A detailed eucalypt family tree helps us see how they came to dominate Australia



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In Australia you can have any tree you want, as long as it’s a eucalypt.
Shutterstock

Andrew Thornhill, James Cook University

Eucalypts dominate Australia’s landscape like no other plant group in the world.

Europe’s pine forests consist of many different types of trees. North America’s forests change over the width of the continent, from redwood, to pine and oak, to deserts and grassland. Africa is a mixture of savannah, rainforest and desert. South America has rainforests that contain the most diversity of trees in one place. Antarctica has tree fossils.

But in Australia we have the eucalypts, an informal name for three plant genera: Angophora, Corymbia and Eucalyptus. They are the dominant tree in great diversity just about everywhere, except for a small region of mulga, rainforest and some deserts.

My research, published today, has sequenced the DNA of more than 700 eucalypt species to map how they came to dominate the continent. We found eucalypts have been in Australia for at least 60 million years, but a comparatively recent explosion in diversity 2 million years ago is the secret to their spread across southern Australia.

Hundreds of species

The oldest known Eucalyptus macrofossil, from Patagonia in South America, is 52 million years old. The fossil pollen record also provides evidence of eucalypts in Australia for 45 million years, with the oldest specimen coming from Bass Strait.

Despite the antiquity of the eucalypts, researchers assumed they did not begin to spread around Australia until the continent began drying up around 20 million years ago, when Australia was covered in rainforests. But once drier environmental conditions kicked in, the eucalypts seized their chance and took over, especially in southeastern Australia.

Eucalypts are classified by their various characteristics, including the number of buds.
Mary and Andrew/flickr, CC BY-NC-SA

There are over 800 described species of eucalypts. Most of them are native only to Australia, although some have managed to naturally escape further north to New Guinea, Timor and Indonesia. Many eucalypts have been introduced to other parts of the world, including California, where Aussie eucalypts make cameos in Hollywood movies.

Eucalypts can grow as tall trees, as various multi-trunk or single-trunk trees, or in rare cases as shrubs. The combination of main characteristics – such as leaf shape, fruit shape, bud number and bark type – provided botanists with enough evidence to describe 800 species and estimate how they were all related to each other, a field of science known as “taxonomy”.

Since the 1990s and early 2000s, taxonomy has been slightly superseded by a new field called “phylogenetics”. This is the study of how organisms are related to each other using DNA, which produces something akin to a family tree.

Phylogenetics still relies on the species to be named though, so there is something to sample. New scientific fields rely on the old. There have been a number of eucalypt phylogenetic studies over the years, but none have ever sampled all of the eucalypt species in one phylogeny.




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Stringybark is tough as boots (and gave us the word ‘Eucalyptus’)


Our new paper in Australian Systematic Botany aimed to change that. We attempted to genetically sample every described eucalypt species and place them in one phylogeny to determine how they are related to each other. We sampled 711 species (86% of all eucalypts) as well as rainforest species considered most closely related to the eucalypts.

We also dated the phylogeny by time-stamping certain parts using the ages of the fossils mentioned above. This allowed us to estimate how old eucalypt groups are and when they separated from each other in the past.

Not so ancient

We found that the eucalypts are an old group that date back at least 60 million years. This aligns with previous studies and the fossil record. However, a lot of the diversification in the Eucalyptus genus has happened only in the last 2 million years.

Gum trees are iconic Australian eucalypts.
Shutterstock

Hundreds of species have appeared very recently in evolutionary history. Studies on other organisms have shown rapid diversification, but none of them compare to the eucalypts. Many species of the eucalypt forests of southeastern Australia are new in evolutionary terms (10 million years or less).

This includes many of the tall eucalypts that grow in the wet forests of southern Australia. They are not, as was previously assumed, ancient remnants from Gondwana, a supercontinent that gradually broke up between 180 million and 45 million years ago and resulted in the continents of Australia, Africa, South America and Antarctica, as well as India, New Zealand, New Guinea and New Caledonia.

The eucalypts that grow natively overseas have only made it out from Australia in the last 2 million years or less. Other groups in the eucalypts such as Angophora and Corymbia didn’t exhibit the same rapid diversification as the Eucalyptus species.




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What we confirmed with the fossil record using our phylogeny is that until very recently, and I mean in terms of the Earth being 4 billion years old, the vegetation of southeastern Australia was vastly different.

At some point in the last 2-10 million years the Eucalyptus arrived in new environmental conditions. They thrived, they most likely helped spread fire to wipe out their competition, and they then rapidly changed their physical form to give us the many species that we see today.

