The story of Rum Jungle: a Cold War-era uranium mine that’s spewed acid into the environment for decades

Gavin Mudd, Author provided

Gavin Mudd, RMIT UniversityBuried in last week’s budget was money for rehabilitating the Rum Jungle uranium mine near Darwin. The exact sum was not disclosed.

Rum Jungle used to be a household name. It was Australia’s first large-scale uranium mine and supplied the US and British nuclear weapons programs during the Cold War.

Today, the mine is better known for extensively polluting the Finniss River after it closed in 1971. Despite a major rehabilitation project by the Commonwealth in the 1980s, the damage to the local environment is ongoing.

I first visited Rum Jungle in 2004, and it was a colourful mess, to say the least. Over later years, I saw it worsen. Instead of a river bed, there were salt crusts containing heavy metals and radioactive material. Pools of water were rich reds and aqua greens — hallmarks of water pollution. Healthy aquatic species were nowhere to be found, like an ecological desert.

The government’s second rehabilitation attempt is significant, as it recognises mine rehabilitation isn’t always successful, even if it appears so at first.

Rum Jungle serves as a warning: rehabilitation shouldn’t be an afterthought, but carefully planned, invested in and monitored for many, many years. Otherwise, as we’ve seen, it’ll be left up to future taxpayers to fix.

The quick and dirty history

Rum Jungle produced uranium from 1954 to 1971, roughly one-third of which was exported for nuclear weapons. The rest was stockpiled, and then eventually sold in 1994 to the US.

Rehabilitation of Rum Jungle began in the 1980s.
Mick Stanic/Flickr, CC BY-NC-SA

The mine was owned by the federal government, but was operated under contract by a former subsidiary of Rio Tinto. Back then, there were no meaningful environmental regulations in place for mining, especially for a military project.

The waste rock and tailings (processed ore) at Rum Jungle contains significant amounts of iron sulfide, called “pyrite”. When mining exposes the pyrite to water and oxygen, a chemical reaction occurs generating so-called “acidic mine drainage”. This drainage is rich in acid, salts, heavy metals and radioactive material (radionuclides), such as copper, zinc and uranium.

Acid drainage seeping from waste rock, plus acidic liquid waste from the process plant, caused fish and macroinvertebrates (bugs, worms, crustaceans) to die out, and riverbank vegetation to decline. By the time the mine closed in 1971, the region was a well-known ecological wasteland.

Once an ecosystem, now a wasteland.
Gavin Mudd, Author provided

When mines close, the modern approach is to rehabilitate them to an acceptable condition, with the aim of minimal ongoing environmental damage. But after working in environmental engineering across Australia for 26 years, I’ve seen few mines completely rehabilitated — let alone successfully.

Many Australian mines have major problems with acid mine drainage. This includes legacy mines from historical, unregulated times (Mount Morgan, Captains Flat, Mount Lyell) and modern mines built under stricter environmental requirements (Mount Todd, Redbank, McArthur River).

This is why Rum Jungle is so important: it was one of the very few mines once thought to have been rehabilitated successfully.

Salts litter the bed of the Finniss River.
Gavin Mudd, Author provided

So what went wrong?

From 1983 to 1986, the government spent some A$18.6 million (about $55.5 million in 2020 value) to reduce acid drainage and restore the Finniss River ecology. Specially engineered soil covers were placed over the waste rock to reduce water and oxygen getting into the pyrite.

The engineering project was widely promoted as successful through conferences and academic studies, with water quality monitoring showing that the metals polluting the Finniss had substantially subsided. But this lasted only for a decade.

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Expensive, dirty and dangerous: why we must fight miners’ push to fast-track uranium mines

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By the late 1990s, it became clear the engineered soil covers weren’t working effectively anymore.

First, the design was insufficient to reduce infiltration of water during the wet season (thicker covers should have been used). Second, the covers weren’t built to design in parts (they were thinner and with the wrong type of soils).

The first reason is understandable, we’d never done this before. But the second is not acceptable, as the thinner covers and wrong soils made it easier for water and oxygen to get into the waste rock and generate more polluting acid mine drainage.

