The link below is to an article that takes a look at a bushwalk in the Warrumbungle National Park. It is a personal account (not by me) of a walk in the Grand High Tops area of the park.
In 2017, I came across an extraordinary document in Sydney’s Mitchell Library: a handwritten list of 178 Aboriginal place names for Dyarubbin, the Hawkesbury River, compiled in 1829 by a Presbyterian minister, the Reverend John McGarvie. I was stunned. I stared at the screen, hardly believing my eyes.
After years of research, my own and others, I thought most of the Aboriginal names for the river were lost forever, destroyed in the aftermath of invasion and dispossession. Yet, suddenly, this cache of riches.
I could see McGarvie had taken a lot of care with this list, correcting spelling and adding pronunciation marks. The names appear in geographic order, so they also record where he and his Darug informant/s travelled along the riverbanks. Perhaps most important of all, McGarvie often included locational clues, like settlers’ farms, creeks and lagoons.
An extraordinary idea dawned on me: what if we could restore these names to their places on the river? And then: what if these beautiful, rolling words — like Bulyayorang and Marrengorra and Woollootottemba — came back into common usage?
Place names have enormous significance in Aboriginal society and culture. As in all societies, they signal the meanings people attach to places, they encode history and geography, they are way-finding devices and common knowledge. Place names are crucial elements of shared understandings of Country, history, culture, rights and responsibilities.
Often place names are parts of larger naming systems — they name places on Dreaming tracks reaching across Country. Singular names can also embed the stories of important events and landmarks involving Ancestral Beings in places and memory. Anthropologist and linguist Jim Wafer points out their use in songs, which are memory devices, or “audible maps … travelling song cycles that narrate mythical journeys”.
Dyarubbin, the Hawkesbury River, flows through the heart of a vast arc of sandstone Country encircling Sydney and the shale-soil Cumberland Plain on the east coast of New South Wales. The river has a deep human history, one of the longest known in Australia.
The ancestors of Darug, Darkinyung and Gundungurra people have lived in this region for around 50,000 years. Their history, culture and spirituality are inseparable from their river Country. A mere two centuries ago, ex-convict settlers took land on the river and began growing patches of wheat and corn in the tall forests. Darug men and women resisted the invasion fiercely and sometimes successfully.
Between 1794 and 1816, Dyarubbin was the site of one of the longest frontier wars in Australian history. Invasion and colonisation kicked off a slow and cumulative process of violence, theft of Aboriginal children, dispossession and the ongoing annexation of the river lands.
Yet despite this sorry history, Dyarubbin’s people managed to remain on their Country, and they still live on the river today.
McGarvie’s list contrasts strikingly with the modern landscapes of the Hawkesbury and Western Sydney. Once, every place on this river and its tributaries had an Aboriginal name. Now only a handful survive on maps and in common usage.
With some important exceptions, the Traditional Owners, the Darug, rarely see themselves represented in key heritage sites, or in the everyday reminders and triggers of public memory – like place names.
Yet Western Sydney is now home to one of the biggest populations of Darug and other Aboriginal people in Australia. Could McGarvie’s list be a way to begin to shift the shape of our landscapes towards a recognition of Darug history and culture?
This idea stayed with me, so I contacted Darug knowledge-holders, artists and educators Leanne Watson, Erin Wilkins, Jasmine Seymour and Rhiannon Wright: the response was instant and enthusiastic. We designed the project together and were thrilled when it won the NSW State Library’s Coral Thomas Fellowship
The project’s Darug researchers want most of all to research, record and recover environmental and cultural knowledge and raise awareness of Darug presence and history in the wider community.
Because the Darug history of Dyarubbin is continuous, the project includes an oral history component, recording 20th century Darug voices and stories of the river.
Looking back, it seems uncanny that McGarvie’s list reappeared when it did — after all, we are in the midst of an extraordinary period of Aboriginal cultural renewal and language revitalisation.
It was obvious that McGarvie’s words could be more than a list of names: it could be the key to a bigger story about the Dyarubbin, the Darug history that was lost, submerged below what historian Tom Griffiths calls “the white noise of history making”.
But to do this, we needed to put the words in their wider context: we needed to see the river whole. So, besides reconnecting the list to Traditional Owners, the project explores Dyarubbin’s history, ecology, geography, archaeology and languages.
