Pest plants and animals cost Australia around $25 billion a year – and it will get worse



AAP

Corey J. A. Bradshaw, Flinders University and Andrew Hoskins, CSIRO

Shamefully, Australia has one of the highest extinction rates in the world.
And the number one threat to our species is invasive or “alien” plants and animals.

But invasive species don’t just cause extinctions and biodiversity loss – they also create a serious economic burden. Our research, published today, reveals invasive species have cost the Australian economy at least A$390 billion in the last 60 years alone.

Our paper – the most detailed assessment of its type ever published in this country – also reveals feral cats are the worst invasive species in terms of total costs, followed by rabbits and fire ants.

Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.

Feral cats are Australia’s costliest invasive species.
Adobe Stock/240188862

Huge economic burden

Invasive species are those not native to a particular ecosystem. They are introduced either by accident or on purpose and become pests.

Some costs involve direct damage to agriculture, such as insects or fungi destroying fruit. Other examples include measures to control invasive species like feral cats and cane toads, such as paying field staff and buying fuel, ammunition, traps and poisons.

Our previous research put the global cost of invasive species at A$1.7 trillion. But this is most certainly a gross underestimate because so many data are missing.




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Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill


As a wealthy nation, Australia has accumulated more reliable cost data than most other regions. These costs have increased exponentially over time – up to sixfold each decade since the 1970s.

We found invasive species now cost Australia around A$24.5 billion a year, or an average 1.26% of the nation’s gross domestic product. The costs total at least A$390 billion in the past 60 years.

Increase in annual costs of invasive species in Australia from 1960 to 2020. The predicted range for 2020 is shown in the upper left quadrant. Note the logarithmic scale of the vertical axis.
CJA Bradshaw

Worst of the worst

Our analysis found feral cats have been the most economically costly species since 1960. Their A$18.7 billion bill is mainly associated with attempts to control their abundance and access, such as fencing, trapping, baiting and shooting.

Feral cats are a main driver of extinctions in Australia, and so perhaps investment to limit their damage is worth the price tag.

Tasmania’s bane — ragwort (Senecio jacobaea)
Adobe Stock/157770032

As a group, the management and control of invasive plants proved the worst of all, collectively costing about A$200 billion. Of these, annual ryegrass, parthenium and ragwort were the costliest culprits because of the great effort needed to eradicate them from croplands.

Invasive mammals were the next biggest burdens, costing Australia A$63 billion.

The 10 costliest invasive species in Australia.
CJA Bradshaw

Variation across regions

For costs that can be attributed to particular states or territories, New South Wales had the highest costs, followed by Western Australia then Victoria.

Red imported fire ants are the costliest species in Queensland, and ragwort is the economic bane of Tasmania.

The common heliotrope is the costliest species in both South Australia and Victoria, and annual ryegrass tops the list in WA.

In the Northern Territory, the dothideomycete fungus that causes banana freckle disease brings the greatest economic burden, whereas cats and foxes are the costliest species in the ACT and NSW.

The three costliest species by Australian state/territory.
CJA Bradshaw

Better assessments needed

Our study is one of 19 region-specific analyses released today. Because the message about invasive species must get out to as many people as possible, our article’s abstract was translated into 24 languages.

This includes Pitjantjatjara, a widely spoken Indigenous language.




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Even the massive costs we reported are an underestimate. This is because of we haven’t yet surveyed all the places these species occur, and there is a lack of standardised reporting by management authorities and other agencies.

For example, our database lists several fungal plant pathogens. But no cost data exist for some of the worst offenders, such as the widespread Phytophthora cinnamomi pathogen that causes major crop losses and damage to biodiversity.

Developing better methods to estimate the environmental impacts of invasive species, and the benefit of management actions, will allow us to use limited resources more efficiently.

Phytophthora cinnamomi, a widespread, but largely uncosted, fungal pathogen.
Adobe Stock/272252666

A constant threat

Fall armyworm, a major crop pest.
Adobe Stock/335450066

Many species damaging to agriculture and the environment are yet to make it to our shores.

The recent arrival in Australia of fall armyworm, a major agriculture pest, reminds us how invasive species will continue their spread here and elsewhere.

As well as the economic damage, invasive species also bring intangible costs we have yet to measure adequately. These include the true extent of ecological damage, human health consequences, erosion of ecosystem services and the loss of cultural values.

Without better data, increased investment, a stronger biosecurity system and interventions such as animal culls, invasive species will continue to wreak havoc across Australia.


The authors acknowledge the Traditional Owners of the lands on which they did this research.

Ngadlu tampinthi yalaka ngadlu Kaurna yartangka inparrinthi. Ngadludlu tampinthi, parnaku tuwila yartangka.The Conversation

Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University and Andrew Hoskins, Research scientist CSIRO Health and Biosecurity, CSIRO

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

‘One of the most damaging invasive species on Earth’: wild pigs release the same emissions as 1 million cars each year


Pixabay

Christopher J. O’Bryan, The University of Queensland; Eve McDonald-Madden, The University of Queensland; Jim Hone, University of Canberra; Matthew H. Holden, The University of Queensland, and Nicholas R Patton, University of CanterburyWhether you call them feral pigs, boar, swine, hogs, or even razorbacks, wild pigs are one of the most damaging invasive species on Earth, and they’re notorious for damaging agriculture and native wildlife.

A big reason they’re so harmful is because they uproot soil at vast scales, like tractors ploughing a field. Our new research, published today, is the first to calculate the global extent of this and its implications for carbon emissions.

Our findings were staggering. We discovered the cumulative area of soil uprooted by wild pigs is likely the same area as Taiwan. This releases 4.9 million tonnes of carbon dioxide each year — the same as one million cars. The majority of these emissions occur in Oceania.

A huge portion of Earth’s carbon is stored in soil, so releasing even a small fraction of this into the atmosphere can have a huge impact on climate change.

The problem with pigs

Wild pigs (Sus scrofa) are native throughout much of Europe and Asia, but today they live on every continent except Antarctica, making them one of the most widespread invasive mammals on the planet. An estimated three million wild pigs live in Australia alone.

A herd of wild pigs
Wild pigs are one of the most widespread invasive animals on Earth.
Shutterstock

It’s estimated that wild pigs destroy more than A$100 million (US$74 million) worth of crops and pasture each year in Australia, and more than US$270 million (A$366 million) in just 12 states in the USA.