The iron-tainted red hues of the Finniss River near the waste rock dumps leaking acid mine drainage.
Gavin Mudd, Author provided

The copper-tainted green hues of the Finniss River near the waste rock dumps leaking acid mine drainage.
Gavin Mudd, Author provided

The stakes are higher

There are literally thousands of recent and still-operating mines around Australia, where acid mine drainage remains a minor or extreme risk. Other, now closed, acid drainage sites have taken decades to bring under control, such as Brukunga in South Australia, Captain’s Flat in NSW, and Agricola in Queensland.

We got it wrong with Rum Jungle, which generated less than 20 million tonnes of mine waste. Modern mines, such as Mount Whaleback in the Pilbara, now involve billions of tonnes — and we have dozens of them. Getting even a small part of modern mine rehabilitation wrong could, at worst, mean billions of tonnes of mine waste polluting for centuries.

So what’s the alternative? Let’s take the former Woodcutters lead-zinc mine, which operated from 1985 to 1999, as an example.

Given its acid drainage risks, the mine’s rehabilitation involved placing reactive waste into the open pit, rather than using soil covers. “Backfilling” such wastes into pits makes good sense, as the pyrite is deeper and not exposed to oxygen, substantially reducing acid drainage risks.

Backfilling isn’t commonly used because it’s widely perceived in the industry as expensive. Clearly, we need to better assess rehabilitation costs and benefits to justify long-term options, steering clear of short-term, lowest-cost approaches.

The Woodcutters experience shows such thinking can be done to improve the chances for successfully restoring the environment.

Getting it right

The federal government funded major environmental studies of the Rum Jungle mine from 2009, including an environmental impact statement in 2020, before the commitment in this year’s federal budget.

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It’s not worth wiping out a species for the Yeelirrie uranium mine

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The plan this time includes backfilling waste rock into the open pits, and engineering much more sophisticated soil covers. It will need to be monitored for decades.

And the cost of it? Well, that was kept confidential in the budget due to sensitive commercial negotiations.

But based on my experiences, I reckon they’d be lucky to get any change from half a billion dollars. Let’s hope we get it right this time.

Gavin Mudd, Associate Professor of Environmental Engineering, RMIT University

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

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Australia: Kakadu Crisis

Burnt ancient nutshells reveal the story of climate change at Kakadu — now drier than ever before

S. Anna Florin., Author provided

S. Anna Florin, University of Wollongong; Andrew Fairbairn, The University of Queensland; Chris Clarkson, The University of Queensland; James Shulmeister, University of Canterbury; Nicholas R Patton, University of Canterbury, and Patrick Roberts, Max Planck Institute for the Science of Human History

Archaeological research provides a long-term perspective on how humans survived various environmental conditions over tens of thousands of years.

In a paper published today in Nature Ecology and Evolution, we’ve tracked rainfall in northern Australia’s Kakadu region over the past 65,000 years. We wanted to know how major changes in rainfall may have affected the region’s Aboriginal communities through time.

Our findings suggest the Kakadu region wasn’t as prone to dry spells as surrounding areas — and it likely functioned as a place of refuge for early Australians as they struggled through harsh and arid conditions.

Learning lessons from leftovers

To generate a rainfall record spanning 65,000 years, we used ancient food waste left behind by the First Australians living at Madjedbebe, a rock shelter on Mirarr country in the Kakadu region.

This site boasts the earliest known evidence of humans living in Australia. It also boasts plenty of Pandanus spiralis, a native plant commonly called “pandanus” or “screw pine”.

This plant, known as “anyakngarra” to the Mirarr people — the Traditional Owners of Madjedbebe — is very important to them.

Anyakngarra (Pandanus spiralis) fruit. The tree is native to northern Australia and ubiquitous around the Top End’s waterholes and floodplains.
Author provided

Its leaves are used for weaving, its trunk to create dye, its fruit flesh is used in a drink and its nuts (the seed kernels within the fruit) are consumed as a rich source of fat and protein.

Anyakngarra’s nuts were also eaten by the First Australians 65,000 years ago. Discarded nut shells have been preserved as burned fragments, disposed of in fireplaces over time.

These small remnants have proven hugely useful for our research team, which includes archaeologists, environmental scientists and Traditional Owners.

