Review of historic stock routes may put rare native plants and animals at risk

TSR-Gate

Since the 19th century, Australian drovers have moved their livestock along networks of stock routes. Often following traditional Indigenous pathways, these corridors and stepping-stones of remnant vegetation cross the heavily cleared wheat and sheep belt in central New South Wales.

The publicly owned Travelling Stock Reserve network of New South Wales is now under government review, which could see the ownership of much of this crown land move into private hands.

But in a study published today in the Australian Journal of Botany we suggest that privatising stock routes may endanger vital woodlands and put vulnerable species at risk.


Read more: How ancient Aboriginal star maps have shaped Australia’s highway network


The review will establish how individual reserves are currently being used. Although originally established for graziers, the patches of bush in the network are now more likely to be used for recreation, cultural tourism, biodiversity conservation, apiary and drought-relief grazing.

This shift away from simply moving livestock has put pressure on the government to seek “value” in the network. The review will consider proposals from individuals and organisations to buy or acquire long-term leases for particular reserves.

It is likely that most proposals to purchase travelling stock reserves would come from existing agricultural operations.

A precious national resource

Travelling stock reserves across New South Wales represent some of the most intact examples of now-endangered temperate grassy woodland ecosystems.

Our research found that changing the status or use of these reserves could seriously impact these endangered woodlands. They criss-cross highly developed agricultural landscapes, which contain very limited amounts of remnant vegetation (areas where the bush is relatively untouched). Travelling stock reserves are therefore crucially important patches of habitat and resources for native plants and animals.

This isn’t the first time a change in ownership of travelling stock reserves has been flagged. Over the last century, as modern transport meant the reserves were used less and less for traditional droving, pressure to release these areas for conventional agriculture has increased.

Cattle grazing_IMG_1197_DANIEL_FLORANCE

To understand what a change in land tenure might mean to the conservation values of these woodlands, we spent five years monitoring vegetation in stock reserves in comparison to remnant woodlands on private farmland.

We found that travelling stock reserves contained a higher number of native plant species, more native shrubs, and less exotic plants than woodland remnants on private land.

The higher vegetation quality in travelling stock reserves was maintained over the five years, which included both the peak of Australia’s record-breaking Millennium Drought and the heavy rainfall that followed, referred to as the “Big Wet”.

The take-home message was that remnant woodland on public land was typically in better nick than in private hands.

Importantly, other studies have found that this high-quality vegetation is critical for many threatened and vulnerable native animals. For example, eastern yellow robins and black-chinned honeyeaters occur more frequently in places with more shrubs growing below the canopy.

superb parrot DAMIAN MICHAEL

The contrast we saw between woodlands in travelling stock reserves and private land reflects the different ways they’re typically managed. Travelling stock reserves have a history of periodic low-intensity grazing, mostly by cattle, with long rest periods. Woodland on active farms tend to be more intensively grazed, by sheep and cattle, often without any strategic rest periods.

The stock reserves’ future

The uncertain future of travelling stock reserves casts doubt on the state of biodiversity across New South Wales.

The current review of travelling stock reserves is considering each reserve in isolation. It flies in the face of the belief of many managers, practitioners and researchers that the true value of these reserves is in the integrity of the entire network – that the whole is greater than the sum of its parts.

Travelling stock reserves protect threatened species, allow the movement of wildlife, are seed sources for habitat restoration efforts, and support the ecosystem of adjacent agricultural land. These benefits depend on the quality of the remnant vegetation, which is determined by the grazing regime imposed by who owns and manages the land.

Of course, not all travelling stock reserves are in good condition. Some are subject to high-intensity livestock grazing (for example, under longer-term grazing leases) coupled with a lack of funding to manage and enhance natural values.

Changing the land tenure status of travelling stock reserves risks increasing grazing pressure, which our study suggests would reduce ecosystem quality and decrease their conservation value.

The travelling stock routes are important parts of our ecosystem, our national heritage, and our landscape. They can best be preserved by remaining as public land, so the entire network can be managed sustainably.

This requires adequate funding for the Local Land Services, so they can appropriately manage pest animals, weeds, erosion and illegal firewood harvesting and rubbish dumping.