Very few other groups in the world have made this amount of change so quickly, and arguably dramatically. The east coast of Australia would look very different if it wasn’t dominated by gum trees.

The next time you’re in a eucalypt forest, take a look around and notice all of the different types of bark and gumnuts and leaves on the trees, and know that all of that diversity has happened quite recently, but with a deep and long link to trees that once grew in Gondwana.

They have been highly advantageous, highly adaptable and, with the exception of a small number of species, are uniquely Australian. They are, as the press would put it, “a great Australian success story”.The Conversation

Andrew Thornhill, Research botanist, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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How indigenous expertise improves science: the curious case of shy lizards and deadly cane toads



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The Balanggarra Rangers are land management representatives of the Balanggarra people, the indigenous traditional owners of the East Kimberley. (L-R) Wes Alberts, Bob Smith (coordinator) James ‘Birdy’ Birch, Isiah Smith, Quentin Gore.
The Kimberley Land Council, Author provided

Georgia Ward-Fear, University of Sydney and Rick Shine, University of Sydney

It’s a common refrain – western ecologists should work closely with indigenous peoples, who have a unique knowledge of the ecosystems in their traditional lands.

But the rhetoric is strong on passion and weak on evidence.

Now, a project in the remote Kimberley area of northwestern Australia provides hard evidence that collaborating with Indigenous rangers can change the outcome of science from failure to success.




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We’ve cracked the cane toad genome, and that could help put the brakes on its invasion


Fighting a toxic invader

This research had a simple but ambitious aim: to develop new ways to save at-risk predators such as lizards and quolls from the devastating impacts of invasive cane toads.

Cane toads are invasive and highly toxic to Australia’s apex predators.
David Nelson

All across tropical Australia, the arrival of these gigantic alien toads has caused massive die-offs among meat-eating animals such as yellow-spotted monitors (large lizards in the varanid group) and quolls (meat-eating marsupials). Mistaking the new arrivals for edible frogs, animals that try to eat them are fatally poisoned by the toad’s powerful toxins.

Steep population declines in these predators ripple out through entire ecosystems.

But we can change that outcome. We expose predators to a small cane toad, big enough to make them ill but not to kill them. The predators learn fast, and ignore the larger (deadly) toads that arrive in their habitats a few weeks or months later. As a result, our trained predators survive, whereas their untrained siblings die.




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Conservation ‘on Country’

But it’s not easy science. The site is remote and the climate is harsh.

We and our collaborators, the Western Australian Department of Biodiversity, Conservation and Attractions, decided at the outset that we needed to work closely with the Indigenous Traditional Owners of the east Kimberley – the Balanggarra people.

So as we cruised across the floodplain on quad bikes looking for goannas, each team consisted of a scientist (university-educated, and experienced in wildlife research) and a Balanggarra Indigenous ranger.

Although our study species is huge – a male yellow-spotted monitor can grow to more than 1.7 metres in length and weigh more than 6kg – the animals are well-camouflaged and difficult to find.

Over an 18-month study, we caught and radio-tracked more than 80 monitors, taught some of them not to eat toads, and then watched with trepidation as the cane toad invasion arrived.




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Excitingly, the training worked. Half of our trained lizards were still alive by the end of the study, whereas all of the untrained lizards died soon after toads arrived.

That positive result has encouraged a consortium of scientists, government authorities, conservation groups, landowners and local businesses to implement aversion training on a massive scale (see www.canetoadcoalition.com), with support from the Australian Research Council.

A yellow-spotted monitor fitted with a radio transmitter in our study. This medium-sized male was trained and lived for the entirety of the study in high densities of cane toads.
Georgia Ward-Fear, University of Sydney



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Cross-cultural collaboration key to success

But there’s a twist to the tale, a vindication of our decision to make the project truly collaborative.

When we looked in detail at our data, we realised that the monitor lizards found by Indigenous rangers were different to those found by western scientists. The rangers found shyer lizards, often further away from us when sighted, motionless, and in heavy cover where they were very difficult to see.

Gregory Johnson, Balanggarra elder and ranger.
Georgia Ward-Fear

We don’t know how much the extraordinary ability of the rangers to spot those well-concealed lizards was due to genetics or experience – but there’s no doubt they were superb at finding lizards that the scientists simply didn’t notice.

And reflecting the distinctive “personalities” of those ranger-located lizards, they were the ones that benefited the most from aversion training. Taking a cautious approach to life, a nasty illness after eating a small toad was enough to make them swear off toads thereafter.

