Saving these family-focused lizards may mean moving them to new homes. But that’s not as simple as it sounds


Holly Bradley, Author provided

Holly Bradley, Curtin University; Bill Bateman, Curtin University, and Darryl Fogarty, Indigenous KnowledgeAm I not pretty enough? This article is part of The Conversation’s series introducing you to unloved Australian animals that need our help.


Spiny-tailed skinks (Egernia stokesii badia), known as meelyu in the local Badimia language in Western Australia, are highly social lizards that live together in family groups — an uncommon trait among reptiles.

They’re culturally significant to the Badimia people but habitat degradation and mining has put them under threat of extinction.

These sturdy, mottled lizards — which live in colonies in the logs of fallen trees and branches — are a candidate for what researchers call “mitigation translocation”.

That’s where wildlife are relocated away from high-risk areas (such as those cleared for urban development or mining) to lower risk areas.

It might sound simple. But research shows these mitigation translocation decisions are often made on an ad hoc basis, without a long-term strategic plan in place.

Example of the range in individual size/age occupying the same permanent log pile structure within the Mid West region of Western Australia.
Holly Bradley, Author provided

Not enough pre-planning or follow-up

There has been much research into assisted relocation of larger, charismatic mammals and birds. But other animals, such as reptiles with a less positive social image, have been less widely studied.

Our recent research has found there is often little pre-planning or follow-up to monitor success of mitigation translocations, even though reptile mitigation translocations do take place, sometimes on a large scale.

In fact, fewer than 25% of mitigation translocations worldwide actually result in long-term self-sustaining populations.

Mitigation translocation methods are also not being improved. Fewer than half of published mitigation translocation studies have explicitly compared or tested different management techniques.

Mitigation translocation studies also rarely consider long-term implications such as how relocated animals can impact the site to which they are moved — for example, if the ecosystem has limited capacity to support the relocated animals.

But it’s not just about ecosystem benefits. Preservation of species such as meelyu also has cultural benefits — but mitigation translocation can only be part of the solution if it’s done strategically.




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The meelyu: a totem species

As part of Holly Bradley’s research into understanding how to protect meelyu from further loss in numbers, she had the privilege to meet with Badimia Indigenous elder, Darryl Fogarty, who identified meelyu as his family’s totem.

Totemic species can represent a person’s connection to their nation, clan or family group.

The meelyu or Western Spiny-tailed Skink is significant to the Badimia people and require translocation as part of mine site restoration and mitigation of population loss.
Holly Bradley, Author provided

Unfortunately, Darryl Fogarty cannot remember the last time he saw the larger meelyu in the area. The introduction of European land management and feral species into Western Australia has upset the ecosystem balance — and this also has cultural consequences.

Preserving totemic fauna in their historic range can be a critical component of spiritual connection to the land for Indigenous groups in Australia.

In the past, this spiritual accountability for the stewardship of a totem has helped protect species over the long term, with this responsibility passed down between generations.

Before European colonisation, this traditional practice helped to preserve biodiversity and maintain an abundance of food supplies.

A strategic approach to future meelyu relocations from areas of active mining is crucial to prevent further population losses — for both ecological and cultural reasons.

Good mitigation translocation design

If we are to use mitigation translocation to shore up their numbers, we need effective strategies in place to boost the chance it will actually help the meelyu.

Good mitigation translocation design includes factors such as:

  • selecting a good site and understanding properly whether it can support new wildlife populations
  • having a good understanding of the animal’s ecological needs and how they fit with the environment to which they’re moving
  • using the right methods of release for the circumstances. For example, is it better to use a soft release method, where an individual animal is gradually acclimatised to its new environs over time? Or a hard release method, where the animal is simply set free in its new area?
  • having a good understanding of the cultural factors involved.

A holistic approach

A holistic approach to land management and restoration practice considers both cultural and ecological significance.

It supports the protection and return of healthy, functioning ecosystems — as well as community well-being and connection to nature.

Mitigation translocation could have a role to play in protection of culturally significant wildlife like the meelyu, but only when it’s well planned, holistic and part of a long term strategy.




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Photos from the field: Australia is full of lizards so I went bush to find out why


The Conversation


Holly Bradley, PhD candidate, Curtin University; Bill Bateman, Associate professor, Curtin University, and Darryl Fogarty, Badimia Elder, Indigenous Knowledge

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

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


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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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.


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._The Conversation

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.

How Traditional Owners and officials came together to protect a stunning stretch of WA coast


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Jim Underwood, Australian Institute of Marine ScienceRecent disasters such as the Black Summer bushfires and the Juukan Gorge destruction highlighted the need to put Indigenous people at the centre of decision-making about Australia’s natural places. But what’s the right way to combine traditional ancient wisdom with modern environmental management?

A project off Western Australia’s northwest coast offers a potential way forward. For the first time in the state’s history, Indigenous knowledge has been central to the design of a marine park.

The protected area will span 660,000 hectares northeast of Broome, taking in the stunning Buccaneer Archipelago and Dampier Peninsula. The area comprises thousands of small islands fringed by coral reefs and seagrass beds. The waters support a rich abundance of species such as corals, fish, turtles and dugongs, as well as humpback whales which give birth in the region.

Often, Indigenous input is sought only in the consultation phase of park planning, once maps have been drawn up. But in this case, Traditional Owners co-designed three marine parks with the state government and will jointly manage them. Traditional ecological and cultural wisdom has been embraced and valued, enhancing Western scientific knowledge of a fragile stretch of Australia’s coast.

two men on boat
Traditional owners have been caring for country for thousands of years.
Nick Thake

Caring for Sea Country

The marine park co-design is a collaboration between WA’s Department of Biodiversity, Conservation and Attractions and Bardi Jawi, Mayala and Dambeemangarddee Traditional Owners. It will comprise three adjoining protected areas, each jointly managed by a Traditional Owner group.

The Buccaneer Archipelago region has the state’s highest concentration of Traditional Owner communities living adjacent to an existing or proposed marine park.

Local Indigenous people refer to these areas as “Sea Country”. They depend on the waters for food and to carry out traditional practices, and have cared for them sustainably for thousands of years.

But to date, the state’s conservation reserve system has not adequately protected these unique and exceptionally diverse marine ecosystems.

Industry, fishing and tourism are putting pressure on the region’s environment. In particular, the recent sealing of Cape Leveque Road improved access to the Dampier Peninsula and will result in massive increases in tourism and boating.

Adding to this, marine heatwaves and other climate-related changes pose a serious threat to corals, macroalgae and seagrass.




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red cliffs at beach
A new sealed road to Cape Leveque will add to pressures on the marine area.
Shutterstock

Genuine two-way partnerships

Combining traditional Indigenous knowledge with a Western approach requires methods that are both culturally appropriate and scientifically robust.

In 2018, Bardi Jawi rangers and staff from the Australian Institute of Marine Science carried out “participatory mapping” to design a mornitoring program for corals and fish. The rangers and marine park planners went on to use this method when designing the marine park.

Participatory mapping starts with Traditional Owners and marine park planners documenting the traditional owners’ ecological knowledge, cultural values and aspirations. From this, maps are developed then built on via on-Country observations.

This process allows scientists to record and understand traditional knowledge of an environment in a way that is also useful for Western conservation and management planning.

people look at map
Participatory mapping involves traditional owners and marine park planners.
Nick Thake

The co-design approach was built on genuine partnerships, mutual respect and two-way learning. The partnerships developed over several years through other joint projects by scientists and Bardi Jawi rangers.

The department listened to and implemented this strong Indigenous voice in the development of the marine parks’ draft plans.

According to the Traditional Owners themselves, the sea is fundamental to the spiritual, social and physical existence. Their diet relies heavily on food from the sea such as fish, turtles, dugongs, crabs and oysters. Under Indigenous laws, traditional owners are required to protect significant features in the sea and for some groups, resources such as pearl shell has traditionally been collected and used for ceremony and trade.

A WA government document outlines how the proposed marine parks contain “special purpose zones” to protect traditional culture and heritage. They allow for seasonal camping areas and places where Traditional Owners can collect customary food and other resources. They will also protect culturally significant features such as cultural sites reefs, seagrass beds and mangrove communities.

The document also says the proposal protects places with “intangible” value related to traditional law, ceremony and stories.

These zones are in addition to sanctuary zones protecting areas of critical habitat, and general use zones where sustainable activities are allowed.




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man sits while fishing on beach
Science informs the activities allowed in each zone.
Shutterstock

Scientific rigour

Protected areas in marine parks must be sized, spaced and positioned to allow “population connectivity” – the dispersal of eggs, larvae, juveniles and adults through the area.

My involvement in the marine park design included participating in a study which led to recommendations for how best to achieve this connectivity.

The study was part of a bigger program to improve and integrate ecological and social science knowledge in this region. This information was incorporated into two-way learning and planning, which fed into the proposed marine park.

Proven on-ground success

Key to the success of the new marine parks will be the practical capacity of Traditional Owners and Rangers. Indigenous sea ranger groups in the region have already shown they can work with both traditional governance and knowledge structures and non-Indigenous Australian organisations.

What’s more, the Bardi Jawi, Dambeemangarddee and Mayala people have their own healthy country plans. These plans clearly document how they have looked after country for millennia and want to continue this in future.

The Bardi Jawi and Dambeemanagrdee people have also established an Indigenous Protected Area which they’ve successfully cared for since 2013.

Healthy Country, healthy people

Some recreational fishers believe the proposed exclusions are unreasonable. But there is growing evidence fish populations benefit from sanctuary networks. And many local fishers recognise the increasing threats to the region and welcome Traditional Owners playing a larger management role.

It’s hoped the final marine parks plan will find the right balance between the needs of Traditional Owners, commercial and recreational fishing, pearling and other uses.

By involving traditional custodians from the start, there’s every chance we will realise the ancient Indigenous idea that healthy Country means healthy people – and that will benefit everyone.


The author would like to acknowledge the Bardi Jawi, Mayala and Dambeemangarddee Traditional Owners and their continuing culture, knowledge, beliefs and spiritual connection to Country. The author recognises they are Australia’s first scientists.The Conversation

Jim Underwood, Research Fellow and Indigenous Partnerships, Australian Institute of Marine Science

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

This adorable mouse was considered extinct for over 100 years — until we found it hiding in plain sight


Wayne Lawler/Australian Wildlife Conservancy, Author provided

Emily Roycroft, Australian National UniversityAustralia has the world’s worst track record for wiping out mammals, with 34 species declared extinct since European colonisation. Many of these are humble native rodents, who’ve suffered the highest extinction rate of any mammal group.

But today, we bring some good news: one rodent species, Gould’s mouse (Pseudomys gouldii), is set to be crossed off Australia’s extinct species list. This means the number of Australia’s extinct mammals will drop from 34 to 33.

Our new research compared genome sequences across Australia’s rodents, including eight extinct species and their 42 living relatives. In a case of historical mistaken identity, we found the Gould’s mouse was genetically indistinguishable from another living species, the Shark Bay mouse (Pseudomys fieldi), also known by the Indigenous name “Djoongari” from the Pintupi and Luritja languages.

But it’s not all good news. A lack of genetic diversity in remaining populations means Djoongari are less resilient to changing environments, including from climate change. We can’t let this species die out — this time, there’d be no coming back.

Back from the dead

When Europeans colonised Australia, they rapidly and catastrophically changed the environments in which native species thrived. The introduction of feral cats, foxes and other invasive species, agricultural land clearing, inappropriate fire management, and new diseases decimated native rodent populations.

Along with many other native mammals, some rodent species were also intensely hunted for bounty in the late 19th and early 20th centuries.

DNA from this specimen of Gould’s mouse, collected in 1837 from the Hunter Valley of NSW, reveals the species should no longer be considered extinct.
Trustees of the Natural History Museum, London Photographer: C. Ching, Author provided

In 1837, a Gould’s mouse specimen was collected for the Natural History Museum, London, from the Hunter Valley of New South Wales. The last verified time it was seen alive was in 1857, near the border of Victoria and NSW.

After genomic analysis of these specimens, we found the species has been hiding in plain sight for more than 100 years, under a different name, thousands of kilometres away in Western Australia. Djoongari will now be reclassified under the scientific name Pseudomys gouldii.

Djoongari is a shaggy-coated mouse weighing 45 grams on average, making it twice the size of the invasive house mouse. It’s omnivorous, and feeds on a variety of flowers, leaves, fungi, insects and spiders. It also build tunnels and runways to travel at night, and uses above-ground nests as refuges during the day.

Not safe yet

The resurrection of the Gould’s mouse is positive news given Australia’s alarming rate of recent extinctions, but the species remains at risk.

Once occurring across mainland Australia, it now survives only on predator-free islands in Shark Bay, WA. Islands have been an important refuge for the species, protecting them from cats, foxes, diseases and other threats on the mainland.

Feral and pet cats are huge threats to small native animals. If you own a cat, make sure you keep it indoors to protect Australia’s wildlife.
Shutterstock

Conservation efforts are underway to protect the mouse in Shark Bay, with insurance populations established on other nearby islands.

Now we know Djoongari once roamed as far east as the Hunter Valley in NSW, there’s greater scope to reintroduce the species to predator-proof protected areas on the mainland. This would mean more insurance populations, but also contribute towards restoring natural ecosystems on mainland Australia — also known as “rewilding”.

However, remnant populations of this once widespread species contain only a fraction of its original genetic diversity.




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Genetic diversity is often used as a proxy for estimating the resilience of a species to threats and its potential to adapt to changes in its environment. When species have low genetic diversity, or are inbred, they are more susceptible to disease, and more likely to accumulate harmful genetic mutations.

Other eye-opening revelations

Our study also examined the genomes of seven other rodent species lost to extinction: the white-footed rabbit rat, lesser stick-nest rat, Bramble Cay melomys, short-tailed hopping mouse, long-tailed hopping mouse, big-eared hopping mouse and long-eared mouse.

Brown rodent
Bramble cay melomys were declared extinct in 2016.
Ian Bell, EHP, State of Queensland, CC BY-SA

In most cases, we found these now-extinct native rodents had relatively high genetic diversity immediately before they became extinct. High genetic diversity usually means large population sizes, suggesting native rodent populations were stable before European invasion.

This puts an end to any suggestion that these species were already on their way out prior to the arrival of Europeans.

Reports from early naturalists back up our findings. In 1846, John Cotton referred to the now-extinct white-footed rabbit rat as “the common rat of the country”. And in 1866, Gerard Krefft described the now-extinct lesser stick-nest rat as occurring in “great numbers”.




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These species went from common to extinct in less than 150 years. That’s alarmingly fast by any standard.

It shows even though genetic diversity in now-extinct rodents was high prior to colonisation, it wasn’t enough. The environment and threats changed so dramatically and rapidly, these species didn’t have the chance to adapt.

There’s a clear lesson in all this

The threats to native wildlife brought by Europeans — including feral cat predation and land clearing — are ongoing. And under climate change, the environment as we know it is set to change further, dramatically.

It’s not enough to only establish insurance populations to save species. We need to control feral predators, protect and restore habitats, and curb emissions, so more species don’t endure a rapid wipe out.

In total, we’ve lost almost 100 species to extinction since 1788, and that’s just those we know about. In native rodents alone, in less than 150 years, the equivalent of more than 10 million years of unique evolutionary history has been lost forever.

Extinction doesn’t usually offer second chances, but we’ve now got another shot to protect Gould’s mouse. We need to act now, before it’s too late.




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Scientists re-counted Australia’s extinct species, and the result is devastating


The Conversation


Emily Roycroft, Postdoctoral Research Fellow, Australian National University

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

We found a secret history of megadroughts written in tree rings. The wheatbelt’s future may be drier than we thought


An almost-dry dam, surrounded by wheat fields, in WA’s wheatbelt region.
Shutterstock

Alison O’Donnell, The University of Western Australia; Edward Cook, Columbia University, and Pauline Grierson, The University of Western AustraliaDrought over the last two decades has dealt a heavy blow to the wheatbelt of Western Australia, the country’s most productive grain-growing region. Since 2000, winter rainfall has plummeted by almost 20% and shifted grain-growing areas towards the coast.

Our recent research, however, found these dry conditions are nothing out of the ordinary for the region.

In fact, after analysing rings in centuries-old tree trunks, we found the region has seen far worse “megadroughts” over the last 700 years. Australia’s instrumental climate records only cover the last 120 or so years (at best), which means these historic droughts may not have previously been known to science.

Our research also found the 20th century was the wettest of the last seven centuries in the wheatbelt. This is important, because it means scientists have likely been underestimating the actual risk of drought – and this will be exacerbated by climate change.

What we can learn from ancient trees

We estimate the risk of extreme climate events, such as droughts, cyclones and floods, based on what we know from instrumental climate records from weather stations. Extending climate records by hundreds or even thousands of years means scientists would be able to get a much better understanding of climate variability and the risk of extreme events.

_Callitris_ trees overlooking a salt lake
Callitris trees overlooking a salt lake. We pulled a column of wood from these tree trunks to investigate past climate changes in the region.
Alison O’Donnell, Author provided

Thankfully we can do just that in many parts of the world using proxy records — things like tree rings, corals, stalagmites and ice cores in Antarctica. These record evidence of past climate conditions as they grow.

For example, trees typically create a new layer of growth (“growth ring”) around their trunks, just beneath the bark, each year. The amount of growth generally depends on how much rain falls in the year. The more it rains, the more growth and the wider the ring.

Tree rings of Callitris columellaris.
Alison O’Donnell, Author provided

We used growth rings of native cypress trees (Callitris columellaris) near a large salt lake at the eastern edge the wheatbelt region. These trees can live for up to 1,000 years, perhaps even longer.

We can examine the growth rings of living trees without cutting them down by carefully drilling a small hole into the trunk and extracting a column (“core”) of wood about the size of a drinking straw. By measuring the ring widths, we developed a timeline of tree growth and used this to work out how much rain fell in each year of a tree’s life.

This method allowed us to reconstruct the last 668 years of autumn-winter rainfall in the wheatbelt.

A tree trunk with a blue scientific instrument attached
A tree borer – a hollow drill used to extract ‘cores’ of wood from tree trunks.
Alison O’Donnell, Author provided

A history of megadroughts

One of the most pressing questions for the wheatbelt is whether the decline in autumn-winter rainfall observed in recent decades is unusual or extreme. Our extended record of rainfall lets us answer this question.

Yes, rainfall since 2000 was below the 668-year average — but it was not extremely low.

The last two decades may seem particularly bad because our expectations of rainfall in the wheatbelt are likely based on memories of higher rainfall. But this frequent wet weather has actually been the anomaly. Our tree rings revealed the 20th century was wetter than any other in the last 700 years, with 12% more rain in the autumn-winter seasons on average than the 19th century.




Read more:
500 years of drought and flood: trees and corals reveal Australia’s climate history


Before the 20th century, the wheatbelt saw five droughts that were longer and more severe than any we’ve experienced in living memory, or have recorded in instrumental records. This includes two dry periods in the late 18th and 19th centuries that persisted for more than 30 years, making them “megadroughts”.

While the most recent dry period has persisted for almost two decades so far, rainfall during this period is at least 10% higher than it was in the two historical megadroughts.

This suggests prolonged droughts are a natural and relatively common feature of the wheatbelt’s climate.

An aerial view of the tree-ring site, home to trees that can live up to 1,000 years.
Hannah Etchells, Author provided

So how does human-caused climate change play into this?

It’s likely both natural climate variability and human-caused climate change contributed to the wheatbelt’s recent decline in rainfall. Unfortunately, it’s also likely their combined influence will lead to even less rainfall in the near future.

What happens now?

Our findings have important implications for assessing the risk of drought. It’s now clear we need to look beyond these instrumental records to more accurately estimate the risk of droughts for the wheatbelt.

But currently, proxy climate records like tree rings aren’t generally used in drought risk models, as there aren’t many of them in the regions scientists want to research.

Improving risk estimates leads to better informed decisions around preparing for and managing the effects of droughts and future natural disasters.




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Our findings are a confronting prospect for the future of farming in the wheatbelt.

Australian farmers have shown tremendous innovation in their ability to adapt in the face of drought, with many shifting from livestock to crops. This resilience will be critical as farmers face a drier, more difficult future.The Conversation

Alison O’Donnell, Research Fellow in Dendroclimatology, The University of Western Australia; Edward Cook, Ewing Lamont Research Professor, Director Of Tree-Ring Lab, Columbia University, and Pauline Grierson, Director, West Australian Biogeochemistry Centre, The University of Western Australia

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

Cyclone Seroja just demolished parts of WA – and our warming world will bring more of the same


Bureau of Meteorology

Jonathan Nott, James Cook UniversityTropical Cyclone Seroja battered parts of Western Australia’s coast on Sunday night, badly damaging buildings and leaving thousands of people without power. While the full extent of the damage caused by the Category 3 system is not yet known, the event was unusual.

I specialise in reconstructing long-term natural records of extreme events, and my historic and prehistoric data show cyclones of this intensity rarely travel as far south as this one did. In fact, it has happened only 26 times in the past 5,000 years.

Severe wind gusts hit the towns of Geraldton and Kalbarri – towns not built to withstand such conditions.

Unfortunately, climate change is likely to mean disasters such as Cyclone Seroja will become more intense, and will be seen further south in Australia more often. In this regard, Seroja may be a timely wake-up call.

Seroja: bucking the cyclone trend

Cyclone Seroja initially piqued interest because as it developed off WA, it interacted with another tropical low, Cyclone Odette. This rare phenomenon is known as the Fujiwhara Effect.

Cyclone Seroja hit the WA coast between the towns of Kalbarri and Gregory at about 8pm local time on Sunday. According to the Bureau of Meteorology it produced wind gusts up to 170 km/hour.

Seroja then moved inland north of Geraldton, weakening to a category 2 system with wind gusts up to 120 km/hour. It then tracked further east and has since been downgraded to a tropical low.

The cyclone’s southward track was historically unusual. For Geraldton, it was the first Category 2 cyclone impact since 1956. Cyclones that make landfall so far south on the WA coast are usually less intense, for several reasons.

First, intense cyclones draw their energy from warm sea surface temperatures. These temperatures typically become cooler the further south of the tropics you go, depleting a cyclone of its power.

Second, cyclones need relatively low speed winds in the middle to upper troposphere – the part of the atmosphere closest to Earth, where the weather occurs. Higher-speed winds there cause the cyclone to tilt and weaken. In the Australian region, these higher wind speeds are more likely the further south a cyclone travels.

Third, most cyclones make landfall in the northern half of WA where the coast protrudes far into the Indian Ocean. Cyclones here typically form in the Timor Sea and move southward or south-west away from WA before curving southeast, towards the landmass.

For a cyclone to cross the coast south of about Carnarvon, it must travel a considerable distance towards the south-west into the Indian Ocean. This was the case with Seroja – winds steered it away from the WA coast before they weakened, allowing the cyclone to curve back towards land.

Reading the ridges

My colleagues and I have devised a method to estimate how often and where cyclones make landfall in Australia.

As cyclones approach the coast, they generate storm surge – abnormal sea level rise – and large waves. The surge and waves pick up sand and shells from the beaches and transport them inland, sometimes for several hundred metres.

These materials are deposited into ridges which stand many metres above sea level. By examining these ridges and geologically dating the materials within them, we can determine how often and intense the cyclones have been over thousands of years.




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Our new model shows Australia can expect 11 tropical cyclones this season


At Shark Bay, just north of where Seroja hit the coast, a series of 26 ridges form a “ridge plain” made entirely of one species of a marine cockle shell (Fragum eragatum). The sand at beaches near the plain are also made entirely of this shell.

The ridge record shows over the past 5,000 years, cyclones of Seroja’s intensity, or higher, have crossed the coast in this region about every 190 years – so about 26 times. Some 14 of these cyclones were more intense than Seroja.

The record shows no Category 5 cyclones have made landfall here over this time. The ridge record prevents us from knowing the frequency of less intense storms. But Bureau of Meteorology cyclone records since the early 1970s shows only a few crossed the coast in this region, and all appear weaker than Seroja.

Emergency services crews in the WA town of Geraldton, preparing ahead of the arrival of Tropical Cyclone Seroja
Emergency services crews in the WA town of Geraldton, preparing ahead of the arrival of Tropical Cyclone Seroja – an event rarely seen this far south.
Department of Fire and Emergency Services WA

Cyclones under climate change

So why does all this matter? Cyclones can kill and injure people, damage homes and infrastructure, cause power and communication outages, contaminate water supplies and more. Often, the most disadvantaged populations are worst affected. It’s important to understand past and future cyclone behaviour, so communities can prepare.

Climate change is expected to alter cyclone patterns. The overall number of tropical cyclones in the Australian region is expected to decrease. But their intensity will likely increase, bringing stronger wind and heavier rain. And they may form further south as the Earth warms and the tropical zone expands poleward.

This may mean cyclones of Seroja’s intensity are likely to become frequent, and communities further south on the WA coast may become more prone to cyclone damage. This has big implications for coastal planning, engineering and disaster management planning.

In particular, it may mean homes further south must be built to cope with stronger winds. Storm surge may also worsen, inundating low-lying coastal land.

Global climate models are developing all the time. As they improve, we will gain a more certain picture of how tropical cyclones will change as the planet warms. But for now, Seroja may be a sign of things to come.




Read more:
Wetlands have saved Australia $27 billion in storm damage over the past five decades


This article is part of Conversation series on the nexus between disaster, disadvantage and resilience. Read the rest of the stories here.The Conversation

Jonathan Nott, Professor of Physical Geography, James Cook University

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

We tested tiger snake scales to measure wetland pollution in Perth. The news is worse than expected


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Damian Lettoof, Curtin University; Kai Rankenburg, Curtin University; Monique Gagnon, Curtin University, and Noreen Evans, Curtin University

Australia’s wetlands are home to a huge range of stunning flora and fauna, with large snakes often at the top of the food chain.

Many wetlands are located near urban areas. This makes them particularly susceptible to contamination as stormwater, urban drainage and groundwater can wash metals — such as arsenic, cadmium, lead and mercury — into the delicate ecosystem.

We know many metals can travel up the food chain when they’re present in the environment. So to assess contamination levels, we caught highly venomous tiger snakes across wetlands in Perth, and repurposed laser technology to measure the metals they accumulated.

In our new paper, we show metal contamination in wild wetland tiger snakes is chronic, and highest in human-disturbed wetlands. This suggests all other plants and animals in these wetlands are likely contaminated as well.

34 times more arsenic in wild wetland snakes than captive snakes

Urban growth and landscape modification often introduces metals into the surrounding environment, such as mining, landfill and waste dumps, vehicles and roadworks, and agriculture.

When they reach wetlands, sediments collect and store these metals for hundreds of years. And if a wetland’s natural water levels are lowered, from agricultural draining for example, sediments can become exposed and erode. This releases the metals they’ve been storing into the ecosystem.

A reflective lake, with green vegetation surrounding it
The wetland in Yanchep National Park, Perth, was supposed to be our ‘clean’ comparison site. Its levels of metal contamination was unprecedented.
Shutterstock

This is what we suspect happened in Yanchep National Park’s wetland, which was supposed to be our “clean” comparison site to more urban wetlands. But in a 2020 study looking at sediment contamination, we found this wetland had higher levels of selenium, mercury, chromium and cadmium compared to urban wetlands we tested.

