Category: Environment

{Brown-headed cowbirds are unconventional mothers. Rather than building nests and nurturing their chicks, they lay their eggs in the nests of other species, leaving their young ones to compete for resources with the foster parents’ own hatchlings. Despite their reputation as uncaring, absentee moms, cowbird mothers are capable of making sophisticated choices among potential nests in order to give their offspring a better chance of thriving, a new study shows.}

Brown-headed cowbirds are known to lay their eggs in the nests of more than 200 other bird species of varying sizes, and typically do so after the host bird has laid her own eggs. The new study, led by a team at the University of Illinois, found that when cowbird mothers chose the nest of a larger host bird, they preferred those that held smaller-than-average eggs for that species. Smaller host eggs give the cowbird eggs a better chance of being successfully incubated; smaller host hatchlings mean the cowbird chicks face less competition for food and nest space.

“It implies a level of resolution in cowbird decision-making that people hadn’t seen before,” said Loren Merrill, a postdoctoral researcher at the Illinois Natural History Survey who conducted the study with INHS scientists Scott Chiavacci and Thomas Benson and Illinois State University researcher Ryan Paitz.

“Scientists originally saw cowbirds as egg dumpers that would put their eggs in any nest they found,” Merrill said. “And while that may be the case in some areas, or for some birds, it doesn’t tell the whole story. In fact, the more people have looked at cowbird behavior, the more our understanding has evolved of exactly how discriminating cowbirds can be.”

The findings are reported in the journal Oecologia.

From April through August for five seasons ending in 2015, the researchers hunted through 16 shrubland sites across Illinois, looking for cowbirds and nests in which cowbirds might place their eggs.

“Nest searching is really fun fieldwork, except when you’re trekking through poison ivy- and hawthorn-infested lands,” Merrill said. “You either get really lucky and see nesting material in a bird’s mouth, and you watch until they lead you to a nest, or you listen and watch for the vocalizations and behaviors the adults use when you are close to a nest.”

Cowbirds use similar tactics to scout for host nests.

“They do a lot of skulking around the underbrush,” Merrill said. “They’ll also perch in an inconspicuous place and just watch. They are cuing in on the behavior of hosts that are building their nests or taking food back to nests.”

The research team found nearly 3,000 nests of 34 bird species and checked each nest roughly every three days. Cowbirds placed eggs in more than 400 of these nests. In addition to weighing and measuring cowbird and host eggs in more than 180 nests, the researchers also tested the composition of some cowbird eggs to determine whether female cowbirds give some eggs an added boost, such as a greater proportion of yolk or higher levels of yolk hormones like testosterone.

“The cowbird could adjust allocation to the egg based on the perceived value of that egg. If she thinks the egg is in a good environment, she can invest more,” Merrill said. “Or, if the host isn’t appropriate and she doesn’t think the environment is favorable, she could invest less.”

The researchers found no variation in egg investment based on the differences among host species or size variations within a host species, however.

“We didn’t see evidence that female cowbirds were adjusting resources in that respect, but that’s not to say it isn’t happening,” Merrill said.

Tracking individual female cowbirds would help scientists better understand how mother cowbirds try to help their offspring.

“It’s really hard to do,” he said. “But being able to track the individual females over time and identify where they are depositing eggs would provide a lot of insight into how much of what we see is an adaptive allocation strategy, or whether the mother’s health and other constraints are driving her behavior.”

Source:Science Daily

{Zebras may use memory to guide their migration each year. Memory based on past average conditions provides a clear signal that best directs zebras to their destination. In contrast, current vegetation conditions along the way are less important for the direction of the migration according to a computer simulation by researchers from Senckenberg. The study, published in Proceedings of the Royal Society B, highlights that migration routes of large terrestrial mammals such as zebras could be more inflexible than previously thought.}

It’s incredible to watch: each year thousands of animals, including zebras, wildebeests and gazelles, migrate in turn with the seasons between foraging grounds. The animals migrate long distances in their search for sufficient and highly nutritious forage. While science has explained certain aspects of this migration, it is not fully understood how the animals know where to go.