Travelling stock reserves are more than just The Long Paddock – they are important public land, whose ecological value has been maintained under public control. They should continue to be managed for the public good.

This article was originally published on The Conversation. Read the original article.

This article was based on research published in Australian Journal of BotanyRead the full article.

Advertisements

Secondary invasion: When invasion success is contingent on other invaders altering the properties of recipient ecosystems

Fig4

Two examples of interacting organisms and how the invasion success of the secondary invader is contingent on the presence of a primary invader modifying a native component of the recipient ecosystem. (a) Mutualism between invasive yellow crazy ants and scale insects removes the native red crab which allows entry into the community by the giant African land snail that were previously predated upon by the native crab (Green et al., 2011). (b) The invasive green crab preferentially predates the native Nutricola clam, allowing the population release of the exotic clam, Gemma gemma, which was competitively inferior to the native clams (Grosholz, 2005). Solid and dashed lines denote direct and indirect interactions respectively. Circles and triangles denote negative and positive interactions, respectively. Clam photographs include ruler for scale (1 mm between lines). All pictures in example (b) by Dr E Grosholz

Positive interactions between exotic species may increase ecosystem-level impacts and potentially facilitate the entry and spread of other exotic species. Invader-facilitated invasion success—”secondary invasion”—is a key conceptual aspect of the well-known invasional meltdown hypothesis, but remains poorly defined and empirically underexplored. Drawing from heuristic models and published empirical studies, we explore this form of “secondary invasion” and discuss the phenomenon within the recognized conceptual framework of the determinants of invasion success. The term “secondary invasion” has been used haphazardly in the literature to refer to multiple invasion phenomena, most of which have other more accepted titles. Our usage of the term secondary invasion is akin to “invader-facilitated invasion,” which we define as the phenomenon in which the invasion success of one exotic species is contingent on the presence, influence, and impacts of one or more other exotic species. We present case studies of secondary invasion whereby primary invaders facilitate the entry or establishment of exotic species into communities where they were previously excluded from becoming invasive. Our synthesis, discussion, and conceptual framework of this type of secondary invasion provides a useful reference to better explain how invasive species can alter key properties of recipient ecosystems that can ultimately determine the invasion success of other species. This study increases our appreciation for complex interactions following invasion and highlights the impacts of invasive species themselves as possible determinants of invasion success. We anticipate that highlighting “secondary invasion” in this way will enable studies reporting similar phenomena to be identified and linked through consistent terminology.

Read the paper in-full here: DOI // PDF

Picture1

Invasibility doesn’t always equal impact: an example of a highly-abundant exotic that is not a damaging invader

File 20170722 28465 ngf5eh

The giant African land snail is a poster child of a global epidemic: the threat of invasive species. The snails are native to coastal East Africa, but are now found across Asia, the Pacific and the Americas – in fact, almost all tropical mainlands and islands except mainland Australia.

Yet, despite their fearsome reputation, our research on Christmas Island’s invasive snail population suggests the risk they pose to native ecosystems has been greatly exaggerated.

Giant African land snails certainly have the classic characteristics of a successful invader: they can thrive in lots of different places; survive on a broad diet; reach reproductive age quickly; and produce more than 1,000 eggs in a lifetime. Add it all together and you have a species recognised as among the worst invaders in the world.

The snails can eat hundreds of plant species, including vegetable crops (and even calcium-rich plaster and stucco), and have been described as a major threat to agriculture.

They have been intercepted at Australian ports, and the Department of Primary Industries concurs that the snails are a “serious threat”.

Despite all this, there have been no dedicated studies of their environmental impact. Some researchers suggest the risk to agriculture has been exaggerated from accounts of damage in gardens. There are no accounts of giant African land snails destroying natural ecosystems.

Quietly eating leaf litter

In research recently published in the journal Austral Ecology, we tested these assumptions by investigating giant African land snails living in native rainforest on Christmas Island.

Giant African land snails have spread through Christmas Island with the help of another invasive species: the yellow crazy ant.

Until these ants showed up, abundant native red land crabs ate the giant snails before they could gain a foothold in the rainforest. Unfortunately, yellow crazy ants have completely exterminated the crabs in some parts of the island, allowing the snails to flourish.

