|REACTIONS OF A KINDLY NATURE|
Frogs and toads have survived on this planet for over two hundred million years and have done so by being sensitive to the environment. They spend their youth in water and as adults live and feed on land, returning to the water for safety and breeding. Their skin is readily absorbent, and their frog spawn is exposed to all water born pollutants. Could pesticides be the culprit in the diminishing stock of these beneficial animals? I decided to investigate this possible connection since my own research into pesticides had indicated its link to the decline of other beneficial animals.
The New Country School, located in Minnesota, is a year around charter school that uses student centered projects as a basis for the curriculum. During a nature studies field trip last August to a wildlife game refuge, students noticed frogs with what seemed to be "developmental problems. . . fully 50% of the frogs caught that day had deformities of their hind legs. Many had one leg which was underdeveloped and webbed together, preventing normal function. One frog captured that day had only one hind leg, while another had two feet on one leg and a bony protrusion from the spine."
Thus began an intensive investigation of the frogs, which is still ongoing in conjunction with scientists from the Minnesota Pollution Control Agency. The exact cause of the deformities found in these frogs may never be known, although circumstantial evidence certainly points in pesticide's direction. Their discoveries soon reached the national news media; the school received a national environmental award. It was portrayed in the media as a cute story about children serving science, but to me it indicated something much more disturbing. It took wide-eyed school children to notice important indicators of danger that we should all be recognizing. This incident in Minnesota is only one of many.
The Journal of Conservation Biology published a study which documents the the decline of toads and frogs in Yosemite. The authors, an ecologist and a zoologist, studied seven native species and found that all but one had declined when compared with a 1915 survey. This was surprising since they never expected these results in the middle of a wilderness, but folks who work in Yosemite have suspected as much. One field biologist reported that twenty years ago he used to have to tiptoe around the yellow-legged frogs, but now he walks without worry. Is such a drastic plunge in numbers within one generation a portent of our frogless future?
The once numerous Southern California red-legged frog is now reduced to a small population around Riverside while the arroyo toad is no longer found in three fourths of its previous territory. The curator of herpetology at the Los Angles Museum of Natural History stated:"There is a series of declines among the amphibians that cannot be explained by the usual means. These are not just declines but appear to be absolute losses. They are not just dropping down, they are in a catastrophe."
As indicators of environmental damage, the significance of these frog studies can not be overlooked, particularly for the red flags they provide about pesticide-related destruction. Part of the reason that pesticides have not been viewed with proper skepticism is because, until recently, they have been examined only individually, and not in their most toxic form, which is in combination. A study appearing last month in "Science" magazine stated that researchers from Tulane University are beginning to see the deadly possibilities of pesticide mixing. Their findings indicate that pesticides in combination boost their toxicity by over a thousand fold, and that these increases lead to birth defects, cancer, and reproductive problems in humans, domestic animals, and wildlife.
Many studies abroad indicate similar findings. The Canadian Wildlife Service has been gathering data about the affects of pesticides on Amphibians from research labs across the country. Their results are not encouraging for frogs or humans. Studies at Trent University in Ontario focused on common pesticides such as Roundup in low concentrations typical of runoff after a normal application to a field or roadside. While not immediately lethal, there were long term effects such as paralysis and inability of frogs to move away from a prod. Green frog tadpoles were never able to survive more than minimal exposure, thus decreasing the population over time.
Another study in southern Quebec measuring the overall health of frogs living in agricultural habitats subjected to pesticides found outbreaks of disease and hind limb deformities. But the worst news was that while some pesticide exposed frogs showed no apparent physiological problems, a study of their eggs indicated a substantial increase in abnormalities.
Pesticides used in apple orchards were studied in Ontario and again the results were disheartening. Orchards using pesticides and the non sprayed reference sites showed significant differences in their frog populations. The sprayed areas contained considerably smaller adult males, fewer young frogs, and stunted tadpole growth; embryos and larvae suffered significantly higher mortality rates.
Mudpuppies along the St. Lawrence and Ottawa river systems were examined in relation to their exposure to pesticides. Pesticide residues were found in the ovarian tissues of Mudpuppies from contaminated waters and X-ray analysis revealed a high incidence of limb deformities. Again they found a more numerous aging population, indicating that something serious was affecting the development of young frogs. These researchers speculated that the cause was toxic stress to the environment.
One of the common herbicides in these studies is Simazine. Simazine is used regularly, in every state, to kill weeds; millions of pounds are poured on fields, roadsides and lawns every year. Our soil has been saturated with this stuff even though Simazine is highly toxic if inhaled, moderately toxic if ingested, and slightly toxic via dermal exposure. The triazine herbicides such as Simazine disturb animal metabolism. Symptoms include difficulty in walking, tremor, convulsions, paralysis, cyanosis, slowed respiration, gut pain, diarrhea and impaired adrenal function. Sheep and cattle are especially susceptible to poisoning by Simazine. Symptoms exhibited by poisoned sheep include lower food intake, higher water intake, tremors, and weakness, especially in the hindquarters.
It's clear that not just frogs and toads are negatively influenced by the presence of pesticides in their environment; the common symptom of hindquarter abnormalities and fetal deformities is certainly no coincidence. If, as biologists have indicated, amphibians are perfect indicators of environmental health, their demise may foreshadow the consequences of our pesticide habits that Rachel Carson warned us about thirty years ago: "where the effects on humans are already known, they are found to be destructive. Beyond these known effects is the even more frightening prospect of damage that cannot be detected for years, and of possible genetic effects that cannot be known for generations, by which time the havoc we have wrought cannot be undone."