Scientist reveals cause of lost magnetism at meteorite site

A University of Alaska Fairbanks scientist has discovered a method for detecting and better defining meteorite impact sites that have long lost their tell-tale craters. The discovery could further the study of not only Earth's geology but also that of other bodies in our solar system.

The key, according to work by associate research professor Gunther Kletetschka at the UAF Geophysical Institute, is in the greatly reduced level of natural remanent magnetization of rock that has been subjected to the intense forces from a meteor as it nears and then strikes the surface.

Rocks unaltered by humanmade or non-Earth forces have 2% to 3% natural remanent magnetization, meaning they consist of that quantity of magnetic mineral grains -- usually magnetite or hematite or both. Kletetschka found that samples collected at the Santa Fe Impact Structure in New Mexico contained less than 0.1% magnetism.

Kletetschka determined that plasma created at the moment of impact and a change in the behavior of electrons in the rocks' atoms are the reasons for the minimal magnetism.

Kletetschka reported his findings in a paper published Wednesday in the journal Scientific Reports.

The Santa Fe Impact Structure was discovered in 2005 and is estimated to be about 1.2 billion years old. The site consists of easily recognized shatter cones, which are rocks with fantail features and radiating fracture lines. Shatter cones are believed to only form when a rock is subjected to a high-pressure, high-velocity shock wave such as from a meteor or nuclear explosion.

Kletetschka's work will now allow researchers to determine an impact site before shatter cones are discovered and to better define the extent of known impact sites that have lost their craters due to erosion.

"When you have an impact, it's at a tremendous velocity," Kletetschka said. "And as soon as there is a contact with that velocity, there is a change of the kinetic energy into heat and vapor and plasma. A lot of people understand that there is heat, maybe some melting and evaporation, but people don't think about plasma."

Plasma is a gas in which atoms have been broken into free-floating negative electrons and positive ions.

"We were able to detect in the rocks that a plasma was created during the impact," he said.

Earth's magnetic field lines penetrate everything on the planet. Magnetic stability in rocks can be knocked out temporarily by a shock wave, as they are when hitting an object with a hammer, for example. The magnetic stability in rocks returns immediately after the shock wave passes.

At Santa Fe, the meteorite's impact sent a massive shock wave through the rocks, as expected. Kletetschka found that the shock wave altered the characteristics of atoms in the rocks by modifying the orbits of certain electrons, leading to their loss of magnetism.

The modification of the atoms would allow for a quick remagnetization of the rocks, but Kletetschka also found that the meteorite impact had weakened the magnetic field in the area. There was no way for the rocks to regain their 2% to 3% magnetism even though they had the capability to do so.

That's because of the presence of plasma in the rocks at the impact surface and below. Presence of the plasma increased the rocks' electrical conductivity as they converted to vapor and molten rock at the leading edge of the shock wave, temporarily weakening the ambient magnetic field.

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One in five galaxies in the early universe could still be hidden behind cosmic dust

Astronomers at the University of Copenhagen's Cosmic Dawn Center have discovered two previously invisible galaxies 29 billion light-years away. Their discovery suggests that up to one in five such distant galaxies remain hidden from our telescopes, camouflaged by cosmic dust. The new knowledge changes perceptions of our universe's evolution since the Big Bang.

Researchers at the University of Copenhagen's Niels Bohr Institute have just discovered two previously invisible galaxies 29 billion light-years away from Earth. The two galaxies have been invisible to the optical lens of the Hubble Space Telescope, hidden behind a thick layer of cosmic dust that surrounds them.

But with the help of the giant ALMA radio telescopes (Atacama Large Milimeter Array) in Chile's Atacama Desert, which can capture radio waves emitted from the coldest, darkest depths of the universe, the two invisible galaxies suddenly appeared.

"We were looking at a sample of very distant galaxies, which we already knew existed from the Hubble Space Telescope. And then we noticed that two of them had a neighbor that we didn't expect to be there at all. As both of these neighboring galaxies are surrounded by dust, some of their light is blocked, making them invisible to Hubble," explains Associate Professor Pascal Oesch of the Cosmic Dawn Center at the Niels Bohr Institute.

