Monsters of the Marsh
They're tattooed by pollution from man-made chemicals that seep into their permeable skins. Ambient ultraviolet radiation (UV-B) from the sun mucks with their development, causing deformities, weakened immune systems, and death. Welcome to the shaky world of amphibians, indicators of ecosystem health.Other wild victims abound. Reptiles have cousins who turn up with reproductive system problems. Some can't find sufficient males for successful population continuation. Still others find themselves to be neither males nor females.Strong scientific evidence suggests that biodiversity seems to be plunging worldwide because of anthropogenic (human-related) activities including habitat stressors such as toxic chemical dumps into the air, water, and soil.In 1992 estimates revealed almost 4,000 species of amphibians and 6,000 reptile species in existence. They're all ectotherms, which means they don't typically pump out enough metabolic heat to increase their own body temperatures over ambient temperatures. As such, they balance their heat intake from the environment with heat loss to it.While a number of amphibian and reptile species seem to require ultraviolet light for regular behavior, reproduction, and metabolizing calcium, too much UV is not such a good thing. Of course, neither is excess pollution.Let's take a peek at what we've so altruistically dealt these impacted animals; how our industrial, agricultural, and domestic purpose chemical broth chokes many; and how increased UV-B radiation decreases their odds at a healthy, normal life.Wafting Toxins, Nasty Effects Picture this. Over 100,000 synthetic chemicals can be found on the global market. Yearly, we pump out 1,000 new man-made concoctions, and most of them are introduced without appropriate tests and reviews. In 1992 the U.S. production of carbon-based synthetic chemicals exceeded 435 billion pounds. Worldwide, five billion pounds of pesticides lurked about in 1989 which included 1,600 chemicals. And production continues to increase. Pesticides are a particularly nasty breed of chemicals, because they're designed to be biologically active and purposefully distributed.The gamut of man-made chemicals includes pesticides (e.g., DDT), industrial chemicals (e.g., PCBs), drugs, and contaminants (e.g., dioxins). But while PCBs, DDT, and dioxins have been the most studied hormone-disrupting chemicals, we should be more concerned about what we don't know of the potential effects on wildlife, particularly at the rate we crank out such chemicals.Hormone-disrupting chemicals make their way into the bodies of amphibians and reptiles and meddle with the endocrine systems by masquerading as a natural hormone. These "hormones" play an important part in altering the amphibians' growth, development, reproduction, and behavior. Particularly susceptible to modifications in hormonal concentrations are embryos and fetuses, which end up displaying the effects later in their development.Amphibians The cause of reduced and malformed populations of amphibians worldwide has attracted much attention and controversy, not unlike the ozone hole issue itself. A survey conducted by the Nature Conservancy two years ago revealed that in the U.S. alone, nearly 38 percent of amphibians face the danger of extinction.In 1995 a group of students on a field trip to a farm pond in southern Minnesota found numerous frogs with abnormal limbs. Organizations, such as the Great Lakes Declining Amphibians Working Group, have sprung up to monitor and report on the state of these animals globally.Amphibians have a long history as environmental health barometers for a number of reasons. For starters, they are in close contact with numerous parts of their natural environment -- in water as larvae and land as adults. Their skins allow them to breath and be directly in contact with sunlight, water, and soil. They're herbivores as larvae and carnivores as adults. They're excellent indicators of local conditions because they don't stray far from home. And because they vary so greatly in class, any characteristics specific to that class can be attributed as the reason for decreased numbers. So it's believed that environmental conditions are the primary basis for their dwindling numbers.Scientists also point to an introduction of exotic predators, competitors, and/or to natural pathogens (organisms that produce diseases) as the reasons for the declining populations. Other camps attribute the bulk of their decline to the destruction or alteration of habitat and to natural variations in their population.While it is very likely that a variety of factors account for the population declines and malformations in amphibians, a growing number of scientists point to chemical contamination on the ground, the waterways resulting from the likes of acid rain and snow, herbicides, pesticides, and increased toxins in the troposphere and stratosphere as main culprits.Amphibian experts also point to the wind-born, endocrine-disrupting chemicals as potentially having a more significant impact than previously thought.Areas high in altitude seem surprisingly susceptible to pollution, as it hitches a ride on the winds. After evaporating, many long-lasting man-made chemicals move around until they find a cooler place, perhaps a peak or mountainous terrain. Here they condense again and settle.Studies on the effects of acid rain's long-distance pollution have revealed numerous chemicals wafting in what seemed like undisturbed mountain areas. Such factors may have been at play in the disappearance of some amphibians in the back country of Australia and of the golden toad of Costa Rica. Interestingly, Monteverde, home to the golden toads, rests not far from where banana farmers soaked the fruit with hazardous pesticides to ensure near-perfect bananas for export to the U.S.Debilitated immune systems from chemical contamination seem to be a feature among dwindling frog populations. A weakened immune system leaves them more vulnerable to fungal and bacterial infections. For example, "red leg," a bacteria commonly found in freshwater and typically of no great consequence to a healthy frog, can become a fatal infection that causes swelling of the inner legs.About 35 U.S. states and three Canadian provinces have reported amphibians with malformations since 1986. Illinois, Michigan, and Indiana are among the states that have reported such abnormalities.Reptiles A common assumption persists that reptiles are hearty creatures able to withstand high doses of chemical introduction. In fact, research illustrates that reptiles have greater susceptibility levels to pesticides than homeotherms. Dose levels that have been typically safe for mammals and birds have