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65,000-year-old plant remains show the earliest Australians spent plenty of time cooking

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In a nutshell

By analysing the isotopic composition in ancient anyakngarra nutshells, we could track rainfall at Madjedbebe. Specifically, we detected how much water (and therefore rainfall) was available to anyakngarra plants in the past.

This analysis is possible due to photosynthesis – the process by which plants convert carbon dioxide in the air into sugars. Anyakngarra plants absorb two isotopes of carbon from the atmosphere: ¹²C and ¹³C. Isotopes are different types of atoms within a chemical element that have the same number of protons but a different number of neutrons. Chemically, the isotopes of carbon are the same, but each has a different atomic “weight”.

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Explainer: what is an isotope?

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When environmental conditions are favourable, an anyakngarra plant will preferentially absorb more ¹²C than ¹³C. But if a plant is stressed by its environment, such as when it’s waterlogged due to seasonal flooding, it begins to absorb more ¹³C.

The isotopic composition (the ratio of ¹²C to ¹³C) is recorded in the sugars used by the plant for new tissue growth, including for the seasonal growth of nuts.

A higher proportion of ¹³C in a nutshell indicates that the plant it came from was waterlogged during its growth season. From this, we can conclude it likely experienced higher levels of rainfall.

Pictured is the anyakngarra fruit, which has a fleshy section (now dried and fibrous) a hard nutshell and multiple white seeds (or nuts) inside.
Author provided

Like an oasis in a desert

Over the past 72,000 years, humans have lived through an ice age in which there were two particularly cold periods called “stadials”. During stadials, glaciers extended to cover parts of North America, northern Europe, northern Asia and Patagonia (in South America).

The height of the second stadial in this ice age was called the Last Glacial Maximum. While this occurred 22,000 to 18,000 years ago, intense cold and dry conditions in Australia started as early as 30,000 years ago.

During this time, water availability was the main challenge in arid northern Australia (rather than low temperatures). The country’s arid zone expanded dramatically and parts of central Australia may have been temporarily abandoned by Aboriginal people.

Yet the “palaeoclimatic” record we generated for Madjedbebe indicates that, although glacial stages did lead to less rainfall, the Kakadu region remained relatively well-watered during these periods.

Our records show that for as long as people have been around, rainfall at Madjedbebe is unlikely to have dropped below current levels. Thus, this area would have helped early Australians survive during long dry spells and may have also attracted others from surrounding areas.

This is our research site, the Madjedbebe rock shelter in the Alligator Rivers region of the Northern Territory.
Dominic O’Brien/Gundjeihmi Aboriginal Corporation, Author provided

Changing with the seasons

Our findings are supported by other archaeological evidence from Madjedbebe. For instance, our research has revealed more stone tools were left at this site during the glacial periods. This implies more people gathered there at these times.

Also, because the Kakadu region was still drier during glacial periods as compared to inter-glacial periods, people had to travel further for food and other important resources.

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Read more:
Buried tools and pigments tell a new history of humans in Australia for 65,000 years

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This is supported by evidence of an increased number of tools being brought to the site from further away. This points to increased mobility and new social arrangements being made as people adjusted to life in a harsher environment.

The challenge moving forward

Notably, over the past 65,000 years the driest time in the Kakadu region was not during the Last Glacial Maximum. It is today.

Rather than being the result of less rainfall occurring, this is likely due to higher evaporation caused by warmer inter-glacial temperatures. Aboriginal communities currently living in the Kakadu region are experiencing unprecedented aridity.

These difficult conditions are exacerbated by the threat of invasive plants and animals and disruption to cultural practices of landscape management, such as vegetation burning.

While the people of Kakadu have spent thousands of years adapting to environmental change, the scale and intensity of today’s anthropogenic impacts on regional climates and local landscapes poses an altogether different challenge.

S. Anna Florin, Research fellow, University of Wollongong; Andrew Fairbairn, Professor of Archaeology, The University of Queensland; Chris Clarkson, Professor in Archaeology, The University of Queensland; James Shulmeister, Professor, School of Earth and Environmental Sciences, University of Canterbury; Nicholas R Patton, Ph.D. Candidate, University of Canterbury, and Patrick Roberts, Research Group Leader, Max Planck Institute for the Science of Human History

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

Kakadu National Park Threatened by Rising Sea Levels

Humpback whales have been spotted in a Kakadu river. So in a fight with a crocodile, who would win?