Wild pigs have also been found to directly threaten 672 vertebrate and plant species across 54 different countries. This includes imperilled Australian ground frogs, tree frogs and multiple orchid species, as pigs destroy their habitats and prey on them.

Their geographic range is expected to expand in the coming decades, suggesting their threats to food security and biodiversity will likely worsen. But here, let’s focus on their contribution to global emissions.

Their carbon hoofprint

Previous research has highlighted the potential contribution of wild pigs to greenhouse gas emissions, but only at local scales.

One such study was conducted for three years in hardwood forests of Switzerland. The researchers found wild pigs caused soil carbon emissions to increase by around 23% per year.

Similarly, a study in the Jigong Mountains National Nature Reserve in China found soil emissions increased by more than 70% per year in places disturbed by wild pigs.

Wild pigs turn over 36,214 to 123,517 square kilometres of soil each year.
Shutterstock

To find out what the impact was on a global scale, we ran 10,000 simulations of wild pig population sizes in their non-native distribution, including in the Americas, Oceania, Africa and parts of Southeast Asia.

For each simulation, we determined the amount of soil they would disturb using another model from a different study. Lastly, we used local case studies to calculate the minimum and maximum amount of wild pig-driven carbon emissions.

And we estimate the soil wild pigs uproot worldwide each year is likely between 36,214 and 123,517 square kilometres — or between the sizes of Taiwan and England.

Most of this soil damage and associated emissions occur in Oceania due to the large distribution of wild pigs there, and the amount of carbon stored in the soil in this region.




Read more:
Feral pigs harm wildlife and biodiversity as well as crops


So how exactly does disturbing soil release emissions?

Wild pigs use their tough snouts to excavate soil in search of plant parts such as roots, fungi and invertebrates. This “ploughing” behaviour commonly disturbs soil at a depth of about five to 15 centimetres, which is roughly the same depth as crop tilling by farmers.

Wild pigs uproot soil in search of food, such as invertebrates and plant roots.
University of Kentucky, Department of Forestry and Natural Resources, Forestry Extension.

Because wild pigs are highly social and often feed in large groups, they can completely destroy a small paddock in a short period. This makes them a formidable foe to the organic carbon stored in soil.

In general, soil organic carbon is the balance between organic matter input into the soil (such as fungi, animal waste, root growth and leaf litter) versus outputs (such as decomposition, respiration and erosion). This balance is an indicator of soil health.

When soils are disturbed, whether from ploughing a field or from an animal burrowing or uprooting, carbon is released into the atmosphere as a greenhouse gas.

This is because digging up soil exposes it to oxygen, and oxygen promotes the rapid growth of microbes. These newly invigorated microbes, in turn, break down the organic matter containing carbon.

Wild pigs have a rapid breeding rate, which makes controlling populations difficult.
Shutterstock

Tough and cunning

Wild pig control is incredibly difficult and costly due to their cunning behaviour, rapid breeding rate, and overall tough nature.

For example, wild pigs have been known to avoid traps if they had been previously caught, and they are skilled at changing their behaviour to avoid hunters.




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In Australia, management efforts include coordinated hunting events to slow the spread of wild pig populations. Other techniques include setting traps and installing fences to prevent wild pig expansion, or aerial control programs.

Some of these control methods can also cause substantial carbon emissions, such as using helicopters for aerial control and other vehicles for hunting. Still, the long-term benefits of wild pig reduction may far outweigh these costs.

Working towards reduced global emissions is no simple feat, and our study is another tool in the toolbox for assessing the threats of this widespread invasive species.




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Tiny Game of Thrones: the workers of yellow crazy ants can act like lazy wannabe queens. So we watched them fight


The Conversation


Christopher J. O’Bryan, Postdoctoral Research Fellow, School of Earth and Environmental Sciences, The University of Queensland; Eve McDonald-Madden, Associate professor, The University of Queensland; Jim Hone, Emeritus professor, University of Canberra; Matthew H. Holden, Lecturer, School of Mathematics and Physics, The University of Queensland, and Nicholas R Patton, Ph.D. Candidate, University of Canterbury

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

Willow trees are notorious pests. But for freshwater animals, they could be unlikely climate heroes


Willow invasion on Happy Valley Creek in north east Victoria.
Author provided; Happy Valley Creek, Victoria, Author provided

Paul McInerney, CSIRO and Tanya Doody, CSIROClimate change will make Australia hotter and drier in future, and we’re starting to see the dangerous consequences of this in our rivers, lakes and streams.

As waters warm and flow patterns alter, the animals who call these waterways home may struggle to survive. Many are ectotherms — meaning that unlike humans, these animals can’t regulate their body temperature, putting them at the mercy of ambient water temperature. And for animals that have evolved in cold water, such as some native crayfish, increased water temperatures can be lethal.

Our new research paper calls for a (possibly controversial) solution: take advantage of willow trees growing along the banks. They can create cool, shady refuges in these warming waterways.

Willows are not native and, in many places, are an invasive weed. But for temperature-sensitive animals, their dense, leafy canopy may make willows the lesser of two evils in a warming climate.

The lesser evil

Willows belong to the genus Salix, and are natives of the northern hemisphere. They were introduced to Australia in the 19th century first as ornamental plants, then later planted to help stabilise river banks to combat erosion.

Today, they’re considered noxious weeds in Australia, South America and southern Africa, are highly invasive and have spread along waterways throughout temperate Australia.

Willows along waterways can prevent light from entering streams and cool water temperature.
Author provided; Yackandandah Creek, Victoria

The harms willows inflict on aquatic ecosystems are well documented. For example, they alter energy dynamics in streams by dropping all their leaves into the water at once, which can reduce water quality and the amount of food for animals.

Dense shading in summer reduces the amount of algae (an important food source) growing on surfaces in streams. Willows also out-shade and use more water than native plants, stopping them from re-colonising.

These reasons are why governments invest in removing willows from our waterways. But what if willows offer some benefits to their invaded ecosystems, too?

Freshwater wildlife in peril

As far as we know, the presence of willows hasn’t caused any extinctions. But in coming years, we can expect to see more animal extinctions due to temperature increases from climate change.

To deal with climate change, temperature-sensitive animals are left with two options: either migrate upstream to cooler water or adapt to warmer water. Both alternatives are problematic.