Early maps showing the old river farms helped us work out where the Darug place names belong and digitally map them. They also record long-lost landscapes of swamps, lagoons and creeks — important places for Aboriginal people that have since been modified or disappeared altogether.
The “Returns of Aboriginal Natives” are lists of Aboriginal people living in New South Wales in the 1830s, including the groups who lived on various parts of Dyarubbin and its tributaries. Reverend McGarvie’s diaries show he knew many of these Darug people.
The letters and journals of Hawkesbury settlers are thoroughly colonial-centred, yet they contain hints about the ways Darug people continued to live on their Country throughout the 19th century.
For example, they befriended some of the settlers, like the Hall family at Lilburndale, and cultivated these relationships over generations. The Hall family papers in the Mitchell Library hold some powerful and poignant traces: store receipts for goods Darug people were purchasing from them, and lists of the work they did at Lilburndale.
The archaeological record for this region is astonishingly rich. Dyarubbin and its tributary Gunanday (the Macdonald River) are part of a much larger archaeological zone, reaching from the Blue Mountains and the Wollemi in the west, up to the Hunter Valley and Lake Macquarie in the north. Many of the major recorded archaeological sites have sacred, spiritual and ceremonial significance, especially those located on high places.
Closer to the river, Paul Irish’s archaeological mapping has revealed how much Darug cultural landscape survives today, within the “settler” landscape.
From Richmond in the south to Higher Macdonald in the north, the river corridors alone are lined with more than 200 archaeological sites, including engravings, grinding grooves and rock shelters, some with scores or hundreds of images in ochre, white clay and charcaol.
Perhaps the most important aspect of the project are the field trips — getting out on Country, following in the footstep of McGarvie and his Darug friends, to see how all of this comes together. For Aboriginal people especially, visiting Country is a spiritual experience: they sense past and present converging, and the presence of their Ancestors.
What about the words on McGarvie’s list? What can they tell us? Linguist Jim Wafer and I worked with the Darug team members on a glossary, scouring dictionaries of seven local and adjacent Aboriginal languages for glosses, or meanings.
Many of these remain tentative; some words have two possible glosses. This project is, after all, only the beginning of what will hopefully be a much longer journey of discovery.
Nevertheless, McGarvie’s list has unlocked a wealth of information as well as intriguing and suggestive patterns — the place names open a marvellous word-window onto the Darug world of Dyarubbin in late 1820s.
They can be roughly grouped in four interrelated and often overlapping categories: the natural world of plants and creatures, geography and landforms, stone and earth, salt and fresh water; the social world of corroboree and contest grounds, camps and places to source materials for tools and implements; a metaphoric pattern — using words for parts of the body (mouth, arm, finger, eyes) for places on the river; and names with spiritual meanings, signifying sacred places.
Are there larger patterns in McGarvie’s list of place names? Here again, mapping the names, relocating them on Country, revealed something about how Darug people thought of Dyarubbin: as a series of zones, each which particular characteristics.
For example, on the west side of the river between Sackville and Wilberforce are 16 named lagoons or words meaning lagoons, including four different words which appear to signify different types of lagoons: Warretya, Warang, Warradé, Warrakia.
It was Warretya (lagoon) Country. Rich in birdlife, fish, turtles, eggs and edible plants, lagoons were very important places for Darug people, especially women, who harvested the edible roots and shoots of water plants such as cumbungi, water ribbon and common nardoo.
There were lagoons on the opposite side of the river, too, but here the series of place names around Cattai Creek tell us that this was Dugga (thick brush/rainforest) Country.
Massive Riverflat forest once lined all of Dyarubbin’s alluvial reaches; in sheltered gullies this forest graded into rainforest. Other place names in this area suggest the tree species which grew in these forests: Boolo, coachwood, Tamangoa, place of Port Jackson figs, Karowerry, native plum tree, Booldoorra, soft corkwood. And there are places named for implements, like clubs (Kanogilba, Berambo), and fish spears (Mating), which may have been fashioned from the fine, hard timbers of some of these trees.
