The search for a single causative factor is often missing the larger picture, they said, and approaches to address the crisis may fail if they don’t consider the totality of causes – or could even make things worse.
No one issue can explain all of the population declines that are occurring at an unprecedented rate, and much faster in amphibians than most other animals, the scientists conclude in a study just published in the Annals of the New York Academy of Sciences.
The amphibian declines are linked to natural forces such as competition, predation, reproduction and disease, as well as human-induced stresses such as habitat destruction, environmental contamination, invasive species and climate change, researchers said.
“An enormous rate of change has occurred in the last 100 years, and amphibians are not evolving fast enough to keep up with it,” said Andrew Blaustein, a professor of zoology at Oregon State University and an international leader in the study of amphibian declines.
“We’re now realizing that it’s not just one thing, it’s a whole range of things,” Blaustein said.
“With a permeable skin and exposure to both aquatic and terrestrial problems, amphibians face a double whammy,” he said. “Because of this, mammals, fish and birds have not experienced population impacts as severely as amphibians – at least, not yet.”
The totality of these changes leads these researchers to believe that the Earth is now in a major extinction episode similar to five other mass extinction events in the planet’s history. And amphibians are leading the field – one estimate indicates they are disappearing at more than 200 times that of the average extinction rate.
Efforts to understand these events, especially in the study of amphibians, have often focused on one cause or another, such as fungal diseases, invasive species, an increase in ultraviolet radiation due to ozone depletion, pollution, global warming, and others. All of these and more play a role in the amphibian declines, but the scope of the crisis can only be understood from the perspective of many causes, often overlapping. And efforts that address only one cause risk failure or even compounding the problems, the researchers said.
“Given that many stressors are acting simultaneously on amphibians, we suggest that single-factor explanations for amphibian population declines are likely the exception rather than the rule,” the researchers wrote in their report. “Studies focused on single causes may miss complex interrelationships involving multiple factors and indirect effects.”
One example is the fungus B. dendrobatidis, which has been implicated in the collapse of many frog populations around the world. However, in some populations the fungus causes no problems for years until a lethal threshold is reached, studies have shown.
And while this fungus disrupts electrolyte balance, other pathogens can have different effects such as a parasitic trematode that can cause severe limb malformations, and a nematode that can cause kidney damage. The combination and severity of these pathogens together in a single host, rather than any one individually, are all playing a role in dwindling frog populations.
Past studies at OSU have found a synergistic impact from ultraviolet radiation, which by itself can harm amphibians, and a pathogenic water mold that infects amphibian embryos. And they linked the whole process to water depths at egg-laying sites, which in turn are affected by winter precipitation in the Oregon Cascade Range that is related to climate change.
The problems facing amphibians are a particular concern, scientists say, because they have been one of Earth’s great survivors – evolving about 400 million years ago before the dinosaurs, persisting through ice ages, asteroid impacts, and myriad other ecological and climatic changes.
Their rapid disappearance now suggests that the variety and rate of change exceeds anything they have faced before, the researchers said.
“Modern selection pressures, especially those associated with human activity, may be too severe and may have arisen too rapidly for amphibians to evolve adaptations to overcome them,” the researchers concluded.
This work was supported by the National Science Foundation and the David and Lucile Packard Foundation. Other collaborators on the study were from the University of Colorado, University of Georgia, University of Pittsburgh, and Pepperdine University.
About the OSU College of Science: As one of the largest academic units at OSU, the College of Science has 14 departments and programs, 13 pre-professional programs, and provides the basic science courses essential to the education of every OSU student. Its faculty are international leaders in scientific research.
Andrew Blaustein | EurekAlert!
Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory
Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine