The impact of megafires on estuaries from Australia’s ‘Black Summer’

Estuaries are one of the most valuable biomes on Earth, and megafires – like Australia’s 2019/20 Black Summer fires – represent an emerging threat to estuarine and coastal ecosystems.

Peer-Reviewed Publication

UNIVERSITY OF SYDNEY

 

IMAGE: THE BURNT ZONE REACHES ALL THE WAY TO THE EDGE OF THE WATER AT CLYDE RIVER/BATEMANS BAY. view more 

CREDIT: JOHN TURNBULL

Australian researchers have explored the impact of bushfires on estuaries in New South Wales, Australia's largest state, finding fires can increase the load of fire-derived pollutants with potentially profound environmental effects. 

Estuaries (where the river meets the sea) are some of the most valuable habitats on earth. As well as being biologically diverse and productive places, they are where ports are located, and a significant portion of the world’s population is concentrated. 

Published today in Environmental Pollution, the researchers say their findings prompt a call for riverside vegetation to be prioritised for protection in fire management plans, and for bushfires to be considered in catchment management plans. These plans are developed to protect the environment and regulate resources, such as fish and water, from the whole catchment area (from tributaries to estuaries).   

Unlike regular bushfires, megafires such as those that occurred during Australia’s 2019-2020 ‘Black Summer’, can surround estuaries. 

Following the Black Summer fires, the research team measured a rapid increase in the concentration of nutrients, metals and pyrogenic carbon (carbon formed by fires) in nearshore areas that could affect the behaviour, survival and reproduction of estuarine species.

“In some catchments, more than 90 percent of the vegetation was burnt, and the fire went right down to the waters edge, leading to a massive amount of pollution in the form of sediment, metals and nutrients entering our waterways,” said senior author Professor Emma Johnston, a marine ecosystems expert and the Deputy Vice-Chancellor (Research) at the University of Sydney.

The researchers found that the material from the Black Summer fires contained traces of metals including copper and zinc, and nutrients such as nitrogen and phosphorus that sunk onto estuarine sediments.

“If there is consistent flushing of the estuary then these trace elements will prime them for productivity. However, if water flow is low and flushing is minimal, they can cause microalgae to breed exponentially, leading to plankton blooms that deplete oxygen supplies and kill fish, with a domino effect on the entire ecosystem,” said Professor Johnston.

Fire Carbon

The study also revealed how much pyrogenic carbon was deposited in estuaries – the bushfires’ calling card.

“We’ve not been concerned about pyrogenic-carbon in these waters before, but now that climate change is increasing the extent and severity of wildfires around the world, we suddenly need to know what concentrations of pyrogenic carbon cause harm. That should be the subject of further study,” Professor Johnston said. 

CAPTION

Post-fire rainfall and runoff leads to input of ash, nutrients and metals in impacted estuaries.

CREDIT

John Turnbull

Impact and Actions

With current climate projections suggesting megafires like Black Summer will occur more frequently in Australia and around the world, the authors say governments must factor our vital estuary habitats into their fire prevention and management plans.

“Considering that excessive nutrient input is one of the main stressors on estuaries, the changes found in our study might have serious implications due to its potential to alter ecological and physico-chemical processes,” said lead author Thayanne Barros, PhD candidate from the University of New South Wales.

Among the actions the authors propose are maintaining natural vegetation buffers to prevent fires from reaching the edge of estuaries, and ecotoxicological assessments of wildfire impacts on estuarine areas.

Post-fire rainfall and runoff leads to input of ash, nutrients and metals in impacted estuaries. Photo credit: John Turnbull

The author’s concern about the impact of fires on waterways is shared by an international research consortium, of which Professor Johnston is a member. The consortium’s new paper names wildfires as one of 15 emerging threats to ocean biodiversity. 

CAPTION

Post-fire rainfall and runoff leads to input of ash, nutrients and metals in impacted estuaries.