In contrast, most of the lizards found by scientists were bold creatures. They learned quickly, but when a potential meal hopped across the floodplain a few months later, the goanna seized it before recalling its previous experience. And even holding a toad briefly in the mouth can be fatal.

Comparisons of conditions under which lizards were initially sighted in the field by scientists and Indigenous rangers (a) proximity to lizards in metres (b) density of ground-cover vegetation (>30cm high) surrounding the lizard (c) intensity of light directly on lizard (light or shade) (d) whether the lizard was stationary or moving (i.e. walking or running). Sighting was considered more difficult if lizards were further away, in more dense vegetation, in shade, and stationary.
Georgia Ward-Fear, University of Sydney

As a result of the intersection between indigenous abilities and lizard personalities, the overall success of our project increased as a result of our multicultural team.

If we had just used the conventional model – university researchers doing all of the work, indigenous people asked for permission but playing only a minor role – our project could have failed, and the major conservation initiative currently underway may have died an early death.

So our study, now published in Conservation Letters, provides an unusual insight – backed up by evidence.

Moving beyond lip service, and genuinely involving Indigenous Traditional Owners in conservation research, can make all the difference in the world.

Georgia Ward-Fear (holding a yellow-spotted monitor) with Balanggarra Rangers Herbert and Wesley Alberts.
David Pearson, WA Department of Biodiversity, Conservation and Attractions

This research was published in collaboration with James “Birdy” Birch and his team of Balanggarra rangers in the eastern Kimberley.The Conversation

Georgia Ward-Fear, Post doctoral fellow and Conservation Ecologist , University of Sydney and Rick Shine, Professor in Evolutionary Biology, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

In Australia, climate policy battles are endlessly reheated


Marc Hudson, University of Manchester

This article is part of a series examining the Coalition government’s record on key issues while in power and what Labor is promising if it wins the 2019 federal election.


It might feel like the past decade of climate policy wars has led us into uncharted political waters. But the truth is, we’ve been sailing around in circles for much longer than that.

The situation in the late 1990s bore an uncanny resemblance to today: a Liberal-led government; a prime minister who clearly favours economic imperatives over environmental ones; emerging internal splits between hardline Liberal MPs and those keen to see stronger climate action; and a Labor party trying to figure out how ambitious it can be without being labelled as loony tree-huggers.

The striking parallels between now and two decades ago tell us something about what to expect in the months ahead.




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After a brief flirtation with progressive climate policy in the 1990 federal election, the Liberals had, by the final years of the 20th century, become adamant opponents of climate action.

In March 1996, John Howard had come to power just as international climate negotiations were heating up. In his opinion, even signing the United Nations climate convention in Rio in 1992 had been a mistake. He expended considerable effort trying to secure a favourable deal for Australia at the crunch Kyoto negotiations in 1997.

Australia got a very generous deal indeed (and is still talking about banking the credit to count towards its Paris target), and Howard was able to keep a lid on climate concerns until 2006. But it was too little, too late, and in 2007 his party began a six-year exile from government as Rudd, then Gillard, then Rudd took the climate policy helm, with acrimonious results.

When Tony Abbott swept to power in 2013, his first act was to abolish the Labor-appointed Climate Commission, which resurrected itself as the independent Climate Council. Next, he delivered his signature election campaign promise: to axe the hated carbon tax (despite his chief of staff Peta Credlin’s later admission that the tax wasn’t, of course, actually a tax).




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Abbott also reduced the renewable energy target, and sought (unsuccessfully) to keep climate change off the agenda at the 2014 G20 summit in Brisbane.

Abbott and his environment minister Greg Hunt did preside over some policy offerings – most notably the Direct Action platform, with the A$2.55 billion Emissions Reduction Fund at its heart, dishing out public money for carbon-reduction projects. The pair also announced an emissions reduction target of 26-28% on 2005 levels by 2030, which Australia took as its formal pledge to the crucial 2015 Paris climate talks.

But by the time nations convened in Paris, Malcolm Turnbull was in the hot seat, having toppled Abbott a few months earlier. Many observers hoped he would take strong action on climate; in 2010 he had enthused about the prospect of Australia going carbon-neutral. But the hoped-for successor to the carbon price never materialised, as Turnbull came under sustained attack from detractors within both his own party and the Nationals.