The study has just been published in the scientific journal, Nature.

With the help of the giant ALMA radio telescopes (Atacama Large Milimeter Array) in Chile's Atacama Desert the two invisible galaxies suddenly appeared. Photo: NASA

10-20 percent of the universe's galaxies are missing

The new discovery suggests that the very early universe contains many more galaxies than previously assumed. They simply lie hidden behind dust consisting of small particles from stars. However, they can now be detected thanks to the highly sensitive ALMA telescope and the method used by the researchers.

Facts about the research:
 

• The two hidden galaxies are so far called REBELS-12-2 and REBELS-29-2.
• The light from the two invisible galaxies has travelled about 13 billion years to reach us.
• The galaxies are now located 29 billion light years away due the universe's expansion.
• Researchers used the ALMA telescope, which is based on radio signals.
• The ALMA Telescope combines the light of all its 66 antennae to create a high resolution image and spectra of the sky.

By comparing these new galaxies with previously known sources in the very early universe, approximately 13 billion years ago, the researchers estimate that between 10 and 20 percent of such early galaxies may still remain hidden behind curtains of cosmic dust.

"Our discovery demonstrates that up to one in five of the earliest galaxies may have been missing from our map of the heavens. Before we can start to understand when and how galaxies formed in the Universe, we first need a proper accounting," says Pascal Oesch.

New super telescope will find the missing galaxies

To help with that task, NASA, ESA and the Canadian Space Agency have built a new super telescope, the James Webb Space Telescope, which is expected to be launched into orbit on the 18th of December 2021.

With its strength and improved technology, the telescope will gaze even deeper into the universe and contribute new knowledge about its origins. This will, among many other things, help Cosmic Dawn researchers at the Niels Bohr Institute see through the cosmic dust.

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Hurricanes expected to linger over Northeast cities, causing greater damage

By the late 21st century, northeastern U.S. cities will see worsening hurricane outcomes, with storms arriving more quickly but slowing down once they've made landfall. As storms linger longer over the East Coast, they will cause greater damage along the heavily populated corridor, according to a new study.

In the new study, climate scientist Andra Garner at Rowan University analyzed more than 35,000 computer-simulated storms. To assess likely storm outcomes in the future, Garner and her collaborators compared where storms formed, how fast they moved and where they ended from the pre-industrial period through the end of the 21st century.

The researchers found that future East Coast hurricanes will likely cause greater damage than storms of the past. The research predicted that a greater number of future hurricanes will form near the East Coast, and those storms will reach the Northeast corridor more quickly. The simulated storms slow to a crawl as they approach the East Coast, allowing them to produce more wind, rain, floods, and related damage in the Northeast region. The longest-lived tropical storms are predicted to be twice as long as storms today.

The study was published in Earth's Future, which publishes interdisciplinary research on the past, present and future of our planet and its inhabitants.

The changes in storm speed will be driven by changes in atmospheric patterns over the Atlantic, prompted by warmer air temperatures. While Garner and her colleagues note that more research remains to be done to fully understand the relationship between a warming climate and changing storm tracks, they noted that potential northward shifts in the region where Northern and Southern Hemisphere trade winds meet or slowing environmental wind speeds could be to blame.

"When you think of a hurricane moving along the East Coast, there are larger scale wind patterns that generally help push them back out to sea," Garner said. "We see those winds slowing down over time." Without those winds, the hurricanes can overstay their welcome on the coast.

Garner, whose previous work focused on the devastating East Coast effects of storms like Hurricane Sandy, particularly in the Mid-Atlantic, said the concern raised by the new study is that more storms capable of producing damage levels similar to Sandy are likely.

And the longer storms linger, the worse they can be, she said.

"Think of Hurricane Harvey in 2017 sitting over Texas, and Hurricane Dorian in 2019 over the Bahamas," she said. "That prolonged exposure can worsen the impacts."

From 2010 to 2020, U.S. coastlines were hit by 19 tropical cyclones that qualified as billion-dollar disasters, generating approximately $480 billion in damages, adjusted for inflation. If storms sit over coasts for longer stretches, that economic damage is likely to increase as well. For the authors, that provides clear economic motivation to stem rising greenhouse gas emissions.