CREDIT

John Turnbull

About the study

The researchers studied six estuaries on the New South Wales coast, at the mouths of the rivers Hastings; Karuah; Georges; Shoalhaven; Clyde; and Moruya immediately before the fires. 

Ms Barros said: “We had just finished collecting samples for a different project when the fires started, so we saw a unique opportunity to conduct a Before-After-Control-Impact study in these areas. The initial samples became our ‘before the fires’ dataset and when the fires ceased we collected the samples for our ‘after the fires dataset’.”

To investigate the potential impacts of bushfires on estuaries, the researchers decided to focus on the soft sandy bottom of the estuaries since this habitat is an important source and sink of elements and plays a major role in global biogeochemical cycles, simultaneously supporting high biodiversity and productivity. 

They analysed the sediments to check for changes in nutrient concentrations, sediment silt content, metals, and different forms of carbon, including pyrogenic carbon (formed by fires) in order to directly link changes in carbon concentration to the bushfires.

Estuaries were categorised according to the percentage of the catchment vegetation that was burnt and the proximity of the burnt zone to the waterway.

The study shows that in those estuaries with a large proportion of the catchment burnt and little gap between the fire and the waterway, the concentration of different forms of carbon, nutrients, metals and silt content significantly increased after the fires. While no significant changes were detected in the unburnt estuaries or those that retained a buffer zone.

The study was a collaboration between researchers at the University of Sydney, CSIRO, Macquarie University, University of New South Wales and received funding support from the World Wide Fund for Nature (WWF).

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JOURNAL

Environmental Pollution

DOI

10.1016/j.envpol.2022.119571 

METHOD OF RESEARCH

Case study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Wildfires cause rapid changes to estuarine benthic habitat

ARTICLE PUBLICATION DATE

1-Sep-2022

Would helping only the least advantaged benefit society as a whole?

Study on social justice in chain-connected and close-knit societies finds that helping the least advantaged section of society may not necessarily benefit everyone

Peer-Reviewed Publication

WASEDA UNIVERSITY

 

IMAGE: STUDY ON SOCIAL JUSTICE IN CHAIN-CONNECTED AND CLOSE-KNIT SOCIETIES FINDS THAT HELPING THE LEAST ADVANTAGED SECTION OF SOCIETY MAY NOT NECESSARILY BENEFIT EVERYONE. view more 

CREDIT: WASEDA UNIVERSITY

John Rawls, one of the 20th century’s most notable political philosophers, proposed a theory of distributive justice known as justice as fairness. According to his theory, once a society successfully guarantees equal basic rights and liberties for everybody, the next step should be to properly regulate any ensuing social and economic inequalities. One of the principles he proposed to do this was the difference principle. Rawls’s difference principle states that inequalities can be justified only if they provide the greatest benefit to the least advantaged group in society. Rawls argued that if a society is chain connected (meaning that the betterment of the least advantaged group leads to the betterment of all other groups in society) and close-knit (i.e., changes in the condition of one group necessarily changes that of all others), the concern that benefiting the least advantaged may not lead to improving society as a whole is nullified, because benefiting one group would, by default, benefit others. In this process, societies could eventually reach an optimal state.

However, in this article, which was published online on July 26, 2022 and is to appear in Volume 84, Issue 4 of the Journal of Politics in October 2022, Associate Professor Hun Chung of Waseda University argues that Rawls’ conjectures are incorrect. “Political philosophy serves as the foundation for a society’s basic political and economic institutions, and can have a profound impact on people’s lives,” Chung explains. The purpose of his study is to make policymakers aware of the possible gaps in such well-established theories.

