one can connect with a lumpy shag

6. Tea room battles: again with the people interaction – it’s fascinating watching the tearoom come alive with fiery debate about which bird should win (& why you shouldn’t jump ship just because your bird didn’t win last year).

7. Because kakī have to win:

No other native bird is more kiwi than the kakī.  They wear an all black jersey, and every day is Red Socks Day. Josie Galbraith

8. Because who doesn’t love a scandal?

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This has opened up a whole thread on Australians and shags – great mid-marking silliness

9. Because it paves the way for Critter of the Year! Yes New Zealand! No one can possibly wait another year for the enjoyment Bird of the Year has brought us! We need to vote on the forgotten fauna – the freaky but awesome Peripatus, the Otaaaaaaaago skink, and the glorious Powelliphanta snail. Come on NZ Entomological Society! Forest & Bird! RNZ! #CritteroftheWeek

And finally…

10. Because of this:

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IMG_9315 (2)Dr Margaret Stanley is an Associate Professor in Ecology, School of Biological Sciences, University of Auckland and is the programme director of the Masters in Biosecurity and Conservation. Her interests in terrestrial community ecology are diverse, but can be grouped into three main research strands: urban ecology; invasion ecology; and plant-animal interactions.

* besides having an awesome husband who steps up to do far more than his share of kid duty 🙂

An introduction to landscape connectivity

Posted by Zach Carter

Landscape connectivity (also known as ecological connectivity or landscape permeability) is the degree to which a landscape facilitates or impedes wildlife movement. Understanding landscape connectivity has become a major conservation priority for ecological managers because it can be used to protect and restore important ecological processes; such examples include: the promotion of gene flow/dispersal, creation of risk assessments to characterise the likelihood of invasive species dispersal, and quantification of habitat fragmentation throughout peri-urban regions.

Conservation CorridorAn example of landscape connectivity in practice: a conservation corridor that traverses the Trans-Canada Highway in Banff National Park to facilitate large mammal movement (image: https://conservationcorridor.org/2012/10/banff-national-park/)

Most commonly, spatially explicit connectivity models use resistance surfaces to represent landscape features. This is a graph-theoretic technique that reflects movement, represented as a pixel value in a grid within a geographic information system. Connectivity models ultimately use resistance surfaces to calculate the ecological cost associated with movement through a landscape between two termini (starting/ending points). It is assumed that the organism of interest will travel in such a way so as to minimise incurred costs. Accurate representation of these movements can then be used to make informed management decisions based on desired outcomes.

Two common models used for calculating ecological distance include the cost distance and current flow methodologies. These methods propose antithetic assumptions regarding the organism(s) emigration trajectory, where the cost distance model assumes the organism has perfect knowledge of the landscape and will, therefore, choose a path that minimises cumulative ecological costs, and the current flow model which treats the landscape as an electrical circuit and assumes the organism has no prior knowledge of the landscape whatsoever. Often these methods cannot elucidate an organism’s true understanding of the landscape and, as such, are used in conjunction to create a more complete picture.

Resistance Surface ExamplesAn example cost distance (fig. A, least-cost path) and current flow (fig. B, probabilistic movement) output for a generalised mammalian disperser as it emigrates from the New Zealand mainland to an offshore island in Fiordland. The red coloured least-cost path (fig. A) represents the path of least resistance as the organism emigrates. The dark coloured areas (fig. B) represent areas of probabilistic movement from an emigrating organism (source: Z Carter).

Current flow has gained much attention recently for use in connectivity modelling because it considers probabilistic movement across all possible paths within a landscape. If maximising connectivity is the desired ecological outcome (e.g. reducing habitat fragmentation), then calculating current flow between two termini within a landscape is a good model to follow (see fig. B above). On the other hand, if the desired ecological outcome is to reduce organism dispersal (e.g. prevent the spread of invasive species) calculating the least-cost path between termini may be a good modelling option because it often overestimates connectivity. In this instance it would be better to overestimate connectivity than to under estimate it in order to produce informative ecological recommendations regarding the potential spread of a pest species.

For more reading I recommend the following publications:

Etherington, T. R. (2015). “Geographical isolation and invasion ecology.” Progress in Physical Geography 39(6): 697-710.

McRae, B. H. and P. Beier (2007). “Circuit theory predicts gene flow in plant and animal populations.” Proceedings of the National Academy of Sciences 104(50): 19885-19890.

Wade, A. A., et al. (2015). “Resistance-surface-based wildlife conservation connectivity modeling: Summary of efforts in the United States and guide for practitioners.” Gen. Tech. Rep. RMRS-GTR-333. Fort Collins, CO: US Department of Agriculture, Forest Service, Rocky Mountain Research Station. 93 p. 333.

 

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Zach Carter is PhD candidate in the School of Biological Sciences at the University of Auckland. His research focuses on developing prioritisation models to assist eradication efforts for the Predator Free 2050 Programme. He is supervised by James Russell and George Perry.

The allee effect: an effective ally to achieve eradication of invasive species?

Posted by Hester Williams @HesterW123

The rise in biological invasion, strongly related to increasing international trade and travel, is creating global ecological and economical challenges.

The process by which biological invasions occur can be divided into three phases: arrival, establishment, and spread. Early intervention in the form of detection and eradication can be one of the most cost-efficient approaches. Eradication is the deliberate elimination of an invading species from an area, and is greatly assisted by prompt detection when the newly established population is still small and not widely spread.

Given the perceived difficulty of eliminating all individuals of a species, the practicality of eradication has often been questioned. However, recent population studies indicate that low density populations of a variety of species are governed by Allee effects and this may facilitate eradication. Allee effects may arise from a variety of mechanisms (e.g. mate-location failure, failure to overcome host defences, failure to satiate predators) and create a population threshold, below which population growth rate is negative. Consequently, eradication may not require directly eliminating all individuals in a population; instead, it may only be necessary to reduce the population below the Allee threshold, and extinction will proceed without further intervention.