Chloe Bracis, a researcher at the German Senckenberg Biodiversity and Climate Research Centre and the Goethe University Frankfurt, has found that memory is the key to directing zebra migration: “Zebras appear to migrate to the location where foraging conditions were best in the past. They seem to navigate to their destination based on memory, and importantly, forecast conditions several months after arrival.”

As part of the study, Bracis and her colleague Thomas Mueller modelled migration routes of zebras using computer simulations. Zebras migrate around 250 kilometers from the Okavango Delta, Botswana to the Makgadikgadi grasslands in November. “We tested two mechanisms which can influence the direction. Simulated zebras could use perception and sense, for example, the vegetation green up in their current surroundings. Alternatively, zebras could use memory, i.e. information from previous migrations, to forecast where to go ,” explains Mueller.

The researchers compared the simulated tracks with real-life tracks from GPS-tagged zebras which were collected by other researchers. Memory using past average conditions was able to predict the migration destination of the modelled zebras up to four times closer than those modelled using perception to find their way. “Memory even beats perception at the largest — that is omniscient — perceptual ranges,” says Bracis and adds “However perception is still important. Other studies have shown the importance of perception of current local conditions on the timing and speed of the zebra migration, but these may be less important for zebras in terms of direction.”

Migration routes of zebras are threatened by climate change and land use change in southern Africa. The zebra migration examined in this study, for instance, was blocked by a fence from the late 60’s until 2004. The researchers therefore see the study as contributing to the conservation of large migratory terrestrial mammals such as zebras. “One can only protect migration routes efficiently if one knows how the animals migrate. If memory of past conditions informs the direction migrating animals take, this suggests migration routes could be relatively inflexible,” concludes Mueller.

Source:Science Daily

{The wildfire that has raged across more than 150,000 acres of the Okefenokee Swamp in Georgia and Florida has sent smoke billowing into the sky as far as the eye can see. Now, new research published by the Georgia Institute of Technology shows how that smoke could impact the atmosphere and climate much more than previously thought.}

Researchers have found that carbon particles released into the air from burning trees and other organic matter are much more likely than previously thought to travel to the upper levels of the atmosphere, where they can interfere with rays from the sun — sometimes cooling the air and at other times warming it.

“Most of the brown carbon released into the air stays in the lower atmosphere, but a fraction of it does get up into the upper atmosphere, where it has a disproportionately large effect on the planetary radiation balance — much stronger than if it was all at the surface,” said Rodney Weber, a professor in Georgia Tech’s School of Earth & Atmospheric Sciences.

The study, which was published May 22 in the journal Nature Geoscience, was sponsored by the NASA Radiation Sciences Program and the NASA Tropospheric Composition Program.

The researchers analyzed air samples collected in 2012 and 2013 by NASA aircraft from the upper troposphere — about seven miles above the earth’s surface — at locations across the United States. They found surprising levels of brown carbon in the samples but much less black carbon.

While black carbon can be seen in the dark smoke plumes rising above burning fossil or biomass fuels at high temperature, brown carbon is produced from the incomplete combustion that occurs when grasses, wood or other biological matter smolders, as is typical for wildfires. As particulate matter in the atmosphere, both can interfere with solar radiation by absorbing and scattering the sun’s rays.

The climate is more sensitive to those particulates as their altitude increases. The researchers found that brown carbon appears much more likely than black carbon to travel through the air to the higher levels of the atmosphere where it can have a greater impact on climate.

“People have always assumed that when you emit this brown carbon, over time it goes away,” said Athanasios Nenes, a professor and Georgia Power Scholar in the School of Earth & Atmospheric Sciences and the School of Chemical & Biomolecular Engineering.

After the brown carbon is carried by smoke plumes into the lower atmosphere, it mixes with clouds. Then it hitches a ride on the deep convection forces that exist in clouds to travel to the upper atmosphere.