Chung considers a close-knit and chain-connected society with three groups: the most advantaged, the least advantaged, and the middle group, as proposed by Rawls. He starts from a hypothetical position where all the groups are at the same level of economic benefit, after which society develops economically and inequalities grow. As the situation of the most advantaged group improves, the benefits are expected to trickle down to all the others. During the process, the difference principle requires society to choose the point at which the economic benefit to the least advantaged group is maximized. Given that society is chain connected and close-knit, Rawls claims that every new stage in implementing the difference principle is better than the preceding stage for every group, till an optimum point is reached. However, Chung finds that in the practical implementation of the difference principle, there can be cases where the expectations of the least advantaged group fall with the increase in benefits for the privileged, even when such steps are necessary to achieve a final social state prescribed by the difference principle. Therefore, the conjecture that every step in implementing the difference principle leads to Pareto improvements (i.e., a change that hinders no one and benefits at least some one) over the previous one is negated.

Next, Chung examines the proposal that the difference principle eventually leads to a Pareto optimal state (which is a balanced state, where any further improvement in one group’s state would necessarily lead to a decline in another group’s state). Even after the difference principle is fully implemented and the economic benefits to the least advantaged group have been maximized, he finds that there may be situations where the other groups may further improve their situations without worsening the situation of the least advantaged group. In short, the difference principle may fail to lead to a Pareto optimal state.

Some people might think that the lexical version of Rawls’s difference principle (which Rawls himself considers and eventually rejects on grounds of redundancy) could solve the problem. To this, Chung argues that although the lexical difference principle (unlike the original difference principle) does lead to a Pareto optimal social state, it can, at best, serve only as a partial solution to the problem as its practical implement still does not guarantee Pareto improvements at all stages of its implementation. Furthermore, the lexical difference principle has its own critical flaws by failing to provide continuous ethical judgments, meaning that it can generate vastly different ethical evaluations to vanishingly small ethical differences. This would violate Aristotle’s well-known principle that requires us to “treat like cases alike,” which means that extremely small differences between any two cases should not have evaluations that widely differ.

In sum, Chung has shown that improvements in the situation of the least favored group does not necessarily entail betterment of all groups at every stage, or even a Pareto optimal state even when society is chain connected and close-knit. Chung’s analysis provides enough scope to reconsider the implementation of the difference principle while making policies on a just and fair society. “My research can make policy designers become self-aware of the potential and unintended (negative) effects of certain policies that aim to improve the situation of a specific targeted social group,” Chung concludes.

Chung’s reassessment of Rawls’s theory of distributive justice goes to show that while the heart is in the right place, the head needs to be as well; more consideration might be needed when using theory for policy implementation to improve the quality of life for all social groups.

 

CAPTION

In a recent paper, Waseda University’s Associate Professor Hun Chung explains how helping the least advantaged group in a society does not automatically benefit other groups and lead to an optimal social state.

CREDIT

Hun Chung, Waseda University

 

Reference

DOI: https://doi.org/10.1086/716968

Authors: Hun Chung

Affiliations: Waseda University

 

About Waseda University
Located in the heart of Tokyo, Waseda University is a leading private research university that has long been dedicated to academic excellence, innovative research, and civic engagement at both the local and global levels since 1882. The University ranks number one in Japan in international activities, including the number of international students, with the broadest range of degree programs fully taught in English. To learn more about Waseda University, visit https://www.waseda.jp/top/en

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JOURNAL

The Journal of Politics

DOI

10.1086/716968 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Chain Connection, Close-Knitness, and the Difference Principle

These mice grow bigger on the rainier sides of mountains. It might be a new rule of nature.

Peer-Reviewed Publication

FIELD MUSEUM

 

IMAGE: THE SHAGGY SOFT-HAIRED MOUSE, FOUND IN THIS STUDY TO EXPERIENCE CHANGES IN SIZE BASED ON WHICH SIDE OF THE ANDES MOUNTAINS THE INDIVIDUAL LIVES ON. view more 

CREDIT: PABLO TETA

Scientists studying mice from the Andes Mountains in Patagonia noticed something they couldn’t explain: the mice from the western side of the mountains were bigger than the ones from the east, but DNA said that they were all from the same species. The researchers examined the skulls of 450 mice from the southern tip of South America, and found that existing biological laws didn’t explain the size differences. Instead, in a new paper in the Journal of Biogeography, the scientists put forth a new hypothesis: the mice on the western slopes were bigger because that side of the mountain range gets more rain, which means there’s more plentiful food for the mice to eat.

