The widespread use of thousands of pesticides, which broadly includes insecticides, herbicides and fungicides, that were once considered safe for wildlife have recently become the subject of many studies. Results from these studies conclude that there is strong evidence linking the application of pesticides and amphibian population declines. The most commonly used pesticide, atrazine, has been shown in both laboratory and field observations to cause hermaphroditism, developmental and behavioral malformations, and the disruption of normal endocrine system functions (Hayes 2002; Storrs 2004). Atrazine levels as low as 0.1 ppb are enough to affect amphibian development and are in contrast to previously held beliefs that high concentrations were required to induce abnormal growth (Hayes 2002).

Instead of very high doses not seen frequently in natural habitats, these studies have shown that ecologically relevant doses observed in watersheds are a concern for amphibians. The overlapping of the amphibian life cycle and agriculture practices has put them at risk to pesticide contamination. Besides possessing thin permeable skin susceptible to chemicals, and spending their lives in and around water, amphibians are in the breeding season when atrazine is typically applied in the spring. This is also a period in which rainfall levels are generally high, runoff is abundant, and amphibians are in the early stages of development. In the United States, the allowable contaminant level of atrazine in drinking water is 3 ppb and short exposures to 200 ppb are not deemed a health risk (Hayes 2002). However, results have indicated that it is not uncommon for atrazine concentrations to be 7x to 75x more than the allowable level in ground and surface waters throughout the U.S. In some Midwestern agricultural regions, contaminating levels have reached as high as 760x this allowable level (Hayes 2002). Thus, the chances of amphibian populations being exposed to at least 0.1 ppb of atrazine, a concentration found to adversely affect amphibian development, are very high.

Independent observations by Storrs and Hayes have both shown that atrazine in lower concentrations can have a greater impact than exposure to higher concentrations. Besides mortality, atrazine has similar properties of endocrine disruptors, which explain the incidents of hermaphroditism, developmental malformations, reproductive abnormalities and growth retardation in both early and late stage amphibians. Depending on the developmental stage, exposure to pesticides and endocrine disruptors are adversely affecting populations and indicate the need to modify current toxicological detection standards to include low level testing procedures.

In addition to modifying traditional thinking and implementing low-level chemical testing to identify possible contamination after the fact, it is essential for continued studies involving the mechanisms by which contaminants are transported after application. Results by Konda (2001) confirmed that the transportation of pesticides by runoff and downward movement through soil layers coincides with precipitation. Stream contamination, pesticide concentration in surface runoff, and presence of pesticides in multiple soil layers increases dramatically the closer rainfall events occur to the time of application. Results from plots with recently applied atrazine and other pesticides had the highest concentrations in runoff when rainfall occurred shortly after this application period, and generally within the first 100 days. Konda explains that the initial leaching of pesticides and runoff concentrations are high, although dependent upon volume and intensity of rainfall, because runoff and erosion are increased by the lack of vegetation that protects the soil later in the crop season. As expected, these high concentrations of pesticides in runoff cause significant stream contamination, and typically produce concentrations higher than U.S standards for atrazine in drinking water.

An understanding of the transportation and retention of pesticides in soil is necessary for the development of protocols to prevent the continued contamination of surface water and groundwater. Although more studies need to be and will be done concerning the mechanisms and movement of pesticides after application, it is clear from these studies that once considered ecologically safe levels of pesticides in both soils and waters are of great concern to the overall health of the environment and testing must be conducted with realistic exposures. Although population declines cannot be solely attributed to the ever increasing presence of pesticides, it is a definite factor that may be working in conjunction with other environmental stressors to affect amphibians world-wide.

You heard it right and as much as I would love to jump into the topic of overfishing and share some thoughts regarding a book I just finished (Tuna: A Love Story), today it’s all about the frogs.  I have commented on the plight of frogs in past postings and even made a video, but there is one piece of the troubling puzzle I have inadvertently avoided. To be honest it never really crossed my mind as frogs are not something I can frequently recall coming across on menus in California, but to qualify that statement I am by no means a regular in the so-called fine dining scene.

And since my days in college zoology and biology are quickly becoming a distant memory, the frog harvesting industry has managed to skid under my radar.  That is until a publication hopped into the journal Conservation Biology and reveals a 20 year global trade pattern in frogs’ legs.

According to the United Nations Commodity Trade Statistics Database, France, USA, Belgium, Italy, and the Netherlands imported more than $38 million dollars in frog’s legs in 2006, and Warkentin, et al, based on previous estimates, put  “import of amphibians for food into the United States at 4000 tons from 1998 through 2002.”  Which when compared to imports topping 6000 tons in 1990 and just under 10,000 tons in 1999 by the European Union , there is no doubt a cultural difference in US appetites and most certainly the reason why Californians such as myself may rarely come in contact with frogs’ legs on the menu. 

Herein lies the problem.  “The frogs’ legs market has shifted from seasonal harvest for local consumption to year-round global trade.” (Warkentin, et al 2009). And like tuna (I just couldn’t resist bringing overfishing up), the need to satisfy the ever hungry consumer  has resulted in loss of domestic stocks by overexploitation. Because commercial stocks are no longer plentiful enough at home, countries like the US and France must outsource harvesting, and hence we enter an era of over-gigging, inhumane killing, loss of biodiversity, and a general breakdown in ecosystem functions that for example helped keep insect populations in balance.  How can the parallels between fisheries and frogs’ legs not be drawn when we have already witnessed declining frog populations due to over harvesting, misidentifying species to preserve commercial profits, and removing up to 160 million frogs from the environment in Indonesia alone over a 10 year period ending in 1998 (Kusrini 2006), and importing 6 million Chinese Edible Frogs from Thailand into Hong Kong in a single year (Lau et al. 1997).

So besides contending with loss of habitat, pollution, disease, invasive species, and climate change, our earth’s co-inhabitants must weather an inexplicable human need to overexploit.  What else can I say, but this is a gig they don’t want and the situation is truly sad.

“Frogs are the most threatened group of animals on Earth. Nearly one-third of the world’s 6,468 amphibian species are threatened with extinction, and at least 150 species have already completely disappeared in recent decades.” SAVE THE FROGS!

*To learn how you can help and get involved in protecting amphibians, check out the nonprofit organization SAVE THE FROGS!

I guess I was not paying that much attention as it was only within the last two weeks that I discovered 2008 had been designated the Year of the Frog.  Well, with a little more than a month to go I thought I would make a contribution to the plight of our amphibian cohabitants.  In the early days of mining, canaries were used as indicators of the presence of poisonous gases.  Acting as an early warning system, miners were alerted to the existence of undetectable noxious gases when the canary died or passed out in its cage.  Upon this observation, the miners would flee the underground cavern to avoid asphyxiation.  Although we have all heard these stories at some point in our lives and through life have been trained to recognize warning signs, our society seems to be overlooking another undetectable danger.

Just like the mine canaries of the past, today’s amphibians are providing an early warning system of the health, or lack of health of their environments.  Frogs, salamanders, toads and other amphibians are quite sensitive to the contamination that is steadily increasing and being released into the environment.  Fertilizers, herbicides, detergents and pesticides, etc. are wreaking havoc on their populations and exponentially increasing the presence of deformities and abnormalities.

Because amphibians breathe, in part, and absorb water through their skin, pollutants are easily entering their bodies.  In addition to the susceptibility of adults to environmental hazards, eggs and larvae are at an even greater risk.  As described by the U.S. Fish and Wildlife Service, “Exposure to contaminants during development can lead to frogs with many different types of malformations, including frogs without eyes, with extra or missing legs and, in some cases, the malformations may be deadly.”

As indictor species, scientists and conservationists are scrambling to determine the cause and effect relationship between the increased number of amphibian malformations and deformities, the health quality of the environment and those species dependent on amphibians for survival; simply stated, the preservation of biodiversity and sustainability of the ecosystem. 

What can you do to protect amphibians?

1. Avoid the use of herbicides and weed killers.  Try mulching and pulling weeds
2. Minimize the use of fertilizers.  Over fertilizing is a common urban problem that results in excesses being carried away by water runoff (as well as pesticides and herbicides) and pollutes critical habitats.  Researchers at Oregon State found low levels of nitrates are enough to kill some species of amphibians (U.S. FWS 2003). 
3. Reduce the use of pesticides.  Homeowners use approximately 10 times more chemical pesticides per acre on their lawns than farmers use on their crops.
4. Plant native species, they are often tolerant to the pests and diseases found in your region.
5. Avoid pesticides that contain DEET (a chemical very harmful to amphibians)
6. Dispose of household products, paints, auto fluids and detergents properly.  Dumping them into sewers and drains often results in contamination of waterways.

Before we completely asphyxiate our wetlands, estuaries, ponds, streams, and environments, let’s take the time to recognize the warning signs currently on display. Promoting responsible actions and working to protect the wildlife and habitats of our communities will ensure survival, rehabilitation and healthier, cleaner environments that benefit all residents who share this planet.