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New assessment suggests Anthropocene started in the 1950s

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New assessment suggests Anthropocene started in the 1950s


New assessment suggests Anthropocene started in the 1950s
Map of geological archive locations used for the detection of anthropogenic fingerprints. Red circles denote 137 locations of geological archives, including varved marine and lake sediments, coral skeletons, ice cores, and tree ring samples. Credit: Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2313098121. https://www.pnas.org/doi/full/10.1073/pnas.2313098121

A team of Earth scientists from the Center for Marine Environmental Studies, the University of Tokyo, The Australian National University, Matsuyama University, Kyoto University, and Shimane University, has found, via a new assessment, that the 1950s is the strongest candidate for the start of the Anthropocene.

In their paper published in Proceedings of the National Academy of Sciences, the group describes how they compared the three top contenders, and why they chose the 1950s, as the most likely marker.

In 2002, Nobel laureate Paul Crutzen suggested that the Holocene had ended and that a new era in planetary history had begun—the Anthropocene. The new era, he suggested, was one dominated by changes to the planet that had occurred because of human behaviors.

Since then, planetary scientists have debated the issue, with some suggesting that there is more than enough evidence to declare the start of a new era, and others claiming there is not yet enough. In this new study, the research team began with the belief that there is enough evidence to support the start of the Anthropocene, and because of that there must be a point at which it began.

In looking at available evidence, the researchers suggest that there are three good candidates; the first being the late 1800s. It was during this period, they note, that the Industrial Revolution began. They also point out that it was a time during which levels of lead began to be spread across major land surfaces, along with stable isotope ratios and changes in the balance of nutrients.

The second candidate they suggest was the early 1900s, which saw changes in pollen across the globe, major increases in black carbon and widespread changes in stable isotopes.

The third candidate, the middle of last century, saw the most measurable global and permanent changes. This was when organic pollutants began showing up all over the world, along with plastics and microplastics. It was also the start of the nuclear age, with evidence of test blasts found everywhere on Earth—and finally, it was the beginning of major impacts resulting from global warming.

After comparing the global impact of all three candidates, the research team concluded it was the third that most likely should be considered as the true start of the Anthropocene. They suggest it shows the most easily seen and measured global changes—changes that would likely take thousands, if not millions of years to change back to Holocene levels, should humans depart the scene.

More information:
Kuwae, Michinobu, Toward defining the Anthropocene onset using a rapid increase in anthropogenic fingerprints in global geological archives, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2313098121. www.pnas.org/doi/full/10.1073/pnas.2313098121

© 2024 Science X Network

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New assessment suggests Anthropocene started in the 1950s (2024, September 30)
retrieved 30 September 2024
from https://phys.org/news/2024-09-anthropocene-1950s.html

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Ants might be pushing montane birds higher up, study finds

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Ants might be pushing montane birds higher up, study finds


ant
Credit: Unsplash/CC0 Public Domain

Mountains are home to 85% of the world’s amphibian, bird, and mammalian species, despite covering only 25% of the Earth’s surface. This makes them a highly diverse ecosystem and a key focus for conservation efforts.

In mountainous regions, species diversity—the measure of how many different species are present—can vary with elevation due to environmental factors like climatic conditions. However, a recent study from the Centre for Ecological Sciences (CES), Indian Institute of Science (IISc) has uncovered a different factor driving bird species diversity at mid-elevations: the presence of ants from the Oecophylla genus.

“In mountains, you often see hump-shaped patterns [of species diversity], and for a long time, people have been interested in why this happens. One of the mechanisms they did not think much about was biotic interactions like competition,” says Kartik Shanker, Professor at CES and co-author of the study published in Ecology Letters.

Oecophylla ants, known for their aggressive and dominant behavior, are voracious predators of insects at the bases of mountains found in the paleotropics, covering Africa, Asia and Oceania. The researchers decided to test how the ants’ presence affects the diversity of insect-eating birds, especially at lower elevations.

A previous study led by co-author Trevor D Price, Professor at the Department of Ecology and Evolution, University of Chicago, showed that the presence of Oecophylla ants at the base of the eastern Himalayas decreased the density of insects and might therefore have an effect on the presence of insect-eating birds. In the current study, the team wanted to see if this pattern was more widespread among other insect-eating species as well.

Led by Umesh Srinivasan, Assistant Professor at CES, the researchers used existing datasets with information about bird species observed at various elevations across different mountain ranges. They categorized the birds into dietary guilds—groups of species with similar dietary requirements, such as insectivores and omnivores.

“We looked at the ranges of these bird species. We noted what bird species [in each guild] occurred at 100 meters, then 200, 300 and so on, for every 100 meters,” explains Srinivasan. “We then classified mountain ranges with or without Oecophylla at the base, and looked at what species were present at different elevations.”