We predicted that the snails, which eat a broad range of food, would have a significant impact on leaf litter and seedling survival.

However, our evidence didn’t support this at all. Using several different approaches – including a field experiment, lab experiment and observational study – we found giant African land snails were pretty much just eating a few dead leaves and little else.

We almost couldn’t distinguish between leaf litter removal by the snails compared to natural decomposition. They were eating leaf litter, but not a lot of it.

We saw almost no impact on seedling survival, and the snails were almost never seen eating live foliage. In one lab trial, we attempted to feed snails an exclusive diet of fresh leaves, but so many of these snails died that we had to cut the experiment short. Perhaps common Christmas Island plants just aren’t palatable.

It’s possible that the giant African land snails are causing other problems on Christmas Island. In Florida, for example, they carry parasites that are a risk to human health. But for the key ecological processes we investigated, the snails do not create the kind of disturbance we would assume from their large numbers.

The assumption that giant African land snails are dangerous to native plants and agriculture comes from an overriding sentiment that invasive species are damaging and must be controlled.

Do we have good data on the ecological impact of all invasive species? Of course not. Should we still try to control all abundant invasive species even if we don’t have evidence they are causing harm? That’s a more difficult question.

The precautionary principle drives much of the thinking behind the management of invasive species, including the giant African land snail. The cost of doing nothing is potentially very high, so it’s safest to assume invasive species are having an effect (especially when they exist in high numbers).

But we should also be working hard to test these assumptions. Proper monitoring and experiments give us a true picture of the risks of action (or inaction).

The ConversationIn reality, the giant African land snail is more the poster child of our own knee-jerk reaction to abundant invaders.

Luke S. O’Loughlin, Research fellow, La Trobe University and Peter Green, Head of Department, Ecology, Environment and Evolution, La Trobe University

This article was originally published on The Conversation. Read the original article.

This article was based on research published in Austral EcologyRead the full article.

The secondary invasion of giant African land snail has little impact on litter or seedling dynamics in rainforest

In the absence of empirical evidence, invasive species are often assumed to have negative impacts because of their conspicuously high abundance. The giant African land snail Achatina(Lissachatinafulica is one such invader where its impact in natural ecosystems remains completely untested. On Christmas Island (Indian Ocean), A. fulica has become established across large tracts of rainforest following the impacts of invasive yellow crazy ant (Anoplolepis gracilipes) in mutualism with non-native scale insects. Yellow crazy ants facilitate the secondary invasion of A. fulica by extirpating native red land crabs (Gecarcoidea natalis) that are normally effective predators of A. fulica. We used a multifaceted approach to investigate some potential impacts of abundant A. fulica in invaded rainforest. Over the course of a wet season, diel activity transects showed that A. fulica consumed detrital material almost exclusively. However, stable isotope analysis did not confidently identify A. fulica as a predominantly detritivorous species. We found no statistically significant treatment effects of A. fulica exclusion on standing leaf litter and seedling recruitment processes during a 6-month manipulative field study. However, litter cover and biomass did remain slightly higher where A. fulica were excluded, albeit with overlapping confidence intervals with control plots. Our study constitutes the first empirical test for impact of A. fulica in a natural ecosystem and suggests that for Christmas Island rainforest, this species is not a damaging invader. Other studies will need to assess the impacts of A. fulica in other natural areas before these findings could be considered broadly applicable.

Littlest exotic species provide evidence for big invasion concept [reprise]

A couple of years ago I published an observational study on invasive ants facilitating exotic snails by killing native crabs. That’s the specifics that may be of limited interest, but the interactions (invader-facilitated invasion success) are broadly relevant to anyone studying the dynamics of multi-invaded complex systems. The overall conclusion is that we need to better recognise influential invasive species as intrinsic properties of recipient communities. You can quickly skim the paper by watching the video below, then I highly recommend reading the rest of this short blog that summarises the whole thing:

Humans have been really good at moving species all over the world, and in turn, exotic species have been really good at becoming abundant and influential in their new environments. However, sometimes the conditions in a new environment wont allow an exotic species to get their foot in the door and become invasive. For that to happen, conditions need to change – and who better placed to drive that change than other, previously successful, exotic species.