Then, in September 2016, a thunderbolt (or rather, a fateful thunderstorm). South Australia’s entire electricity grid was knocked out by freak weather, plunging the state into blackout, and the state government into a vicious tussle with Canberra. The dispute, embodied by SA Premier Jay Weatherill’s infamous altercation with the federal energy minister Josh Frydenberg, spilled over into a wider ideological conflict about renewable energy.




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A year since the SA blackout, who’s winning the high-wattage power play?


With tempers fraying on all sides, and still no economy-wide emissions policy in place, business began to agitate for increasingly elusive investment certainty (although they had played dead or applauded when Gillard’s carbon price was under attack).

In an era of policy on the run, things accelerated to a sprinter’s pace. Frydenberg suggested an emissions intensity scheme might be looked at. Forty-eight hours later it was dead and buried.

Turnbull commissioned Chief Scientist Alan Finkel to produce a report, which included the recommendation for a Clean Energy Target, prompting it to be vetoed in short order by the government’s backbench.

Within three months Frydenberg hurriedly put together the National Energy Guarantee (NEG), which focused on both reliability and emissions reduction in the electricity sector. The policy gained support from exhausted business and NGOs, but not from the Monash Forum of Tony Abbott and cohorts, who preferred the sound of state-funded coal instead. And then, in August 2018, the NEG was torpedoed, along with Turnbull’s premiership.

The next man to move into the Lodge, Scott Morrison, was previously best known in climate circles for waving a lump of coal (kindly provided, with lacquer to prevent smudging, by the Minerals Council of Australia) in parliament.




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Morrison’s problems haven’t eased. His energy minister Angus Taylor and environment minister Melissa Price have each come under attack for their apparent lack of climate policy ambition, and Barnaby Joyce and a select few fellow Nationals recently endangered the fragile truce over not mentioning the coal.

Meanwhile, Labor, with one eye on the Green vote and another on Liberal voters appalled by the lack of action on climate change, are trying to slip between Scylla and Charybdis.

Shorten’s offering

While Labor has decided not to make use of a Kyoto-era loophole (taking credit for reduced land-clearing), its newly released climate policy platform makes no mention of keeping fossil fuels in the ground, dodges the thorny issue of the Adani coalmine, and has almost nothing to say on how to pay the now-inevitable costs of climate adaptation.

What will the minor parties say? Labor’s policy is nowhere near enough to placate the Greens’ leadership, but then the goal for Labor is of course to peel away the Greens support – or at least reduce the haemorrhaging, while perhaps picking up the votes of disillusioned Liberals.

Overall, as Nicky Ison has already pointed out on The Conversation, Labor has missed an “opportunity to put Australians’ health and well-being at the centre of the climate crisis and redress historical injustices by actively supporting Aboriginal and other vulnerable communities like Borroloola to benefit from climate action”.




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Labor’s climate policy: a decent menu, but missing the main course


And so the prevailing political winds have blown us more or less back to where we were in 1997: the Liberals fighting among themselves, business despairing, and Labor being cautious.

But in another sense, of course, our situation is far worse. Not only has a culture war broken out, but the four hottest years in the world have happened in the past five, the Great Barrier Reef is suffering, and the Bureau of Meteorology’s purple will be getting more of a workout.

We’ve spent two decades digging a deeper hole for ourselves. It’s still not clear when or how we can climb out.The Conversation

Marc Hudson, PhD Candidate, Sustainable Consumption Institute, University of Manchester

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The swamp foxtail’s origin is hidden in its DNA



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Swamp foxtail is prized in ornamental gardens across Australia.
John Tann/Flickr, CC BY-SA

Roderick John Fensham, The University of Queensland

Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.


Swamp foxtail (Cenchrus purpurascens) is a delightful grass that forms a neat tussock up to a metre tall with a distinctive fluffy spikelet that resembles a fox’s tail.

Foxtails are widely used in horticulture. The purple forms are particularly popular in ornamental gardens and some have even become invasive weeds.

The foxtail grasses are more commonly seen in these cultivated settings, which has led to much confusion about swamp foxtails’ origins in Australia. The species is simultaneously an exotic weed from Asia, the dominant grass in an endangered Australian ecosystem and a rare native species in isolated desert springs.



The Conversation

Is it native?

It was uncertain for a while whether swamp foxtail is actually native to Australia. Although Europeans collected it near Sydney, it was possible the seeds had come with livestock on the early ships.

This theory was put to rest by genetic studies that found small populations have existed in inland Queensland for hundreds of thousands of years.

The species spread southward and was first recorded in Victoria in the 1970s.

