New approach needed to save Australia's non-perennial rivers

Non-perennial rivers, which stop flowing at some point each year, dominate surface water movement across Australia, yet monitoring the continued health of these vital waterways demands a new type of research attention.

More than 70% of this nation's rivers are non-perennial due to a combination of ancient landscape, dry climates, highly variable rainfall regimes, and human interventions that have altered riverine environments.

An extensive review of current research incorporating geomorphology, hydrology, biogeochemistry, ecology and Indigenous knowledges identifies prevailing factors that shape water and energy flows in Australia's non-perennial rivers -- but the review also points to research deficiencies that must be addressed if these river systems are to be preserved and protected.

"Australia relies on our rivers, and has a strong history of research to understand river flows and ecosystems and the human impacts on them. Now, we must address emerging threats to river systems due to climate change and other anthropogenic impacts," says lead author of the review, Dr Margaret Shanafield, from Flinders University's College of Science and Engineering.

"We have to work together to tackle emerging threats to our rivers. If we are going to plug gaps in existing knowledge, which this review identifies, then a new style of inter-disciplinary scientific research is necessary to achieve the required outcomes."

While dominant research themes in Australia focus on drought, floods, salinity, dryland ecology and water management, four other areas of research attention are urgently needed, namely:

•     Integrating Indigenous and western scientific knowledge;
•     Quantifying climate change impacts on hydrological and biological function;
•     Clarifying the meaning and measurement of "restoration" of non-perennial systems;
•     Understanding the role of groundwater.

Addressing these areas through multi-disciplinary efforts supported by technological advances will provide a map for improved water research outcomes that the rest of the world can follow.

"Australia is globally unique in its spread and diversity of non-perennial rivers spanning climates and landforms -- but most, if not all, of the classes of non-perennial rivers found in Australia also occur in other regions of the world with similar climates and geology," says Dr Shanafield.

"Therefore, the evolving body of knowledge about Australian rivers provides a foundation for comparison with other dryland areas globally where recognition of the importance of non-perennial rivers is expanding."

The review authors are concerned that Australian non-perennial river research has been driven by the needs of its inhabitants for survival, agriculture, resource economics, environmental concern and politics.

"Considering the continent's ancient geological history and its harsh, arid climate, it comes as no surprise that significant attention has been directed toward water resource management during drought periods, the reduction of salinisation, and gaining insights into the intricate dynamics of the transient rivers that are a defining feature of central Australia," says the review.

"The prevalence of prolonged drought periods has had a marked impact on driving research -- so it is critical to address the knowledge gaps this review has identified, given that increasing trends in hydrological droughts are projected to negatively impact streamflow not just in Australia, but also in South America, southern Africa, and the Mediterranean."

The review authors -- a multi-disciplinary collective of scientists from across more than two dozen institutions and government departments -- say more investment in long-term hydrological monitoring is desperately needed to increase water management knowledge that can address the competing water needs of communities, agriculture, mining and ecosystems in a dry environment -- not only in Australia, but throughout the world.

"We anticipate that changing global water fluxes and continued groundwater pumping will cause more of the world's rivers to become non-perennial, accelerating our need to understand these systems across many disciplines," says Dr Shanafield.

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Climate change will see Australia's soil emit CO2 and add to global warming

New Curtin University research has shown the warming climate will turn Australia's soil into a net emitter of carbon dioxide (CO2), unless action is taken.

Soil helps to keep the planet cool by absorbing carbon, however as the climate gets warmer its ability to retain carbon decreases -- and in some instances can start to release some carbon back into the air.

A global research team -- led by Professor Raphael Viscarra Rossel from Curtin's School of Molecular and Life Sciences -- predicted the changes in the amount of carbon in Australia's soil between now and the year 2100.

To do so, the team ran simulations using three different paths for society: an eco-focused 'sustainable' scenario, a 'middle-of-the-road' scenario and another which predicted a continued reliance on 'fossil-fuelled development'.

