Light and shade: how the natural ‘glazes’ on the walls of Kimberley rock shelters help reveal the world the artists lived in

Helen Green, The University of Melbourne and Damien Finch, The University of MelbourneThe Kimberley region is host to Australia’s oldest known rock paintings. But people were carving engravings into some of these rocks before they were creating paintings.

Rock art sites on Balanggarra Country in the northeast Kimberley region are home to numerous such engravings. The oldest paintings are at least 17,300 years old, and the engravings are thought to be even older — but they have so far proved much harder to date accurately.

Cupules, or circular man-made hollows, ground into a dark mineral coating at a rock art site on the Drysdale River, Balanggarra country.
Photo by Damien Finch

But in research published today in Science Advances, we report on a crucial clue that could help date the engravings, and also reveal what the environment was like for the artists who created them.

Some of the rocks themselves are covered with natural, glaze-like mineral coatings that can help reveal key evidence.

What are these glazes?

These dark, shiny deposits on the surface of the rock are less than a centimetre thick. Yet they have detailed internal structures, featuring alternating light and dark layers of different minerals.

Our aim was to develop methods to reliably date the formation of these coatings and provide age brackets for any associated engravings. However, during this process, we also discovered it is possible to match layers found in samples collected at rock shelters up to 90 kilometres apart.

Radiocarbon dating suggests these layers were deposited around the same time, showing their formation is not specific to particular rock shelters, but controlled by environmental changes on a regional scale.

Dating these deposits can therefore provide reliable age brackets for any associated engravings, while also helping us better understanding the climate and environments in which the artists lived.

Marsupial tracks scratched into a glaze like coating at a rock art shelter in the north east Kimberley.
Photo by Cecilia Myers/Dunkeld Pastoral Company; illustration by Pauline Heaney/Rock Art Australia

Microbes and minerals

Our research supports earlier findings that layers within the glaze structure represent alternating environmental conditions in Kimberley rock shelters, that repeated over thousands of years.

Our model suggests that during drier conditions, bush fires produce ash, which builds up on shelter surfaces. This ash contains a range of minerals, including carbonates and sulphates. We suggest that under the right conditions, these minerals provided nutrients that allowed microbes to live on these shelter surfaces. In the process of digesting these nutrients, the microbes excrete a compound called oxalic acid, which combines with calcium in the ash deposits to form calcium oxalate.

A: dark coloured, smooth mineral coating at a Kimberley rock shelter; B: alternating layering, as seen in the field; C: alternating layering as seen in a cross-sectioned coating under a microscope.
Photos by Cecilia Myers; microscope image by Helen Green

As this process repeats over millennia, the minerals become cemented together in alternating layers, with each layer creating a record of the conditions in the rock shelter at that time.

Samples of the glazes were collected for analysis in close collaboration and consultation with local Traditional Owners from the Balanggarra native title region, who are partners on our research project. Using a laser, we vaporised tiny samples from the coatings to study the chemical composition of each layer. The dark layers were mostly made of calcium oxalate, while lighter layers contained mainly sulphates. We propose darker layers represent a time when microbes were more active and lighter layers represent drier periods.

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Read more:
How climate change is erasing the world’s oldest rock art

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Linking the layers

These dark calcium oxalate layers also contain carbon that was absorbed from the atmosphere and digested by the microbes that created these deposits. This meant we could use a technique called radiocarbon dating to determine the age of these individual layers.

Using a tiny drill, we removed samples from distinct dark layers in nine glazes collected from different rock shelters across the northeast Kimberley.

A: micro-drilling samples from individual layers for radiocarbon dating; B: Laser ablation maps showing the distribution of the element calcium within the different layers; C: radiocarbon dating of individual layers identified four key growth periods.
Photo by Andy Gleadow; illustration by Pauline Heaney

Despite coming from different locations, these layers all seem to have been deposited at the same time, during four key intervals spanning the past 43,000 years.

This suggests the formation of each layer was determined mainly by shifts in environmental conditions throughout the Kimberley, rather than by the distinct conditions in each particular rock shelter.

The records held by these glazes over such a large time period – including the most recent ice age – means they could help us better understand the environmental changes that directly affected human habitation and adaptation in Australia.

Hypothetical example of how layered mineral coatings can be used to date engraved rock art in Kimberley rock shelters.
Pauline Heaney

Stories in stone

Research we published earlier this year shows how the subjects painted in early Kimberley rock art changed from mostly animals and plants around 17,000 years ago, to mostly decorated human figures about 12,000 years ago.