These Dugga place names suggest something significant about Dyarubbin’s human and ecological history, too. The settler invasion is often assumed to have completely destroyed earlier landscapes, converting the bush to cleared, farmed fields. But these tree and forest names suggest that parts of the great forests survived for over three decades, and that Darug people went on using them.
Perhaps most significant and evocative are the place names which signal sacred zones on Dyarubbin. There are two different words meaning “rainbow”: Dorumbolooa and Gunanday.
Both are located in places with dramatic cliffs and sharp river bends. These words are probably linked with Gurangatty, the great Eel Being, who is associated with rainbows, and who created the river and its valley in the Dreaming, leaving awesome chasms and sinuous bends in his wake. McGarvie’s list reconnects us with the sacred river.
Such words remind us of something obvious, and profound. If Aboriginal people are to be at the centre of their own stories, we need to look beyond European history and landscapes, beyond European knowledge and ways of thinking, and towards an Aboriginal sense of Country — the belief that people, animals, Law and Country are inseparable, that the land is animate and inspirited, that it is a historical actor.
Leanne Watson’s painting Waterholes, inspired by the project, expresses this sense of Country. Her painting represents the beautiful lagoons around Ebenezer near Wilberforce and all the nourishment and materials they offered people. Now we can name some of those lagoons: Boollangay, Marrumboollo, Kallangang.
What now? Two exhibitions are planned for 2021: one at the State Library of NSW, and the other at Hawkesbury Regional Gallery. Staff at NSW Spatial Services/the NSW Geographic Names Board have generously offered their skills and time to create a digital Story Map, which will allow readers to virtually explore Darug Dyarubbin.
A series of illustrated essays, or “story cycle”, to be published on the online Dictionary of Sydney at the State Library of New South Wales, will present more in-depth narratives. Ultimately, we plan to launch dual naming projects, which will restore these names to Dyarubbin Country.
These are truth-telling projects: they will tell the story of invasion, dispossession and frontier war. But they will also explore Darug history, culture, places and names, and the way Dyarubbin and its surrounding high lands still throb with spiritual meaning and power, and the “ancient sovereignty” of Aboriginal people.
Grace Karskens, Emeritus Professor of History, UNSW; Erin Wilkins, Aboriginal Cultural Educator, trainer and facilitator, Indigenous Knowledge; Jasmine Seymour, Artist, writer, illustrator, primary school teacher, Indigenous Knowledge; Leanne Watson, Artist, educator, book illustrator, Indigenous Knowledge, and Rhiannon Wright, Aboriginal Education Officer, Indigenous Knowledge
Twenty years ago, UNESCO inscribed the greater Blue Mountains area on the World Heritage List for having “outstanding universal value”.
If you’ve travelled to the Blue Mountains, with its rugged sandstone cliff faces, hidden waterfalls and rich diversity of life, this value is undeniable. The Dharug and Gundungurra traditional owners long understood this value as they lived within and cared for Country (Ngurra) and, in turn, were nourished by it.
Last week, the International Union for Conservation of Nature (IUCN) — the official advisor to UNESCO — rated the site as being of “significant concern”, a drop from “good with some concerns”. It’s now in the second-lowest category.
The news may be grim, but there are signs of hope. Despite threats of climate change, bushfires and decades of pollution, efforts are being made to minimise lingering impacts, and results are encouraging.
The Greater Blue Mountains World Heritage Area covers just over one million hectares, divided into eight protected areas.
The largest protected area is Wollemi National Park (499,879 ha) in the north. This park is, famously, home to the last wild population of Wollemi Pine. These trees have a deeply ancient lineage tracing back to when the Earth’s land masses were all part of the supercontinent Gondwana over 100 million years ago.
Wollemi pines are dinosaur trees
The World Heritage area harbours 1,500 plant species, and 127 of them are rare or threatened. And in an outstanding example of the area’s uniqueness, it also contains more than 90 Eucalypt species — 13% of the global total.
The World Heritage area is also an important habitat for many rare and threatened animal species.
One celebrated seasonal visitor is the critically endangered regent honeyeater. Also under threat, and unique to the Blue Mountains, is the leura skink, which survives only in a handful of sensitive and vulnerable wetland communities.
In its new report, the IUCN lists eight current threats undermining the greater Blue Mountains area. The most worrying – those considered “very high threats” in the report — are climate change and bushfires.