Willow trees on a river bank
Willow trees can out-shade native plants and stop them from re-colonising.
Shutterstock

Some animals, such as two-spined blackfish, aren’t well suited to (or potentially even capable of) long distance travel to cooler water. And many of our rivers have barriers, such as dams, weirs and waterfalls, making migration impossible.

If animals stay put, Australia’s climate is now warming at such a fast rate, some may struggle to adapt quickly enough. The critically endangered barred galaxias is another cool water adapted fish unlikely to successfully migrate to other habitats to escape warming climate, but remains at risk if it doesn’t.




Read more:
Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill


To give wildlife a fighting chance at survival, we need to consider a patchwork of new and alternative approaches to stream management, such as creating “climatic refugia”. These are places where local climate is cooler than the regional climate, providing areas animals can escape to when temperatures get extreme.

Warmer temperatures may cause the populations of some freshwater species, such as the Murray River turtle, to grow.
Author provided

Trees and shrubs growing along the edges of streams (riparian vegetation) do this when they shade the water surface, helping to mediate water temperature.

This could make willows a useful tool for natural resource managers as we see increases in extreme heat days.

Happy Valley Creek

For our research paper, we use a case study from north-east Victoria to illustrate how dense willow invasions can reduce stream water temperature and create climatic refugia.




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We logged water temperature in Happy Valley Creek at three locations: at an upstream native forested site, a midstream site with no vegetation, and a downstream site that was heavily shaded by invasive willows.

We expected water temperature to increase with distance downstream as it moves from cool upland areas to warmer lowland areas. Instead, we found the water temperature at the willow shaded site could be a few degrees cooler than the midstream site, particularly during periods of extreme heat.

Fish among rocks
Some animals, like the two-spined blackfish, are unlikley to migrate to cooler waters.
Alan Couch/Wikimedia, CC BY-SA

Many streams are fringed by native vegetation that provide comparable heat protection to animals as willows, and we should protect these from willow invasion.

But in locations where willow removal activities are unlikely to be successful in the long-term, it may be better to prioritise willow removal elsewhere. For example, if willows can’t be removed from upstream catchments, they’ll continue to recolonise downstream. And if there’s no funding for follow-up activities, willows may re-establish following removal.

Where willows are rampant, they may already be protecting populations of heat-sensitive animals from temperature extremes. Removing them could have unintended consequences for such animals.

An absence of shade from bank-side vegetation can increase stream temperatures.
Author provided; Happy Valley Creek, Victoria

What’s the end goal?

It’s important to clarify we’re not suggesting willow removal activities should stop to prevent further widespread invasion. But as our climate changes, we need to objectively consider what ecosystems will be sustainable in the future, and prioritise our restoration efforts accordingly.

We need to decide what state we’re trying to manage our ecosystems to — the likely endpoint.




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Given current river regulations, land-use and changing climate, restoring all ecosystems to a pre–European state may not be sustainable or even possible at this point.

For willow-dominated, degraded catchments, there may be more value in promoting willows as refuges from the temperature extremes of climate change, rather than pursuing an ideal that may not even be possible.The Conversation

Paul McInerney, Research scientist, CSIRO and Tanya Doody, Principle Research Scientist, CSIRO, CSIRO

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

Mouse plague: bromadiolone will obliterate mice, but it’ll poison eagles, snakes and owls, too


Masked owl (Tyto novaehollandiae), one of many birds of prey at great risk of secondary poisoning
Belinda Davis, Author provided

Robert Davis, Edith Cowan University; Bill Bateman, Curtin University; Damian Lettoof, Curtin University; Maggie J. Watson, Charles Sturt University, and Michael Lohr, Edith Cowan UniversityIt’s the smell that hits you first. The scent of urine and decomposing bodies. Then you notice other signs: scuttles and squeaks, small dead bodies leaking blood, tails sticking out of hubcaps.

If you’ve lived through a mouse plague, you’ve seen this, and smelled the stench of mice dying of poison baits.

As a desperate measure to help combat the mouse plague devastating rural communities across New South Wales, the state government yesterday secured 5,000 litres of bromadiolone. This is a bait that’s usually illegal to roll out at the proposed scale.

This is a bad idea. While bromadiolone effectively kills mice, it also travels up the food chain to poison predators who eat the mice, and other species. And these predators, from wedge-tailed eagles to goannas, are coming out in droves to feast on their abundant prey.

When your prey is everywhere

Animal plagues in Australia are fuelled by the “boom and bust” of rainfall.

We have natural, flood-driven population explosions of the native long-haired rat, with accompanying booms of letter-winged kites, their predator. We also have locust plagues when the conditions are right, leading to antechinus or mice plagues which eat the locusts.

Since at least the late 1800s, we’ve had terrible plagues of the introduced house mouse (Mus musculus). But rarely has it been this bad, with conditions currently seeming worse than the last plague in 2011, which caused over A$200 million in crop damage alone.

High numbers of birds of prey — nankeen kestrels, black-shouldered kites and barn owls — are often reported feasting on plague mice.

Snakes, goannas, native carnivores such as quolls, and feral cats and foxes, also take advantage of the abundant food. Pets, especially cats and some dogs, are highly likely to consume mice under these conditions, too.

Poisoning the food web

Laying out poison baits is one way people try to end mouse infestations and plagues. So-called “anticoagulant rodenticides” are divided into first and second generations, based on when they were first synthesised and the differences in potency.

Wedge-tailed eagle
Wedge-tailed eagles are among the predators that take advantage of the house mouse plague.
Shutterstock

Second generation anticoagulant rodenticides have higher toxicities than first generation, and are lethal after a single feed. First generation rodenticides, on the other hand, require rodents to feed on them for consecutive days to be lethal.

But mouse-eating predators are highly exposed to second generation rodenticides. For most animal species, the lethal doses of rodenticide aren’t yet known.

A scientific review from 2018 documented the poisoning of 31 bird, five mammal and one reptile species. Second generation aniticoaugulant rodenticides were implicated in the death of these animals.

Our research from 2020 found urban reptiles are highly exposed to second generation rodenticides, too. This includes mouse-eating snakes, called dugites, which had up to five different rodent poisons in them.

We also found poisons in frog-eating tiger snakes, and in omnivorous bobtail skinks which eat fruit, vegetation and snails. This is even more concerning because it shows how second generation rodenticides can saturate the entire foodweb, affecting everything from slugs to fish.