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This 17,500-year-old kangaroo in the Kimberley is Australia’s oldest Aboriginal rock painting

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Other researchers have discovered that during this 5,000-year period there were rapid rises in sea level, in particular around 14,500 years ago, as well as increased rainfall.

We interpret the change in rock art styles as a response to the social and cultural adaptations triggered by the changing climate and rising sea levels. Paintings of human figures with new technologies such as spear-throwers might show us how people adapted their hunting style to the changing environment and the availability of different types of food.

By dating the natural mineral coatings on the rock surfaces that acted as a canvas for this art, we can hopefully better understand the world in which these artists lived. Not only will this give us more certainty about the position of particular paintings within the overall Kimberley stylistic rock art sequence, but can also tell us about the environments experienced by First Nations people in the Kimberley.

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We thank the Balanggarra Aboriginal Corporation, the Centre for Accelerator Science at the Australian National Science and Technology Organisation, Rock Art Australia and Dunkeld Pastoral Co for their collaboration on this research._

Helen Green, Research Fellow, The University of Melbourne and Damien Finch, Research fellow, The University of Melbourne

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

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How climate change is erasing the world’s oldest rock art

This Warty Pig is part of a panel dated to more than 45,500 years in age.
Basran Burhan/Griffith University, Author provided

Jillian Huntley, Griffith University; Adam Brumm, Griffith University; Adhi Oktaviana, Griffith University; Basran Burhan, Griffith University, and Maxime Aubert, Griffith UniversityIn caves on the Indonesian island of Sulawesi, ancient peoples marked the walls with red and mulberry hand stencils, and painted images of large native mammals or imaginary human-animal creatures.

These are the oldest cave art sites yet known — or at least the oldest attributed to our species. One painting of a Sulawesi warty pig was recently dated as at least 45,500 years old.

Since the 1950s, archaeologists have observed these paintings appear to be blistering and peeling off the cave walls. Yet, little had been done to understand why.

So our research, published today, explored the mechanisms of decay affecting ancient rock art panels at 11 sites in Sulawesi’s Maros-Pangkep region. We found the deterioration may have gotten worse in recent decades, a trend likely to continue with accelerating climate change.

These Pleistocene (“ice aged”) cave paintings of Indonesia have only begun to tell us about the lives of the earliest people who lived in Australasia. The art is disappearing just as we’re beginning to understand its significance.

Australasia’s rock art

Rock art gives us a glimpse into the ancient cultural worlds of the artists and the animals they may have hunted or interacted with. Even rare clues into early people’s beliefs in the supernatural have been preserved.

Climate change could erase ancient Indonesian cave art.

We think humans have been creating art of some kind in Australasia — which includes northern Australia, Papua New Guinea and Indonesia — for a very long time. Used pigments are among the earliest evidence people were living in Australia more than 60,000 years ago.

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

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Tens of thousands of distinctive rock art sites are scattered across Australasia, with Aboriginal people creating many styles of rock art across Australia.

Until as recently as 2014, scholars thought the earliest cave art was in Europe — for example, in the Chauvet Cave in France or El Castillo in Spain, which are 30,000 to 40,000 years old. We now know people were painting inside caves and rockshelters in Indonesia at the same time and even earlier.

Hand stencils in one of the study sites at Leang Sakapao cave.
Linda Siagian, Author provided

Ongoing surveys throughout Australasia turn up new rock art sites every year. To date, more than 300 painted sites have been documented in the limestone karsts of Maros-Pangkep, in southern Sulawesi.

Cave paintings in Sulawesi and Borneo are some of the earliest evidence we have that people were living on these islands.

Tragically, at almost every new site we find in this region, the rock art is in an advanced stage of decay.

Big impacts from small crystals

To investigate why these prehistoric artworks are deteriorating, we studied some of the oldest known rock art from the Maros-Pangkep region, scientifically dated to between at least 20,000 and 40,000 years old.

Expanding and contracting salt crystals are causing rock art to flake off the cave walls.
Linda Siagian, Author provided

Given these artworks have survived over such a vast period, we wanted to understand why the painted limestone cave surfaces now appear to be eroding so rapidly.

We used a combination of scientific techniques, including using high-powered microscopes, chemical analyses and crystal identification to tackle the problem. This revealed that salts growing both on top of and behind ancient rock art can cause it to flake away.

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Indonesian cave paintings show the dawn of imaginative art and human spiritual belief

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Salts are deposited on rock surfaces via the water they’re absorbed in. When the water solution evaporates, salt crystals form. The salt crystals then swell and shrink as the environment heats and cools, generating stress in the rock.