Although the researchers couldn’t explain how, they also found that during the journey through the clouds, the brown carbon became more concentrated relative to black carbon.

“The surprise here is that the brown carbon gets promoted when you go through the cloud, compared to black carbon,” Nenes said. “This suggests that there may be in-cloud production of brown carbon that we were not aware of before.”

Source:Science Daily

{Planting trees is a popular strategy to help make cities “greener,” both literally and figuratively. But scientists have found a counterintuitive effect of urban vegetation: During heat waves, it can increase air pollution levels and the formation of ozone. Their study appears in ACS’ journal Environmental Science & Technology.}

Previous research has shown that planting trees in cities can have multiple benefits, including storing carbon, controlling storm water and cooling areas off by providing shade. This has spurred efforts in cities across the U.S. and Europe to encourage the practice. However, it’s also known that trees and other plants release volatile organic compounds, or VOCs, that can interact with other substances and contribute to air pollution. And when it’s hot, plants release higher levels of VOCs. Galina Churkina and colleagues wanted to investigate what effects heat waves and urban vegetation might have on air pollution.

The researchers compared computer models of air pollutant concentrations in the Berlin-Brandenburg metropolitan area in Germany in the summer of 2006, when there was a heat wave, and the summer of 2014, which had more typical seasonal temperatures. The simulation showed that during the summer of 2006, VOCs from urban greenery contributed to about 6 to 20 percent of the ozone formation, and that during the heat wave period, the contribution spiked to up to 60 percent. The researchers suggest that in addition to tree-planting campaigns, efforts to improve cities’ environments should include other measures such as reducing vehicular traffic, a major source of nitrogen oxides that can react with VOCs and form ozone.

Source:Science Daily

{After analyzing the blood of a survivor of the 2013-16 Ebola outbreak, a team of scientists from academia, industry and the government has discovered the first natural human antibodies that can neutralize and protect animals against all three major disease-causing ebolaviruses. The findings, published online in the journal Cell, could lead to the first broadly effective ebolavirus therapies and vaccines.}

Ebolaviruses infections are usually severe, and often fatal. There are no vaccines or treatments approved by the Food and Drug Administration for treating these viruses. Some two dozen ebolavirus outbreaks have occurred since 1976, when the first outbreak was documented in villages along the Ebola River in the Democratic Republic of Congo (formerly Zaire). The largest outbreak in history — the 2013-16 Western African epidemic — caused more than 11,000 deaths and infected more than 29,000 people.

Monoclonal antibodies, which bind to and neutralize specific pathogens and toxins, have emerged as one of the most promising treatments for Ebola patients. A critical problem, however, is that most antibody therapies target just one specific ebolavirus. For example, the most advanced therapy — ZMappTM, a cocktail of three monoclonal antibodies — is specific for Ebola virus (formerly known as “Ebola Zaire”), but doesn’t work against two related ebolaviruses (Sudan virus and Bundibugyo virus) that have also caused major outbreaks.

“Since it’s impossible to predict which of these agents will cause the next epidemic, it would be ideal to develop a single therapy that could treat or prevent infection caused by any known ebolavirus,” says study co-leader Zachary A. Bornholdt, Ph.D., director of antibody discovery at Mapp Biopharmaceutical, Inc. “Our discovery and characterization of broadly neutralizing human antibodies is an important step toward that goal,” adds study co-leader, Kartik Chandran, Ph.D. , professor of microbiology & immunology at Albert Einstein College of Medicine.

The study was also co-led by John M. Dye, Ph.D., chief of viral immunology at the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID).

In earlier research, Dr. Bornholdt and Laura M. Walker, Ph.D., a senior scientist at Adimab, LLC, isolated 349 distinct monoclonal antibodies from a survivor of the 2013-16 Ebola epidemic. In the current study, the multi-institutional research team found that two of those 349 antibodies, known as ADI-15878 and ADI-15742, potently neutralized infection by all five known ebolaviruses in tissue culture. Both antibodies were able to protect animals (mice and ferrets) that had been exposed to a lethal dose of the three major agents: Ebola virus, Bundibugyo virus and Sudan virus.