IMG_3275

It is well established that the impacts of invasive species can seriously alter ecosystem properties. For example, the invasion of a highly-flammable grass will increase fire intensity and frequency in that environment. What is less established is how these altered ecosystems can now be invaded by other, previously unsuccessful, exotic species – in short, exactly how one exotic species will indirectly help another.

The concept being described here is that of ‘secondary invasion’. Most people will have an implicit understanding of the idea based on the more everyday notion of ‘secondary inflections’. A body contracts some pathogen (successful primary invader) making the body ill (altering the conditions of the environment) which leads to the body contracting other infections it otherwise wouldn’t have caught (previously unsuccessful secondary invader).

In ecological research, secondary invasion is a key part of the ‘invasional meltdown hypothesis’ (two invaders working together that amplifies impacts and accelerates more invasions) but was not explicitly defined as such by the authors. Actually, the concept itself remains undefined in the scientific literature and in desperate need of some dedicated investigation and empirical evidence.

A heavily invaded rainforest ecosystem on Christmas Island has long provided some of the strongest evidence in support of the ‘invasional meltdown hypothesis’, and is now also lending key support to this concept of secondary invasion.

The highly abundant red land crab dominates Christmas Island (natural densities of around 1 crab every square meter) and is responsible for the unique open structure and sparse ground layer typical of the rainforest ecosystem on the island (see below). Enter the invasive yellow crazy ant, that when fueled by the sugar of exotic honeydew-producing scale insects, cause local extinctions of the red land crab. The deletion of this ecosystem-engineer causes a pulse recruitment of seedlings and the build-up and persistence of leaf litter. The influence of the crab as a predator is also removed. The end result is an environment with a completely different set of conditions that other invasive species will respond to.

forest

The rainforest community on Christmas Island has quite different characteristics before and after the impacts of primary invaders.

These changes were recognised early on as a great benefit to the exotic giant African land snail, which had been hanging-out on the island since WWII but had never been able to enter the rainforest without being quickly eaten by abundant red land crabs. The yellow crazy ant (primary invader) had indirectly caused the invasion success of the giant African land snail (secondary invader) by deleting the red land crab and creating enemy-free space (altering the conditions of the environment).

However, the giant African land snail is just one of many land snail species on Christmas Island – most of which are exotic and all of which are very small (20 – 1 mm in length). In a study published earlier this year in Biological Invasions, Pete Green and myself investigated whether the invasion success of these snails also depended on the yellow crazy ants altering the environment.

We found that in rainforest where the yellow crazy ant had removed the red land crab these smaller snails were an order of magnitude more abundant – the difference of only a few individuals compared to hundreds for every sample of leaf litter. When comparing intact to impacted rainforest there was no difference in total number of species (~20) or species composition as calculated from presence absence data, meaning all species were essentially at all sites.

Data

The key results shortened from O’Loughlin & Green (2015) Biological Invasions 17, 2659 – 2674. Data is from quadrats during one wet across four forest states; Intact (abundant red crabs, native control), Supercolony (abundant yellow crazy ant, no red crabs), Ghosted (no red crabs, no yellow crazy ants), Recovered (previously a supercolony that was managed and had red crabs return).

This pattern of success was markedly different from what had been initially observed for the giant African land snail. These smaller species were able to enter the rainforest where crabs were present without issue. Yet they still responded positively (increased abundance) when the invasive ants deleted the native crabs. So how does this help inform our concept of secondary invasion?

When considering what determines invasion success, we need to establish when a species goes from simply being ‘exotic’ to ‘invasive’. It is generally considered that ‘invasive’ be reserved for those species that are well established in highly abundant populations, with the capacity to quickly spread and potential to impact the environment. That means the conditions limiting a species could be at any of the earliest points on the invasion pathway – either at the transport, entry or establishment stage.

What we have here on Christmas Island – with our investigation of the entire land snail fauna – is evidence for two distinct pathways of secondary invasion. A true-entry model (the giant African land snail that could not get into the rainforest at all) and a population-release model (the other smaller exotic species that could enter the rainforest but only persist at very low abundances). Both were indirectly facilitated by primary invaders to establish high abundant populations – by definition, ‘invasive’ – but from different starting points.

