(Press-News.org) The planet's current biodiversity, the product of 3.5 billion years of evolutionary trial and error, is the highest in the history of life. But it may be reaching a tipping point.
In a new review of scientific literature and analysis of data published in Science, an international team of scientists cautions that the loss and decline of animals is contributing to what appears to be the early days of the planet's sixth mass biological extinction event.
Since 1500, more than 320 terrestrial vertebrates have become extinct. Populations of the remaining species show a 25 percent average decline in abundance. The situation is similarly dire for invertebrate animal life.
And while previous extinctions have been driven by natural planetary transformations or catastrophic asteroid strikes, the current die-off can be associated to human activity, a situation that the lead author Rodolfo Dirzo, a professor of biology at Stanford, designates an era of "Anthropocene defaunation."
Across vertebrates, 16 to 33 percent of all species are estimated to be globally threatened or endangered. Large animals – described as megafauna and including elephants, rhinoceroses, polar bears and countless other species worldwide – face the highest rate of decline, a trend that matches previous extinction events.
Larger animals tend to have lower population growth rates and produce fewer offspring. They need larger habitat areas to maintain viable populations. Their size and meat mass make them easier and more attractive hunting targets for humans.
Although these species represent a relatively low percentage of the animals at risk, their loss would have trickle-down effects that could shake the stability of other species and, in some cases, even human health.
For instance, previous experiments conducted in Kenya have isolated patches of land from megafauna such as zebras, giraffes and elephants, and observed how an ecosystem reacts to the removal of its largest species. Rather quickly, these areas become overwhelmed with rodents. Grass and shrubs increase and the rate of soil compaction decreases. Seeds and shelter become more easily available, and the risk of predation drops.
Consequently, the number of rodents doubles – and so does the abundance of the disease-carrying ectoparasites that they harbor.
"Where human density is high, you get high rates of defaunation, high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission," said Dirzo, who is also a senior fellow at the Stanford Woods Institute for the Environment. "Who would have thought that just defaunation would have all these dramatic consequences? But it can be a vicious circle."
The scientists also detailed a troubling trend in invertebrate defaunation. Human population has doubled in the past 35 years; in the same period, the number of invertebrate animals – such as beetles, butterflies, spiders and worms – has decreased by 45 percent.
As with larger animals, the loss is driven primarily by loss of habitat and global climate disruption, and could have trickle-up effects in our everyday lives.
For instance, insects pollinate roughly 75 percent of the world's food crops, an estimated 10 percent of the economic value of the world's food supply. Insects also play a critical role in nutrient cycling and decomposing organic materials, which helps ensure ecosystem productivity. In the United States alone, the value of pest control by native predators is estimated at $4.5 billion annually.
Dirzo said that the solutions are complicated. Immediately reducing rates of habitat change and overexploitation would help, but these approaches need to be tailored to individual regions and situations. He said he hopes that raising awareness of the ongoing mass extinction – and not just of large, charismatic species – and its associated consequences will help spur change.
"We tend to think about extinction as loss of a species from the face of Earth, and that's very important, but there's a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well," Dirzo said. "Ironically, we have long considered that defaunation is a cryptic phenomenon, but I think we will end up with a situation that is non-cryptic because of the increasingly obvious consequences to the planet and to human wellbeing."
The coauthors on the report include Hillary S. Young, University of California, Santa Barbara; Mauro Galetti, Universidade Estadual Paulista in Brazil; Gerardo Ceballos, Universidad Nacional Autonoma de Mexico; Nick J.B. Isaac, of the Natural Environment Research Council Centre for Ecology and Hydrology in England; and Ben Collen, of University College London.
Stanford biologist warns of early stages of Earth's 6th mass extinction event
ELSE PRESS RELEASES FROM THIS DATE:
Antioxidant biomaterial promotes healing
When a foreign material like a medical device or surgical implant is put inside the human body, the body always responds. According to Northwestern University's Guillermo Ameer, most of the time, that response can be negative and affect the device's function. "You will always get an inflammatory response to some degree," said Ameer, professor of biomedical engineering in Northwestern's McCormick School of Engineering and Applied Science and professor of surgery in the Feinberg School of Medicine. "A problem with commonly used plastic materials, in particular, is that ...
