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Where have all the frogs gone?
Earth in Mind, a book by notable environmental educator David Orr, opens with two memorable and frightening statistics:
- Male sperm counts worldwide have fallen by 50% since 1938;
- There has been a marked decline in populations of amphibians - frogs, toads, salamanders, and newts - world-wide.
I first encountered David Orr's book in 2004, when, as a bright-eyed young instructor in an urban community college, I sought to share with my inner-city students the beauty and value of nature. I particularly wanted them to understand the urgency of the species extinction disaster that is facing all inhabitants on this planet - humans, animals, plants, even fungi. Orr's statistics eloquently articulated the inextricable bond between human and environmental health.
Enviroblog readers are very familiar by now with the dangers synthetic industrial chemicals pose to human reproduction, especially normal reproductive development of baby boys. Endocrine disrupting-chemicals, such as phthalates and bisphenol A, have been strongly associated with problems in fetal development and fertility.
It now appears that animals in the wild are as much or even more at risk for reproductive disorders and other toxic effects that threaten their survival. We can let the numbers speak for themselves. As reported by Amphibian Ark, a conservation organization, half of the approximately 6,000 species of amphibians may become extinct, and the remaining half is in trouble.
Scientists have fiercely debated the primary cause of the decline of the amphibian population. Certainly, loss and fragmentation of habitat, degraded air and water quality and changes in ecosystem structure because of climate change have contributed to the disappearance of frogs from our rivers and streams.
New research strongly indicates that amphibians are especially at risk from widespread application of agricultural pesticides.
Amphibians have highly permeable skin, which makes them particularly vulnerable to chemical contaminants. Moreover, unlike lizards, birds or mammals, whose developing offspring is protected by an egg shell or by the mother's body, the most sensitive, hormonally-regulated stages of amphibian development occur in the aquatic environment, where the defenseless tadpole is exposed to agricultural, industrial and urban contaminants. Imagine what is happening year after year as generations of frogs are being hit literally by truckloads and plane-loads of water pollutants.
Studies by Tyrone Hayes of the University of California at Berkeley and many other scientists has demonstrated that agricultural chemicals such as the herbicide atrazine, a ubiquitous, persistent contaminant of ground and surface water, have endocrine-disrupting properties that strongly affect amphibians. Atrazine both chemically castrates and feminizes exposed male amphibian larvae and also retards tadpole development and growth, inducing edema, erratic swimming and irregular behavior.
And exposure to atrazine is not a frog-only problem. EWG tap water database reported that between 1998 and 2003, 19.1 million people in 702 communities rank water contaminated with atrazine. In 345 of these communities, tap water was contaminated at levels above health-based thresholds established by EPA. Atrazine is the second most-commonly used pesticide in US agriculture, with 74-80 million pounds applied to the fields every year. No wonder so much of it ends up in our drinking water sources.
New research presented last week at the annual meeting of the Society of Environmental Toxicology and Chemistry indicated that atrazine suppresses immune system in an endangered species of northern leopard frog Rana pipiens. University of South Florida scientist Jason Rohr found that atrazine-exposed leopard frogs are especially susceptible to parasitic flatworms known as trematodes. As described in the journal Nature, trematode infections of amphibians can cause limb malformations, kidney damage and debility, most often with lethal consequences. The presence of phosphate, a fertilizer ingredient, aggravated the disease in frogs.
This research tells us that we need to look at the effects of chemical pollution not only in the laboratory but also in the real world. Rohr and his team found that atrazine suppressed the immune system of frogs, making them easy targets for parasites. Moreover, atrazine and phosphate spurred growth of aquatic plants that, in turn, triggered an increase in the population of snails that feed on them. The snails host flatworms, which are parasites that prey on the already-debilitated frogs.
The University of South Florida team concluded that their study, taken together with data on endocrine disruption, hermaphroditism and mortality in amphibians, raises serious concerns about the relationship between atrazine and global amphibian losses. They also noted that the important nexus between amphibian disease rates and pesticide and fertilizer pollution in water would not have been detected in standard studies used to register chemicals in the United States and Europe because these studies are typically conducted on laboratory animals, one chemical at a time. Clearly, this regulatory and legislative gap needs to be addressed. That's why the Environmental Working Group is backing the Kid-Safe Chemicals Act, federal legislation that promises comprehensive reforms, including a requirement that manufacturers prove their chemicals are safe before they go on the market.
Each of us can take one step immediately to help protect those beautiful frogs and salamanders, so that our children will be able to see them in the neighborhood pond, not just in a glass tank at a distant metropolitan zoo. It is very simple and very powerful: we need to support local organic farming and vote with our wallets as well as our ballots to promote sustainable agriculture that protects the health of humans and wild animal species alike.
Photo by ~sage~
well the hybriding of kangaroos and frog which jump and hop as in the hops hopping and the relevants to spinal cords as in the nature of the injury to Reevees the genetic studies of the injury.....trajectory of the spinal cord to the nape of the neck perhaps a tranfer of neurones .........