Often the focus of research is at a global scale, with big data, attempting to make the broadest generalization on the nature of something (which is of course important). The results and implications of this publication demonstrates that the intricate details of specific phenomena will continue to be understood through dedicated small-scale investigations, on literally some of the littlest species.

Christmas (Island) special

I’ve been busy this back half of 2016, doing the field work for the well-monitored experimental release of the new biocontrol agent on Christmas Island, and haven’t gotten around to updating my pages with either a research blog or a comic….. Now I don’t have to because Matteo Farinella has nailed it. Great Christmas present…..

Matteo Farinella Blog

Christmas is upon us and I realised that I have been so busy this year (between my new research project and my new books) that I didn’t have time to draw any short stories, which have always been my favourite format. So, when I learnt about the troubles of Christmas Island on the new Planet Earth (and later discovered that the story is even more complicated) I decided that it was time for a little personal project. This short comic is the result, it’s inspired by science – because of course it is – but I hope it can also be read as fiction and enjoyed regardless of the science. However, if you do want to know more of the biology here is all all the info you need. Happy holidays!

christmasisland00christmasisland01christmasisland02christmasisland03christmasisland04ChristmasIsland05.jpgchristmasisland06christmasisland07christmasisland08

View original post

Volunteer opportunities – Connell Rainforest Research Plot Network

Are you interested in contributing to one of the world’s longest running, plot-based study of rainforest community dynamics?

In 1963, Professor Joseph H. Connell (University of California, Santa Barbara) initiated two research plots in Queensland to improve our understanding of the mechanisms that maintain high diversity in complex, species rich tropical and subtropical rainforests.

At these plots, stand and demographic data for rainforest trees, saplings and seedlings have been collected at 1-6 year intervals for 50 years! These data have been instrumental in informing long-held assumptions as to how rainforests can maintain such high diversity, rather than becoming dominated by only a few common species.

Putting a team together 

It is time again to conduct another re-census of both plots and we’re looking to put together a team of keen volunteers to do this with us! What we need is a group of 8-10 people, for roughly 10-12 workdays for each plot, to get all the work done. Exact dates are currently being finalised, but the very likely times are as follows:

Monday 7th November – Sunday 20th November (two weeks) Davies Creek Plot, Dinden National Park (25 km southwest of Cairns) Tropical rainforest

Monday 21st November – Sunday 4th December (two weeks) O’Reilly’s Plot, Lamington National Park (84 km south of Brisbane) Subtropical rainforest 

The work itself involves regular length days out on the plots, relocating and recording data for all plants tagged and mapped (up to 2,000 trees and over 10,000 seedlings). Volunteers will need to be field hardy and have the capacity to collect high-quality scientific data.

Who are we looking for? 

We are looking for any person with a strong interest in ecological research, and the scientific rigour to work hard and efficiently in the field. These positions would suit science undergrads or recent graduates that want to get some more practical field experience, or anyone else with a strong interested in botany, being out in a rainforest, or contributing to important long-term research.

We take care of all flights, accommodation, transportation, and food expenses for the field trips.

We will likely preference applicants that are able to do both trips (4 week commitment), but we would definitely still like to hear from you if you are only available for re-census of one plot or the other (2 week commitment).

Getting in contact

If you think you’re the right person for this work, send your expressions of interest to Dr Luke O’Loughlin (l.oloughlin@latrobe.edu.au). Please include in your email information about yourself that addresses how you would be a great asset to the team (e.g. skills, past experience, plays well with others, etc) and attach a current CV (that includes your contact details). Use the subject heading “Connell plots volunteer” in your correspondence.