Northern Territory Government

Vanessa Pirotta, Macquarie University

In recent months, three humpback whales were spotted in the East Alligator River in the Northern Territory’s Kakadu National Park. Contrary to its name, the river is full of not alligators but crocodiles. And its shallow waters are no place for a whale the size of a bus.

It was the first time humpback whales had been recorded in the river, and the story made international headlines. In recent days, one whale was spotted near the mouth of the river and scientists are watching it closely.

The whales’ strange detour threw up many questions. How did they end up in the river? What would they eat? Would they get stuck on the muddy river bank?

And of course, there was one big question I was repeatedly asked: in an encounter between a crocodile and a humpback whale, which animal would win?

The whales swam into a crocodile-infested river.
Dean Lewins/AAP

Scientists double-take

The humpback whales were first spotted in September this year by marine ecologist Jason Fowler and fellow scientists, during a fishing trip. Fowler told the ABC:

I noticed a big spout, a big blow on the horizon and I thought that’s a big dolphin … We were madly arguing with each other about what we were actually seeing. After four hours of raging debate we agreed we were looking at humpback whales in a river.

The whales had swum about 20 kilometres upstream. Fowler photographed the humpback whales’ dorsal fins as evidence, and reported the unusual sighting to authorities and scientists.

Thankfully, two whales returned to sea on their own, leaving just one in need of help. There was concern it might become stranded in the shallow, murky tidal waters. If this happened, it might be attacked by crocodiles – more on this in a minute.

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Experts considered a variety of tactics to encourage the whale back out to sea. These included physical barriers such as nets or boats, and playing the sounds of killer whales – known predators of humpback whales.

But none of these these options was needed. After 17 days, the last whale swam back to sea on its own.

The whale that spent two weeks in the river has recently returned and been spotted swimming around the mouth of the river. It appears to have lost weight – most likely the result of migration. It is now being monitored nearby in Van Diemen Gulf.

Questions are now being raised about the health of the animal, and why it has not headed south for Antarctic feedings waters.

A humpback whale that spent two weeks in the East Alligator River has recently been spotted nearby.
Dr Carol Palmer

So why were whales in the river?

The whales are part of Australia’s west coast humpback whale population, which each year travels from cold feeding waters off Antarctica to warm waters in the Kimberley to breed.

There are various theories as to why they swam into the East Alligator River. Humpback whales are extremely curious, and may have entered the river to explore the area.

Alternatively, they may have made a navigation error – also the possible reason behind September’s mass stranding of pilot whales in Tasmania.

And the big question – what about the crocs?

Long-term, a humpback whale’s chances of surviving in the East Alligator River are slim. The lower salinity level may cause them skin problems, and they may become stranded in the shallow waters – unable to move off the muddy bank. Here the animal might die from overheating, or its organs may be crushed by the weight of its body. Or, of course, the whale may be attacked by crocodiles.

In this case, my bet would be on the whale – if it was in relatively good condition and could swim well. Humpback whales are incredible powerful creatures. One flick of their large tail would often be enough to send a crocodile away.

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If a croc bit a whale, their teeth would likely penetrate the whale’s skin and thick blubber. But it would take a lot more to do serious harm. Whale skin has been shown to heal after traumatic events, including the case of a humpback whale cut by a boat propeller in Sydney 20 years ago. Dubbed Bladerunner, it survived but still bears deep scars.

Humpback whales are very large and powerful. One flick of their tail could send a crocodile away.
Dr Vanessa Pirotta

What next?

The whale sighting continues to fascinate experts. Scientists are hoping to take poo samples from the whale in Van Diemen Gulf, and could also collect whale snot to learn more about its health. However, the best case scenario would be to see the whale swim willingly to offshore waters.

This unusual tale will no doubt go down in Australian whale history. If nothing else, it reminds us of the vulnerability – and resilience – of these marine giants.

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The author would like to thank Northern Territory Government whale expert Dr Carol Palmer for her assistance with this article.