“There are a bunch of ecogeographic rules that scientists use to explain trends that we see again and again in nature,” says Noé de la Sancha, a research associate at Chicago’s Field Museum, an assistant professor of Environmental Science and Studies at DePaul University, and the paper’s corresponding author. “With this paper, I think we might have found a new one: the rain shadow effect can cause changes of size and shape in mammals.”

The mice that de la Sancha and his colleagues examined in this study are shaggy soft-haired mice, Abrothrix hirta. “They’re very cute little buggers, they have soft white bellies,” says de la Sancha. “They live in the mountains, which makes them unique, but they’re also found in lower elevations. Overall, they’re not very well-studied.”

De la Sancha’s colleague, Pablo Teta of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” in Buenos Aires, Argentina, began studying the shaggy soft-haired mice as part of his doctoral thesis. “He saw that some individuals of the species were really big, and some were really small. He thought they were different species. But their mitochondrial DNA suggested that they were one species, even though they’re so different,” recalls de la Sancha. “We wanted to explore why that is, to see if they were following some sort of rule.”

There are lots of “rules” of nature explaining patterns that we see in life. For instance, Bergmann’s rule explains why animals of the same species are bigger in higher latitudes. White-tailed deer in Canada are larger and bulkier than their skinny Floridian cousins. Bergmann’s rule explains that this is because having a thicker body in relation to your surface area helps you retain heat better, the same way that big pieces of food take longer to cool down than smaller bites.

To try to find a pattern to explain the differences in size, the researchers used statistical analyses to compare measurements of 450 mouse skulls. They then tried to map their findings onto different biological rules to see if any fit. Bergmann’s rule didn’t work; there wasn’t a strong correlation between mouse size and how far north or south the specimen lived. Other rules emphasize the role of temperature or precipitation, with mixed results for different groups and situations. This team did not find that latitude, or one of 19 other bioclimatic, temperature, or precipitation variables, best described the mice’s varying shapes and sizes. However, there did seem to be a pattern with longitude-- how far east or west the mice lived.

De la Sancha and his colleagues realized this might be related to what biologists call the “resource rule.” “This rule suggests that where there are more resources, individuals from the same species tend to be larger than where there are fewer resources,” says de la Sancha. “For instance, some deer mice that are found in deserts and other habitats tend to be smaller in drier portions of their habitats. Another hypothesis suggests that some animals tend to be smaller in mountains versus adjacent plains in North America. Our study found a mixed result of these rules.”

The sizes of mice seemed to be following the resource rule, but the question still remained: why were there more resources on the western slopes of the southern Andes than on the eastern slopes? De la Sancha had a “Eureka!” moment while teaching a class of undergraduates at Chicago State University.

“Believe it or not, when I was teaching ecology, one of the things that I was teaching about was the rain shadow effect,” says de la Sancha.

The rain shadow effect is a product of the way that water vapor travels over mountain ranges. The air over the ocean picks up water vapor, and as the ocean naturally warms, this water vapor rises. Prevailing winds, like the jet stream that goes from west to east, push this air from the ocean to the land, and as the air makes its way over mountain ranges, it gets colder as it goes up in elevation. The water vapor in the cold air condenses and falls as rain. If the mountain is really high, the air will run out of moisture by the time it gets to the far side of the peak. “Essentially, one side of the mountain will be humid and rainy, and the other will have cold, dry air. On some mountains, the difference is extreme. One face can be a tropical rainforest, and the other side will be almost desert-like,” says de la Sancha. “There is a rain shadow effect in most mountains on the planet, we see this phenomenon all over the world.”