European records

Robert Brown, the botanist who accompanied Matthew Flinders as he circumnavigated the continent, made the the earliest European collections of the swamp foxtail near Sydney in 1802.

Despite the early date of the collections, it is feasible that the swamp foxtail was brought to Sydney within 14 years of settlement as a byproduct among grain or hay. However, while the species occurs naturally in Asia, the Javanese ports were not on the typical travelling route from Europe.




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The intrepid adventurer Ludwig Leichardt later collected this species near the Gwydir River region. This collection provides more convincing evidence the swamp foxtail is native to Australia. It seems unlikely that, in the early years of colonisation, the swamp foxtail had been transported overland with the squatters who were spreading out from their successful properties in the Hunter Valley.

The spread southward

The history of herbarium records, from collections in the late 1800s and early 1900s, suggests swamp foxtail might have been native to Queensland and New South Wales.

Collections south of these locations happened after 1940. The species was not recorded in Victoria until the 1970s. It seems almost certain the swamp foxtail spread southward during the 20th century, in some places as an undesirable weed.

Unusual and isolated habitats

Aboriginal fire management possibly maintained natural grassy openings among the northern NSW rainforests. The curious “grasses”, as they were named, are well documented on early survey plans of the Big Scrub country. Many a place name, Howards Grass Road and Lagoon Grass Road among them, bear testament to their existence.

An extremely isolated population of the swamp foxtail at Elizabeth Springs in western Queensland.
Rod Fensham

The surveyors provided detailed recordings of the dominant grass on the valley floors: the “foxtail”. The swamp foxtail is now rather rare on the valley floors of the Richmond and the Tweed River valleys, replaced by crops on prime agricultural land. It managed to survive in a few locations west of Murwillumbah and on springs, but large expanses of the foxtail grasslands have succumbed to the plough.

A particularly unusual habitat for the swamp foxtail is the artesian springs that feed permanent wetlands in the semi-deserts of inland Queensland. The swamp foxtail occurs there in very local populations separated by hundreds of kilometres.

This raises the question: is the swamp foxtail a recent arrival on these tiny, strange and isolated ecosystems, or are these ancient populations?

Genetic studies have provided conclusive evidence of an ancient origin. The oldest lineage is the population at Elizabeth Springs to the south of Boulia. Its molecular signature suggests this population has been isolated for hundreds of thousands of years.

Where swamp foxtail does occur at springs, it is always accompanied by rare species that are seen only in those unusual wetlands.




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Crossing continents and climates

Swamp foxtail demonstrates the complexity of defining a species’ origin. This species probably evolved in Asia, because this is where most of its relatives are found. It found its way to Australia, possibly through a migratory bird that dropped a seed in a desert spring.

It then had a second migration, either from the springs or from a repeat dispersal from Asia, and found a niche in the valley floors of subtropical landscapes. It was abundant in these moist and fertile habitats when Europeans colonised the continent in 1788.

Since then, the swamp foxtail has spread to temperate climates where it has become invasive and, in some situations, a minor pest. Quite a journey.The Conversation

Roderick John Fensham, Associate Professor of Biological Sciences, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Mercury pollution from decades past may have been re-released by Tasmania’s bushfires



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Tasmania’s fires may have released mercury previously absorbed by trees.
AAP Image

Larissa Schneider, Australian National University; Kathryn Allen, University of Melbourne, and Simon Haberle, Australian National University

Tasmania’s bushfires may have resulted in the release of significant amounts of mercury from burnt trees into the atmosphere. Our research shows that industrial mercury pollution from decades past has been locked up in west Tasmanian trees.

Mercury occurs naturally in Earth’s crust. Over the past 200 years, industrial activities have mobilised mercury from the crust and released it into the atmosphere. As a consequence, atmospheric mercury concentrations are now three to four times higher than in the pre-industrialisation era.

Mining is the largest source of the global atmospheric mercury, accounting for 37% of mercury emissions. When Europeans first arrived in Australia, there was, of course, no Environmental Protection Act in place to limit emissions from industrial activities. In western Tasmania, where mining has occurred for more than a century, this meant mercury was being released without control into the local atmosphere until changes in technology, market conditions, and later, regulation, conspired to reduce emissions.




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Because mercury is also very persistent in the environment, past mining activity has generated a reservoir of mercury that could be released to the atmosphere under certain conditions. This is a concern because even small amounts of mercury may be toxic and may cause serious health problems. In particular, mercury can threaten the normal development of a child in utero and early in its life.