It found Australian soil will be a net emitter and could account for 8.3 per cent of Australia's total current emissions under the 'sustainable' scenario and more than 14 per cent by 2045 under the 'middle-of-the-road' and 'fossil-fuelled' scenarios.

By 2100, soil emissions under both scenarios are predicted to account for an even higher proportion of total emissions, but the predictions are more uncertain.

While some areas with arable farmland could continue to store carbon, the study found it would not be enough to offset the amounts of carbon lost from the soil in areas which are more sensitive to warmer weather, such as coastal regions and Australia's vast rangelands.

Australian soil holds an estimated 28 gigatons of carbon, 70 per cent of which is stored in these rangelands.

"Unless farming methods are further improved so farmland soils can continue to store carbon, any gains and benefit will likely decrease by 2045 and worsen in time, if the Earth continues to warm at its current rate," Professor Viscarra Rossel said.

"This means Australia's soil could release even more carbon into the air instead of storing it, which will in turn make climate change worse.

"If emissions continue at the current rate, the Earth's temperature is expected to reach 2 degrees above pre-industrial temperatures sometime this century, which is predicted to have dire consequences and

potentially catastrophic impacts for the planet."

Professor Viscarra Rossel said more sustainable pathways and improved management and conservation of soils were essential for Australia to meet its emissions reduction goals.

"Ensuring Australia's rangeland soils can maintain their carbon stocks is imperative: capturing and storing additional carbon will require interdisciplinary science, innovation, cultural awareness and effective policies" Professor Viscarra Rossel said.

"It will be challenging, given the rangelands' drier and more variable climate, its relatively sparse vegetation and other factors such as bushfires -- however, only a slight change over such large areas will make a positive difference.

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Tanks of the Triassic: New crocodile ancestor identified

Dinosaurs get all the glory. But aetosaurs, a heavily armored cousin of modern crocodiles, ruled the world before dinosaurs did. These tanks of the Triassic came in a variety of shapes and sizes before going extinct around 200 million years ago. Today, their fossils are found on every continent except Antarctica and Australia.

Scientists use the bony plates that make up aetosaur armor to identify different species and usually don't have many fossil skeletons to work with. But a new study led by researchers at The University of Texas at Austin centers on an aetosaur suit of armor that has most of its major parts intact.

The suit -- called a carapace -- is about 70% complete and covers each major region of the body.

"We have elements from the back of the neck and shoulder region all the way to the tip of the tail," said William Reyes, a doctoral student at the UT Jackson School of Geosciences who led the research. "Usually, you find very limited material."

The research was published in The Anatomical Record.

Reyes and his collaborators used the armor to identify the specimen as a new aetosaur species -- which they named Garzapelta muelleri. The name "Garza" recognizes Garza County in northwest Texas, where the aetosaur was found, and "Pelta" is Latin for shield, a nod to aetosaurs' heavily fortified body. The species name "muelleri" honors the paleontologist who originally discovered it, Bill Mueller.

Garzapelta lived about 215 million years ago and resembled a modern American crocodile -- but with much more armor.

"Take a crocodile from modern day, and turn it into an armadillo," said Reyes.

The bony plates that covered Garzapelta and other aetosaurs are called osteoderms. They were embedded directly in the skin and formed a suit of armor by fitting together like a mosaic. In addition to having a body covered in bony plates, Garzapelta's sides were flanked by curved spikes that would have offered another layer of protection from predators. Although crocodiles today are carnivores, scientists think that aetosaurs were primarily omnivorous.

The spikes on Garzapelta are very similar to those found in another aetosaur species, but surprisingly, researchers found that the two species are only distantly related. The similarities, they discovered, are an example of convergent evolution, the independent evolution of similar traits in different species. The development of flight in insects, birds, mammals and now-extinct pterosaurs is a classic example of this phenomenon.

According to Reyes, an array of unique features on Garzapelta's plates clearly marked it as a new species. They range from how the plates fit together to unique bumps and ridges on the bones. However, figuring out where Garzapelta fit into the larger aetosaur family tree was more of challenge. Depending on which portion of the armor the researchers emphasized in their analysis, Garzapelta would end up in very different places. Armor that ran down its back resembled armor from one species, while its midsection spikes resembled armor from another.

Once the researchers determined that the spikes evolved independently, they were able to work out where Garzapelta fit best among other aetosaur species. Nevertheless, Reyes said the research shows how convergent evolution can complicate things.

"Convergence of the osteoderms across distantly related aetosaurs has been noted before, but the carapace of Garzapelta muelleri is the best example of it and shows to what extent it can happen and the problems it causes in our phylogenetic analyses," Reyes said.

Garzapelta is part of the Texas Tech University fossil collections. It spent most of the past 30 years on a shelf before Reyes encountered it during a visit. Bill Parker, an aetosaur expert and park paleontologist at Petrified Forest National Park who was not part of the research, said that university and museum collections are a critical part of making this type of research possible.

"These specimens weren't just dug in the field yesterday," he said. "They've been sitting in the museum for decades and it just takes someone like Will to come along and finally decide to study them and make them come to life."

In addition to different species having different armor, it's possible that an animal's age or sex could also affect armor appearance. Reyes is currently exploring these questions by studying aetosaur fossils in the Jackson School's collection, most of which were found during the 1940s as part of excavations done by the Works Progress Administration.

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Birds set foot near South Pole in Early Cretaceous, Australian tracks show

The discovery of 27 avian footprints on the southern Australia coast -- dating back to the Early Cretaceous when Australia was still connected to Antarctica -- opens another window onto early avian evolution and possible migratory behavior.

PLOS ONE published the discovery of some of the oldest, positively identified bird tracks in the Southern Hemisphere, dated to between 120 million and 128 million years ago.

"Most of the bird tracks and body fossils dating as far back as the Early Cretaceous are from the Northern Hemisphere, particularly from Asia," says Anthony Martin, first author of the study and a professor in Emory University's Department of Environmental Sciences. "Our discovery shows that there were many birds, and a variety of them, near the South Pole about 125 million years ago."

Martin is a geologist and paleontologist focused primarily on ichnology -- the study of traces of life such as tracks, burrows, nests and tooth marks.

The international team of co-authors also includes researchers from Monash University and the Museums Victoria Research Institute in Australia; the Benemérita Normal School of Coahuila in Mexico and the Smithsonian Institution.

A possible migratory route

The 27 bird tracks vary in form and size and are among the largest known from the Early Cretaceous. They range from seven to 14 centimeters wide, which is similar to tracks of modern-day shorebirds, such as small herons and oystercatchers.

The tracks were found in the Wonthaggi Formation south of Melbourne. The rocky coastal strata mark where the ancient supercontinent Gondwana began to break up around 100 million years ago when Australia separated from Antarctica.

The polar environment at that time was a rift valley with braided rivers. Although the mean annual air temperature was higher during the Cretaceous than today, during the polar winters the ecosystem experienced deep, freezing temperatures and months of darkness.

The Wonthaggi avian tracks occurred on multiple stratigraphic levels, indicating a recurrent presence of a variety of birds. It also suggests seasonal formation of the tracks during polar summers, perhaps on a migratory route.

"The birds would likely have been stepping on soft sand or mud," Martin says. "Then the tracks may have been buried by a gentle river flow that deposited more sand or mud on top of them."

A scarcity of bird fossils

The Wonthaggi Formation is famous for its variety of polar dinosaur bones, although bird-fossil finds are extremely rare. The Cretaceous strata of the formation has yielded only one tiny bird bone -- a wishbone -- and a few feathers.

"Birds have such thin and tiny bones," Martin says. "Think of the likelihood of a sparrow being preserved in the geologic record as opposed to an elephant."

Birds are also lightweight and don't leave much of a foot impression, he adds.

Martin and colleagues discovered two 105-million-year-old bird tracks in Australia's Eumeralla Formation in 2013, making them the oldest from Australia at the time.