Bobtail skink
Bobtail skinks don’t eat poisoned mice, but they’ve still been found with poison in their systems.
Shutterstock

Bromadiolone is particularly dangerous, even to humans

The NSW government secured bromadiolone baits as part of its $50 million mouse plague support package for regional communities.

Five thousand litres of the poison can treat around 95 tonnes of grain, and the government will provide it for free to primary producers once federal authorities approve its use.

Bromadiolone is usually restricted to use in and around buildings. But given the widespread impacts on wildlife, using bromadiolone at the proposed scale will do more harm than good.

Past research on bromadiolone has shown residues persist for up to 135 days in the carcasses of voles (another rodent species). In international studies, bromadiolone has been found in the livers of a host of birds of prey, including a range of owl species, red kites, sparrowhawks and golden eagles.

Flock of chickens
Humans can be exposed, too, by eating the eggs of chickens that ate the mice.
Shutterstock

And it’s not just a problem for wildlife, humans are also at risk of exposure. For example, we can get exposed from eating eggs from chickens that feed on poisoned mice, or more directly from eating other animals that may have ingested poisoned mice.

A 2013 study looked at chicken eggs for human consumption, and detected bromadiolone in eggs between five and 14 days after the chicken ingested the poison. It’s not yet clear how many of these eggs we’d have to eat for us to get sick.

So what are the alternatives?

There are highly effective first generation rodenticides that provide viable solutions for managing mouse plagues. They may take a little longer to kill mice, but the upshot is they don’t stick around in the environment. A 2020 study found house mice in Perth didn’t have genetic resistance to first generation rodenticides, which suggests they’re effectively lethal.

Another approach has been to use zinc phosphide, a poison which is unlikely to secondarily poison other animals that eat the poisoned mice. However, zinc phosphide is still extremely toxic and will kill sheep, cows, pets and even humans if directly eaten.

Rolling out double-strength zinc phosphide may be the lesser of the evils in causing secondary poisoning, but only if used very carefully.

And another way to help control the mouse plague is to limit food resources for mice on farms. Farmers can minimise grain on ground, and Australia should invest in research for grain storage facilities that are less permeable to mice.

Mouse plagues are a regular cycle in Australia. Natural predators not only help create healthy, natural ecosystems, but also they help with mouse control. Second generation rodenticides will only destroy and weaken the predator populations we need to help us combat the next plague.The Conversation

Robert Davis, Senior Lecturer in Wildlife Ecology, Edith Cowan University; Bill Bateman, Associate professor, Curtin University; Damian Lettoof, PhD Candidate, Curtin University; Maggie J. Watson, Lecturer in Ornithology, Ecology, Conservation and Parasitology, Charles Sturt University, and Michael Lohr, Adjunct Lecturer, Edith Cowan University

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

Feral desert donkeys are digging wells, giving water to parched wildlife


Erick Lundgren, University of Technology Sydney; Arian Wallach, University of Technology Sydney, and Daniel Ramp, University of Technology SydneyIn the heart of the world’s deserts – some of the most expansive wild places left on Earth – roam herds of feral donkeys and horses. These are the descendants of a once-essential but now-obsolete labour force.

These wild animals are generally considered a threat to the natural environment, and have been the target of mass eradication and lethal control programs in Australia. However, as we show in a new research paper in Science, these animals do something amazing that has long been overlooked: they dig wells — or “ass holes”.

In fact, we found that ass holes in North America — where feral donkeys and horses are widespread — dramatically increased water availability in desert streams, particularly during the height of summer when temperatures reached near 50℃. At some sites, the wells were the only sources of water.

Feral donkeys and horses dig wells to desert groundwater.
Erick Lundgren

The wells didn’t just provide water for the donkeys and horses, but were also used by more than 57 other species, including numerous birds, other herbivores such as mule deer, and even mountain lions. (The lions are also predators of feral donkeys and horses.)

Incredibly, once the wells dried up some became nurseries for the germination and establishment of wetland trees.

Numerous species use equid wells. This includes mule deer (top left), scrub jays (middle left), javelina (bottom left), cottonwood trees (top right), and bobcats (bottom right).
Erick Lundgren

Ass holes in Australia

Our research didn’t evaluate the impact of donkey-dug wells in arid Australia. But Australia is home to most of the world’s feral donkeys, and it’s likely their wells support wildlife in similar ways.

Across the Kimberley in Western Australia, helicopter pilots regularly saw strings of wells in dry streambeds. However, these all but disappeared as mass shootings since the late 1970s have driven donkeys near local extinction. Only on Kachana Station, where the last of the Kimberley’s feral donkeys are protected, are these wells still to be found.

In Queensland, brumbies (feral horses) have been observed digging wells deeper than their own height to reach groundwater.

https://www.kachana-station.com/projects/wild-donkey-project/
Some of the last feral donkeys of the Kimberley.
Arian Wallach

Feral horses and donkeys are not alone in this ability to maintain water availability through well digging.

Other equids — including mountain zebras, Grevy’s zebras and the kulan — dig wells. African and Asian elephants dig wells, too. These wells provide resources for other animal species, including the near-threatened argali and the mysterious Gobi desert grizzly bear in Mongolia.

These animals, like most of the world’s remaining megafauna, are threatened by human hunting and habitat loss.

Other megafauna dig wells, too, including kulans in central Asia, and African elephants.
Petra Kaczensky, Richard Ruggiero

Digging wells has ancient origins

These declines are the modern continuation of an ancient pattern visible since humans left Africa during the late Pleistocene, beginning around 100,000 years ago. As our ancestors stepped foot on new lands, the largest animals disappeared, most likely from human hunting, with contributions from climate change.




Read more:
Giant marsupials once migrated across an Australian Ice Age landscape


If their modern relatives dig wells, we presume many of these extinct megafauna may have also dug wells. In Australia, for example, a pair of common wombats were recently documented digging a 4m-deep well, which was used by numerous species, such as wallabies, emus, goannas and various birds, during a severe drought. This means ancient giant wombats (Phascolonus gigas) may have dug wells across the arid interior, too.

Likewise, a diversity of equids and elephant-like proboscideans that once roamed other parts of world, may have dug wells like their surviving relatives.

Indeed, these animals have left riddles in the soils of the Earth, such as the preserved remnants of a 13,500-year-old, 2m-deep well in western North America, perhaps dug by a mammoth during an ancient drought, as a 2012 research paper proposes.