Vanessa Pirotta, Wildlife scientist, Macquarie University

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

Introducing the Maliwawa Figures: a previously undescribed rock art style found in Western Arnhem Land

A Maliwawa macropod found in the Namunidjbuk clan estate of the Wellington Range.
P. Taçon

Paul S.C.Taçon, Griffith University and Sally K. May, Griffith University

Western Arnhem Land, Northern Territory, has a remarkable range and number of rock art sites, rivalling that of Europe, southern Africa and various parts of Asia. Several thousand sites have been documented and each year new discoveries are made by various research teams working closely with local Aboriginal communities.

Today, in the journal Australian Archaeology, we and colleagues introduce an important previously undescribed rock art style. Consisting of large human figures and animals, the style is primarily found in northwest Arnhem Land, and has been named Maliwawa Figures by senior Traditional Owner Ronald Lamilami.

Infographic summarising some of the main features of Maliwawa rock art .
Infographic: P. Taçon; digital tracing: Fiona Brady

We recorded 572 Maliwawa paintings at 87 rock shelters over a 130-kilometre east-west distance, from Awunbarna (Mount Borradaile) to the Namunidjbuk clan estate of the Wellington Range, a region home to unique and internationally significant rock art of various types.

Maliwawa Figures consist of red to mulberry naturalistic human and animal forms shaded with stroked lines. Occasionally they are in outline with just a few strokes within. Almost all were painted but there is one drawing.

The figures are often large (over 50 cm high), sometimes life-size, although there are also some small ones (20–50 cm in height). Various lines of evidence suggest the figures most likely date to between 6,000 to 9,400 years of age.

Map of Kakadu/Arnhem Land showing the general location of the Awunbarna and Namunidjbuk areas.
Produced by A. Jalandoni; base map by Stamen Design [OpenStreetMap].

Animal-human relationships

In the Maliwawa paintings, human figures are frequently depicted with animals, especially macropods (kangaroos and wallabies), and these animal-human relationships appear to be central to the artists’ message. In some instances, animals almost appear to be participating in or watching some human activity.

Another key theme is a male or indeterminate human figure holding an animal, often a snake, or another human figure or an object.

Such scenes are rare in early rock art, not just in Australia but worldwide. They provide a remarkable glimpse into past Aboriginal life and cultural beliefs.

Scene of two male Maliwawas with ball headdresses reaching down to a shorter indeterminate human figure with a snake behind the male on the right and behind the left male a female and a macropod, Namunidjbuk. An indeterminate human figure with a cone and feather headdress is above.
P Tacon

Maliwawa animals are usually in profile. Some macropods are shown in a human-like sitting pose with paws in front, resembling a person playing a piano. Depictions of animal tracks (footprints) and geometric designs are rare.

Macropods, birds, snakes and longtom fish are the most frequent animal subjects, comprising three quarters of total fauna. But, more generally, mammals are most common.

There are seven depictions of animals long extinct in the Arnhem Land region, consisting of four thylacines and three bilby-like creatures. At one Namunidjbuk site there is a rare depiction of a dugong.

Digital tracing of panel of three bilby-like animals, Awunbarna.
Digital tracing: Fiona Brady

A third of human depictions were classified as male because they have male genitalia depicted. Females, identified because breasts were shown, are rare, comprising only 5% of human depictions. Almost 59% of human figures could not be determined to be either male or female because they lack sex-specific characteristics.

Human figures generally have round-shaped or oval-shaped heads; some have lines on the head suggestive of hair. 30% of human figures are shown with headdresses, of which there are ten different forms. The most common is a ball headdress, followed by oval, cone and feather.

Large male Maliwawa human figures from an Awunbarna site. The largest male is 1.15 metres wide by 1.95 metres high.
P Tacon.

Maliwawa males are usually in profile and often have a bulging stomach above a penis. A few Maliwawa females are also shown with an extended abdomen.

National significance

Most Maliwawa Figures are in accessible or visible places at low landscape elevations rather than hidden away, or at shelters high in the landscape. This suggests they were meant to be seen, possibly from some distance. Often, Maliwawa Figures dominate shelter walls with rows of figures in various arrangements.

We first found some of these figures during a survey in 2008-2009 but they became the focus of further field research from 2016 to 2018.