In some cases, the result is the stone surface crumbling into a powder. In other instances, salt crystals form columns under the hard outer shell of the old limestone, lifting the art panel and separating it from the rest of the rock, obliterating the art.

On hot days, geological salts can grow to more than three times their initial size. On one panel, for example, a flake half the size of a hand peeled off in under five months.

Climate extremes under global warming

Australasia has an incredibly active atmosphere, fed by intense sea currents, seasonal trade winds and a reservoir of warm ocean water. Yet, some of its rock art has so far managed to survive tens of thousands of years through major episodes of climate variation, from the cold of the last ice age to the start of the current monsoon.

Limestone karsts of Maros and Pangkep Regencies, in South Sulawesi, Indonesia.
Shutterstock

In contrast, famous European cave art sites such as Altamira in Spain and Lascaux in France are found in deep caves, in more stable (temperate) climates, so threats to rock art are different and generally weathering is less aggressive.

But now greenhouse gases are magnifying climatic extremes. In fact, global warming can be up to three times higher in the tropics, and the wet-dry phases of the monsoon have become stronger in recent decades, along with more numerous La Niña and El Niño events.

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Climate explained: will the tropics eventually become uninhabitable?

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The net effect is that temperatures are higher, there are more hot days in a row, droughts are lasting longer, and other extreme weather such as storms (and the flooding they cause) are more severe and frequent.

What’s more, monsoonal rains are now captured in rice fields and aquaculture ponds. This promotes the growth of art-destroying salt crystals by raising humidity across the region and especially in nearby caves, prolonging the shrink and swell cycles of salts.

Makassar’s culture heritage department, Balai Pelestarian Cagar Budaya, undertaking rock art monitoring in Maros-Pangkep.
Rustan Lebe/Griffith University, Author provided

What happens now?

Apart from the direct threats associated with industrial development — such as blasting away archaeological sites for mining and limestone quarrying — our research makes it clear global warming is the biggest threat to the preservation of the trpoics’ ancient rock art.

There’s a pressing need for further research, monitoring and conservation work in Maros-Pangkep and across Australasia, where cultural heritage sites are under threat from the destructive impacts of climate change.

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Rio Tinto just blasted away an ancient Aboriginal site. Here’s why that was allowed

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In particular, we urgently need to document the remaining rock art in great detail (such as with 3D scanning) and uncover more sites before this art disappears forever.

If humans are ultimately causing this problem, we can take steps to correct it. Most importantly, we need to act now to stop global temperature increases and drastically cut emissions. Minimising the impacts of climate change will help preserve the incredible artworks Australasia’s earliest people left to us.

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Read more:
Indonesian cave paintings show the dawn of imaginative art and human spiritual belief

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Jillian Huntley, Research Fellow, Griffith University; Adam Brumm, Professor, Griffith University; Adhi Oktaviana, PhD Candidate, Griffith University; Basran Burhan, PhD candidate, Griffith University, and Maxime Aubert, Professor, Griffith 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.
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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.

Why scientific monitoring of the effects of industry on our priceless WA rock art is inadequate

The Burrup Peninsula, or Murujuga, contains over a million individual works of rock art by the Yaburara people.
Shutterstock.com

John Black, University of Western Australia

Scientific studies used to monitor the impact of industry on Aboriginal rock art in north west Western Australia are inadequate, potentially exposing more than a million individual artworks to damage, according to a recent paper published by myself and co-authors in the journal Rock Art Research.

The rock art is located near the towns of Dampier and Karratha and is known as the Burrup Peninsula, or Murujuga. It is a priceless, irreplaceable, cultural and archaeological treasure. The peninsula is also home to industry including an iron ore export port, natural gas processing, liquefying and export facilities, an ammonia-urea fertiliser plant and most recently, an ammonium nitrate production facility for explosives.

The industry and port produce thousands of tonnes of acid-forming emissions each year, permitted under environmental regulations. The impact of these emissions has been monitored through several scientific studies, which claimed there was no consistent impact on the rock art.

However our paper shows that the four main studies cannot be used to monitor the impact of industry on the art due to methodological errors. For example, one study subjected rocks to acid-forming emissions and concluded that there was no consistent change in colour. But there were just not enough repeat measurements to gain any sensible conclusion about the effect of emissions on rock colour.

Another experiment examining the effects of varying acid and other chemical concentrations was conducted using iron ore, which has no relevance to the rocks on which the art is situated. Measurements of colour change between 2004 and 2014 were also made on the rock art and background rock at seven different sites. But the instruments used for measuring change in rock surface colour were designed for indoor use and were inappropriate for the highly variable, hot rock surfaces of Murujuga. Typically, instruments were located at only one place on the rock surface during a measurement each year and this was insufficient to represent the highly variable rock surface.