In the middle of his lecture, de la Sancha realized that the rain shadow could explain why there was more food on the western side of the Andes, and thus, why the mice there were bigger. “That same day, I went home and wrote to Pablo,” he remembers. “I was like, ‘Dude, we need to talk about the rain shadow.’”

The rain shadow indeed neatly matched up with the rodents’ sizes-- the first time, to de la Sancha’s knowledge, that anyone has demonstrated the effects of the rain shadow on mammal size. And while so far it’s only been shown for one species of mouse, de la Sancha suspects that he and his colleagues have hit on a larger truth-- perhaps even the basis for a rule of its own someday.

“It’s exciting, because it could potentially be something that's more universal. We think it may be more of a rule than an anomaly,” says de la Sancha. “It’d be worthwhile to test it on lots of different taxa.”

However, the findings may mean that the shaggy soft-haired mice, and many of their fellow mammals, are in for a rough time. “The scary part is that we show that, at least to some effect,  climate patterns are important to determine the mice’s morphology-- their shape and size, either directly or indirectly through the resources they can find,” says de la Sancha. “With climate change, we know we’re going to see dramatic changes in temperature throughout the year, and changes in precipitation. While they might not be the most important variables affecting the mice’s well-being, they are important in determining available food sources.” If the weather patterns change and affect the plants that grow in the region, the mice might no longer be able to thrive as they once did.

Plus, de la Sancha notes, animals are already moving up mountains to escape the effects of climate change. “At a certain point, you run out of mountain,” he says. “There’s nowhere else to go. We don’t know what’s going to happen, but it doesn’t seem good.”

The unclear future of these mice in the face of climate change, according to de la Sancha, is a good reason to study animals like mice that often go unnoticed. “It’s important to understand how little we know about most small mammals,” he says. “They can be good indicators of long-term changes in our environment. We need to study them more. Our findings also show why museum collections are so important. This study was based on museum collections from Argentina, Chile, and the US, it’s an amalgamation of years and years of collecting and big data sets.

“This paper would not have been possible without museum collections and highlights the importance of museum- and collection-based research and its support worldwide,” notes Teta. “This type of research helps us better understand the big-picture, universal rules of how life on Earth works.”

CAPTION

Figure from the paper showing how the rain shadow affects mice.

CREDIT

Teta et al, 2022

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JOURNAL

Journal of Biogeography

ARTICLE TITLE

Andean rain shadow effect drives phenotypic variation in a widely distributed Austral rodent

ARTICLE PUBLICATION DATE

1-Sep-2022

Ecologists use the latest dental scanning technology to study young coral

Peer-Reviewed Publication

BRITISH ECOLOGICAL SOCIETY

 

IMAGE: A 3D MODEL OF A BABY CORAL SKELETON SCANNED BY DR KATE QUIGLEY'S DENTAL SCANNER. view more 

CREDIT: DR KATE QUIGLEY

Inspired by a trip to the dentist, Dr Kate Quigley presents a new method for monitoring coral size and growth that reduces surveying time by 99%. The methodology and findings are published in the British Ecological Society journal, Methods in Ecology and Evolution.

Dr Kate Quigley, a senior research scientist at the Minderoo Foundation who conducted the research at the Australian Institute of Marine Science, and James Cook University, has developed a new non-destructive method for rapidly and safely scanning coral – cutting down on previously laborious and lengthy surveying techniques.

Inspired by a visit to the dentist, Dr Quigley remarked on the similarities between coral and our teeth – both being calcium-based and requiring measuring tools that can withstand wet surfaces. “One day, I was at the dentist, and they rolled out this new scanning machine. I knew immediately that it was something that could apply to scanning very small corals given corals and teeth actually share many similar properties. The rest is history!”