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Acting like long-lost megafauna

Feral equids are resurrecting this ancient way of life. While donkeys and horses were introduced to places like Australia, it’s clear they hold some curious resemblances to some of its great lost beasts.

Our previous research published in PNAS showed introduced megafauna actually make Australia overall more functionally similar to the ancient past, prior to widespread human-caused extinctions.

Donkeys share many similar traits with extinct giant wombats, who once may have dug wells in Australian drylands.
Illustration by Oscar Sanisidro

For example, donkeys and feral horses have trait combinations (including diet, body mass, and digestive systems) that mirror those of the giant wombat. This suggests — in addition to potentially restoring well-digging capacities to arid Australia — they may also influence vegetation in similar ways.

Water is a limited resource, made even scarcer by farming, mining, climate change, and other human activities. With deserts predicted to spread, feral animals may provide unexpected gifts of life in drying lands.

Feral donkeys, horses (mapped in blue), and other existing megafauna (mapped in red) may restore digging capacities to many drylands. Non-dryland areas are mapped in grey, and the projected expansion of drylands from climate change in yellow.
Erick Lundgren/Science, Author provided

Despite these ecological benefits in desert environments, feral animals have long been denied the care, curiosity and respect native species deservedly receive. Instead, these animals are targeted by culling programs for conservation and the meat industry.

However, there are signs of change. New fields such as compassionate conservation and multispecies justice are expanding conservation’s moral world, and challenging the idea that only native species matter.The Conversation

Erick Lundgren, PhD Student, Centre for Compassionate Conservation, University of Technology Sydney; Arian Wallach, Lecturer, Centre for Compassionate Conservation, University of Technology Sydney, and Daniel Ramp, Associate Professor and Director, Centre for Compassionate Conservation, University of Technology Sydney

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

Tiny Game of Thrones: the workers of yellow crazy ants can act like lazy wannabe queens. So we watched them fight


Wes Mountain/The Conversation, CC BY-ND

Pauline Lenancker, James Cook University and Lori Lach, James Cook UniversityThe invasive ant world is a competitive one, rife with territorial battles and colony raids. And yellow crazy ants (Anoplolepis gracilipes), one of the world’s worst invasive species, have an especially interesting trait: they’re the only invasive ant known to have workers who can reproduce.

Worker reproduction has big implications for a colony’s social dynamic. So we observed and experimented with more than 200 captive colonies of yellow crazy ants to understand what triggers worker reproduction and the potential costs and benefits for the colony.

We used a range of techniques, including removing queens and observing worker behaviour, and setting up ant gladiator rings to test how well reproductive workers fought other ants.

It wasn’t just for fun — learning about ants’ basic biology, including reproduction, may allow us to better understand their success and tailor management programs to help save the ecosystems they threaten.

Life in the queendom

Yellow crazy ants are thought to originate in southern or southeastern Asia but have spread across much of the Indo-Pacific, including several locations in Australia. They’re most well known for the cascade of ecological effects they’ve caused on Christmas Island by killing red land crabs and contributing to the damage, such as tree die-back, caused by scale insects.

Attempts to control or locally eradicate them are ongoing on Christmas Island, in Arnhem Land, and several locations in Queensland, including in and around the Wet Tropics World Heritage Area.

Yellow crazy ants, accidentally introduced by cargo ships, and subsequently multiplying to number in the billions, threaten the yearly crab migration on Christmas Island.

Like honey bees and wasps, yellow crazy ants are social insects. In these colonies, queens, workers and males all play distinct roles.

Queens and workers are all females. The queens reproduce, while the aptly named workers are the colony’s labourers, primarily responsible for bringing in food, caring for the queens’ offspring and defending the colony. The sole role of males is to mate with a queen before dying.

This elaborate task division is thought key to the success of social insects. However, in yellow crazy ant colonies, workers challenge the reproductive monopoly of the queen and produce males.

We could differentiate workers with active ovaries from regular workers by looking at their abdomen, which would be oversized as eggs take up space in the larger workers’ abdomen.

Five yellow crazy ants, four of which have large abdomens
In this picture, the worker ant on the far right has a regular-sized abdomen while the other workers have abdomen that looks swollen.
Dr Peter Yeeles, Author provided

When the queen was present, typically less than 20% of workers in our captive colonies had oversized abdomens. When we removed the queen, as much as half of the workers became oversized. We returned the queen after two months, and found the number of oversized workers decreased.

Our findings are consistent with the idea queens inhibit worker reproduction through pheromones, one of many chemical signals in ant colonies influencing ant worker behaviour and colony dynamics. Indeed, an ant queen’s failure to “smell” fertile may leave her subject to eviction or execution.

More lazy than crazy

So, did our yellow crazy ant queen wannabes behave more like workers or royalty? Our observations of oversized and normal workers revealed stark differences in behaviour.

Regular workers foraged during 85% of observations, whereas oversized workers were seen looking for food in only 5% of observations. Most of the time, oversized workers were immobile and remained sheltered inside their nests.

Three yellow crazy ants
Regular-sized workers are territorial and aggressive.
Peter Yeeles, Author provided

These oversized workers are slow to move when the nests are disturbed, not displaying the fast, erratic movement for which the species is named. Their behaviour was more similar to queens than workers.

Colony and resource defence is another important task for workers, as yellow crazy ant colonies often compete with native ants.

To test how these sluggish workers compare to normal workers in colony defence, we placed three oversized workers in one container, three regular workers in another, and paired each group with one gladiator, the charismatic green tree ant.

Green tree ants (Oecophylla smaragdina) are native and known for being very aggressive and territorial.

Our two videos show the typical response of oversized and regular workers.

In the first video, each encounter between a yellow crazy ant and green tree ant ends with the green tree ant rapidly retreating, often after having her legs bitten and pulled by the yellow crazy ant.

In the second video, you can see how oversized workers were more sedentary, less aggressive and less likely to start fighting with the green tree ant than normal workers in the first video. They were also less likely to kill their oppon-ant.

It seems oversized workers are lazy and would be ineffective at defending the colony. So why do they occur at all?

Like walking vending machines

Generally, ant colonies need workers to function and only the queen can produce this caste. In the ant world, the death of the queen signifies the death of the colony.

However, if the queen dies after laying eggs, including one destined to become a queen, then the virgin queen who eventually emerges can mate with a worker-produced male. This is important because males are unlikely to be present unless the colony is very large.