The severe fires of last summer inflicted long-lasting damage to many Blue Mountains species that contribute to the unique biodiversity of the area. And climate change is an emerging environmental pressure threatening the delicate ecology of the region through rising temperatures and changes to rainfall.
The IUCN also rated invasive plant and animal species, such as foxes, feral cats, horses, cattle and deer, as a high threat. Mining and quarrying, habitat alteration and several specific aspects of climate change (storms, drought, temperature extremes) were also listed.
The IUCN also named potential threats from planned operations, including future noise pollution from the new international airport in Western Sydney. Another is the impact of periodic flooding from a proposal to raise the wall of Warragamba Dam for flood mitigation purposes.
Climate change and bushfires require massive, coordinated national and international responses, but some major issues in the Blue Mountains can start to be resolved on relatively smaller scales.
For decades, the Blue Mountains have been flogged by a number of human pressures, such as an outdated sewage system from the City of the Blue Mountains and pollution from coal mining. While the environment hasn’t fully recovered, we’re pleased to see successes in the recovery efforts.
For decades, inadequate sewerage systems polluted multiple streams and rivers in the Blue Mountains.
In 1987, the Sydney Water Corporation started a 25-year, $250 million scheme to reduce water pollution from this inadequately treated sewage. And by 2010, a massive upgrade to the region’s sewage system closed 11 antiquated treatment plants.
All Blue Mountains wastewater is now treated to a higher standard at Winmalee in the lower Blue Mountains and is released away from waterways in the World Heritage area.
Another important pressure in the Greater Blue Mountains Area is from coal mining, with UNESCO expressing concerns in 2001 about water pollution from mines, such as the one operated by Clarence Colliery.
This mine is in state forest adjacent to the World Heritage area boundary. Research from 2017 found wastewater discharging from the mine was severely contaminating water quality of the Wollangambe River and damaging the ecology for more than 20 kilometres.
Two years earlier, Clarence Colliery, owned by Centennial Coal, was prosecuted after more than 2,000 tonnes of coal material (a slurry of water and coal particles) spilled into the Wollangambe River.
Centennial Coal agreed to comply with a new EPA licence in 2017 requiring the disposal of less polluting wastes.
The latest results from October of this year are very encouraging. They show an enormous reduction (more than 95%) in the zinc concentration in mine waste, compared to 2012 levels.
For an internationally important site like this, which is home to more than 80,000 residents, all levels of government must adopt the concept of “planetary health”. This recognises that human health entirely depends on the health of natural systems and embraces Indigenous knowledge.
We’re pleased to see the Blue Mountains City Council is already on board. It recently announced plans to establish a planetary health leadership centre in Katoomba in partnership with universities and other educational institutions.
So while there is much to grieve, we can celebrate small successes in the Blue Mountains’ journey, which show it is indeed possible for a diverse array of parties and the broader community to work cooperatively, and start to better protect it.
Ian Wright, Senior Lecturer in Environmental Science, Western Sydney University; Anthony Capon, Director, Monash Sustainable Development Institute, Monash University, and Leo Robba, Lecturer, Visual Communications / Social Design, Western Sydney University
Thomas Murray, Griffith University; Ana Paula da Silva, Griffith University; Darrell Strauss, Griffith University; Guilherme Vieira da Silva, Griffith University, and Rodger Tomlinson, Griffith University
Over the past six months, tourists and locals have been shocked to see Byron’s famous Main Beach literally disappearing, inundated with water and debris. In October, lifesavers were forced to temporarily close the beach because they couldn’t get rescue equipment onto the sand. Resident Neil Holland, who has lived in the area for 47 years, told the ABC:
It’s the first time I’ve seen it this bad in all the time that I’ve been here, and it hasn’t stopped yet. The sand is just being taken away by the metre.
So what’s happening? To find the answer, we combined a brief analysis of satellite imagery with previous knowledge about the process behind the erosion and how it has been occurring at Byron Bay. The erosion is due to a process known as “headland bypassing”, and it is quite different to erosion from storms.
Headland bypassing occurs when sand moves from one beach to another around a solid obstruction, such as a rocky headland or cape. This process is mainly driven by wave energy. Along the coast of southeast Australia, waves generate currents that move sand mostly northward along the northern NSW coastline, and on towards Queensland.