An eagle eye

Co-author Melissa Lowery, a local volunteer fossil hunter, first spotted some of the tracks in the current discovery in 2020. Dubbed "the doyenne of dinosaur discovery," Lowery has found hundreds of bones and more than 100 dinosaur footprints.

"Melissa is incredibly skilled at finding fossil tracks," Martin says. "Some of these tracks are subtle even for me, and I have lots of experience and training."

Most of the tracks were only exposed at low tide and some of them were encrusted by marine life such as algae, barnacles and mollusks.

Due to international travel restrictions in Australia during the COVID-19 pandemic, Martin had to wait until 2022 before he could travel to the site to lead the analyses of the tracks.

He was joined in the field by co-authors Patricia Vickers-Rich, professor of paleontology at Monash University, and Thomas Rich, curator of vertebrate aleontology at Museums Victoria Research Institute. The couple have led a major effort since the 1970s to uncover fossils in the Australian state of Victoria and to interpret the biota of Gondwana.

Also assisting in the field analyses were co-authors Mike Hall, a geologist at Monash University, and Peter Swinkels, a taxidermist at Museums Victoria Research Institute and an expert at preserving specimens through moldings and casts.

The thinness of the toes relative to the track lengths, the wide angles between the toes and the thin sharp claws and rear toes on some of the tracks helped Martin to verify their avian identity.

Co-author Claudia Serrano-Brañas, a paleontologist at the Benemérita Normal School of Coahuila and the National Museum of Natural History, Smithsonian Institution, verified similarities between the Australian bird footprints and ancient bird footprints from other parts of the world.

Swinkels created resin casts of the Australian tracks that brought into greater relief some of the nuances of the impressions. The casts provide a tool for further study. They also serve to preserve the finds. The silty, sandstone beds containing the footprints are rapidly eroding under the coastal tides and waves.

Read more at Science Daily

Why there are no kangaroos in Bali (and no tigers in Australia)

If you travel to Bali, you won't see a cockatoo, but if you go to the neighbouring island of Lombok, you will. The situation is similar with marsupials: Australia is home to numerous marsupial species, such as the kangaroo and the koala. The further west you go, the sparser they become. While you will find just two representatives of these typically Australian mammals on the Indonesian island of Sulawesi, you will search in vain for them on neighbouring Borneo. Australia, on the other hand, is not home to mammals that you will typically find in Asia, such as bears, tigers or rhinos.

This abrupt change in the composition of the animal world already caught the eye of the British naturalist and co-discoverer of evolutionary theory Alfred Russell Wallace, who travelled through the Indo-Australian Archipelago from 1854 to 1862 to collect animals and plants. He described an (invisible) biogeographical line running between Bali and Lombok and Borneo and Sulawesi that marked the westernmost distribution of Australian fauna.

Fascinating change of wildlife

Biodiversity researchers have long been fascinated by this abrupt change of creatures along the Wallace Line. How these distribution patterns came about, however, has not yet been clarified in detail.

One explanation is plate tectonics. Forty-five million years ago, the Australian Plate began to drift northwards and slid under the mighty Eurasian Plate. This brought two land masses closer together that had previously been far apart. It became easier for land creatures to colonise one continent from the other. Tectonic movements also gave rise to the creation of countless (volcanic) islands between the two continents, which animals and plants used as stepping stones to migrate westwards or eastwards.

More Asian animals in Australia than vice versa

But why more species found their way from Asia to Australia -- countless poisonous snakes, thorny lizards (Moloch horridus), hopping mice (Notomys sp.) or flying foxes bear witness to this -- than the other way round has been a mystery until now.

In order to better understand this asymmetrical vertebrate distribution along the Wallace Line, researchers led by Loïc Pellissier, Professor of Ecosystems and Landscape Evolution at ETH Zurich, have created a new model. It combines reconstructions of the climate, plate displacements between 30 million years ago and the present day and a comprehensive data set for around 20,000 birds, mammals, reptiles and amphibians that are recorded in the region today.