Over the next 3-4 weeks, I’ll be taking names and getting in contact with people with more details and lock-in plans after we finalise logistics (probably the first week of August). I will endeavour to reply to received emails but I am currently away in the field with only occasional access to email. If you don’t hear from me, rest assured that your name is on the list and I will be giving you a call in a few weeks. Thanks

More information

For a detailed account of site history and what a re-census entails, see this glossy-science-magazine story about the last survey effort;  READ IT HERE

To see a little bit more of the site and what others have thought of the experience, see what a few of us have posted on Twitter; SEE IT HERE


THIS RESEARCH IS SUPPORTED BY :

Dept. Ecology, Environment and Evolution, La Trobe University // The Long Term Ecological Research Network (LTERN) // Terrestrial Ecosystem Research Network (TERN // National Collaborative Research Infrastructure Strategy

The invasional meltdown hypothesis and an oceanic island

The following is the introduction chapter (Chapter 1) from my Ph.D thesis Invader-invader mutualism facilitates secondary invasions in rainforest on Christmas Island.

PIC.png

The intact rainforest of Christmas Island is characterised by abundant red land crabs, a patchy distribution of leaf litter and a structurally simple understory.

Biological invasions

Biological invasions are a major and increasing element of global change (Mack et al. 2000, Wonham and Pachepsky 2006, Pyšek and Richardson 2010). The impact of species invasions poses a significant threat to biodiversity through species loss and altered ecosystem function (Mack et al. 2000, Crooks 2002, Ricciardi 2007) as well as having significant economic consequences (Luque et al. 2014). These costs are associated with, i) the loss of primary production (Wilby and Thomas 2002), ii) loss of biodiversity and other impacts on natural ecosystems (Vilà et al. 2011, Simberloff et al. 2013), iii) the effort and resources required to reduce the entry and spread of new invasive species and the eradication of those already established (Eiswerth and Johnson 2002, Pyšek and Richardson 2010). So extensive is the problem that the research discipline of invasion biology (Elton 1958, Simberloff and Vitule 2013) has developed over the past few decades to examine important questions related to the spread and impacts of invasive species. Along with climate change and habitat loss, biological invasions, and their impacts, are considered a main driver of global environmental change (Didham et al. 2005, Tylianakis et al. 2008). Understanding the determinants of invasion success continues to be intensely studied (Catford et al. 2009, Lockwood et al. 2009, Blackburn et al. 2011) in order to better predict which species will become invasive and what the impacts of these successful species are likely to be.   Continue reading

How to collect that wild swarm of bees

**DISCLAIMER** This is not in anyway my area of expertise and I was merely an observer of the action. Step 1 is most important – if you have your own swarm of bees – call somebody who knows something about that stuff!

WELCOME TO  FUN WITH BEES: a step-by-step guide to collecting that wild swarm of European honey bees (Apis mellifera) that turned up in your garden that one time……

IMG_0559

Continue reading

Littlest exotic species provide evidence for big invasion concept

Humans have been really good at moving species all over the world, and in turn, exotic species have been really good at becoming abundant and influential in their new environments. However, sometimes the conditions in a new environment wont allow an exotic species to get their foot in the door and become invasive. For that to happen, conditions need to change – and who better placed to drive that change than other, previously successful, exotic species.

IMG_3275

It is well established that the impacts of invasive species can seriously alter ecosystem properties. For example, the invasion of a highly-flammable grass will increase fire intensity and frequency in that environment. What is less established is how these altered ecosystems can now be invaded by other, previously unsuccessful, exotic species – in short, exactly how one exotic species will indirectly help another. Continue reading

The slides and the script: ATBC presentation from Honolulu 2015

The following post features the slides and (roughly) what I said when presenting part of my research at the Association for Tropical Biology and Conservation annual conference held in Honolulu, Hawai’i the other week (12 – 16 July 2015). I was presenting in the ‘invasive species’ session on the Thursday afternoon (last session of the last day!) which included many interesting talks. I present this here for anyone who happened to miss the talk but was otherwise interested in some of the content. Throughout the post the relevant text comes after the slide:

Invasive Giant African Land Snails (Achatina fulica) have little to impact in rainforest

OLoughlin-ATBC-2015

Aloha, today I’m going to tell you about some research I’ve conducted as part of my PhD research, where we looked for any impacts of invasive Giant African Land Snails, when in high-abundance, in a natural – rainforest – setting. And I have obviously given away the answer in the title of this talk – we determined that this potentially damaging invader was nothing more than an aesthetic atrocity – in the context of this study. So how did we come to this conclusion… Continue reading