These studies form the basis for government regulation, which permits industry to release acid-forming emissions. While there is no conclusive evidence that industry emissions have damaged the rock art, recent measurements of the surface of rocks near industry by Dr Ian MacLeod, former Director of the Western Australian Maritime Museum, found acidity to have increased 1,000 times above pre-industrial levels.

We showed in another scientific paper published earlier this year that acid dissolves the outer surface layer of the rocks causing them to become thinner, lighter in colour and to flake away. Once the outer surface layer is removed, the rock art is lost.

The federal government is conducting a senate inquiry into the health of the Murujuga rock art, with a delayed final report due in late November. I argue that, at the very least, industry must install technology to reduce acid emissions and ammonium nitrate dust particles to virtually zero. Other rock art experts have called for a cessation of all industry on the peninsula in a recent editorial in Rock Art Research.

Priceless history

The Murujuga rock art captures over 45,000 years of human culture, activity and spiritual beliefs through ever changing environments from when the sea was more than 100 km from its current position and through the last ice age, 20,000 years ago.

The petroglyphs include some of the oldest known representations of the human face in the world. There are images of extinct mammals including megafauna, the fat-tailed kangaroo and thylacine. There are elaborate geometric designs that could have been used for navigation or an early form of mathematics. There are many depictions of hunting and cultural ceremonies as well as existing animals, birds and sea creatures.

Artwork depicting a thylacine, a species which has been extinct in the Pilbarra for 3,000 years.
Friends of Australian Rock Art

The Murujuga inhabitants created this rock art until February 1868, when virtually the entire Yaburara indigenous population was exterminated in a massacre.

Massacre of the Yaburara, only three years after European settlement in 1865, has deprived us from knowing the storylines and cultural meaning of the petroglyphs. Equally significantly, the massacre broke continuous inhabitation of the area, which has allowed successive Western Australian governments to develop in the midst of the rock art one of the largest industrial complexes in the Southern Hemisphere.

Industry and art

Construction of the industries is estimated by archaeologists working on Murujuga to have resulted in the destruction of over 30,000 petroglyphs through removal and physical damage. Atmospheric emissions from the industries are immense.

Dampier port, which is adjacent to the petroglyphs, is one of the busiest bulk-ports in the world with over 19,000 ship movements each year. These ships burn high sulphur bunker fuel, with one ship emitting as much as 5,000 tonnes of sulphur dioxide per year.

The gas and fertiliser plants emit around 34,000 tonnes of acid forming compounds into the air each year. The recent starting up of the ammonium nitrate plant revealed a huge yellow-orange cloud of nitrogen dioxide with concentrations of over 1,000 parts per million. The emission of nitrogen dioxide from the plant will occur around six times each year, whenever certain industrial chemicals needed for ammonium nitrate production require replacing.

These emissions are permitted under state and federal environmental regulation. Both nitrogen and sulphur dioxide react with water to form acids which are deposited on the rock surfaces.

The construction of the LNG facility in 2008.
Friends of Australian Rock Art

Extraordinary origins

The rock art at Murujuga is threatened by acid because of its unique geological properties. The natural blue-grey rock, formed from cooling magma, weathers very slowly to form a yellow coloured weathering rind, which may grow by 5 mm in 30,000 years.

The yellow coloured rind is covered with a dark brown-black coating called a patina or rock varnish. The petroglyphs were formed by using hard pieces of rock to break through the patina and expose the rind.

This patina is an extraordinary substance. It is formed by specialised bacteria and fungi on the rock surface, where there is seldom moisture and rock temperatures can exceed 70℃. To survive the harsh conditions, the organisms build a mineral sheath. When they die, their body and sheath combine with clay from the dust to form the hard, dark-coloured patina.

Destruction of the outer patina results in disappearance of the rock art. There is evidence that the patina is flaking on some rocks with petroglyphs. The patina becomes thin and flakes away under acidic conditions.

Protecting the art

Elsewhere in the world countries have been vigilant in protecting natural and cultural heritage from acid emissions. In the US cars are banned or severely limited in many national parks because the acid formed from nitrogen dioxide, produced from vehicle exhaust, will damage the forests.

In France, the 1.4 million annual visitors to the 17,000-year-old Lascaux cave paintings do not see the actual paintings, but a replica in an adjoining cave because of the damage caused by emissions from human breath.