However, sand does not flow evenly or smoothly along the coast: when sand arrives at a beach just before a rocky headland, it builds up against the rocks and the beach grows wider. When there is too much sand for the headland to hold, or there’s a change in wave conditions, some sand will be pushed around the headland – bypassing it – before continuing its journey up the coast.
This large lump of moving sand is called a “sand pulse” or “sand slug”. The sand pulse needs the right wave conditions to move towards the shore. Without these conditions, the beach in front of the pulse is deprived of sand and the waves and currents near the shore erode the beach.
Headland bypassing was first described in the 1940s. However, only about 20 years ago was it recognised as an important part of the process controlling sand moving along the coast. Since then, with better technology and more data, researchers have studied the process in more detail, and helped to shed light on how headland bypassing might affect long-term coastal planning.
Recent studies have shown wave direction is particularly important to headland bypassing. Importantly, weather patterns that produce waves are affected by climate drivers including the El Niño Southern Oscillation and the Interdecadal Pacific Oscillation. So, future changes in the way these drivers behave will affect the waves and currents that move sand along our coast, which in turn affects headland bypassing and beach erosion.
In October and November this year, a large amount of sand was present just north of Cape Byron, from Wategos Beach to The Pass Beach. As this sand pulse grew, Clarkes Beach, and then Main Beach, were starved of their usual sand supply and began to erode.
The sand pulse is visible on satellite images from around April 2020. Each month, it slowly moves westward into the bay. As the sand pulse grows, the beach ahead of the pulse gradually erodes. At present Main Beach is at the eroding stage.
Similar erosion was observed at Main Beach in the early 1990s. The beach became wider again from 1995 to 2007. From 2009 onwards, the shoreline erosion slowly began again, and became very noticeable in the past six months.
The effect of sand pulses on beach erosion is not exclusive to Byron Bay. It has been described previously in other locations, such as NSW’s Kingscliff Beach in 2011. In that case, the erosion risked damaging a nearby holiday park and bowling club.
Mild waves from the east to northeast, which usually occur from October to April each year, will help some of the sand pulse move onto Clarkes Beach and then further along to Main Beach. This normally happens over several months to a year. But it’s hard to say exactly when the beach will be fully restored.
This uncertainty underscores the need to better forecast these processes. This would help us to predict when bypassing sand pulses will occur and to manage beach erosion.
Climate change is expected to affect wave conditions, although the exact impact on the headland bypassing process remains unclear. However, better predictions would allow the community to be informed early about expected impacts, and officials could better manage and plan for future erosion.
Meanwhile, Byron Bay waits and watches – knowing at least that the erosion problem will eventually improve.
Thomas Murray, Research Fellow (Coastal Management), Griffith University; Ana Paula da Silva, PhD Candidate, Griffith University; Darrell Strauss, Senior Research Fellow, Griffith University; Guilherme Vieira da Silva, Research Fellow, Griffith University, and Rodger Tomlinson, Director – Griffith Centre for Coastal Management, Griffith University
It’s been a busy couple of months in global energy and climate policy. Australia’s largest trading partners – China, South Korea and Japan – have all announced they will reach net-zero emissions by about mid-century. In the United States, the incoming Biden administration has committed to decarbonising its electricity system by 2035.
These pledges have big implications for Australia. With some of the best renewable resources in the world, we have much to gain from the transition. And this week, the New South Wales government embraced the opportunity.
Its new A$32 billion Electricity Infrastructure Roadmap will, among other things, support the construction of 12 gigawatts of new renewable energy capacity by 2030. This is six times the capacity of the state’s Liddell coal-fired power station, set to close in 2023.
The roadmap was developed by NSW Environment Minister Matt Kean through extensive consultation with industry and others, including ourselves. While we believe a national carbon price is the best way to reduce emissions, the NSW approach nonetheless sets an example for other states looking to increase renewable energy capacity. So let’s take a closer look at the plan.
The roadmap acknowledges that within 15 years, three-quarters of NSW’s coal-fired electricity supply is expected to reach the end of its technical life. It says action is needed now to ensure cheap, clean and reliable electricity, and to set up NSW as a global energy superpower.