"The work produced yet more evidence of a dire need to cut emissions of greenhouse gases now to stop the climate warming," Garner said.

Read more at Science Daily

Snow cover critical for revegetation following forest fires

With wildfires devastating mountain ecosystems across the western United States, their successful forest revegetation recovery hinges on, among other factors, an adequate lasting snowpack, according to research by the University of Nevada, Reno and Oregon State University.

"Our study illustrated that summer precipitation, snow cover and elevation were all important drivers of revegetation success," said Anne Nolin, a hydrologist and geography professor at the University of Nevada, Reno and formerly at Oregon State University. "In particular, we found that snow cover was a critical explanatory variable for revegetation in the Oregon and Washington Cascades. This could help inform revegetation management practices following severe wildfires."

Climate change has already increased the fraction of winter precipitation that falls as rain rather than snow, reduced the spring snow water equivalent -- a metric for how much water snow contains -- and caused snowmelt to begin earlier in the spring than it used to, Nolin explained. Pacific Northwest snowpacks have seen the greatest declines of any seasonal snow region in the West.

The research, led by Nolin, examined the 260,000-square-mile Columbia River Basin in the Pacific Northwest. She teamed with co-author Andrew Wilson, a graduate research assistant in OSU's College of Earth, Ocean, and Atmospheric Science, and co-author Kevin Bladon of OSU's College of Forestry for the study.

The NASA-supported study featured before-and-after vegetation analyses for two dozen high-severity wildfires. The fires occurred over a 10-year period among the four distinct subregions of the Columbia River Basin. There are many short- and long-term effects from these fires, including erosion, debris flows and water quality issues, which can affect the health of aquatic ecosystems and downstream community water supply, highlighting the importance of understanding post-fire forest rehabilitation.

In their paper published in the Journal of Geophysical Research -- Biogeosciences, "Assessing the Role of Snow Cover for Post-Wildfire Revegetation Across the Pacific Northwest," the findings show that given the trends of increasing wildfire activity, lower snowpacks, and earlier snow disappearance dates across the Pacific Northwest, forests will likely experience more frequent drought conditions, which will negatively impact the success of post?wildfire vegetation recovery with a number of impacts to the ecosystem.

"This knowledge may be used to facilitate adaptive post-fire management policies and decisions to ensure long-term forest health," Nolin, who is also director of the University of Nevada, Reno's Graduate Program of Hydrological Sciences, said. "For example, depending on the sub-region and species composition, reseeding efforts following low snow winters might employ more drought tolerant species or, replanting could be delayed one to two years until snowmelt and soil moisture conditions are more favorable for seedling propagation.

"However, climate change projections and shifting wildfire regimes have increased concerns about post-fire regeneration and, as such it is imperative that we broaden our understanding of the role of snowpacks in post-wildfire forest regeneration. The snowpacks' role in aiding revegetation will become increasingly important across the West. And where snowpacks have declined, there likely will be ecosystem transitions that look like a shift from forest to non-forest and from evergreen to deciduous vegetation."

Wildfires continue to burn more area each year across many regions of the planet, including the Pacific Northwest. The Pacific Northwest's largest watershed, the Columbia River Basin contains a variety of fire-prone landscapes that have seen almost 900 fires since 2010, serves as critical habitat for more than 700 species and is a water source for seven states.

"As wildfire activity continues to increase and intensify in the Northwest, understanding what shapes revegetation on severely burned forested landscapes is vital for guiding management decisions," co-author Bladon said.

After the occurrence of a wildfire, revegetation over the burned area is critical to maintain or re-establish ecosystem functions from forests such as biodiversity, erosion control, water purification and habitat provision.

"Snow matters to regrowing vegetation following fire, and with double impacts of declining snowpacks and increasing wildfires it is critical that we understand how these changes are affecting Pacific Northwest forests," Nolin said. "Positive relationships between snow cover and summer precipitation with post-fire greening suggest that active post-fire revegetation efforts will help facilitate recovery, especially during years when severe wildfires are followed by early snowmelt years or below average summer precipitation."