The researchers found patterns consistent with Oecophylla ants competing with insect-eating birds for food at lower elevations. This could then have ended up pushing these birds higher up in the mountains—the species diversity was highest at an elevation of about 960 meters. Other bird groups like nectar-eating and fruit-eating birds—which weren’t competing with Oecophylla ants—reduced in species diversity as the elevation increased.

The presence or absence of Oecophylla ants at the base of mountains, therefore, was a good predictor of why the diversity of insect-eating birds peaked at mid-elevations, the team found.

“With climate change, if the ants shift their ranges towards higher elevations, this might impact the bird species at higher elevations as well,” adds Srinivasan.

More information:
Umesh Srinivasan et al, Ant impacts on global patterns of bird elevational diversity, Ecology Letters (2024). DOI: 10.1111/ele.14497

Citation:
Ants might be pushing montane birds higher up, study finds (2024, September 30)
retrieved 30 September 2024
from https://phys.org/news/2024-09-ants-montane-birds-higher.html

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How our research used round numbers to zero in on tax evasion

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How our research used round numbers to zero in on tax evasion


Rounding up: how our research used round numbers to zero in on tax evasion
Sample of 22.5 million tax returns between 1991 and 2018. The graph is limited to taxpayers who owed tax and had tax withheld. Diamonds indicate counts at hundred-dollar thresholds. For visual clarity the number owing zero has been excluded. Credit: Journal of Public Economics (2024). DOI: 10.1016/j.jpubeco.2024.105195

Australia’s tax system is needlessly complex, and that’s making it costly in ways that aren’t obvious.

New research from our team at the Australian National University’s Tax and Transfer Policy Institute, in the Journal of Public Economics, has identified one of the unexpected ways it is wasting our time, and found pretty clear evidence of tax evasion along the way—evidence the Tax Office will be able to use.

Here’s what we did.

Examining 27 years of de-identified individual tax files, we noticed a striking number of returns generating “round number” refunds.

By “round number,” I mean refunds whose last digit is zero.

Zeros are exceptionally popular

We found, for instance, far more refunds of exactly $1,000 than of $999 or $995, or even $1,005 or $1,015.

This phenomenon was particularly striking at zero (many fewer people got refunds of slightly less than zero, which would have meant they owed money) and also apparent at tens and hundreds as well as thousands.

Analyzing what the returns with round numbers had in common, we found they were more likely than other returns to be

  • driven by efforts to evade and minimize tax rather than simply earn income
  • driven by things that are costly for the Tax Office to audit (such as work-related expense deductions).
  • prepared by agents (zeros were twice as common in agent-prepared returns)

Next, we matched our data about zeros with data from the Tax Office’s random audit program. We found that, when audited, returns with round number refunds were significantly more likely to be wrong. Specifically, they were more likely to overstate the refund that was owed.

More than a quirky preference

This suggests round number refunds are not just a quirky preference—they signal something going on, most likely something going wrong.

That “something” seems to be the manipulation of claims that are costly to verify, principally work-related expense deductions and business income.

Expense deductions and business income are significantly larger in returns with round number refunds than in those without.

It is important to note we found some tax agents got round number returns a lot while others did it very little or not at all.

More like evasion than planning

When taxpayers switch from “low-rounding” to “high-rounding” agents, we see a one-off hike in the returns those people receive, with no further increases thereafter.

This is likely to mean that agents who specialize in round-number returns are not working with their clients over time to rearrange their affairs to minimize tax or to better document legitimate deductions.

Were that the case, we would see the value of these returns increase over time.

This makes the behavior of these agents more consistent with tax evasion than tax planning.

We can fight it, or use it as a tool

One simple response to this abuse would be to remove many of the deductions and lower tax rates for everyone.

Another would be to copy the United States and offer all taxpayers a large “standard deduction,” inviting only those that want a larger one to go to the effort of itemizing their claims. (The US standard deduction is currently US$14,600 for singles and US$29,200 for couples filing jointly.)

In the meantime, the Tax Office might be able to put our findings to good use.

It could identify the clients the agents who get round number returns as targets for audits. They are more likely than others to be improperly claiming.

In the longer term, this strategy won’t work as well. The agents who have been delivering round number returns will become aware that their clients are being targeted and change their behavior.

This means that after a while nothing will work as well as tax reform. It would save taxpayers time and make the system more fair for everyone.