The plan involves a coordinated approach to transmission, generation and storage. By 2030, the government aims to:
deliver about 12 gigawatts of new transmission capacity through so-called “renewable energy zones” in three regional areas by 2030. It would most likely be generated by wind and solar
support about 3 gigawatts of energy storage to help back up variable renewable energy supplies. This would involve batteries, pumped hydro, and “hydrogen ready” gas peaking power stations
attract up to A$32 billion in private investment in regional energy infrastructure investment by 2030
support more than 6,300 construction and 2,800 ongoing jobs in 2030, mostly in regional NSW
reduce NSW’s carbon emissions by 90 million tonnes.
The plan also aims to see the average NSW household save about A$130 a year in electricity costs, although this might be hard to achieve in practice. And regional landholders hosting renewable projects on their properties are expected to earn A$1.5 billion in revenue over the next 20 years.
One of the most innovative aspects of the NSW proposal is that generators will have two options when it comes to selling their electricity.
First, the government will appoint an independent “consumer trustee” to purchase electricity from generators at an agreed price – giving the generators the long-term certainty they need to invest. The trustee would then sell this electricity either directly to the market, or through contracts to retailers.
But the trustee will encourage generators to first seek a better price by finding their own customers, such as energy consumers and other electricity retailers.
This system is different to the approach adopted in Victoria and the ACT, where government contracts remove any incentive for generators to participate in the energy market. Over time, this limits market competition and innovation.
The NSW plan improves on existing state policies in another way – by aligning financial incentives to the physical needs of the system. The Consumer Trustee will enter into contracts with projects that produce electricity at times of the day when consumers need it, and not when the system is already oversupplied.
While this won’t be easy for the trustee to model, this approach is likely to benefit consumers more than in other jurisdictions where lowest-cost projects seem to be preferred, irrespective of whether the energy they produced is needed by consumers.
One shortcoming of the roadmap is it does not financially reward existing low-emissions electricity generators in NSW, nor does it charge carbon-heavy electricity producers for the emissions they produce. This could be corrected in the future by integrating the policy into a nationally consistent carbon price, which transfers the cost of carbon pollution onto heavy emitters.
NSW’s ageing coal-fired power stations are chugging along – albeit with ever-declining reliability. But it’s only a matter of time before something expensive needs fixing. This was the case with Hazelwood in Victoria: the old walls of the boilers had thinned to less than 2 millimetres. The repair cost was prohibitive and the station closed with just five months’ notice. Electricity prices shot up in response to unexpectedly reduced supply.
In NSW, the consumer trustee will be tasked with helping ensuring replacement generation is delivered in a timely way. This means developing new generation capacity well ahead of announced coal plant closures.
This is a helpful development. But ultimately a stronger measure will be needed to ensure coal plants give early notice of their intention to exit the market. The Grattan Institute has previously suggested coal generators put up bonds that are forfeited if they close early. We think this model is worth considering again.
As the world’s largest exporter of coal and LNG, Australia has much to lose as global economies shift to zero emissions. But our renewable energy potential means we also have much to gain.
Australia needs a durable, nationally consistent policy framework if we’re to seize the opportunities of the global transition to clean energy. The NSW roadmap is a significant step in the right direction.
The extreme, recent drought has devastated many communities around the Murray-Darling Basin, but the processes driving drought are still not well understood.
Our new study helps to change this. We threw a weather model into reverse and ran it back for 35 years to study the natural processes leading to low rainfall during drought.
And we found the leading cause for drought in the Murray-Darling Basin was that moisture from oceans didn’t reach the basin as often as normal, and produced less rain when it did. In fact, when moisture from the ocean did reach the basin during drought, the parched land surface actually made it harder for the moisture to fall as rain, worsening the already dry conditions.
These findings can help resolve why climate models struggle to simulate drought well, and ultimately help improve our ability to predict drought. This is crucial for our communities, farmers and bushfire emergency services.
The most recent drought was relentless. It saw the lowest rainfall on record in the Murray-Darling Basin, reduced agricultural output, led to increased food prices, and created tinder dry conditions before the Black Summer fires.