Similarly, the UK government announced in January this year they are building a £1.4 billion tunnel to remove cars form the vicinity of their 4,500-year-old heritage in Stonehenge.

While removing industry may be the best solution to ensure the rock art’s safety, it may not be practical. Governments and industry must recognise their social responsibilities and ensure sufficient technology is in place to reduce acid forming emissions to near zero.

John Black, Honorary Research Fellow, University of Western Australia

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

Huge fires are burning northern Australia every year: it’s time to get them under control

Owen Price, University of Wollongong

On October 1, 2015 a fire lit to manage weeds at the Ranger Uranium Mine burned through 14,000 hectares of Kakadu National Park, threatening important rock-art sites and closing several tourist attractions.

The Northern Territory Government and Energy Resources of Australia (the mine operators) are conducting enquiries to work out what went wrong and how to prevent similar accidents in the future, because like all natural disasters each one is an opportunity to learn.

As it happens, this fire coincided with the publication this month of my research that helps us to understand the problem posed by unplanned fires in the savannas of northern Australia.

That research highlights a 60-day window between August 9 and October 7 each year when huge fires can occur and these contribute an inordinate amount to the total area burnt across the north.

Going up in smoke

Before August mild weather and moisture in the vegetation constrain fires. After October rain and high humidity do the same. Natural fires, caused by lightning, occur from November onwards, and although these account for more than 60% of unplanned fires started, they cause less than 10% of the total area burnt.

Rather, it is fires in the high risk window that are the real problem for fire management over a vast slab of Australia and they are neither natural nor planned.

My study used MODIS satellite mapping to examine the ignition date, duration and eventual size of 126,000 fires in Arnhem Land over a 10 year period. The largest fire ignited in late August 2004 and burned 445,000 hectares, 30 times the area burnt by the Ranger Mine or equivalent to a quarter of the size of Kakadu, our country’s largest national park.

But other regions have it worse: an accidental fire in the northern Tanami ignited on August 4 2011 burnt an area at least 5 million ha. There are 22 European countries smaller than that. So the Ranger Mine fire is in no way unique: it just happened to occur in a highly visible area.

Let’s take a step back and consider what is at stake with fires such as these. Research over many decades have shown that many species of fire-sensitive plants and animals are in decline across the north this is at least partially related to the loss of traditional burning practices which has led to an increase in fire frequency and a predominance of high-intensity late dry season fires (such as the Ranger Mine fire).

It is not certain whether high fire frequency or high fire intensity is the main problem, but it is probably a bit of both.

Stop fires starting

Managers of country such as Kakadu National Park and Arnhem Land recognise this problem and have taken steps to wrest back control of the fire regime. Their main tool is the use of planned burning in the early dry season fires (April – July), akin to traditional burning practices.

By treating the land with a patchwork of these low intensity, low impact fires, subsequent fires can be prevented or constrained to protect sensitive areas. In some areas, including Kakadu and Western Arnhem Land, between 10% and 30% of the country is burnt each year by planned burns. This year 31% of Kakadu National Park had been treated in this way and this patchwork of burnt areas was the context in which the Ranger Mine fire started.

This approach has been successful at reducing the area burnt by unplanned late dry season fires, but it is only a partial fix. The Ranger Mine fire illustrates the main problem: that fires will burn around previously burnt patches.

This fire spread through a small gap between previous patches (at point A on the map below), enlarging its size five-fold. It is fair to say that the southern and western progress of the fire was contained by the planned burning. This protected Nourlangie Rock and Jabiru township and the fire could have been much larger without it.

The large fire that threatened Aboriginal heritage burned around previous burnoffs.
Owen Price, Author provided

The consequence of this “leaky” patchwork of protection is that early dry season burning on its own does not do much to reduce the overall area burnt. Rather it replaces high intensity late dry season fires with low intensity fires (which itself is a good thing).

This replacement phenomenon has been demonstrated
using fine scale fire mapping in Western Arnhem Land. My new study points out that if reducing fire frequency across the north is a goal (and it ought to be), then we need to place more focus on stopping fires starting in the main danger period (mid August to mid October).

Achieving substantial reduction in these ignitions is a huge challenge, and I don’t have any easy answers, but it would help if burn-offs such as the one that started the Ranger Mine fire were not allowed at this risky time of year.

Owen Price, Senior Research Fellow, Centre for Environmental Risk Management of Bushfires, University of Wollongong

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

Australia: Rock Art At Risk

The link below is to a series of articles reporting on threat to Australia’s rock art by mining.

For more visit:
http://www.theglobalmail.org/features/in/rock-art-at-risk/