More information:
Robert Breunig et al, Rounded Up: Using round numbers to identify tax evasion, Journal of Public Economics (2024). DOI: 10.1016/j.jpubeco.2024.105195

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

Citation:
Rounding up: How our research used round numbers to zero in on tax evasion (2024, September 30)
retrieved 30 September 2024
from https://phys.org/news/2024-09-rounding-tax-evasion.html

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A river is pushing up Mount Everest’s peak

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A river is pushing up Mount Everest’s peak


Mount Everest
Credit: Pixabay/CC0 Public Domain

Mount Everest is about 15 to 50 meters taller than it would otherwise be because of uplift caused by a nearby eroding river gorge, and continues to grow because of it, finds a new study by UCL researchers.

The study, published in Nature Geoscience, found that erosion from a river network about 75 kilometers from Mount Everest is carving away a substantial gorge. The loss of this landmass is causing the mountain to spring upwards by as much as 2 millimeters a year and has already increased its height by between 15 and 50 meters over the past 89,000 years.

At 8,849 meters high, Mount Everest, also known as Chomolungma in Tibetan or Sagarmāthā in Nepali, is the tallest mountain on Earth, and rises about 250 meters above the next tallest peak in the Himalayas. Everest is considered anomalously high for the mountain range, as the next three tallest peaks—K2, Kangchenjunga and Lhotse—all only differ by about 120 meters from each other.

A significant portion of this anomaly can be explained by an uplifting force caused by pressure from below Earth’s crust after a nearby river eroded away a sizable amount of rocks and soil. It’s an effect called isostatic rebound, where a section of the Earth’s crust that loses mass flexes and “floats” upwards because the intense pressure of the liquid mantle below is greater than the downward force of gravity after the loss of mass.

It’s a gradual process, usually only a few millimeters a year, but over geological timeframes can make a significant difference to the Earth’s surface.

The researchers found that, because of this process, Mount Everest has grown by about 15 to 50 meters over the last 89,000 years, since the nearby Arun river merged with the adjacent Kosi river network.

Co-author, Ph.D. student Adam Smith (UCL Earth Sciences) said, “Mount Everest is a remarkable mountain of myth and legend and it’s still growing. Our research shows that as the nearby river system cuts deeper, the loss of material is causing the mountain to spring further upwards.”

Today, the Arun river runs to the east of Mount Everest and merges downstream with the larger Kosi river system. Over millennia, the Arun has carved out a substantial gorge along its banks, washing away billions of tons of earth and sediment.

Co-author Dr. Jin-Gen Dai of the China University of Geosciences, said, “An interesting river system exists in the Everest region. The upstream Arun river flows east at high altitude with a flat valley. It then abruptly turns south as the Kosi river, dropping in elevation and becoming steeper. This unique topography, indicative of an unsteady state, likely relates to Everest’s extreme height.”

The uplift is not limited to Mount Everest, and affects neighboring peaks including Lhotse and Makalu, the world’s fourth and fifth highest peaks respectively. The isostatic rebound boosts the heights of these peaks by a similar amount as it does Everest, though Makalu, located closest to the Arun river, would experience a slightly higher rate of uplift.

Co-author Dr. Matthew Fox (UCL Earth Sciences) said, “Mount Everest and its neighboring peaks are growing because the isostatic rebound is raising them up faster than erosion is wearing them down. We can see them growing by about two millimeters a year using GPS instruments and now we have a better understanding of what’s driving it.”

By looking at the erosion rates of the Arun, the Kosi and other rivers in the region, the researchers were able to determine that about 89,000 years ago the Arun river joined and merged with the Kosi river network, a process called drainage piracy.

In doing so, more water was funneled through the Kosi river, increasing its erosive power and taking more of the landscape’s soils and sediments with it. With more of the land washed away, it triggered an increased rate of uplift, pushing the mountains’ peaks higher and higher.

Lead author Dr. Xu Han of China University of Geosciences, who carried out the work while on a China Scholarship Council research visit to UCL, said, “The changing height of Mount Everest really highlights the dynamic nature of the Earth’s surface. The interaction between the erosion of the Arun river and the upward pressure of the Earth’s mantle gives Mount Everest a boost, pushing it up higher than it would otherwise be.”

More information:
Jin-Gen Dai, Recent uplift of Chomolungma enhanced by river drainage piracy, Nature Geoscience (2024). DOI: 10.1038/s41561-024-01535-w. www.nature.com/articles/s41561-024-01535-w

Citation:
A river is pushing up Mount Everest’s peak (2024, September 30)
retrieved 30 September 2024
from https://phys.org/news/2024-09-river-mount-everest-peak.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
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‘Vegetarian’ possums eat meat when the weather’s cold

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‘Vegetarian’ possums eat meat when the weather’s cold


'Vegetarian' possums eat meat when the weather's cold
Our cameras captured many images of brushtail possums at kangaroo carcasses. Image A) a sole brushtail possum, B) a group of possums feeding on a carcass, C) a confrontation between two brushtail possums at a carcass, D) vigilance at a carcass, E) shows a confrontation between a feral cat and a brushtail possum at a carcass. Credit: Patt Finnerty

When dead animals are left lying around in nature, who takes advantage of the free feed—carnivores or herbivores? The answer may surprise you.