Follow-up studies showed that the two antibodies isolated from the Ebola patient work by interfering with a critical step in the process by which ebolaviruses infect cells and then multiply inside them. The two antibodies encounter the virus while it’s still in the bloodstream, and bind to glycoproteins (proteins to which carbohydrate chains are attached) that project from its surface. The virus, with its hitchhiking antibodies still bound to it, then attaches to a cell and enters the lysosome — a membrane-bound structure within the cell that is filled with enzymes for digesting foreign and cellular components. The virus must then fuse with the lysosome membrane to escape into the host cell’s cytoplasm, where it can multiply. However, the antibodies prevent the virus from breaking out of its lysosomal “prison,” thus stopping infection in its tracks.

“Knowing precisely where the antibodies attach to the glycoprotein molecules and when and how they act to neutralize ebolaviruses, we can begin to craft broadly effective immunotherapies,” says Dr. Dye. “That knowledge has already allowed us to create a cocktail of monoclonal antibodies that we are testing in larger animal models for possible use in treating infected patients,” adds Dr. Bornholdt.

The researchers also pinpointed the human genes that are the likely source of the immune cells that produce the two antibodies. These and other findings could help speed the development of vaccines to prevent ebolavirus infection. “We’d like to synthesize vaccine immunogens [proteins that trigger antibody production] that can elicit the same types of broadly protective antibodies in people,” says Dr. Chandran.

Source:Science Daily

{Growing plants and then storing the CO2 they have taken up from the atmosphere is no viable option to counteract unmitigated emissions from fossil fuel burning, a new study shows. The plantations would need to be so large, they would eliminate most natural ecosystems or reduce food production if implemented as a late-regret option in the case of substantial failure to reduce emissions. However, growing biomass soon in well-selected places with increased irrigation or fertilization could support climate policies of rapid and strong emission cuts to achieve climate stabilization below 2 degrees Celsius.}

“If we continue burning coal and oil the way we do today and regret our inaction later, the amounts of greenhouse gas we would need to take out of the atmosphere in order to stabilize the climate would be too huge to manage,” says Lena Boysen from the Potsdam Institute for Climate Impact Research (PIK), Germany, lead-author of the study to be published in a journal of the American Geophysical Union, Earth’s Future. Plants suck CO2 out of the atmosphere to build their woody roots, stems and leaves. This is low-tech terrestrial carbon dioxide removal that could be combined with high-tech carbon storage mechanisms, for example underground.

Three scenarios: Business as usual, Paris pledges, or ambitious CO2 reductions

“Even if we were able to use productive plants such as poplar trees or switchgrass and store 50 percent of the carbon contained in their biomass,” says Boysen, “in the business-as-usual scenario of continued, unconstrained fossil fuel use the sheer size of the plantations for staying at or below 2°C of warming would cause devastating environmental consequences.” The scientists calculate that the hypothetically required plantations would in fact replace natural ecosystems around the world almost completely.

If CO2 emissions reductions are moderately reduced in line with current national pledges under the Paris Climate Agreement, biomass plantations implemented by mid-century to extract remaining excess CO2 from the air still would have to be enormous. In this scenario, they would replace natural ecosystems on fertile land the size of more than one third of all forests we have today on our planet. Alternatively, more than a quarter of land used for agriculture at present would have to be converted into biomass plantations — putting at risk global food security.

Only ambitious emissions reductions and advancements in land management techniques between 2005-2100 could possibly avoid fierce competition for land. But even in this scenario of aggressive climate stabilization policy, only high inputs of water, fertilizers and a globally applied high-tech carbon-storage-machinery that captures more than 75 percent of extracted CO2 could likely limit warming to around 2°C by 2100. To this end, technologies minimizing carbon emissions from cultivation, harvest, transport and conversion of biomass and, especially, long-term Carbon Capture and Storage (CCS) would need to improve worldwide.