Climates in areas of origin decisive

In the latest issue of Science, the researchers now show that adaptations to the climates in the areas of origin are partly responsible for the uneven distribution of Asian and Australian faunal representatives on both sides of the Wallace Line.

In addition to plate tectonics, the environmental conditions that prevailed millions of years ago were decisive for the exchange between the two continents. Based on simulations, the researchers found that animals originating from Asia were more likely to "hop" across the Indonesian islands to reach New Guinea and northern Australia.

These islands featured a tropically humid climate, which they were comfortable with and had already adapted to. The Australian wildlife was different, having evolved in a cooler climate that had become increasingly drier over time, and was therefore less successful in gaining a foothold on the tropical islands than the fauna migrating from Asia.

The Asian climate thus favoured creatures that reached Australia via the tropical islands of the faunal region known as Wallacea, especially those that could tolerate a wide range of climates. This made it easier for them to settle on the new continent. "The historical context is crucial for understanding the biodiversity distribution patterns observed today and was the missing piece of the puzzle explaining the enigma of Wallace's line," says first author Alexander Skeels, a postdoctoral researcher in Pellissier's group.

Competitive advantages for tropical species

Traits of species that evolved in tropical habitats include faster growth and higher competitiveness to enable them to withstand the pressure of coexistence with many other species. In harsher climates, such as the colder and drier regions of Australia, organisms usually have to evolve special adaptations to cope with drought and heat stress. These include behavioural adaptations such as nocturnal activity and physiological adaptations to minimise water loss. "Many Australian frogs bury themselves in the ground and remain dormant for long periods for this reason," Skeels points out. "Something that is rare in tropical frogs."

The findings are important for the researchers: "They make it clear that we can only understand today's distribution patterns of biodiversity if we include the geological development and climatic conditions of prehistoric times in our considerations," says Pellissier.

The heritage of long past epochs has shaped the patterns of biodiversity right up to the present. It also helps us to understand why more species are found in the tropics today than in temperate latitudes. "To fully understand the distribution of biodiversity and the processes that maintain it in the present, we need to find out how it came about," says the researcher.

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South Africa, India and Australia shared similar volcanic activity 3.5 billion years ago

Cratons are pieces of ancient continents that formed several billions of years ago. Their study provides a window as to how processes within and on the surface of Earth operated in the past. Cratons preserve relics of our young Earth as they host a variety of rock assemblages such as greenstones and granites. Greenstones are rock assemblages that primarily comprise of sub-marine volcanic rocks with minor sedimentary rocks. They are the best archives to study early Earth surface processes. A new study published in Precambrian Research by a team of researchers, led by Dr Jaganmoy Jodder of the University of the Witwatersrand's Evolutionary Studies Institute shows that the Singhbhum Craton in India hosts remarkably well preserved volcanic and sedimentary rocks as old as 3.5 billion years, and that it has similar geologic history to parts of South Africa and Australia.

The team that included researchers from the University of the Witwatersrand (Wits University), University of Johannesburg (UJ) and Chinese Academy of Sciences, Beijing, examined volcanic and sedimentary rocks from the Daitari greenstone belt in the Singhbhum Craton of India that were formed approximately 3.5 billion years ago. Jodder and his co-workers conducted detailed field-based studies and precise Uranium-Lead (U-Pb) radiometric-age dating to evaluate the geology of the ancient greenstone rocks. Based on their study, the researchers established key geological timelines that illustrate the tectonic evolution of the Daitari greenstones.

"The Daitari greenstone belt shares a similar geologic make-up when compared to the greenstones exposed in the Barberton and Nondweni areas of South Africa and those from the Pilbara Craton of north-western Australia," says Jodder.

Sub-marine volcanic eruptions were common between 3.5 and 3.3 billion-years-ago, which are largely preserved as pillowed lava within the greenstones of the Singhbhum, Kaapvaal and Pilbara cratons. More importantly the style of volcanism decoded from the silicic rocks provide evidence for explosive sub-marine to sub-aerial settings.