In Australia, people tend to think carnivores—such as dingoes, ravens, foxes and wedge-tailed eagles—lead the clean-up crew.

But our new research shows common brushtail possums—often thought to be herbivores—also dine on animal carcasses.

Understanding when and where brushtail possums scavenge is important. It can improve our knowledge of how carcasses are disposed of in nature, and how nutrients cycle through ecosystems.

Seeking a nutritious meal

Scavenging may provide specific essential nutrients otherwise lacking in herbivore diets.

Carcasses often contain much greater levels of crude protein than leafy greens do. Similarly, chewing on bones, may increase the intake of calcium and phosphorus, two key minerals essential for growth.

Scavenging on carrion may also help herbivores meet nutritional requirements in regions where typical food resources may be restricted during some seasons. Similarly, in times of drought, thirst may also drive herbivores to scavenge in an attempt to extract fluids from carcasses.

Though it may seem gruesome, scavenging is crucial to healthy ecosystems. Clearing carcasses from the landscape by feeding them back into food chains recycles nutrients into living systems.

Our previous research has found native marsupial herbivores feasting on the dead.

In alpine Australia, possums accounted for 61% of all recorded carcass scavenging—a proportion far surpassing species more typically considered carcass consumers.

In our latest research, we wanted to understand the factors that influence carrion consumption by brushtail possums in different ecosystems.

What we did

We monitored fresh eastern gray kangaroo carcasses across both alpine (Kosciuszko National Park) and temperate (Wolgan Valley, Greater Blue Mountains National Park) regions in New South Wales. We also compared sites in both open (grassland with no canopy cover) and closed (woodland) habitats, in cool and warm seasons.

At each carcass, we used a remote camera “trap” to record scavenging behaviors.

We found possums were one of the main scavengers, often feeding from carrion more than typical scavengers such as dingoes and ravens.

Possum scavenging rates varied by habitat and season. Regardless of region, possums scavenged exclusively in closed canopy habitats under the trees, probably for protection from predators and other scavengers such as dingoes, red foxes, and wedge-tailed eagles.

Out in the cold

Possum scavenging activity varied according to the season.

In temperate regions, possums scavenged only in winter when other food resources were limited.

In alpine areas, where food is scarce even in summer, possums scavenged year-round. But they still ate more from carcasses in cooler months. This may be necessary for possums to get the nutrition they need when other normal food resources—such as leaves, flowers and fruit—are limited.

Competition between scavengers may also change with the seasons. For example, in alpine regions, we saw fewer large scavengers such as dingoes in winter, possibly reducing competition and making it easier for possums to access carrion.

During warmer months, insect activity increases. These tiny scavengers often start eating a carcass within minutes of its death, accelerating its decomposition. It means animals such as possums have less time to feed on the carrion.

Flexible ‘herbivores’ around the world

Previous research has shown many herbivore diets are more flexible than previously thought. All over the world, certain plant-eaters have been found scavenging on animal remains—especially when other food sources are limited, such as during drought or after fire.

In Africa, hippopotamuses were found to have consumed flesh from the carcasses of other animals. In the United States, white-tailed deer fed on discarded fish.

Similarly, on a small island off Cape Town, introduced European fallow deer ate dead rabbits. On the Eurasian tundra (treeless plains), reindeer devoured lemming carcasses. In Italy, crested porcupine ate dead pigeons.

These are all still primarily herbivorous animals, they just happen to dip into carcass resources when they need to.

Improving our understanding of ‘bloody hungry’ herbivores

Our study found brushtail possums are an important scavenging species across several Australian ecosystems. It also highlights how scavenging can vary with a region, season and habitat.

Understanding the unusual foraging behavior of the common brushtail possum could also help inform more effective wildlife management. Specifically, understanding how carcasses can support possum populations during cooler months in places like New Zealand, where they are considered an invasive pest, may lead to more effective control measures.

Our methods could also help scientists understand herbivore scavenging in other environments. This may provide valuable insights into the complexities of food webs and how nutrients move through ecosystems.

More information:
Patrick B. Finnerty et al, Brushing up on carcass consumption: Investigating spatiotemporal scavenging dynamics of brushtail possums in Australian ecosystems, Austral Ecology (2024). DOI: 10.1111/aec.13598

Provided by
The Conversation


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

Citation:
‘Vegetarian’ possums eat meat when the weather’s cold (2024, September 30)
retrieved 30 September 2024
from https://phys.org/news/2024-09-vegetarian-possums-meat-weather-cold.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.





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