Ultra Violet Radiation Now Causing World’s Amphibians to Go the Way of the Dodo By Dr. Michael A. Bengwayan, Ph. D., Environmental Science Environment News Network

Ultra Violet Radiation Now Causing  World’s Amphibians to Go the Way of the Dodo

By Dr. Michael A. Bengwayan, Ph. D., Environmental Science

Environment News Network

Baguio City, Philippines (Jan 3, 2018)—Anyone looking for a silver bullet that will explain all the amphibian deaths and declines in Asia and around the world, is going to be disappointed, scientists say.

Fourteen species of amphibians have vanished in Australia recently.  The golden toad is now extinct in Costa Rica, and five amphibians no longer exist in the United States. Amphibians are declining in Europe, Asia, South America and Africa.

Global declines of amphibians refer to the phenomenon of the population declines and even extinctions of amphibian species around the world. Assessments of the world’s amphibians  from 2004  to  2008 found that nearly a third of the known species of amphibians are globally threatened with extinction and that at least 42% of known amphibian species are experiencing population losses.

“This is an incredibly complex problem, a disturbing one and there’s no end in sight”,  scientist Vance T. Vredenburg,  of San Francisco State University, of San Francisco, California said.

It is now certain that multiple causes are contributing to the troubles of amphibians, said Vradenburg, and the lack of a single definite cause does not diminish the seriousness of this alarming ecological phenomenon.

 UV-B radiation, Pathogens Emerging Culprits

“At this point we can say that there are several causes of amphibian declines which include rising levels of UV-B radiation in sunlight, pathogens, pollutants, habitat destruction, introduced predators, pesticides, and most recently, fertilizers,” Vredenburg said.

“But the overall result is that this group of animals which has been around since the time of dinosaurs is now in serious decline around the world.  Ultra-violet rays coupled with pathogens and high nitrate levels are enough to cause amphibian deaths or deformities,” he ddded.

Vredenburg’s colleagues Kellie Whittaker, Michelle S Koo, and David B Wake of the University of California, Berkeley, CA, USA  authors of Global Declines of Amphibians said  the rapidity and extent of these declines, far more dramatic than those described for birds, mammals, or reptiles, forecast impending extinction of numerous amphibian species during the coming decades.

Increase in UV–B has been hypothesized to contribute to increased amphibian decline. Global atmospheric changes caused by anthropogenic activities are well documented and one result is a reduction of stratospheric ozone, leading to an increase in the amount of biologically damaging ultraviolet radiation (UV–B) reaching the Earth’s surface 

Unlike Vredenburg, they say however that the greatest threat is presented by a virulent fungal pathogen that is causing the infectious disease chytridiomycosis, which has decimated entire assemblages of amphibians worldwide. This pathogen, Batrachochytrium dendrobatidis, is responsible for what may well be the greatest disease-caused loss of biodiversity in recorded history, having caused population crashes or extinctions (often within a single year) of at least 200 species of frogs, even in relatively undisturbed, remote habitats, the  herpetologists said.

The American Association  for the Advancement of Sciences (AAAS) say amphibian immune defenses are being adversely being affected because of global warming and pollution. One  group of chytrid fungi that affects amphibians  is a parasite that feeds primarily on algae which often blooms in areas with excess nitrogen from farm runoff.

Extent of Amphibian Decline

The geographic extent of amphibian declines is worldwide.

The international Union for the Conservation of Nature (IUCN) says  the areas most strongly affected are located in Central and South America, the Caribbean, the wet tropics of eastern Australia , and western North America.

 The islands of the Caribbean and Pacific have some of the highest percentages (up to 100%) of endemic species that are threatened or endangered, but have relatively few species. 

Less is known about the status of species in Africa and Asia. But some species-rich countries have alarmingly high percentages of threatened and endangered species (e.g., 70% for Sri Lanka, based on the online resource IUCN 2010).

The authors of Global Declines of Amphibians emphasized the worldwide amphibian decline is multi-pronged. Deforestation, lake and pond draining and farming in amphibian-rich habitats worldwide are worsening the amphibian die-offs, they said.

Frogs  Most Threatened

Esteemed Philippine herpetologist Dr. Angel Alcala  of Silliman University says with the current rapid extermination of animals, plants and other species  the real "sixth mass extinction",  is the amphibian branch of the tree of life that is undergoing the most drastic pruning.

Of the 107 Philippine amphibians,  26 species  are Highly Vulnerable, 48 species  are Moderately Vulnerable, 27 species  are Vulnerable, and 6 species are Least Vulnerable to climate change , Dr. Alcala said.

As of September 2016, the International Union for Conservation of Nature (IUCN) lists 848 endangered amphibian species,  13% of all evaluated amphibian species are listed as endangered.

Frogs are the most threatened, IUCN reported climate change, habitat destruction and disease could drive more than half of all Europe's frogs, toads and newts to extinction within 40 years.

These include water frogs, robber frogs, robust frogs, shrub frogs, forest frogs, rain frogs, cryptic frogs, true frogs, fleshbelly frogs, glass frogs,  litter frogs, screeching frogs, poison dart frogs, hemiprachtids, fork-tongued frogs, narrow-mouthed frogs, hylids, puddle frogs, reed frogs and ground frogs.

Frogs are more sensitive to climate change than other  amphibians because they exhibit habitat and microhabitat specialization and  that they are significantly less vagile. Many of the effects of climate change might be indirect, involving such factors as manifestations of disease or pathogen-host dynamics, and may involve interactions with other stressors.

Saving Frogs

To save some of the world’s frogs, the Declining Amphibian Task Force of the Smithsonian Institute is using methods borrowed from ornithology—including backyard pond observations and frog call counts modeled after breeding bird surveys—to help collect data needed to devise solutions.

Although some biologists view captive breeding as a last-resort conservation action, the IUCN endorses captive breeding as a proactive conservation measure, one that should be initiated while a species is still available. IUCN, through its Amphibian Specialist Group, sponsors the Amphibian Ark, which tracks ex situ captive breeding activities for amphibians around the world. However, captive breeding is costly and involves many problems to hurdle.

But the most practical approach maybe one launched by local environmentalists of Benguet State University  (BSU)in the Philippines. Professors, teachers, students and farmers are constructing frog ponds for them to multiply and educating students on the importance of frogs.

Led by Dr. Grace T. Bengwayan, BSU’s Save the Frogs Project  has taken an interdisciplinary and integrative approach to rescue the prized amphibians. “This project has implications for how you do science”, Grace said.

“In a sense,  it is about defining the whole conceptual focus of ecology, particularly in that to understand the problem, we have to do a better job in integrating humans into ecological and evolutionary theory,” Dr. Grace said.