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Trees in forests all over the world are getting younger, shorter

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May 29 (UPI) — Trees in forests around the world are getting younger and shorter as a result of human-caused climate change and other environmental stressors.

New research, published Friday in the journal Science, suggests rising global temperatures and atmospheric CO2 concentrations over the last century, combined with an uptick in environmental stress and extreme weather events, have significantly altered the makeup of the planet’s forests.

The changes have left old growth forests especially vulnerable.

For the study, researchers recorded satellite measurements of global forests and completed a survey of the scientific literature on forest health over the last several decades. Their efforts showed increases in tree mortality have left many forests dominated by younger, shorter stands.

“This trend is likely to continue with climate warming,” lead study author Nate McDowell, an earth scientist with the Pacific Northwest National Laboratory, said in a press release.

“A future planet with fewer large, old forests will be very different than what we have grown accustomed to,” McDowell said. “Older forests often host much higher biodiversity than young forests and they store more carbon than young forests.”

According to the new study, clear-cutting, wildfire, insects and disease have all destabilized forests across the globe, increasing tree mortality rates and reducing the overall biomass of global forests.

The barrage of environmental stressors has proved especially harmful to old growth while creating opportunities for younger saplings.

“Mortality is rising in most areas, while recruitment and growth are variable over time, leading to a net decline in the stature of forests,” said McDowell.

“Unfortunately, mortality drivers like rising temperature and disturbances such as wildfire and insect outbreaks are on the rise and are expected to continue increasing in frequency and severity over the next century,” McDowell added. “So, reductions in average forest age and height are already happening and they’re likely to continue to happen.”

When forests undergo dramatic changes in their composition, whole ecosystems can become destabilized, threatening the plants and animals that reside there.

A threat to forest health is a threat to biodiversity, and research suggests biodiversity and carbon storage — two of the most vital ecological services provided by forests — are essential to climate change mitigation.

Old growth forests, those most threatened by climate change and other harmful human activities, host more biodiversity and store more carbon than younger forests.



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Sounds made by fluttering feathers help fork-tailed flycatchers communicate

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Sept. 22 (UPI) — Scientists have added another species to the list of birds that use sounds made with their feathers to communicate.

The male fork-tailed flycatcher, a passerine bird species native to the American tropics, creates unique sounds by fluttering its feathers at high frequencies, according to research published Wednesday in the journal Integrative and Comparative Biology.

“Back in the 1960’s, scientists noticed that they produce a distinctive sound only during a particular flight display,” researcher Christopher Clark, told UPI in an email.

“And those species of flycatcher in the genus Tyrannus, those that make the most distinctive sounds have the most distinctly shaped outer primary feathers,” said Clark, an associate professor of evolutionary biology at the University of California Riverside.

For the latest research, scientists conducted field studies to better understand both the mechanics of the feather fluttering and its communicative utility.

“We found that the birds don’t produce sounds every time they fly, but only under specific behavioral contexts,” lead study author Valentina Gomez told UPI in an email.

“One is during the pre-dawn display, after waking up. They begin displaying by singing and then they include feather songs. They also produce these sounds during territorial displays,” said Gomez, a doctoral student at the University of Illinois at Chicago.

To study the fluttering’s acoustic qualities, scientists captured males with mist netting, and used cameras and microphones to record the sounds the birds made as they escaped and retreated.

Fork-tailed flycatchers are quite territorial and aggressively defend their nests. Males are especially aggressive, regularly engaging in aerial battles with other males over mating opportunities and territory. They’re also more than willing to attack larger birds that stray too close to their nests.

Researchers used a taxidermy hawk outfitted with microphones and a camera to measure the movement of the fork-tailed flycatcher’s feathers during displays of aggression. The recordings revealed a difference in the sounds made by two subspecies, one that migrates long distances and another that is more stationary.

“Differences in migration likely influenced the shape of feathers and this affects the frequency at which they flutter,” Gomez said.

In effect, the two subspecies have developed dialects. Researchers suspect this phenomenon might help drive speciation, or species divergence.

“The evolution of different movement behaviors promotes the initial trigger of the speciation process,” Gomez said. “Through time, correlated evolution of morphological traits affects how they communicate.”

In other words, the difference in sound-making didn’t jumpstart the speciation process, but Gomez and her research partners hypothesize that the development of feather-flapping dialects works to reinforce the divergence.