Drought in the Murray-Darling Basin is associated with global climate phenomena that drive changes in ocean and atmospheric circulation. These climate drivers include the El Niño and La Niña cycle, the Indian Ocean Dipole and the Southern Annular Mode.
Each influences the probability of rainfall over Australia. But drivers like El Niño can only explain around 20% of Australian rainfall — they only tell part of the story.
To fully understand the physical processes causing droughts to begin, persist and end, we need to answer the question: where does Australia’s rainfall come from? It may seem basic, but the answer isn’t so simple.
Broadly, scientists know rainfall derives from evaporation from two main sources: the ocean and the land. But we don’t know exactly where the moisture supplying Australia’s rainfall originally evaporates from, how the moisture supply changes between the seasons nor how it might have changed in the past.
To find out, we used a sophisticated model of Australia’s climate that gave data on atmospheric pressure, temperature, humidity, winds, rainfall and evaporation.
We put this data into a “back-trajectory model”. This traced the path of water from where it fell as rain, backwards in time through the atmosphere, to uncover where the water originally evaporated from. We did this for every day it rained over Australia between 1979 and 2013.
Not surprisingly, we found more than three-quarters of rain falling in Australia comes from evaporation from the surrounding oceans. So what does this mean for the Murray-Darling Basin?
During the Millennium Drought and other big drought years (such as in 1982), the Murray-Darling Basin heavily relied on moisture transported from the Tasman and Coral seas for rain. Moisture evaporated off the east coast needs easterly winds to transport it over the Great Dividing Range and into the Murray-Darling Basin, where it can form rain.
This means low rainfall during these droughts was a result of anomalies in atmospheric circulation, which prevented the easterly flow of ocean moisture. The droughts broke when moisture could once again be transported into the basin.
The Murray-Darling Basin was also one of the regions in Australia where most “rainfall recycling” happens. This is when, following rainfall, high levels of evaporation from soils and plants return to the atmosphere, sometimes leading to more rain – particularly in spring and summer.
This means if we change the way we use the land or the vegetation, there is a risk we could impact rainfall. For example, when a forest of tall trees is replaced with short grass or crops, humidity can go down and wind patterns change in the atmosphere above. Both of these affect the likelihood of rain.
In the northern part of the basin, less evaporation from the dry land surface exacerbated the low rainfall.
On the other hand, when the drought broke, more moisture evaporated from the damp land surface, adding to the already high levels of moisture coming from the ocean. This meant the region got a surplus of moisture, promoting even more rain.
This relationship was weaker in the southern part of the basin. But interestingly, rainfall there relied on moisture originating from evaporation in the northern basin, particularly during drought breaks. This is a result we need to explore further.
Rainfall and moisture sources for Australia and the Murray-Darling Basin are changing. In the past 35 years, the southeast of the country has been receiving less moisture in winter, and more in summer.
This is likely due to increased easterly wind flows of moisture from the Tasman Sea in summer, and reduced westerly flows of moisture from the Southern Ocean in winter.
This has important implications, particularly for agriculture and water resource management.
For example, more rainfall in summer can be a problem for horticultural farms, as it can make crops more susceptible to fungal diseases, decreases the quality of wine grape crops and affects harvest scheduling.
Less winter rain also means less runoff into creeks and rivers — a vital process for mitigating drought risk. And this creates uncertainty for dam operators and water resource managers.
Understanding where our rainfall comes from matters, because it can improve weather forecasts, seasonal streamflow forecasts and long-term rainfall impacts of climate change. For a drought-prone country like Australia — set to worsen under a changing climate — this is more crucial than ever.
Chiara Holgate, Hydrologist & PhD Candidate, Australian National University; Albert Van Dijk, Professor, Water and Landscape Dynamics, Fenner School of Environment & Society, Australian National University, and Jason Evans, Professor, UNSW
In the next few weeks, federal Environment Minister Sussan Ley will decide whether to approve a New South Wales quarry expansion that will destroy critical koala breeding grounds.
The case, involving the Brandy Hill Quarry at Port Stephens, is emblematic of how NSW environment laws are failing wildlife — particularly koalas. Efforts to erode koala protections hit the headlines last week when NSW Nationals leader John Barilaro threatened to detonate the Coalition over the issue.