Back-to-back Maliwawa macropods in the ‘piano player’ pose, Namuidjbuk.
P. Tacon

In Australia, we are spoiled with rock art — paintings, drawings, stencils, prints, petroglyphs (engravings) and even designs made from native beeswax in rock shelters and small caves, on boulders and rock platforms. Often in spectacular and spiritually significant landscapes, rock art remains very important to First Nation communities as a part of living culture.

There are as many as 100,000 sites here, representing tens of thousands of years of artistic activity. But even in 2020, new styles are being identified for the first time.

What if the Maliwawa Figures were in France? Surely, they would be the subject of national pride with different levels of government working together to ensure their protection and researchers endeavouring to better understand and protect them.

We must not allow Australia’s abundance of rock art to lead to a national ambivalence towards its appreciation and protection.

The Maliwawa Figures demonstrate how much more we have to learn from Australia’s early artists. And who knows what else is out there waiting to be found.
​

Paul S.C.Taçon, Chair in Rock Art Research and Director of the Place, Evolution and Rock Art Heritage Unit (PERAHU), Griffith University and Sally K. May, Senior Research Fellow, Griffith University

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

The mystery of the Top End’s vanishing wildlife, and the unexpected culprits

A brush-tailed rabbit-rat, one of the small mammals disappearing in northern Australia.
Cara Penton, Author provided

Alyson Stobo-Wilson, Charles Darwin University; Brett Murphy, Charles Darwin University; Graeme Gillespie, University of Melbourne; Jaana Dielenberg, The University of Queensland, and John Woinarski, Charles Darwin University

Only a few decades ago, encountering a bandicoot or quoll around your campsite in the evening was a common and delightful experience across the Top End. Sadly, our campsites are now far less lively.

Northern Australia’s vast uncleared savannas were once considered a crucial safe haven for many species that have suffered severe declines elsewhere. But over the last 30 years, small native mammals (weighing up to five kilograms) have been mysteriously vanishing across the region.

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Scientists and national park managers are failing northern Australia’s vanishing mammals

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The reason why the Top End’s mammals have declined so severely has long been unknown, leaving scientists and conservation managers at a loss as to how to stop and reverse this tragic trend.

Alyson Stobo-Wilson with a savanna glider. Gliders are among the mammals rapidly declining in northern Australia.
Alyson Stobo-Wilson, Author provided

Our major new study helps unravel this longstanding mystery. We found that the collective influence of feral livestock — such as buffaloes, horses, cattle and donkeys — has been largely underestimated. Even at quite low numbers, feral livestock can have a big impact on our high-value conservation areas and the wildlife they support.

The race for solutions

In 2010, Kakadu National Park conducted a pivotal study on Top End mammals. It found that between 1996 and 2009, the number of native mammal species at survey sites had halved, and the number of individual animals dropped by more than two-thirds. Similar trends have since been observed elsewhere across the Top End.

Given the scale and speed of the mammal declines, the need to find effective solutions is increasingly urgent. It has become a key focus of conservation managers and scientists alike.

The list of potential causes includes inappropriate fire regimes, feral cats, cane toads, feral livestock, and invasive weeds.

Many small and medium-sized mammals are in rapid decline in northern Australia.

With limited resources, it’s essential to know which threats to focus on. This is where our study has delivered a major breakthrough.

We looked for patterns of where species have been lost and where they are hanging on. With the help of helicopters to reach many remote areas, we used more than 1,500 “camera traps” (motion-sensor cameras to record mammals) and almost 7,500 animal traps (such as caged traps) to survey 300 sites across the national parks, private conservation reserves and Indigenous lands of the Top End.

A new spotlight on feral livestock

We found most parts of the Top End have very few native mammals left. The isolated areas where mammals are persisting have retained good-quality habitat, with a greater variety of plant species and dense shrubs and grasses.

This habitat provides more shelter and food for native mammals, and has fewer cats and dingoes, which hunt more efficiently in open areas. In contrast, sites with degraded habitat have much less food and shelter available, and native mammals are more exposed to predators.