Coral reefs are among the earth's most productive ecosystems and provide essential nutritional and protective services to people across the globe. These important ecosystems have suffered serious declines over recent decades – spurring a flurry of research around their basic biology and restoration. Understanding the critical life stage of juvenile coral allows scientists to predict ecosystem changes, the impacts of disturbance and their potential for recovery.

Reconstructing coral 3D models reveals insights into their health and response to pressures like rising temperatures or acidification. Several methods exist to build and assess these 3D models, yet their effectiveness is reduced when constructing measurements at small scales.

Dr Quigley said: “At the moment, it is difficult to accurately measure very small objects in 3D, especially if you are interested in measuring small live animals, like coral, without hurting them.

“During my PhD it would take half a day to produce one scan, and I was interested in scanning hundreds of corals at a time.

“For the first time, this new method will allow scientists to measure thousands of tiny corals fast, accurately and without any negative health impacts on the coral. This has the potential to expand large-scale monitoring of ocean health and for up-scaling coral reef restoration.”

To assess the effectiveness of these dental scanners, namely the ITero Element 5D Flex, Dr Quigley measured juvenile corals at the Australian Institute of Marine Science’s National Sea Simulator. The coral, from the Great Barrier Relief, were temporarily removed from their indoor aquarium and their surface area and volume recorded before being returned to the tanks.

On average it took less than three minutes to scan and build a model of each individual coral compared to over 4 hours with previous methods – a 99% decrease in the time required to carry out such measurements. Dr Quigley recorded equally fast and precise performance when measuring and comparing models of dead skeletons and living coral tissue. Removing the need to sacrifice live animals to take measurements.

Whilst this is a massive step forward in cutting down the time involved in monitoring and studying small marine animals, 3D scans still need to be processed manually, which slows down analysis. Dr Quigley hopes that the next avenue for this research is to try and create an automatic analysis pipeline from scanning to measurement, potentially using AI.

At present, this technology can only be used to perform measurements out of the water. The hardware is not waterproof as the scanner relies on confocal laser technology.

“Potentially the scanner could be made completely waterproof. However, it is unclear how well the laser technology would work completely submerged underwater. We have taken this technology on the boat before and brought up wild and laboratory-reared corals for measurement, so we are getting there!”

CAPTION

Dr Kate Quigley used dental scanning machinery to measure baby coral straight from the boat.

CREDIT

Dr Kate Quigley

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JOURNAL

Methods in Ecology and Evolution

DOI

10.1111/2041-210X.13959 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

A fast, precise, in-vivo method for micron-level 3D models of corals using dental scanners

ARTICLE PUBLICATION DATE

31-Aug-2022

Discovery and naming of Africa’s oldest known dinosaur

A Virginia Tech graduate student found and unearthed the fossil with other paleontologists during two digs in Zimbabwe in 2017 and 2019. Sterling Nesbitt, an associate professor in the Department of Geosciences, said

Peer-Reviewed Publication

VIRGINIA TECH

 

IMAGE: ARTISTIC RECONSTRUCTION OF MBIRESAURUS RAATHI (IN THE FOREGROUND) WITH THE REST OF THE ZIMBABWEAN ANIMAL ASSEMBLAGE IN THE BACKGROUND. IT INCLUDES TWO RHYNCHOSAURS (AT FRONT RIGHT), AN AETOSAUR (AT LEFT), AND A HERRERASAURID DINOSAUR CHASING A CYNODONT (AT BACK RIGHT). ILLUSTRATION COURTESY OF ANDREY ATUCHIN. view more 

CREDIT: VIRGINIA TECH

An international team of paleontologists led by Virginia Tech has discovered and named a new, early dinosaur. The skeleton — incredibly, mostly intact — was first found by a graduate student in the Virginia Tech Department of Geosciences and other paleontologists over the course of two digs, in 2017 and 2019.

The findings of this new sauropodomorph — a long-necked dinosaur — newly named Mbiresaurus raathi were been published today in the journal Nature. The skeleton is, thus far, the oldest dinosaur skeleton ever found in Africa. The animal is estimated to have been 6 feet long with a long tail. It weighed anywhere from 20 to 65 pounds. The skeleton, missing only some of the hand and portions of the skull, was found in northern Zimbabwe.