Koala populations are already under huge pressure. A NSW parliamentary inquiry in June warned the koala faces extinction in the state by 2050 if the government doesn’t better control land clearing and habitat loss.
Ley could either continue these alarming trends, or set a welcome precedent for koala protection. Her decision is also the first big test of federal environment laws since an interim review found they were failing wildlife. So let’s take a closer look at what’s at stake in this latest controversy.
The NSW government gave approval to Hanson Construction Materials, a subsidiary of Heidelberg Cement, to expand the existing Brandy Hill Quarry in Seaham in Port Stephens.
The project would provide concrete to meet Sydney’s growing construction demands, as the state fast-tracks infrastructure projects to help the economy recover from COVID-19.
The approval came despite the known presence of koalas in the area. A koala survey report, completed on behalf of the developer in 2019, determined the project would “result in a significant impact to the koala”.
The report recommended the quarry expansion be referred to the federal Environment Minister under the Environment Protection and Biodiversity Conservation (EPBC) Act 1999, for its potential impacts on “Matters of National Environmental Significance”.
The expansion site intersects habitat with preferred high quality koala feed and shelter trees. This habitat is established forest containing various key mature Eucalyptus trees, including the forest red gum and swamp mahogany.
The survey report didn’t propose any mitigation strategies to sustain the habitat. Instead, it suggested minimisation measures, such as ecologists to be present during habitat clearing, low speed limits for vehicles on site, and education on koalas for workers.
In support of a community grassroots campaign (Save Port Stephens Koalas), we produced an report on the effect of the quarry expansion on koalas. The report now sits with Ley ahead of her decision, which is due by October 13.
The expansion will clear more than 50 hectares of koala habitat. We found koalas breeding within 1 kilometre of the current quarry boundary, which indicates the expansion site is likely to destroy critical koala breeding habitat.
During the breeding season, male koalas bellow to attract females. Within 1km of the boundary we observed a female koala and a bellowing male koala 96m apart. A second male was reported bellowing 227m from the quarry boundary.
What’s more, the site expansion occurs within a NSW government listed Area of Regional Koala Significance. The expansion site actually has higher average koala habitat suitability than all remaining habitat on the quarry property.
CSIRO research from 2016 suggests koalas in Port Stephens can move hundreds of metres in a day and up to 5km in one month. Movement is highest during the breeding season. This potential for koalas to move away was a key reason the NSW government approved the expansion.
Koalas can move in to the remaining property to breed, or they can move away from it. But habitat outside the expansion site is, on average, lesser quality, and this is where the expansion would force the koalas to move to.
This habitat fragmentation would not only result in lost access to potential breeding grounds, but also further restrict movement and expose koalas to threats such as predation or road traffic.
Lastly, the expansion would sever a crucial East–West corridor koalas likely use to move across the landscape and breed.
It may seem surprising this destructive project was approved by the NSW government. But it’s a common story under the state’s protections.
The expansion approval is an example of how the NSW government relaxed the regulatory requirements for land clearing between 2016 and 2017. This led to a 13-fold increase in land clearing approvals, and tipped the balance away from sustainable development.
The expansion shines another spotlight on NSW’s poor biodiversity offset laws.
Biodiversity offsets involve compensating for environmental damage in one location by improving the environment elsewhere. Under the expansions approval, the developer was required to protect an estimated 450 hectares of habitat as offset.
But the recent parliamentary inquiry into NSW koalas recommended offsetting of prime koala habitat — such as that involved in the quarry expansion — be prohibited, which would mean not destroying the habitat in the first place.
The NSW decision also does not account for the Black Summer Bushfires which claimed 5,000 koalas and burned millions of hectares of koala habitat. The Port Stephens population was unburned but more than 75% of its habitat has been lost since colonial occupation. Securing this population is important for the overall security of koalas in the state.
Rejections under these laws are rare; just 22 of 6,500 projects referred for approval under the act have been refused. However, it’s not impossible.
Earlier this year Ley rejected a wind-farm in Queensland which threatened unburned koala habitat. If Ley gives full consideration to the evidence in our report, she should make the same decision.
Lachlan G. Howell, PhD Candidate | School of Environmental and Life Sciences, University of Newcastle and Ryan R. Witt, Conjoint Lecturer | School of Environmental and Life Sciences, University of Newcastle