Feral horses can overgraze and trample over habitat, making it far less suitable for small native mammals.
Jaana Dielenberg, Author provided

Across northern Australia, habitat quality is primarily driven by two factors: bushfires and introduced livestock, either farmed or feral.

Our surveys revealed that areas with more feral livestock have fewer native mammals. This highlights that the role of feral livestock in the Top End’s mammal declines has previously been underestimated.

Even at relatively low densities, feral livestock are detrimental to small mammals. Through overgrazing and trampling, they degrade habitat and reduce the availability of food and shelter for native mammals.

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Read more:
The world’s best fire management system is in northern Australia, and it’s led by Indigenous land managers

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Frequent, intense fires also play a big role. Australia’s tropical savannas are among the most fire-prone on Earth, but fires that are too frequent, too hot and too extensive remove critical food and shelter.

Yet, even if land managers can manage fires to protect biodiversity, for example by reducing the occurrence of large, intense fires, the presence of feral livestock will continue to impede native mammal recovery.

Even small numbers of feral livestock can play a big role in native mammal declines.
Northern Territory Government, Author provided

A new way to manage cats

Cats have helped drive more than 20 Australian mammals to extinction. So it’s not surprising we found fewer native mammals at our sample sites where there were more cats.

However, our results suggest the best way to manage the impact of cats in this region may not be to simply kill cats, which is notoriously difficult across vast, remote landscapes. Instead, it may be more effective to manage habitat better, tipping the balance in favour of native mammals and away from their predators.

A feral cat at one of the study sites. Cats have helped cause more than 20 native mammal extinctions.
Northern Territory Government, Author provided

The combination of prescribed burning to protect food and shelter resources, and culling feral livestock, might be all that’s needed to support native mammals and reduce the impact of feral cats.

What about dingoes?

Many scientists have suggested dingoes could also be part of the solution to reducing cat impacts — as cats are believed to avoid dingoes. With this in mind, we explored the relationship between the two predators in this study.

One of more than 1,000 motion detection cameras used in this study.
Jaana Dielenberg, Author provided

We found no evidence dingoes influenced the distribution of feral cats. In fact, survey sites with more dingoes had fewer native small mammals, suggesting a negative impact by dingoes.

But, unlike cats, culling dingoes is not an option because they provide other important ecological roles, and are culturally significant for Indigenous (and non-Indigenous) Australians.

Controlling herbivores, not predators

Our study suggests an effective way to halt and reverse Top End mammal losses is to protect and restore habitat. For example, by improving fire management and controlling feral livestock through culling.

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Read more:
EcoCheck: Australia’s vast, majestic northern savannas need more care

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It is also very important to conserve the environments that still have high-quality habitat and healthy mammal communities, such as the high-rainfall areas along the northern Australian coast. These areas provide refuge for many of our most vulnerable mammal species.

The native black-footed tree-rat has had major declines across northern Australia. It’s vulnerable to cats and is now restricted to areas that still have good quality habitat, fewer herbivores and less frequent fire.
Hugh Davies, Author provided

The tropical savannas of northern Australia are the largest remaining tract of tropical savanna on Earth and new species are still being discovered.

While there’s more research to be done, it’s crucial we start managing habitat better, before we lose more of our precious mammal species.

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The authors would like to gratefully acknowledge the support from many Indigenous ranger groups, land managers and Traditional Owners. This includes the Warddeken, Bawinanga, Wardaman and Tiwi rangers, the Traditional Owners and land managers of Kakadu, Garig Gunak Barlu, Judbarra/Gregory, Litchfield and Nitmiluk National Parks, Djelk, Warddeken and Wardaman Indigenous Protected Areas, and Fish River Station and was facilitated by the Northern, Tiwi and Anindilyakwa Land Councils.

Alyson Stobo-Wilson, Postdoctoral Research Associate, Charles Darwin University; Brett Murphy, Associate Professor / ARC Future Fellow, Charles Darwin University; Graeme Gillespie, Honorary Research Fellow, University of Melbourne; Jaana Dielenberg, Science Communication Manager, The University of Queensland, and John Woinarski, Professor (conservation biology), Charles Darwin University

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

Kakadu Upgrades

Australia: Climate Targets Further Threatened by Northern Territory Gas Plans

Australia: Northern Territory – Rain Arrives