"Following silicic volcanism, sedimentary rocks that comprise sub-marine turbidity current deposits formed upon drowning of the volcanic vent. This provided us with an age estimate for the sub-marine sedimentary rocks that got deposited approximately 3.5 billion years ago, which was based on precise detrital U-Pb zircon data."

Studies of ancient greenstones are important not only to understand the diverse volcanic processes but well-preserved greenstones preserve minor sedimentary rocks that formed under sub-marine settings.

"These volcano-sedimentary rocks provide clues related to habitable environments on the young Earth and can be regarded as time capsules to help us better understand the evolutionary tale of the planet in its early stages," says Jodder.

Jodder and the team of researchers propose that these ancient continents may have been subjected to geologically similar processes 3.5 billion years ago.

"However, we are not certain about their palaeo-geographic positioning. And thus, cannot validate that they once formed part of a supercontinent," says Jodder.

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Quarter-ton marsupial roamed long distances across Australia's arid interior

One of Australia's first long-distance walkers has been described after Flinders University palaeontologists used advanced 3D scans and other technology to take a new look at the partial remains of a 3.5 million year old marsupial from central Australia.

They have named a new genus of diprotodontid Ambulator, meaning walker or wanderer, because the locomotory adaptations of the legs and feet of this quarter-tonne animal would have made it well suited to roam long distances in search of food and water when compared to earlier relatives.

Researchers say the skeleton of Ambulator keanei, found on the Australian Wildlife Conservancy's Kalamurina Station in northern South Australia by Flinders University researchers in 2017, belongs to a species in the family Diprotodontidae, a group of four-legged herbivores that were the largest marsupials to ever exist.

"Diprotodontids are distantly related to wombats -- the same distance as kangaroos are to possums -- so unfortunately there is nothing quite like them today. As a result, palaeontologists have had a hard time reconstructing their biology," says Jacob van Zoelen, a PhD candidate at the Flinders University Palaeontology Laboratory.

The largest species, Diprotodon optatum, grew to the size of a car, weighing up to 2.7 tonnes. Diprotodontids were an integral part of Australian ecosystems until the last species became extinct about 40,000 years ago.

During the period when Ambulator keanei was alive (the Pliocene), there was an increase in grasslands and open habitat as Australia became drier. Diprotodontids likely had to travel much greater distances to obtain enough food and water to keep them going.

"We don't often think of walking as a special skill but when you're big any movement can be energetically costly so efficiency is key," says Mr van Zoelen.

"Most large herbivores today such as elephants and rhinoceroses are digitigrade, meaning they walk on the tips of their toes with their heel not touching the ground.

"Diprotodontids are what we call plantigrade, meaning their heel-bone (calcaneus) contacts the ground when they walk, similar to what humans do. This stance helps distribute weight when walking but uses more energy for other activities such as running."

Diprotodontids display extreme plantigrady in their hands as well, by modifying a bone of the wrist, the pisiform, into a secondary heel, Mr van Zoelen explains.

This 'heeled hand' made early reconstructions of these animals look bizarre and awkward, he says.

"Development of the wrist and ankle for weight-bearing meant that the digits became essentially functionless and likely did not make contact with the ground while walking. This may be why no finger or toe impressions are observed in the trackways of diprotodontids.

"So, diprotodontids such as Ambulator may have evolved this morphology to traverse great distances more efficiently. This morphology also allowed for greater weight to be supported, allowing diprotodontids to get very big indeed.

"Eventually, this led to the evolution of the giant and relatively well-known Diprotodon."

Most studies on the group have focused on the skull, as associated skeletons are rare in the fossil record. As such, the newly described skeleton is of great importance and is even more special as it is the first to be found with associated soft tissue structures.

Using 3D-scanning technology, the Flinders team was able to compare the partial skeleton with other diprotodontid material from collections all over the world.

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