“The discovery of Mbiresaurus raathi fills in a critical geographic gap in the fossil record of the oldest dinosaurs and shows the power of hypothesis-driven fieldwork for testing predictions about the ancient past,” said Christopher Griffin, who graduated in 2020 with a Ph.D. in geosciences from the Virginia Tech College of Science.

Griffin added, “These are Africa’s oldest-known definitive dinosaurs, roughly equivalent in age to the oldest dinosaurs found anywhere in the world. The oldest known dinosaurs — from roughly 230 million years ago, the Carnian Stage of the Late Triassic period — are extremely rare and have been recovered from only a few places worldwide, mainly northern Argentina, southern Brazil, and India.”

Sterling Nesbitt, associate professor of geosciences, also is an author on the study. “Early dinosaurs like Mbiresaurus raathi show that the early evolution of dinosaurs is still being written with each new find and the rise of dinosaurs was far more complicated than previously predicted,” he said.

The international team at the heart of this discovery include paleontologists from the National Museums and Monuments of Zimbabwe, the Natural History Museum of Zimbabwe, and Universidade de São Paulo, São Paulo, Brazil.

Finding Mbiresaurus raathi and other fossils

Found alongside Mbiresaurus were an assortment of Carnian-aged fossils, including a herrerasaurid dinosaur, early mammal relatives such as cynodonts, armored crocodylian relatives such as aetosaurs, and, in Griffin’s description, “bizarre, archaic reptiles” known as rhynchosaurs, again typically found in South America and India from this same time period.

(Mbiresaurus is derived from Shona and ancient Greek roots. "Mbire" is the name of the district where the animal was found and also is the name of an historic Shona dynasty that ruled the region. The name "raathi" is in honor of Michael Raath, a paleontologist who first reported fossils in northern Zimbabwe.)

From their findings, Mbiresaurus stood on two legs and its head was relatively small head like its dinosaur relatives. It sported small, serrated, triangle-shaped teeth, suggesting that it was an herbivore or potentially omnivore.

Part of the 2019 expedition team in Harare, capital of Zimbabwe, before fieldwork. Left to right: Kudzie Madzana, Edward Mbambo, Sterling Nesbitt, George Malunga, Christopher Griffin, Darlington Munyikwa. 

“We never expected to find such a complete and well-preserved dinosaur skeleton,” said Griffin, now a post-doctorate researcher at Yale University. “When I found the femur of Mbiresaurus, I immediately recognized it as belonging to a dinosaur and I knew I was holding the oldest dinosaur ever found in Africa. When I kept digging and found the left hip bone right next to the left thigh bone, I had to stop and take a breath — I knew that a lot of the skeleton was probably there, still articulated together in life position.”

Nesbitt, who is a member of the Virginia Tech Global Change Center, part of the Fralin Life Sciences Institute, added, “Chris did an outstanding job figuring out a place to test his ideas about early dinosaur evolution, went there, found incredible fossils, and put it all together in a fantastic collaboration that he initiated.”

A theory on dinosaur dispersal

In addition to the discovery of Mbiresaurus, the group of researchers also have a new theory on dinosaur migration, including the when and where.

Africa, like all continents, was once part of the supercontinent called Pangea. The climate across Pangea is thought to have been divided into strong humid and arid latitudinal belts, with more temperate belts spanning higher latitudes and intense deserts across the lower tropics of Pangea. Scientists previously believed that these climate belts influenced and constrained animal distribution across Pangea, said Griffin.

“Because dinosaurs initially dispersed under this climatic pattern, the early dispersal of dinosaurs should therefore have been controlled by latitude,” Griffin said. “The oldest dinosaurs are known from roughly the same ancient latitudes along the southern temperate climate belt what was at the time, approximately 50 degrees south.”