Tree rings can reveal past mercury contamination

How much mercury has been released into the Australian environment and when has remained largely unknown. However, in a new study we show how mercury levels in Tasmania have dramatically changed over the past 150 years due to mining practices. Long-lived Huon pine, endemic to western Tasmania, is one of the most efficient bioaccumulators of mercury in the world. This makes it a good proxy for tracking mercury emissions in western Tasmania. If concentrations of mercury in the atmosphere are high in a given year, this can be detected in the annual ring of Huon pine for that year.

Mercury pollution from past mining practices in western Tasmania has left a lasting environmental legacy. The sampled trees contained a significant reservoir of mercury that was taken up during the peak mining period in Queenstown. Changes in mercury concentrations in the annual rings of Huon pine are closely aligned with changes in mining practices in the region.

Increased concentrations coincide with the commencement of pyritic copper smelting in Queenstown in 1896. They peak between 1910 and 1920 when smelting was at its height. In 1922, concentrations begin to decline in parallel with the introduction of a new method to separate and concentrate ores. This method required only one small furnace instead of 11 large ones. In 1934, a new dust-collection apparatus was installed in the smelter’s chimney, coinciding with the further decrease in mercury concentrations in nearby Huon pine.

Temporal tree rings of Huon pine, revealing historical mercury pollution.
Author provided

Toxic elements or compounds taken up by vegetation can also be released back into the local environment. Bushfires that burn trees that have accumulated mercury may release this mercury as vapour, dust or fine ash, potentially exposing people and wildlife to the adverse effects of mercury. It is estimated that bushfires release 210,000kg of mercury into the global atmosphere each year. As these fires become more frequent and ferocious in Australia, mercury concentrations in the atmosphere are likely to increase. Mercury released by bushfires can persist in the atmosphere for a year, allowing for long-distance transportation depending on wind strength and direction. This means that mining activity from over a century ago may have regional implications in the near future. The Tasmanian fires in December-February burned almost 200,000 hectares, including areas around Queenstown.

It is not currently possible to know how much mercury has been released by these recent fires. Our results simply highlight the potential risk and the need to better understand the amount of mercury taken up by vegetation that may one day be released back to the atmosphere via bushfires.

Re-release of historical mercury emissions by bushfires.
Author provided



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Dry lightning has set Tasmania ablaze, and climate change makes it more likely to happen again


Although there is no simple way to remove bio-accumulated mercury from trees, the history of mercury contamination recorded in tree rings provides important lessons. Decreased uptake of mercury after upgrades to the Queenstown copper smelter operations demonstrates the positive impact that good management decisions can have on the amount of mercury released into the environment.

To control mercury emissions globally, the United Nations Environment Programme (UNEP) has developed the Minamata Convention on Mercury. Its primary goal is to protect human health and the environment from the negative effects of mercury. Australia has signed the convention and but has yet to ratify it. Once ratified, Australia would be required to record sources of mercury and quantify emissions, including those from bushfires.

But to do this, the government must first be able to identify environmental reservoirs of mercury. Our study, the first of its kind in the Southern Hemisphere, shows that the long-lived Huon pine can be used to for this purpose. Further work to determine what other tree species record atmospheric emissions of mercury and other toxic elements in other regions of Australia is required.The Conversation

Larissa Schneider, DECRA fellow, Australian National University; Kathryn Allen, Academic, Ecosystem and Forest Sciences, University of Melbourne, and Simon Haberle, Professor, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Like cats and dogs: dingoes can keep feral cats in check



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Feral cats are linked to the extinction of at least 20 Australian mammals.
Shutterstock

Mike Letnic, UNSW and Ben Feit

The role of dingoes in the Australian landscape is highly debated between ecologists, conservationists and graziers. They kill livestock, but also hunt introduced animals and keep kangaroo populations in check.

Now new research sheds more light on the benefits dingoes bring to the outback. For the first time, our research clearly shows that dingoes suppress feral cat numbers.

Our research, published recently in Ecosystems, used the world’s largest fence to compare essentially identical environments with and without dingoes. Over the course of the six-year study, dingoes drove down cat numbers – and kept them down.




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Feral cats are out of control

Feral cats are a serious conservation threat. They have been linked to the extinction of at least 20 mammal species in Australia and threaten the ongoing survival of more than 100 native species.

For our study, we asked whether “top-down” pressure from dingoes (through direct killing and competition for food) had a greater influence on controlling cat numbers than “bottom-up” effects (the availability of shared food sources preyed on by cats).