The loss of habitat and fragmentation, which are detrimental to rare and endangered species, are complementary in attempts to eradicate an invasive species from an area. Although habitat loss is not a cause of an Allee effect, it can reduce population size such that the population could then become succeptible to an Allee effect. Fragmentation of an invasive species population (through management actions such as host removal /fragmentation) could result in reduced patch-to-patch dispersal as well as reducing the population densities in each fragmented patch to below the Allee threshold. Thus, sufficiently small and distant patches could lead to extinction of the population.

My studies use Neolema ogloblini, a biocontrol agent for Tradescantia fluminensis, as proxy for an invasive insect pest species (Fig 1).

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Fig 1: The leaf beetle, Neolema ogloblini, a biocontrol agent for Tradescantia fluminensis, with typical adult damage.

Experiments completed last summer have indicated that at small population sizes, establishment of this beetle is moderated by an Allee effect. This summer I will test the effectiveness of host removal as a management tool to achieve eradication by exploiting the Allee effect. I will remove a selected number of host patches within a meta-population of Neolema ogloblini, thereby fragmenting the remaining population and in turn subjecting it to Allee effects to achieve eradication (Fig 2).

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Fig 2: Host removal as management tool to achieve eradication through exploitation of the Allee effect. A selected number of host patches within a meta-population of Neolema ogloblini will be removed (denoted by white patches), fragmenting the remaining population and in turn subjecting it to Allee effects to achieve eradication.

Results of this experiment will ultimately give guidance on what eradication approaches are more or less promising for particular invasive species.

 

Hester 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 an 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.

Why do tropical rat eradications fail?

Posted by James Russell @IsldJames

The answer is self-evident: because we didn’t kill all the rats. However, the answer to the question “why didn’t we kill all the rats” is more complex. Tropical rat eradications currently fail more often than those in temperate or polar regions (16.1% vs 6.3%). If we discount operational reasons (i.e. the eradication wasn’t undertaken properly), the two prevailing biological hypotheses are that either with rats constantly breeding some pups may be able to survive and re-populate the island, or food is so abundant that not all adult rats diet switch to the poison bait.

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A radio-collared rat on Reiono Island (Photo: James Russell)

Experimental rat eradications have proven very profitable in the past for advancing the science of rat eradications, but not everyone wants to allow their rat eradication for conservation to be an experiment, particularly when this increases the risk of failure. This week a team of scientists from University of Auckland (Araceli Samaniego, Markus Gronwald, James Russell) have been undertaking an experiment in association with a tropical rat eradication on Reiono Island in French Polynesia. The 22 hectare island will be treated with poison to eradicate the rats which are widespread across the otherwise relatively pristine island dominated by Pisonia forest and native seabirds and reptiles.

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An alive 5 day old rat pup (Photo: James Russell)

The team have radio-collared over 60 female rats and will track them throughout the course of the eradication. They will monitor their nests to determine the likelihood of any baby rats surviving over the two weeks of the eradication. This intensive monitoring effort will reveal the most detailed data yet on the behaviour of rats during a tropical eradication campaign, and hopefully inform future rat eradications on tropical islands so that they may be as successful as those undertaken in temperate and polar regions around the world.

For more information see the special issue of Biological Conservation on tropical rat eradication.

Conservation in Aotearoa in 2030

Posted by Cate Macinnis-Ng @LoraxCate

The theme for this year’s University of Auckland Winter Lecture Series is Aotearoa in 2030. James Russell and I were invited to speak about conservation in Aotearoa in 2030. James covered the vision for Predator Free 2050 and I talked about some things we need to think about to make the most of the One Billion Trees policy. In short, we need to think carefully about which trees we plant where.

You can view this recording of the talk for more details.

 

Maintaining biodiversity in urban areas

Post by Anna Frances Probert @AFProbert

Urbanisation has come at a cost to greenspaces and biodiversity. Worldwide, pressures for development to sustain our growing human population has led to the loss of vast areas of natural habitats and agricultural land. The associated loss of habitats that sustain populations of native species is considered a driving force in global biodiversity declines.

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Greenspace in a very urban setting; Central Park, New York. Photo: Walkerssk Pixabay

Greenspace is a general term used to characterise vegetated areas of land, whether that be a natural ecosystem such as forest, or a park and recreation area. The benefits of greenspace are broad-reaching; greenspaces can function to increase the quality of living and well-being of residents and visitors to the area. Growing evidence supports the notion that greenspace is an important component of healthy urban living, and greenspace is now a priority area for urban planners. Furthermore, greenspaces provide habitat for biodiversity, providing pockets of refuge within the urban matrix, and allowing the movement of species across the landscape. The protection of greenspace is therefore an important priority to maintain and promote biodiversity in urban areas.

At a smaller scale, urban gardens can act as a type of greenspace, particularly when interconnected with other gardens. Urban residents can therefore play an important role in the maintenance of native biodiversity, by using their gardens and other outdoor spaces in ways that support populations of native birds and invertebrates. Promoting biodiversity in smaller pockets can build up to become part of larger habitat and movement networks that support populations throughout the landscape.

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A bug hotel provides habitat for invertebrates such as wēta. Photo: anpe Pixabay

So what can you do to help in your backyard? Well, many councils are now beginning to provide excellent online resources for community members learn about how to support local wildlife. Whether it is building a wētā hotel in your backyard or porch, planting kaihua (a native jasmine, which I have climbing inside my central Auckland apartment) and other native plants, or keeping your cat indoors and installing predator traps, there are many ways we can participate in enhancing our local environment, for both the benefit of people and biodiversity.

 

 

 

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.