Drawing upon all possible measures instead of waiting for first-best solutions

“As scientists we are looking at all possible futures, not just the positive ones,” says co-author Wolfgang Lucht from PIK. “What happens in the worst case, a widespread disruption and failure of mitigation policies? Would plants allow us to still stabilize climate in emergency mode? The answer is: no. There is no alternative for successful mitigation. In that scenario plants can potentially play a limited, but important role, if managed well.” The scientists investigated the feasibility of biomass plantations and CO2 removal from a biosphere point of view. To this end, they used global dynamic vegetation computer simulations.

So far, biomass plantations as a means for CO2 removal have often been considered as a comparatively safe, affordable and effective approach. “Our work shows that carbon removal via the biosphere cannot be used as a late-regret option to tackle climate change. Instead we have to act now using all possible measures instead of waiting for first-best solutions,” says co-author Tim Lenton of the University of Exeter, UK. “Reducing fossil fuel use is a precondition for stabilizing the climate, but we also need to make use of a range of options from reforestation on degraded land to low-till agriculture and from efficient irrigation systems to limiting food waste.”

“In the climate drama currently unfolding on that big stage we call Earth, CO2 removal is not the hero who finally saves the day after everything else has failed. It is rather a supporting actor that has to come into play right from the beginning, while the major part is up to the mitigation protagonist,” says co-author Hans Joachim Schellnhuber, Director of PIK. “So this is a positive message: We know what to do — rapidly ending fossil fuel use complemented by a great variety of CO2 removal techniques. We know when to do it — now. And if we do it, we find it is still possible to avoid the bulk of climate risks by limiting temperature rise to below 2 degrees Celsius.”

Source:Science Daily

{Not only migratory birds use a built-in magnetic compass to navigate correctly. A new study from Lund University in Sweden shows that non-migratory birds also are able to use a built-in compass to orient themselves using the Earth’s magnetic field.}

The researchers behind the current study have received help from a group of zebra finches to study the magnetic compass of what are known as resident birds, that is, species that do not migrate according to the season. Zebra finches are popular pet birds in many homes. Originally, they come from Indonesia and Australia where they search for food in a nomadic way.

“We wanted to know how a magnetic compass works in non-migratory birds like these,” says Atticus Pinzón-Rodríguez, doctoral student in biology at the Faculty of Science at Lund University.

In the current study, researchers have looked closer at the zebra finches’ ability to utilise the Earth’s magnetic field and the different properties of this built-in compass. The results show that the zebra finches use a magnetic compass with very similar functions to that of migratory birds, i.e. one with a very specific light dependency and thus sensitivity to different colours and light intensities.

“Our results show that the magnetic compass is more of a general mechanism found in both migratory birds and resident birds. It seems that although zebra finches do not undertake extensive migration, they still might be able to use the magnetic compass for local navigation,” says Atticus Pinzón-Rodríguez.

Although the magnetic compass of birds has been studied by the research community for a long time, the understanding of how it works is still very incomplete, according to Atticus Pinzón-Rodríguez.

The present study was published recently in the scientific Journal of Experimental Biology.

Source:Science Daily

{Researchers in the USA and Japan say they may have found the cause of the first mass extinction of life.}

There have been five mass extinctions since the divergent evolution of early animals 600 -450 million years ago. The cause of the third and fourth was volcanic activity, while an asteroid impact led to the fifth. But triggers of the first and second mass extinctions had, until now, been unknown.

The first mass extinction occurred at the end of the Ordovician. This age is between the divergence of the Ordovician and land invasion of vascular land plant and animals. Animals in the Ordovician-Silurian comprised marine animals like corals, trilobites, sea scorpion, orthoceras, brachiopods, graptolite, crinoid and jawless fish. Approximately 80% of species disappeared at the end of the Ordovician.