Dingoes drive down the population of introduced animals.
Kim/flickr, CC BY-SA

We conducted our study by comparing the numbers of dingoes, cats and their major prey species on either side of the dingo fence in the Strzelecki Desert. The fence runs along the borders of New South Wales and South Australia and was originally built to exclude dingoes from sheep grazing lands in NSW.

The state border follows the longitude line 141 east, so the fence does not demarcate any natural boundary. It simply cuts a straight line through sand dunes with similar landforms and vegetation on either side. Thus the dingo fence provides a unique opportunity to study apex predators’ effects on ecosystems: dingoes are common on the SA side, “outside” the fence, whereas on the NSW “inside” of the fence, dingoes are rare due to intensive persecution by humans.




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Let’s move the world’s longest fence to settle the dingo debate


We collected data from sites on either side of the fence in the Strzelecki Desert, at roughly four-month intervals between 2011 and 2017. Dingo and cat scat was collected at each site, to analyse and compare diets, and spotlight searches were used to record numbers of dingoes, feral cats, as well as two of their common shared food sources: rabbits and hopping mice.

Spotlight surveys revealed dingoes to be virtually absent from study areas inside the fence, with only four dingoes recorded during the study. Where dingoes were rare inside the fence, cat numbers closely followed fluctuations of their prey species consistently over the six-year span of our study. As prey numbers increased, cat numbers also increased, and similarly as prey numbers declined, cat numbers also declined.

A feral cat in outback Australia.
Shutterstock

Outside the fence, where dingoes were common, it was quite a different story. There, cat numbers were consistently lower, with numbers of both cats and dingoes following fluctuations in prey numbers across the first two years of the study. However, from 2013 onward, dingo numbers remained high and matched trends in their prey numbers for the remainder of the study.

During this time, cat numbers remained low, and by the end of 2015, cats had virtually disappeared from our study sites outside the fence and were not recorded during spotlight surveys between November 2015 and the end of our study in July 2017.

The most likely explanation for this drastic reduction in cat populations is through interference competition – either by dingoes killing some cats or by scaring others away from habitats in which they would usually hunt. Indeed, we occasionally found cat remains in dingo scats, which suggests dingoes prey on cats.

Although our scat analyses indicated that dingoes and cats eat similar foods, there was no evidence that competition for food was a major factor in how dingoes reduce cat populations. This is because prey were plentiful outside the fence, where dingoes were common and cats were rare.




Read more:
Why do some graziers want to retain, not kill, dingoes?


This research show how dingoes can help conservation efforts by suppressing feral cat populations. It adds to previous work showing dingoes are important in maintaining healthy ecosystems, as they reduce and eradicate feral herbivores like pigs and goats, and stop kangaroos from overpopulating districts.


This article was updated on April 5 to credit Ben Feit as a co-author.The Conversation

Mike Letnic, Professor, Centre for Ecosystem Science, UNSW and Ben Feit, Post-doctoral researcher

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Invasive ants: federal budget takes aim but will it be a lethal shot?



File 20190404 131415 1ag8r2w.jpg?ixlib=rb 1.1
Argentine ants are a fact of life in many parts of Australia, but can still potentially be banished from Norfolk Island.
Davefoc/Wikimedia Commons, CC BY-SA

Lori Lach, James Cook University

Amid all the usual items we expect to see in the federal budget was one that raised eyebrows: A$28.8 million for three ant eradication programs.

Yet amid the inevitable media puns about the government “upping the ant-e”, we should note that these funds are for the continuation of existing programs that have already attracted significant funding and made substantial progress. Stopping now would have meant previous funding was wasted.

The funds will go a long way towards protecting Australia’s economy and environment from the damage wrought by invasive ants. But despite the apparent cash splurge, it nevertheless falls short of what is really needed.

Of the $28.8 million, $18.3 million was for the National Red Imported Fire Ant Eradication Program. These funds are part of a $411 million, ten-year program begun in 2017 to eradicate red imported fire ants from southeast Queensland, the only place they are found in Australia.




Read more:
Cannibalism helps fire ants invade new territory


Removing these pests will avoid an estimated $1.65 billion in total costs to 19 different parts of the economy. With previous funding, the program eradicated these ants from 8,300 hectares near the Port of Brisbane, making it the world’s largest ant eradication to date.

The Yellow Crazy Ant Eradication Program was allocated $9.2 million over three years. Yellow crazy ants have caused a cascade of ecological effects on Christmas Island, and at their peak abundance temporarily blinded a Queensland cane farmer with their acid spray.