So while workers lack organs for receiving and storing sperm, their ability to produce males asexually may extend the life of the colony.

What’s more, oversized workers can produce sterile eggs as well, which serve as food for the queen and other colony members. We believe these workers may be like walking vending machines within the colony, providing food when conditions aren’t suitable for foraging.

A male yellow crazy ant with one female eye and one male eye.
A male yellow crazy ant with one female eye and one male eye.
Pauline Lenancker, Author provided

We also found males with mismatched eyes. These odd-looking individuals may possess a female eye on one side and a smaller male eye on the other side.

Such individuals are potentially sex mosaics, with male and female genes spread across their body in patches. Whether these individuals function as normal males is a question for further research.

What’s next?

Researchers don’t know the full story of yellow crazy ant reproduction, but it’s likely to be highly complex and potentially unique. Our study contributes to solving this mystery.

Eradication and control programs for yellow crazy ants will benefit from understanding their reproductive system and behaviour. It can shed light on how even a few workers and eggs — who may be inadvertently moved around by humans or persist after control treatment — could eventually build into large numbers.

Likewise, understanding foraging behaviour is useful for planning insecticidal baiting, because effective baiting relies on foraging ants bringing bait back to the colony to share with queens and larvae.

We have no doubt future genetic work and experiments will shed further light on the fascinating reproductive biology of yellow crazy ants.




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The Conversation


Pauline Lenancker, Research scientist, James Cook University and Lori Lach, Associate Professor, James Cook University

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

Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill


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Corey J. A. Bradshaw, Flinders University; Boris Leroy, Muséum national d’histoire naturelle (MNHN); Camille Bernery, Université Paris-Saclay; Christophe Diagne, Université Paris-Saclay, and Franck Courchamp, Université Paris-SaclayThey’re one of the most damaging environmental forces on Earth. They’ve colonised pretty much every place humans have set foot on the planet. Yet you might not even know they exist.

We’re talking about alien species. Not little green extraterrestrials, but invasive plants and animals not native to an ecosystem and which become pests. They might be plants from South America, starfish from Africa, insects from Europe or birds from Asia.

These species can threaten the health of plants and animals, including humans. And they cause huge economic harm. Our research, recently published in the journal Nature, puts a figure on that damage. We found that globally, invasive species cost US$1.3 trillion (A$1.7 trillion) in money lost or spent between 1970 and 2017.

The cost is increasing exponentially over time. And troublingly, most of the cost relates to the damage and losses invasive species cause. Meanwhile, far cheaper control and prevention measures are often ignored.

Yellow crazy ants attacking a gecko
Yellow crazy ants, such as these attacking a gecko, are among thousands of invasive species causing ecological and economic havoc.
Dinakarr, CC0, Wikimedia Commons

An expansive toll

Invasive species have been invading foreign territories for centuries. They hail from habitats as diverse as tropical forests, dry savannas, temperate lakes and cold oceans.

They arrived because we brought them — as pets, ornamental plants or as stowaways on our holidays or via commercial trade.

The problems they cause can be:

  • ecological, such as causing the extinction of native species
  • human health-related, such as causing allergies and spreading disease
  • economic, such as reducing crop yields or destroying human-built infrastructure.

In Australia, invasive species are one of our most serious environmental problems – and the biggest cause of extinctions.

Feral animals such as rabbits, goats, cattle, pigs and horses can degrade grazing areas and compact soil, damaging farm production. Feral rabbits take over the burrows of native animals, while feral cats and foxes hunt and kill native animals.




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Invasive species are Australia’s number-one extinction threat


Wetlands in the Northern Territory damaged by invasive swamp buffalo (Bubalus bubalis)
Warren White

Introduced insects, such as yellow crazy ants on Christmas Island, pose a serious threat to a native species. Across Australia, feral honeybees compete with native animals for nectar, pollen and habitat.

Invasive fish compete with native species, disturb aquatic vegetation and introduce disease. Some, such as plague minnows, prey on the eggs and tadpoles of frogs and attack native fish.

Environmental weeds and invasive fungi and parasites also cause major damage.

Of course, the problem is global – and examples abound. In Africa’s Lake Victoria, the huge, carnivorous Nile perch — introduced to boost fisheries – has wiped out more than 200 of the 300 known species of cichlid fish — prized by aquarium enthusiasts the world over.

And in the Florida Everglades, thousands of five metre-long Burmese pythons have gobbled up small, native mammals at alarming rates.




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Invasive predators are eating the world’s animals to extinction – and the worst is close to home


cichlid fish
In Africa, numbers of the beautiful cichlid fish have been decimated by Nile perch.
Shutterstock

Money talks

Despite the serious threat biological invasions pose, the problem receives little political, media or public attention.

Our research sought to reframe the problem of invasive species in terms of economic cost. But this was not an easy task.

The costs are diverse and not easily compared. Our analysis involved thousands of cost estimates, compiled and analysed over several years in our still-growing InvaCost database. Economists and ecologists helped fine-tune the data.

The results were staggering. We discovered invasive species have cost the world US$1.3 trillion (A$1.7 trillion) lost or spent between 1970 and 2017. The cost largely involves damages and losses; the cost of preventing or controlling the invasions were ten to 100 times lower.

Clearly, getting on top of control and prevention would have helped avoid the massive damage bill.




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Average costs have been increasing exponentially over time — trebling each decade since 1970. For 2017 alone, the estimated cost of invasive species was more than US$163 billion. That’s more than 20 times higher than the combined budgets of the World Health Organisation and the United Nations in the same year.

Perhaps more alarming, this massive cost is a conservative estimate and likely represents only the tip of the iceberg, for several reasons:

  • we analysed only the most robust available data; had we included all published data, the cost figure would have been 33 times higher for the estimate in 2017
  • some damage caused by invasive species cannot be measured in dollars, such as carbon uptake and the loss of ecosystem services such as pollination
  • most of the impacts have not been properly estimated
  • most countries have little to no relevant data.
A bucket by a lake with a sign reading 'Biosecurity station. Please dip your feet and nets'
Prevention strategies, such as biosecurity controls, are a relatively cheap way to deal with invasive species.
Shutterstock

Prevention is better than cure

National regulations for dealing with invasive species are patently insufficient. And because alien species do not respect borders, the problem also requires a global approach.