Griffin and others from the Paleobiology and Geobiology Research Group at Virginia Tech purposefully targeted northern Zimbabwe as the country fell along this same climate belt, bridging a geographic gap between southern Brazil and India during the Late Triassic Age.

More so, these earliest dinosaurs were restricted by climatic bands to southern Pangea, and only later in their history dispersed worldwide. To bolster this claim, the research team developed a novel data method of testing this hypothesis of climatic dispersal barriers based on ancient geography and the dinosaurian family tree. The breakdown of these barriers, and a wave of northward dispersal, coincided with a period of intense worldwide humidity, or the Carnian Pluvial Event.

After this, barriers returned, mooring the now-worldwide dinosaurs in their distinct provinces across Pangea for the remainder of the Triassic Period, according to the team. “This two-pronged approach combines hypothesis-driven predictive fieldwork with statistical methods to independently support the hypothesis that the earliest dinosaurs were restricted by climate to just a few areas of the globe,” Griffin said.

Brenen Wynd, also a doctoral graduate of the Department of Geosciences, helped build the data model. “The early history of dinosaurs was a critical group for this kind of problem. Not only do we have a multitude of physical data from fossils, but also geochemical data that previously gave a really good idea of when major deserts were present,” he said. “This is the first time where those geochemical and fossil data have been supported using only evolutionary history and the relationships between different dinosaur species, which is very exciting.”

A boon for Zimbabwe and Virginia Tech paleontology

The unearthing of one of the earliest dinosaurs ever found — and most of it fully intact — is a major win for the Natural History Museum of Zimbabwe. “The discovery of the Mbiresaurus is an exciting and special find for Zimbabwe and the entire paleontological field,” said Michel Zondo, a curator and fossil preparer at the museum. “The fact that the Mbiresaurus skeleton is almost complete, makes it a perfect reference material for further finds. It is the first sauropodomorph find of its size from Zimbabwe, otherwise most of our sauropodomorph finds from here are usually of medium- to large-sized animals.”

Darlington Munyikwa, deputy executive director of the National Museums and Monuments of Zimbabwe, added, “The unfolding fossil assemblage from the Pebbly Arkose Formation in the Cabora Bassa Basin, which was hitherto known for paucity of animal fossils, is exciting. A number of fossil sites [are] waiting for future exploration were recorded, highlighting the potential of the area to add more valuable scientific material.”

Much of the Mbiresaurus specimen is being kept in Virginia Tech's Derring Hall as the skeleton is cleaned and studied. All of the Mbiresaurus skeleton and the additional found fossils will be permanently kept at Natural History Museum of Zimbabwe in Bulawayo, Zimbabwe.

“This is such an exciting and important dinosaur find for Zimbabwe, and we have been watching the scientific process unfold with great pride,” said Moira Fitzpatrick, the museum’s director. She was not involved in the study. “It has been a pleasure to work with Dr. Griffin,and we hope the relationship will continue well into the future.”

The discovery of Mbiresaurus also marks another highpoint for the Paleobiology and Geobiology Research Group. In 2019, Nesbitt authored a paper detailing the newly named tyrannosauroid dinosaur Suskityrannus hazelae. Incredibly, Nesbitt discovered the fossil at age 16 as a high school student participating in a dig expedition in New Mexico in 1998.

“Our group seeks out equal partnerships and collaborations all over the world and this project demonstrates a highly successful and valued collaboration,” Nesbitt said. “We will continue studying the many fossils from the same areas as where the new dinosaur came from and explore the fossil beds further.”

Funding for the dig and follow-up research came from several sources, including National Geographic Society, the U.S. National Science Foundation, Geological Society of America, Paleontological Society, Virginia Tech Graduate School, Virginia Tech Department of Geosciences, and the Fundação de Amparo à Pesquisa do Estado de São Paulo in Brazil.

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JOURNAL

Nature