In the study, summer precipitation consistently appeared as the most important variable driving post-fire revegetation across all four subregions. Snow cover frequency, along with elevation, were shown to be secondary but significantly influential explanatory variables for revegetation in the Oregon and Washington Cascades.

More than 80% of wildfires in the western United States from 2000 to 2012 burned within a seasonal snow zone, a time period that overlaps with the years studied by the scientists.

"As wildfire activity continues to increase and intensify in the Northwest, understanding what shapes revegetation on severely burned forested landscapes is vital for guiding management decisions," Bladon said. "But variables such as snow cover frequency, pre-fire forest composition, and elevation, were also shown to be significantly influential for revegetation in the Oregon and Washington Cascades."

Wildfire season length in the western U.S. overall has increased by roughly 25 days in recent decades, including a massive increase in the Northwest from the mid-1970s, when it was 23 days, to 116 days in the early 2000s. That's attributable mainly to warmer temperatures and drier conditions in the spring and summer.

"Snow cover has a strong influence on postfire vegetation greening, but the influence varied depending on subregion and dominant prefire conifer species, with the biggest impacts at low to moderate elevations in the Washington Cascades, the Oregon Cascades and western Montana Rockies," Nolin said. "And with current climate change projections, snowpacks' role in aiding revegetation will become increasingly important across the West."

Bladon suggests fire can be looked at as an opportunity for forests to reassemble into ecosystems better suited to survive warmer winters, longer fire seasons and more drought stress.

Read more at Science Daily

Scientists solve 50-year-old mystery behind plant growth

A team of researchers led by UC Riverside has demonstrated for the first time one way that a small molecule turns a single cell into something as large as a tree. For half a century, scientists have known that all plants depend on this molecule, auxin, to grow. Until now, they didn't understand exactly how auxin sets growth in motion.

The word auxin is derived from the Greek word "auxein," meaning "to grow." There are two main pathways that auxin uses to orchestrate plant growth, and one of them is now described in a new Nature journal article.

Plant cells are encased in shell-like cell walls, whose primary layer has three major components: cellulose, hemicellulose, and pectin.

"Cellulose works like rebar in a high rise, providing a broad base of strength. It's reinforced by hemicellulose chains and sealed in by pectin," said UCR botany professor and research team leader Zhenbiao Yang.

These components define the shape of plant cells, resulting in sometimes-surprising formations like the puzzle-piece-shaped leaf epidermis cells that Yang has been studying for the last two decades. These shapes help tightly glue cells together and provide physical strength for plants against elements such as the wind. With everything locked so tightly by the cell walls, how is movement and growth possible?

One theory posits that when plants are ready to grow, auxin causes their cells to become acidic, loosening the bonds between components and allowing the walls to soften and expand. This theory was proposed half a century ago, but how auxin activates the acidification remained a mystery until now.

Yang's team discovered auxin creates that acidity by triggering the pumping of protons into the cell walls, lowering their pH levels. The lower pH activates a protein, expansin, appropriately named because it breaks down links between cellulose and hemicellulose, allowing the cells to expand.

The pumping of protons into the cell wall also drives water uptake into the cell, building inner pressure. If the cell wall is loose enough and there is enough pressure inside the cell, it will expand.

"Like a balloon, expansion depends on how thick the outsides are, versus how much air you're blowing in," Yang explained. "Lowering the pH in a cell wall can allow water outside of a cell to move in, fueling turgor pressure and expansion."

There are two known mechanisms by which auxin regulates growth. One is the pH lowering that Yang's team described. Another is auxin's ability to turn on gene expression in the nucleus of the plants' cells, which in turn increases the amount of expansion and other growth-regulating factors in the cell.

The latter mechanism also lowers the pH of the cell and facilitates growth. UC San Diego professor of cell biology Mark Estelle is a leading authority in this field. He discovered and researches this other mechanism.

"Dr. Yang's recent work represents a significant advance in our understanding of how auxin regulates cell expansion. It's been known that acidification of the extracellular space promotes cell expansion but it wasn't known how this happens," Estelle said. "It's exciting to see an old problem being solved."

It is an understatement to say that auxin simply "contributes" to plant growth. It is essential to nearly every aspect of a plant's growth and development, including aspects that are important to agriculture such as fruit, seed and root development, shoot branching, and leaf formation. Even the plant's correct responses to gravity and light depend on auxin to ensure roots head down while the shoots grow up toward light.

Read more at Science Daily

Antarctic ice-sheet destabilized within a decade

After the natural warming that followed the last Ice Age, there were repeated periods when masses of icebergs broke off from Antarctica into the Southern Ocean. A new data-model study led by the University of Bonn (Germany) now shows that it took only a decade to initiate this tipping point in the climate system, and that ice mass loss then continued for many centuries. Accompanying modeling studies suggest that today's accelerating Antarctic ice mass loss also represents such a tipping point, which could lead to irreversible and long-lasting ice retreat and global sea level rise. The study has now been published in the journal Nature Communications.

To understand what the consequences of current and future human-induced climate warming may be, it helps to take a look at the past: how did sea-level changes look like during times of natural climate warming? In a recent study, an international research team led by Dr. Michael Weber from the Institute of Geosciences at the University of Bonn investigated this question. In doing so, they focused on the Antarctic Ice Sheet as the largest remaining ice sheet on Earth.

There, they searched for evidence of icebergs that broke off the Antarctic continent, floated in the surrounding ocean and melted down in the major gateway to lower latitudes called "Iceberg Alley." In the process, the icebergs released encapsulated debris that accumulated on the ocean floor. The team took sediment cores from the deep ocean in 3.5 km water depth from the area, dated the natural climate archive and counted the ice-rafted debris.

The scientists identified eight phased with high amounts of debris which they interpret as retreat phases of the Antarctic Ice Sheet after the Last Glacial Maximum about 19,000 to 9,000 years ago, when climate warmed and Antarctica shed masses of icebergs repeatedly into the ocean. The result of the new data-model study: each such phase destabilized the ice sheet within a decade and contributed to global sea-level rise for centuries to a millennium. The subsequent re-stabilization was equally rapidly within a decade.

The research team found three other independent pieces of evidence for such post-glacial tipping points: Model experiments showing the melting of the entire Antarctic ice sheet, a West Antarctic ice core documenting ice-sheet elevation draw-down and drill cores revealing a step-wise ice-sheet retreat across the Ross Sea shelf.

Today's ice mass loss could be start of long-lasting period

The results are also relevant for ice retreat observed today: "Our findings are consistent with a growing body of evidence suggesting the acceleration of Antarctic ice-mass loss in recent decades may mark the begin of a self-sustaining and irreversible period of ice sheet retreat and substantial global sea level rise," says study leader Dr. Michael Weber from the University of Bonn.

Combining the sediment record with computer models of ice sheet behaviour the team showed that each episode of increased iceberg calving reflected increased loss of ice from the interior of the ice sheet, not just changes in the already-floating ice shelves. "We found that iceberg calving events on multi-year time scales were synchronous with discharge of grounded ice from the Antarctic Ice Sheet," said Prof. Nick Golledge from the University of Wellington (New Zealand), who led the ice-sheet modelling.

Dr. Zoë Thomas, a co-author of the study from the University of New South Wales in Sydney, Australia, then applied statistical methods to the model outputs to see if early warning signs could be detected for tipping points in the ice sheet system. Her analyses confirmed that tipping points did indeed exist. "If it just takes one decade to tip a system like this, that's actually quite scary because if the Antarctic Ice Sheet behaves in future like it did in the past, we must be experiencing the tipping right now," Thomas said.

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Scientists capture humor’s earliest emergence

Young children's ability to laugh and make jokes has been mapped by age for the first time using data from a new study involving nearly 700 children from birth to 4 years of age, from around the world. The findings, led by University of Bristol researchers and published in Behavior Research Methods, identifies the earliest age humour emerges and how it typically builds in the first years of life.

Researchers from Bristol's School of Education sought to determine what types of humour are present in early development and the ages at which different types of humour emerge. The team created the 20-question Early Humour Survey (EHS) and asked the parents of 671 children aged 0 to 47 months from the UK, US, Australia, and Canada, to complete the five-minute survey about their child's humour development.

The team found the earliest reported age that some children appreciated humour was 1 month, with an estimated 50% of children appreciating humour by 2 months, and 50% producing humour by 11 months. The team also show that once children produced humour, they produced it often, with half of children having joked in the last 3 hours.

Of the children surveyed, the team identified 21 different types of humour. Children under one year of age appreciated physical, visual and auditory forms of humour. This included hide and reveal games (e.g., peekaboo), tickling, funny faces, bodily humour (e.g., putting your head through your legs), funny voices and noises, chasing, and misusing objects (e.g., putting a cup on your head).

One-year-olds appreciated several types of humour that involved getting a reaction from others. This included teasing, showing hidden body parts (e.g., taking off clothes), scaring others, and taboo topics (e.g., toilet humour). They also found it funny to act like something else (e.g., an animal).

Two-year-olds' humour reflected language development, including mislabelling, playing with concepts (e.g., dogs say moo), and nonsense words. Children in this age group were also found to demonstrate a mean streak as they appreciated making fun of others and aggressive humour (e.g., pushing someone).

Finally, 3-year-olds were found to play with social rules (e.g., saying naughty words to be funny), and showed the beginnings of understanding tricks and puns.

Dr Elena Hoicka, Associate Professor in Bristol's School of Education and the study's lead author, said: "Our results highlight that humour is a complex, developing process in the first four years of life. Given its universality and importance in so many aspects of children's and adults' lives, it is important that we develop tools to determine how humour first develops so that we can further understand not only the emergence of humour itself, but how humour may help young children function cognitively, socially, and in terms of mental health.

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Reading the mind of a worm

It sounds like a party trick: scientists can now look at the brain activity of a tiny worm and tell you which chemical the animal smelled a few seconds before. But the findings of a new study, led by Salk Associate Professor Sreekanth Chalasani, are more than just a novelty; they help the scientists better understand how the brain functions and integrates information.

"We found some unexpected things when we started looking at the effect of these sensory stimuli on individual cells and connections within the worms' brains," says Chalasani, member of the Molecular Neurobiology Laboratory and senior author of the new work, published in the journal PLOS Computational Biology on November 9, 2021.

Chalasani is interested in how, at a cellular level, the brain processes information from the outside world. Researchers can't simultaneously track the activity of each of the 86 billion brain cells in a living human -- but they can do this in the microscopic worm Caenorhabditis elegans, which has only 302 neurons. Chalasani explains that in a simple animal like C. elegans, researchers can monitor individual neurons as the animal is carrying out actions. That level of resolution is not currently possible in humans or even mice.

Chalasani's team set out to study how C. elegans neurons react to smelling each of five different chemicals: benzaldehyde, diacetyl, isoamyl alcohol, 2-nonanone, and sodium chloride. Previous studies have shown that C. elegans can differentiate these chemicals, which, to humans, smell roughly like almond, buttered popcorn, banana, cheese, and salt. And while researchers know the identities of the small handful of sensory neurons that directly sense these stimuli, Chalasani's group was more interested in how the rest of the brain reacts.

The researchers engineered C. elegans so that each of their 302 neurons contained a fluorescent sensor that would light up when the neuron was active. Then, they watched under a microscope as they exposed 48 different worms to repeated bursts of the five chemicals. On average, 50 or 60 neurons activated in response to each chemical.

By looking at basic properties of the datasets -- such as how many cells were active at each time point -- Chalasani and his colleagues couldn't immediately differentiate between the different chemicals. So, they turned to a mathematical approach called graph theory, which analyzes the collective interactions between pairs of cells: When one cell is activated, how does the activity of other cells change in response?

This approach revealed that whenever C. elegans was exposed to sodium chloride (salt), there was first a burst of activity in one set of neurons -- likely the sensory neurons -- but then about 30 second later, triplets of other neurons began to strongly coordinate their activities. These same distinct triplets weren't seen after the other stimuli, letting the researchers accurately identify -- based only on the brain patterns -- when a worm had been exposed to salt.

"C. elegans seems to have attached a high value to sensing salt, using a completely different circuit configuration in the brain to respond," says Chalasani. "This might be because salt often represents bacteria, which is food for the worm."

The researchers next used a machine-learning algorithm to pinpoint other, more subtle, differences in how the brain responded to each of the five chemicals. The algorithm was able to learn to differentiate the neural response to salt and benzaldehyde but often confused the other three chemicals.

"Whatever analysis we've done, it's a start but we're still only getting a partial answer as to how the brain discriminates these things," says Chalasani.

Still, he points out that the way the team approached the study -- looking at the brain's network-wide response to a stimulus, and applying graph theory, rather than just focusing on a small set of sensory neurons and whether they're activated -- paves the way toward more complex and holistic studies of how brains react to stimuli.

The researchers' ultimate goal, of course, isn't to read the minds of microscopic worms, but to gain a deeper understanding of how humans encode information in the brain and what happens when this goes awry in sensory processing disorders and related conditions like anxiety, attention deficit hyperactivity disorders (ADHD), autism spectrum disorders and others.

Read more at Science Daily

Study confirms that Gabon is the largest stronghold for critically endangered African forest elephants

The most comprehensive survey conducted of elephant numbers in the Central African nation of Gabon since the late 1980s has found elephants occurring in higher numbers than previously thought.

The study, which was conducted by the Wildlife Conservation Society (WCS), Gabon's National Park Agency (ANPN) and Vulcan using a new non-invasive survey technique, estimates that 95,000 forest elephants (Loxodonta cyclotis) now live in Gabon, confirming it as the principal stronghold for this species, which is considered Critically Endangered by IUCN. The technical improvements enabled a more accurate estimate than previous methods confined to dung counts.

The findings provide hope for the future of the species and the impact that conservation-focused policies can have in encouraging wildlife protection if effectively implemented. The study's results, published in the journal Global Ecology and Conservation, mark the first-known DNA-based assessment of a free-ranging large mammal in Africa.

Said Emma Stokes, WCS Regional Director for Central Africa and a co-author of the study: "These results underscore the importance of Gabon as a critical stronghold for forest elephants -- containing some 60-70 percent of Africa's forests elephants. Gabon, together with the northern Republic of Congo, probably hold as many as 85 percent of remaining forest elephants -- in large and relatively stable populations. With significant declines in forest elephants reported across much of the rest of the Congo Basin, these two nations will determine the future for the forest elephant in Africa."

President Ali Bongo Ondimba of Gabon said: "Managing forests, protecting our parks and fighting organised criminal and terrorist groups, who plunder our natural resources, is not easy.

It requires constant vigilance, technical knowhow, logistical capacity, sustainable funding and most importantly, courageous, dedicated, incorruptible forest managers."

Lee White, Minister of Water and Forests, the Sea, the Environment charged with Climate Planning and Land Use Plan, said: "These results demonstrate that Gabon, under the active leadership of President Ali Bongo Ondimba, has been able to buck the trend of forest elephant decline. This is down to the courage and dedication of our national parks rangers, who are very much in the line of fire. In Africa there is a clear link between healthy elephant numbers and natural resource governance -- most countries that have lost their elephant populations have also experienced civil war and instability."

Christian Tchemambela, ANPN Executive Secretary, said: "The data on the forest elephant population is now clearer. This is a big step forward. Our teams have developed more reliable methods, particularly in our genetics laboratory. This scientific evidence can now be used to support decision-making."

The team used spatial capture-recapture (SCR) techniques based on non-invasive molecular sampling from dung. Unlike savannah elephants (Loxodonta africana), which can be accurately counted by aerial surveys, forest elephants often live deep in rainforests making their populations more difficult to estimate. African forest elephants were recently acknowledged by IUCN as a separate species from savannah elephants.

The study found that Gabon has not only more forest elephants than any other country but also the largest intact habitat in the species' range, with elephants found over more than 250,000 square kilometers (96,500 square miles) which represents some 90 percent of the country.

Although elephants were found across Gabon, the highest elephant densities were found in relatively flat areas where there was more suitable elephant habitat available (i.e. forests or forest-savannah mosaics). The lowest elephant densities were found in more hilly terrain or in areas with less suitable elephant habitat (i.e. near cities, or roads).

The team found low elephant densities immediately adjacent to international borders. Neither protected areas nor human pressure in Gabon strongly predict elephant densities. This means that good elephant habitat is not necessarily restricted to protected areas.