International cooperation must include financial assistance for developing countries where invasions are expected to increase substantially in the coming decades, and where regulations and management are most lacking.

Proactive measures to prevent invasion must become a priority. As the old saying goes, an ounce of prevention is better than a pound of cure. And this must happen early – if we miss the start of an invasion, control in many cases is impossible.

More and better research on the economic costs of biological invasions is essential. Our current knowledge is fragmented, hampering our understanding of patterns and trends, and our capacity to manage the problem efficiently.

We hope quantifying the economic impacts of invasive species will mean political leaders start to take notice. Certainly, confirmation of a A$1.7 trillion bill should be enough to get the ball rolling.




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The Conversation


Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University; Boris Leroy, Maître de conférences en écologie et biogéographie, Muséum national d’histoire naturelle (MNHN); Camille Bernery, Doctorante en écologie des invasions, Université Paris-Saclay; Christophe Diagne, Chercheur post-doctorant en écologie des invasions, Université Paris-Saclay, and Franck Courchamp, Directeur de recherche CNRS, Université Paris-Saclay

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

Victoria’s new feral horse plan could actually protect the high country. NSW’s method remains cruel and ineffective


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Don Driscoll, Deakin UniversityFeral horses are a catastrophic problem for the environment, particularly in the high country that crosses the New South Wales and Victoria border. To deal with this growing issue, the Victorian government has released a draft feral horse action plan, which is open for comment until April 23.

It comes after Victoria’s old action plan from 2018 proved ineffective, with feral horse numbers increasing in the most recent counts in 2019. This is similar to New South Wales’ current performance, where feral horses are legally protected and numbers are essentially unmanaged.

This new Victorian plan has flaws, but it’s still likely to perform better than the old plan (and the very low benchmark set by NSW), as it generally aims to deploy evidence-based management of national parks.

As Victoria gets on top of its feral horse problem, NSW will be left further behind with a degrading environment and rising costs of horse management.

The feral horse threat

Feral horses degrade ecosystems and threaten native Australian species with their heavy trampling and excessive grazing. They damage waterways and streamside vegetation which, in turn, threatens species that live in and alongside the streams, such as the alpine spiny crayfish, the alpine water skink and the Tooarrana broad-toothed rat. All of these are threatened species.

Damage from feral horses could worsen as ecosystems recover from the extensive 2019-20 eastern Australian bushfires. Horse grazing could delay animals’ habitat recovery and horse trampling could exacerbate stream degradation after fires.

In fact, there are 24 species that need protection from feral horses after the fires, as identified by the Australian government’s wildlife and threatened species bushfire recovery expert panel in September.

All of this ecosystem destruction translates into substantial economic costs. Frontier Economics released a report in January this year showing the potential benefits of horse control in Kosciuszko National Park was A$19-50 million per year. The benefits accrue through improved recreational opportunities, improved water quality and reduced car crashes involving feral horses.

In contrast, horse control could cost as little as A$1 million per year and up to $71 million, depending on the methods used. Frontier Economics concluded the costs that are incurred by keeping feral horses far outweigh the cost of eradication.

Alpine water skink
Alpine water skinks are among the vulnerable native species threatened by feral horses.
DEPI/Flickr, CC BY-SA

Victoria’s new feral horse plan

The draft Victorian feral horse action plan aims to:

  1. remove isolated populations on the Bogong High Plains within three years and prevent new populations from establishing
  2. contain and reduce feral horses in the eastern Alps by removing 500 horses in the first year
  3. use the most humane, safe and effective horse control methods.

The first aim makes complete sense. Removing small populations will always be more humane, cheaper and better for the environment than leaving them uncontrolled.

The second aim is perplexing. Based on 2019 surveys, the draft action plan says there are approximately 5,000 horses in the eastern Alps and the population is growing at 15% per year. If the government continues to remove 500 horses per year after the first year, it could see the population rise to more than 9,000 over ten years, despite culling 5,000 horses in that time.




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In contrast, removing 2,000 horses per year could see the population controlled within three years. Reducing horse numbers rapidly results in the fewest horses having to be culled in the long term.

The third aim of the Victorian draft action plan gives appropriate and strong emphasis to animal welfare. Controlling horse numbers can be morally challenging, and requires a clear understanding of the trade-offs.

Without horse control, native animals are killed when their habitat is destroyed, unique Australian ecosystems are degraded, horses themselves starve or die of thirst in droughts, and the economic costs of inaction escalate. To avoid these costs, horse numbers must be reduced by culling.

This is the grim reality, but with careful attention to animal welfare, the draft strategy will ensure horse control is managed humanely, with control methods based on evidence rather than hyperbole.

Money wasting in NSW

Victoria’s plan is in stark contrast to the NSW government’s approach. In 2018, the NSW government passed the so-called “brumby bill”, which protects feral horses in Kosciuszko National Park.




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The current method of control in NSW is to capture the horses and transport them to an abattoir if they cannot be re-homed. But evidence shows culling has fewer animal welfare concerns than this method.

And in the latest round of money-wasting horse management, the NSW government trapped 574 horses over the past year, but released 192 females and foals back into the park. If the program is aimed at reducing horse numbers, releasing the most fertile animals back into the population is counter-productive.

Regenerating plants and burnt trees in fire-damaged alpine region
Feral horses are exacerbating the damage from recent bushfires in the High Country.
Shutterstock

What’s more, removing 300-400 horses per year has little impact on overall numbers. There are around 14,000 horses in Kosciuszko National Park, with a growth rate of 23% per year. This means more than 3,000 horses must be removed just to prevent the population from getting bigger.

The high country without feral horses

If the Victorian draft plan can be improved to invest in rapid horse reduction and ecosystem restoration, we can expect to see quagmires created by trampling horses return to functioning ecosystems and the recovery of threatened species.

Stream banks can be stabilised and then dense grass tussocks and sedges will return, creating homes for threatened skinks, crayfish and the Tooarrana broad-toothed rat.

While Kosciuszko’s alpine ecosystems continue to decline under the NSW government’s political impasse, the Victorian Alps will become the favoured destination for tourists who want to see Australia’s nature thriving when they visit national parks.