And at Herdsman Lake, our most urban wetland five minutes from the Perth city centre, we found concentrations of arsenic, lead, copper and zinc in sediment up to four times higher than government guidelines.




Read more:
Does Australia really have the deadliest snakes? We debunk 6 common myths


In our new study on tiger snake scales, we compared the metal concentrations in wild wetland tiger snakes to the concentrations that naturally occurs in captive-bred tiger snakes, and to the sediment in the previous study.

We found arsenic was 20-34 times higher in wild snakes from Herdsman Lake and Yanchep National Park’s wetland. And snakes from Herdsman Lake had, on average, eight times the amount of uranium in their scales compared to their captive-bred counterparts.

Tiger snake on the ground, near rubbish.
Our research confirmed snake scales are a good indicator of environmental contamination.
Damian Lettoof, Author provided

Tiger snakes usually prey on frogs, so our results suggest frogs at these lakes are equally as contaminated.

We know for many organisms, exposure to a high concentration of metals is fatally toxic. And when contamination is chronic, it can be “neurotoxic”. This can, for example, change an organism’s behaviour so they eat less, or don’t want to breed. It can also interfere with their normal cellular function, compromising immune systems, DNA repair or reproductive processes, to name a few.

Snakes in general appear relatively resistant to the toxic effects of metal contamination, but we’re currently investigating what these levels of contamination are doing to tiger snakes’ health and well-being.

Our method keeps snakes alive

Snakes can be a great indicator of environmental contamination because they generally live for a long time (over 10 years) and don’t travel too far from home. So by measuring metals in older snakes, we can assess the contamination history of the area they were collected from.

Typically, scientists use liver tissue to measure biological contamination since it acts like a filter and retains a substantial amount of the contaminants an animal is exposed to.

But a big problem with testing the liver is the animal usually has to be sacrificed. This is often not possible when studying threatened species, monitoring populations or working with top predators.

Two black swans in a lake, near cut grass
Sediment in Herdsman Lake had four times higher heavy metal levels than what government guidelines allow.
Shutterstock

In more recent years, studies have taken to measuring metals in external “keratin” tissues instead, which include bird feathers, mammal hair and nails, and reptile scales. As it grows, keratin can accumulate metals from inside the body, and scientists can measure this without needing to kill the animal.

Our research used “laser ablation” analysis, which involves firing a focused laser beam at a solid sample to create a small crater or trench. Material is excavated from the crater and sent to a mass spectrometer (analytical machine) where all the elements are measured.

This technology was originally designed for geologists to analyse rocks, but we’re among the first researchers applying it to snake scales.

Laser ablation atomises the keratin of snake scales, and allowed us to accurately measure 19 contaminants from each tiger snake caught over three years around different wetlands.

Wild tiger snake
Snakes generally appear resistant to the toxic effects of heavy metals.
Kristian Bell/Shutterstock

We need to minimise pollution

Our research has confirmed snake scales are a good indicator of environmental contamination, but this is only the first step.

Further research could allow us to better use laser ablation as a cost-effective technology to measure a larger suite of metals in different parts of the ecosystem, such as in different animals at varying levels in the food chain.

This could map how metals move throughout the ecosystem and help determine whether the health of snakes (and other top predators) is actually at risk by these metal levels, or if they just passively record the metal concentrations in their environment.




Read more:
Our toxic legacy: bushfires release decades of pollutants absorbed by forests


It’s difficult to prevent contaminants from washing into urban wetlands, but there are a number of things that can help minimise pollution.

This includes industries developing strict spill management requirements, and local and state governments deploying storm-water filters to catch urban waste. Likewise, thick vegetation buffer zones around the wetlands can filter incoming water.The Conversation

Damian Lettoof, PhD Candidate, Curtin University; Kai Rankenburg, Researcher, Curtin University; Monique Gagnon, Researcher, Curtin University, and Noreen Evans, Professor, Curtin University

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