Moose drool inhibits growth of toxic fungus: York U research
TORONTO, June 24, 2014 – Some sticky research out of York University shows a surprisingly effective way to fight against a certain species of toxic grass fungus: moose saliva (yes… moose saliva). Published in this month's Biology Letters, "Ungulate saliva inhibits a grass–endophyte mutualism" shows that moose and reindeer saliva, when applied to red fescue grass (which hosts a fungus called epichloë festucae that produces the toxin ergovaline) results in slower fungus growth and less toxicity. "Plants have evolved defense mechanisms to protect themselves, such as thorns, ...
Study shows role of media in sharing life events
MADISON — To share is human. And the means to share personal news — good and bad — have exploded over the last decade, particularly social media and texting. But until now, all research about what is known as "social sharing," or the act of telling others about the important events in our lives, has been restricted to face-to-face interactions. A new study, published in the current issue of the journal Computers in Human Behavior, investigates what happens when people share via new media. What media do people choose for sharing their important personal events? How ...
Election surprises tend to erode trust in government
Athens, Ga. – When asked who is going to win an election, people tend to predict their own candidate will come out on top. When that doesn't happen, according to a new study from the University of Georgia, these "surprised losers" often have less trust in government and democracy. And the news media may be partly to blame, according to Barry Hollander, author of the study and UGA professor in the Grady College of Journalism and Mass Communication. "You need the trust of those in a democracy for democracy to be successful," said Hollander. "We have become more fragmented ...
Link between ritual circumcision procedure and herpes infection in infants examined
PHILADELPHA—A rare procedure occasionally performed during Jewish circumcisions that involves direct oral suction is a likely source of herpes simplex virus type 1 (HSV-1) transmissions documented in infants between 1988 and 2012, a literature review conducted by Penn Medicine researchers and published online in the Journal of the Pediatric Infectious Disease Society found. The reviewers, from Penn's Center for Evidence-based Practice, identified 30 reported cases in New York, Canada and Israel. The practice—known as metzitzah b'peh—and its link to HSV-1 infections ...
Penn study: Incisionless transcatheter aortic valve replacement surgery cuts hospital length of stay
PHILADELPHIA – New research from Penn Medicine shows that incisionless transcatheter aortic valve replacement (TAVR) surgery cuts length of hospital stay by 30 percent and has no impact on post-operative vascular complication rates when compared with conventional transfemoral TAVR, which requires an incision in the groin. The complete study is available in the current issue of Circulation: Cardiovascular Interventions. TAVR involves the replacement of the aortic valve without a traditional open-heart surgical approach. It is a treatment for aortic stenosis, a narrowing ...
Piggy-backing cells hold clue to skin cancer growth
Skin Cancer cells work together to spread further and faster, according to a new study published in Cell Reports. The discovery could lead to new drugs to tackle melanoma, the most deadly form of skin cancer. Cancer Research UK scientists at The University of Manchester found that some melanoma cells are particularly fast growing, but not very good at invading the surrounding tissue, while other melanoma cells are the opposite – highly invasive but slow-growing. In a tumour, the faster growing cells 'piggy-back' along with the more invasive cells, so together they ...
Rutgers study explores attitudes, preferences toward post-Sandy rebuilding
NEW BRUNSWICK, N.J. – A yearlong study funded by the New Jersey Recovery Fund and conducted by researchers at the Edward J. Bloustein School of Planning and Public Policy at Rutgers University has found that individual property owners in Sandy-affected towns are skeptical about the likelihood of community-based rebuilding solutions. Of the more than 400 online survey respondents, 45 percent indicated they were "pessimistic" or "very pessimistic" that the parts of their town affected by Superstorm Sandy would be rebuilt better than they were before the storm; another 24 ...
Joblessness could kill you, but recessions could be good for your health
Being unemployed increases your risk of death, but recessions decrease it. Sound paradoxical? Researchers thought so too. While previous studies of individuals have shown that employees who lose their jobs have a higher mortality rate, more comprehensive studies have shown, unexpectedly, that population mortality actually declines as unemployment rates increase. Researchers from Drexel University and the University of Michigan in Ann Arbor set out to better understand these seemingly contradictory findings. Using a nationally representative panel of individuals across ...
Artificial intelligence identifies the musical progression of the Beatles
Music fans and critics know that the music of the Beatles underwent a dramatic transformation in just a few years, but until now there hasn't been a scientific way to measure the progression. That could change now that computer scientists at Lawrence Technological University have developed an artificial intelligence algorithm that can analyze and compare musical styles, enabling research into the musical progression of the Beatles. Assistant Professor Lior Shamir and graduate student Joe George had previously developed audio analysis technology to study the vocal communication ...