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The Conversation


Don Driscoll, Professor in Terrestrial Ecology, Deakin University

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

Australia must control its killer cat problem. A major new report explains how, but doesn’t go far enough


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Sarah Legge, Australian National University; Chris Dickman, University of Sydney; Jaana Dielenberg, Charles Darwin University; John Woinarski, Charles Darwin University, and Tida Nou, The University of Queensland

Australia is teeming with cats. While cats make great pets, and can bring owners emotional, psychological and health benefits, the animals are a scourge on native wildlife.

Cats kill a staggering 1.7 billion native animals each year, and have played a major role in most of Australia’s 34 mammal extinctions. They continue to pose an extinction threat to at least another 120 species.

Long-nosed potoroo
The long-nosed potoroo is extremely vulnerable to cats.
Shutterstock

A recent parliamentary inquiry into the problem of feral and pet cats in Australia has affirmed the issue is indeed of national significance. The final report, released last week, calls for a heightened, more effective, multi-pronged and coordinated policy, management and research response.

As ecologists, we’ve collectively spent more than 50 years researching Australia’s cat dilemma. We welcome most of the report’s recommendations, but in some areas it doesn’t go far enough, missing major opportunities to make a difference.

Night curfews aren’t good enough

The report recommends Australia’s 3.8 million pet cats be subject to night-time curfews. This measure would benefit native nocturnal mammals, but won’t save birds and reptiles, which are primarily active during the day.


Wes Mountain/The Conversation, CC BY-ND

Pet cats kill 83 million native reptiles and 80 million native birds in Australia each year. From a wildlife perspective, keeping pet cats contained 24/7 is the only responsible option.

It’s clearly possible: one third of Australian pet cat owners already keep their pets contained all the time.

Stopping pet cats from roaming is also good for the cats, which live longer, safer lives when kept exclusively indoors. It would also substantially reduce the number of people falling ill from cat-dependent diseases each year.




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Other strategies for improving pet cat management proposed in the report include pet cat registration, subsidised programs for early age desexing, public education campaigns to promote responsible pet cat ownership, and improving the consistency of rules and legislation nationally.

Cat on a windowsill
Indoor cats live longer than cats allowed to roam.
Jaana Dielenberg

The report is also unambiguously opposed to “trap-neuter-release” programs, in which un-owned cats in urban areas are desexed and then released. We agree with this finding, as these programs aren’t effective at reducing the population of stray cats, nor preventing those cats from killing wildlife and spreading disease.

We need more wildlife havens

One of the inquiry’s flagship recommendations is a national conservation project dubbed “Project Noah”. This would involve an ambitious expansion of Australia’s existing network of reserves free from introduced predators, both on islands and in mainland fenced areas. The reserves provide havens — or a fleet of “arks” — for vulnerable native wildlife.

This measure is vital. 2019 research found Australia has more than 65 native mammal species and subspecies that can’t persist, or struggle to persist, in places with even very low numbers of cats or foxes. This includes the bilby, numbat, quokka, dibbler and black-footed rock wallaby.

Boodie
Boodies used to occur across two-thirds of Australia, but now only exist within havens.
McGregor/Arid Recovery

Australia already has more than 125 havens, 100 of which are islands. These have prevented 13 mammal species from going extinct, such as boodies and greater stick-nest rats. In total, these havens have protected populations of 40 mammal species susceptible to cats and foxes.

This is a good start, but we need more investment in havens to prevent extinctions. More than 25 species are highly sensitive to cat and fox predation, but aren’t yet protected in the haven network. This includes the central rock-rat, which is more likely than not to become extinct within 20 years without new action.

What’s more, some species, such as the long-nosed potoroo, exist in just one haven. To avoid issues such as inbreeding and to ensure disasters like a fire at any single haven don’t take out an entire species, each species should be represented across several havens, in reasonable population sizes.

The report didn’t specify how the havens network should be expanded. But 2019 research found to get each species needing protection into at least three havens, Australia requires at least 35 new, strategically located islands or mainland fenced areas.

Fence with scenic hills behind
The predator proof fence at the Australian Wildlife Conservancy’s Newhaven Sanctuary, one of the largest cat- and fox-free havens on mainland Australia.
Australian Wildlife Conservancy

What about the rest of the country?

Havens cover less than 1% of Australia. So what we do in the other 99% of the landscape — including across conservation reserves like national parks — is vital.

Yet the parliamentary inquiry report lacks clear recommendations to expand cat control more broadly, including at important conservation sites such as in Kakadu National Park.

The impact of roaming pet cats on Australian wildlife.

The report reaffirms the need to cull feral cats, and to set new targets for culling, without specifying what those targets are. We agree some culling is important, especially at sites with very vulnerable threatened wildlife.

But in many parts of Australia, broad-scale habitat management is a more cost-effective way to reduce cat harm. This involves making habitat less suitable for cats and more suitable for native wildlife, for example, by reducing rabbit numbers, fire frequency and grazing by feral herbivores such as cattle and horses.

Research has shown fewer rabbits leads to fewer cats. Rabbits are a favoured prey of many cats, so they boost feral cat numbers, which then also hunt native wildlife.




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One cat, one year, 110 native animals: lock up your pet, it’s a killing machine


And cats gravitate to areas with less vegetation because it’s easier to catch prey. These areas include those with frequent fires, or where feral herbivores have reduced vegetation through grazing and trampling.

Better habitat with more vegetation gives native animals places to hide from predators, and more food and shelter. It’s a bit like giving the last little pig a house of bricks instead of trying to fist-fight the wolf.

Feral horses, such as these in Kakadu National Park, eat and damage vegetation making conditions more favourable for cats to hunt.
Jaana Dielenberg

A major step forward

Over the past two decades, Australia has slowly woken up to the damage cats cause to nature. This has led to more research, management and policy to address the problem.

Some state governments, environment groups and scientists have worked hard to develop feral cat control options, and the 2015 Australian Threatened Species Strategy did much to focus national attention and resourcing to the issue.




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Don’t let them out: 15 ways to keep your indoor cat happy


The parliamentary inquiry is a major step forward, and many recommendations are sound. But overall, its recommendations call for incremental improvement.

Australia’s laws clearly fail to provide a safety net for wildlife. The cat issue is part of a larger problem with how we manage habitat, biodiversity and threats to nature – and fixing that requires wholesale change.The Conversation

Sarah Legge, Professor, Australian National University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Jaana Dielenberg, University Fellow, Charles Darwin University; John Woinarski, Professor (conservation biology), Charles Darwin University, and Tida Nou, Project officer, The University of Queensland

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