A team led by Dr. David S. Jones of Amherst College and Professor Kunio Kaiho of Tohoku University, looked into possible triggers of the first mass extinction. They took sedimentary rock samples from two places — North America and southern China — and analyzed the mercury (Hg) in them. They found Hg enrichments coinciding with the mass extinction in both areas.

This, they believe, is the product of large volcanic eruptions because Hg anomaly was also observed in other large igneous province volcanisms.

Huge volcanic eruptions can produce sulfate aerosols in the stratosphere. Sulfate aerosols are strong, light-reflecting aerosols, and cause global cooling. This rapid climate change is believed to be behind the loss of marine creatures.

Kaiho’s team is now studying the second mass extinction in the hopes of further understanding the cause and processes behind it.

Source:Science Daily

{New study reveals how changes in Martian rainfall shaped the planet}

Heavy rain on Mars reshaped the planet’s impact craters and carved out river-like channels in its surface billions of years ago, according to a new study published in Icarus. In the paper, researchers from the Smithsonian Institution and the Johns Hopkins University Applied Physics Laboratory show that changes in the atmosphere on Mars made it rain harder and harder, which had a similar effect on the planet’s surface as we see on Earth.

The fourth planet from the sun, Mars has geological features like the Earth and moon, such as craters and valleys, many of which were formed through rainfall. Although there is a growing body of evidence that there was once water on Mars, it does not rain there today.

But in their new study, geologists Dr. Robert Craddock and Dr. Ralph Lorenz show that there was rainfall in the past — and that it was heavy enough to change the planet’s surface. To work this out, they used methods tried and tested here on Earth, where the erosive effect of the rain on the Earth’s surface has important impacts on agriculture and the economy.

Valley networks on Mars show evidence for surface runoff driven by rainfall. “Many people have analyzed the nature of rainfall on the Earth, but no one had thought to apply the physics to understanding the early Martian atmosphere,” said Dr. Craddock of the Smithsonian Institution.

To understand how rainfall on Mars has changed over time, the researchers had to consider how the Martian atmosphere has changed. When Mars first formed 4.5 billion years ago, it had a much more substantial atmosphere with a higher pressure than it does now. This pressure influences the size of the raindrops and how hard they fall.

Early on in the planet’s existence, water droplets would have been very small, producing something like fog rather than rain; this would not have been capable of carving out the planet we know today. As the atmospheric pressure decreased over millions of years, raindrops got bigger and rainfall became heavy enough to cut into the soil and start to alter the craters. The water could then be channeled and able to cut through the planet’s surface, creating valleys.

“By using basic physical principles to understand the relationship between the atmosphere, raindrop size and rainfall intensity, we have shown that Mars would have seen some pretty big raindrops that would have been able to make more drastic changes to the surface than the earlier fog-like droplets,” commented Dr. Lorenz of John Hopkins University, who has also studied liquid methane rainfall on Saturn’s moon Titan, the only other world in the solar system apart from Earth where rain falls onto the surface at the present day.

They showed that very early on, the atmospheric pressure on Mars would have been about 4 bars (the Earth’s surface today is 1 bar) and the raindrops at this pressure could not have been bigger than 3mm across, which would not have penetrated the soil. But as the atmospheric pressure fell to 1.5 bars, the droplets could grow and fall harder, cutting into the soil. In Martian conditions at that time, had the pressure been the same as we have on Earth, raindrops would have been about 7.3mm — a millimeter bigger than on Earth.

“There will always be some unknowns, of course, such as how high a storm cloud may have risen into the Martian atmosphere, but we made efforts to apply the range of published variables for rainfall on Earth,” added Dr. Craddock. “It’s unlikely that rainfall on early Mars would have been dramatically different than what’s described in our paper. Our findings provide new, more definitive, constraints about the history of water and the climate on Mars.”

Source:Science Daily