Said the lead author of the study, Alice Laguardia of WCS: "Our findings offer a useful nationwide baseline and status update for forest elephants that will inform adaptive management and stewardship of one of the last remaining forest elephant strongholds. These results are of interest to local, national, and international decision-makers concerned with the conservation of this species and its habitat, with the important ecological role of forest elephants on climate regulation potential of forests, and with forest elephants as a useful indicator for healthy, intact and well-governed forests."

But it was not all good news, with researchers reporting that pockets of low elephant density from recent poaching events remain and have yet to recover.

Across Central Africa, forest elephants have been decimated by ivory poachers in recent years across their range. Gabon is unique in the region in having elephants still distributed at relatively high densities across most of the country. With the exception of Gabon and parts of northern Congo, many other countries have experienced catastrophic declines in forest elephant populations over the last two decades: a WCS-led study released in 2014 documented a 65 percent decline in forest elephant numbers between 2002 and 2013.

Elephants can act as a useful indicator of healthy forests and that good management of forests both inside and outside of protected areas can have benefits for both climate and biodiversity. A 2019 study linked forest elephant presence to significantly greater carbon storage through their browsing that effectively thins the forest of smaller trees, thus promoting growth of larger, more carbon rich trees.

"We believe conservation efforts must be founded on solid data," said Lara Littlefield, Executive Director of Partnerships & Programs at Vulcan. "The 2016 Great Elephant Census of savannah elephants led to support for programs that benefitted threatened populations and communities. We are confident this important new study will lead to targeted efforts to protect endangered forest elephants."

Read more at Science Daily

Breeding plants with genes from one parent

Scientists are a step closer to breeding plants with genes from only one parent. New research led by plant biologists at the University of California, Davis, published Nov. 19 in Science Advances, shows the underlying mechanism behind eliminating half the genome and could make for easier and more rapid breeding of crop plants with desirable traits such as disease resistance.

The work stems from a discovery made over a decade ago by the late Simon Chan, associate professor of plant biology in the UC Davis College of Biological Sciences, and colleagues.

Plants, like other sexual organisms, inherit a matching set of chromosomes from each parent. In order to transmit a favorable trait, such as pest or drought resistance, to all their offspring, the plant would have to carry the same genetic variant on each chromosome. But creating plants that "breed true" in this way can take generations of cross-breeding.

In 2010, Chan and postdoctoral fellow Ravi Maruthachalam serendipitously discovered a way to eliminate the genetic contribution from one parent while breeding the lab plant Arabidopsis. They had modified a protein called CENH3, found in the centromere, a structure in the center of a chromosome. When they tried to cross wildtype Arabidopsiswith plants with modified CENH3, they got plants with half the normal number of chromosomes. The part of the genome from one parent plant had been eliminated to create a haploid plant.

That work was published in Nature in March 2010, setting off efforts to achieve the same result in crop plants such as maize, wheat and tomato.

Clearing up a mystery

But replicating Chan's exact strategy outside Arabidopsis has so far proved fruitless, said Professor Luca Comai, UC Davis Department of Plant Biology and Genome Center, who is senior author on the new paper. Recently, other labs have created plants with one set of chromosomes by manipulating CENH3, but it's not clear how the results are related.

"The mechanistic basis of CENH3 effects on haploid induction was mysterious," Comai said. There appear to be different rules for each species, he said.

Much of that mystery has now been cleared up. Mohan Marimuthu, researcher at the UC Davis Genome Center and Department of Plant Biology, with Comai, Maruthachalam (now at the Indian Institute of Science Education and Research, Kerala) and colleagues found that when CENH3 protein is altered, it is removed from the DNA in the egg before fertilization, weakening the centromere.

"In the subsequent embryonic divisions, the CENH3-depleted centromeres contributed by the egg fail to compete with the CENH3-rich ones contributed by the sperm and the female genome is eliminated," Comai said.

The finding that any selective depletion of CENH3 engenders centromere weakness explains the original results by Chan and Maruthachalam as well as new results from other labs in wheat and maize, Comai said. This new knowledge should make it easier to induce haploids in crop plants, he said.

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