Similarly, while the sound-making feathers of fork-tailed flycatchers may have initially evolved in response to pressures unrelated to communication, researchers claim the birds now utilize their sound-making abilities with intentionality. They’ve harnessed the power of their fluttering features for the purposes of communication.

“The birds alter how they are flapping their wings when they produce sound; their wingbeat frequency goes up by quite a bit,” Clark said. “The altered kinematics is another clue that this is ‘intentional.'”

While non-vocal communication has been observed in a variety of bird genus and species, scientists suspect the prevalence of the practice is underestimated.

Researchers hope that future investigations of feather-based communication among flycatchers will offer new insights into why so many birds have evolved non-vocal communication over and over again.

While the latest findings suggest the fork-tailed flycatcher relies on feather-based communication for pair bonding and displays of aggression, many questions about the fluttering’s utility remain.

“We still need to learn a lot about bird acoustic perception,” Gomez said.



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Once exposed to humans, animals start to lose their fear of predators

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Sept. 22 (UPI) — New research suggests animals begin to lose their fear of predators once they start encountering humans on a regular basis.

For the study, scientists surveyed the findings of 173 peer-reviewed papers on predator avoidance behaviors and traits deployed by 102 species of domesticated, captive and urbanized mammals, birds, reptiles, fish and mollusks.

The analysis, published Tuesday in the journal PLOS Biology, showed predator avoidance traits and behaviors, including vigilance, freezing and fleeing, decreased as a result of exposure to humans.

Researchers found individual variation in anti-predator characteristics increased upon a species’ initial exposure to humans, but then gradually decreased after generations of human exposure.

“While it is well known that the fact of being protected by humans decreases anti-predator capacities in animals, we did not know how fast this occurs and to what extent this is comparable between contexts,” lead researcher Benjamin Geffroy, biologist at the University of Montpellier in France, said in a news release.

The findings suggest behavioral flexibility allows for the initial increase in the variability of anti-predator traits, but researchers suspect genetic changes solidify declines in predator avoidance as subsequent generations adjust to the presence of humans.

In the studies analyzed by Geffroy and his colleagues, domesticated animals lose their anti-predator traits much more quickly than urbanized animals, which can cause problems when domesticated or urbanized species are released back into the wild.

“We also integrated physiological traits in the study but they were much less numerous that behavioral traits,” Geffroy said. “We believe they should be systematically investigated to draw a global pattern of what is happening at the individual level.

“We need more data to understand whether this occurs also with the mere presence of tourists,” Geffroy said.



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Search and rescue dogs fared well after work at 9/11 sites, study says

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Search and rescue dogs used during the 9/11 attacks lived as long as dogs not at the World Trade Center in New York City and the Pentagon, a new study finds.

“I was at Ground Zero and I would hear people make comments like, ‘Did you hear that half of the dogs that responded to the bombing in Oklahoma City died of X, Y, or Z?’ Or they’d say dogs responding to 9/11 had died,” said Dr. Cynthia Otto, director of the University of Pennsylvania’s Working Dog Center, in Philadelphia. “It was really disconcerting.”

Otto and her School of Veterinary Medicine colleagues’ findings are reassuring.

Dogs that participated in search-and-rescue efforts after 9/11 lived as long as search-and-rescue dogs not at the scene — a median of about 12.8 years, meaning half died sooner, half did not. They also outlived the life spans of their breed. There was no difference in the dogs’ cause of death.

“Honestly, this was not what we expected it’s surprising and wonderful,” said Otto, a veterinarian.

The researchers expected to see respiratory problems in the exposed dogs, but they did not. The most common cause of death was age-related conditions, such as arthritis and cancer.

For the study, Otto collected data on 95 dogs that had worked at the World Trade Center, the nearby Fresh Kills Landfill in Staten Island, N.Y., or Pentagon disaster sites in Washington, D.C. They compared these dogs with 55 search-and-rescue dogs that were not deployed on 9/11.

“We anticipated that the dogs would be the ‘canary in the coal mine’ for the human first responders since dogs age faster than humans and didn’t have any of the protective equipment during the response,” Otto said in a university news release. “But we didn’t see a lot that was concerning.”

Generally, these dogs are stronger and healthier than pets, which might partly explain why the dogs fared well, she said.

The findings were published Sept. 21 in the Journal of the American Veterinary Medical Association.

More information

For more on responder health after 9/11, visit the New York State Department of Health.

Copyright 2020 HealthDay. All rights reserved.



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