The Wet Tropics Management Authority, which runs the program, had requested $6 million per year for six years to continue removing the ant from in and around the Wet Tropics World Heritage Area. The federal funding is $3 million short of this, and the authority is still waiting to hear whether the Queensland government will provide the remainder.

Since 2013, the program has received $9.5 million from the federal government (and $3 million from the Queensland government). No yellow crazy ants have been observed in about half of the target area in more than a year. A yet-to-be published analysis estimates the benefit-cost ratio for the program as 178:1.

“It’s a mop-up operation… we’ve got our foot on the throat of this thing.”

A further $1.3 million was allocated to the Argentine Ant Eradication Strategy on Norfolk Island in the South Pacific. Argentine ants have invaded places with Mediterranean-type climates all over the world, including southwestern Western Australia and parts of southern Australia, and become firmly established. But unlike those areas, the population on Norfolk Island is still considered small enough to be eradicable, and federally funded efforts to remove them began in 2010.

Yellow crazy ants in Queensland and Argentine ants on Norfolk Island directly threaten World Heritage Areas. The ants can have significant impacts on native birds, mammals, insects, reptiles, amphibians, and plants. Getting rid of them is important for meeting Australia’s international obligations to protect World Heritage sites.

What is ant eradication?

Ant eradication means removing all individuals of a particular ant species from a given area.

The first step is to define the extent of that area. Depending on the species, this may involve visual searches and/or placing lures such as sausages, cat food, or jam to attract the ants. The public can help by notifying relevant authorities of unusual ants in their gardens, and by not transporting materials that have ants on them.

The second step is treatment. Currently, the only way to eradicate ants is with insecticidal baits. Ants’ social structure makes this particularly challenging: killing the queens is vital for eradication, but queens typically stay sheltered in the nest – the only ants we see out foraging are workers.

Some of the most problematic ant species can have hundreds of queens and tens of thousands of workers per nest. They can reach extraordinarily high densities, partly because invasive ant species, unlike most of our native ant species, do not fight one another for territories.

Yellow crazy ants, proving it is possible to feel sorry for a cockroach.
Bradley Rentz/Wikimedia Commons, CC BY-SA

Beating ants means turning their biology against them. Bait needs to be attractive enough for workers to bring back to the colony and share, but not so deadly that they die before they get there. (And yes, this means if you’re spraying foraging ants in your kitchen you won’t get rid them for good, because the queens are somewhere hidden, laying more eggs and making more ants.)

Most ant eradication programs take three to four years to fine-tune their baiting regime because of a multitude of factors that need to be considered, such as seasonal changes in ant foraging behaviour and food preference, and the desire to avoid harming non-target species. Typically, two to six treatments are required, depending on the ant species, the size of the area, and the habitat type.

Beating the 1%

The hardest part of ant eradication is the end-game. Getting rid of the final 1% requires first finding them. This may mean painstaking searches through hundreds of hectares of bushland and residential areas, and the placement of hundreds of thousands of lures. Detector dogs can be very helpful, but they cannot be used in all environments and also need substantial resources for training, handling, and maintenance.

Ironically, it is at this stage that public and political support for eradication programs is most likely to wane, because ant numbers are too low to be seen as a threat to the public, economy or environment. Yet it is vital not to stop now, or else the remaining 1% will simply build up their numbers again. Experienced staff are also lost when programs suffer cuts or delays in their funding.




Read more:
Eradicating fire ants is still possible, but we have to choose now


Disappointingly not mentioned in the budget was funding for eradicating electric ants. Like red imported fire ants, electric ants have a painful sting, and when left to multiply will eventually turn gardens and swimming pools into no-go zones. They also pose a significant threat to native animals such as the southern cassowary, and can blind animals as large as elephants.

They are currently only found in the Cairns region. The National Electric Ant Eradication Program, funded by federal and state governments, ran from 2006 until 2017 and had likely reduced numbers down to that last 1%. The program has been running on state funding with reduced staff since then, but several new detections in the past three months demonstrate the cost of the gap in funding.

In those inevitable “federal budget winners and losers” lists, invasive ants have found themselves firmly in the losers column for 2019. But it’s worth remembering that most of the world’s roughly 15,000 known ant species provide vital services for the functioning of our ecosystems.

They aerate soil and redistribute its nutrients, protect plants from herbivores, disperse seeds, and repurpose dead organisms. They may even help slow down the spread of those pesky invasive ants that are much less friendly.The Conversation

Lori Lach, Associate Professor, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.