resulted in death for some reptilians.Altered aquatic habitats negatively impact reptiles. Strong links exist between man-made chemicals and impacted populations of alligators and turtles, and among the cited effects have been sterility in females, feminized behavior in males, and partial development of sexual organs in males.In 1980, a spill from a chemical company in Lake Apopka, Florida, dumped numerous pesticides into the water. Among the damaging concoctions was dicofol, a close cousin of DDT also known for its hormone disrupting properties, and DDE, a broken down version of DDT. These chemicals became the lead suspects in causing unfortunate reproductive abnormalities in the American alligator and the red-eared turtle ten years after the original spill.The American alligator penises there were one third to one half smaller than ones in alligators from other lakes. Testicles were structurally abnormal. In females, abnormal eggs and follicles prevailed as did higher-than-normal estrogen levels. The hormonal balance of juvenile alligators was out of whack, and the ratios of hormones in males exemplified those usually found in females. Such dysfunctionality in the reproductive organs of both sexes led to a decrease in the juvenile alligator population.While these alligators were exposed to greater levels of toxins due to their carnivorous, top-predator level in the food chain, red-eared turtle populations also took a hard hit. Despite their plant-based diet, which exposes them to lower pollution susceptibility, the red-eared turtle faced a serious shortage of males along with an increase in unsexed turtles. Those that would have developed into males found themselves in the "gender-bending" abyss of neither (known as intersex), because their sexual development was disrupted by the hormone mimicking chemicals.Next time we feel that our species floats above the likes of others, especially reptiles, let's remember this: the estrogen that courses through our veins is exactly the same type that meanders in turtles.Here Comes the Sun An important factoid not well disseminated is that UV-B radiation can cause the collapse of "photoactive" chemicals already in the environment and make them more lethal. So even if amphibians weren't directly deformed by UV-B, the radiation could be jacking up the toxicity of the numerous chemicals that afflict their populations.An observation gaining recognition is that the increase in UV-B resulting from the depletion of the ozone layer in the stratosphere causes biological damage in amphibians which leads to malformities and population declines. This hypersensitivity to modest increases of UV-B radiation, which may lead to mutations or cell death, has been observed in lab and field studies.One of the most significant studies was recently conducted in natural conditions of amphibians in the Cascade Mountains of Oregon by researchers from Oregon State University and Yale University. Researchers Andrew Blaustein and Joseph Kiesecker concluded that ambient UV-B radiation can cause increased levels of deformity and mortality in some frog species and other amphibians, such as long-toed salamanders.They noted that long-toed salamander embryos unprotected from UV-B hatched less than 15 percent of the time, and almost 92 percent of the ones that did hatch were deformed. By contrast, 95 percent of the embryos that were protected from UV-B hatched, and 99 percent of those hatched were normal. The researchers also noted that UV-B may damage amphibians' disease defense mechanisms, thus making them more susceptible to disease and parasites.As we've learned, UV-B affects many properties of immune systems. Ultraviolet radiation also affects amphibian DNA by tearing apart the bonds that hold the molecule from breaking. The changed DNA can then stress the cells or cause them to die. Some amphibians can repair damaged DNA by activating an enzyme called photolyase, which displaces the damaging components. Amphibian species with dwindling populations are typically those with eggs that crank out reduced levels of photolyase thus rending them more susceptible to UV-B damage.Tiny Monsters, Progeny of Chemicals & UV-B The range of amphibian deformities reported has been vast and by no means merely a national affliction. Australia, Costa Rica, Brazil, Chile, Argentina, Ukraine, Czech Republic, Africa, Sweden, United Kingdom, and Japan are among those that indicate similar findings. Whether caused by synthetic chemicals, the impact of their pollution, UV-B radiation, or a combination of all, the effects of the malformations and mortality rates are serious.They include major limb deformities such as missing or partial legs, extra limbs, bent or contorted limbs, limbs with little muscle or that have developed extensions, and missing digits. Besides extra or missing eyes, extra skin or dysfunctional webbing that inhibits movement, others have dysfunctional internal organs including severely extended bladders.Damaged urinary systems and dysfunctional reproductive systems, including thin testes, are the order of the day for some of these unfortunate "sentinels." Others have to put up with malfunctioning digestive systems, skeletal irregularities, such as curved spines, head malformations, heart abnormalities, facial defects, and DNA damage.Irreplaceable Consequences The connections within ecosystems cannot be ignored. Amphibians and reptiles have a long history. They've thrived for 350 million years amid meteors, comets, dinosaurs, and pre-industrial humans. They have intricate links to the ecological chain.In some cases, amphibians represent the most common vertebrates, especially in forest and wetland ecosystems, and their demise has the potential of causing havoc for lots of other species. As larvae, they represent a key food source for insects, mammals, birds, and fish. As adults, they hunt mosquitoes, flies, fish, birds, and some small mammals themselves. These adults also serve as major food items for predators, including reptiles.To some humans, amphibians symbolize giant warehouses of medicinal products produced from the chemical secretions of their glands and skin. These chemicals have applications as heart stimulants, painkillers, and organ glues, and they have antibacterial and antiviral attributes. If amphibians disappear, so do these potential cures.For some of us, it's not the pharmaceutical potential of amphibians or the wallet, shoe, or belt value of reptiles that's at risk. Instead, we mourn the loss of these species because of the inherent right they should have had to simply coexist. And we lament the suffering they must endure.Our species is the maverick responsible for the continuing release of chemicals that contaminate wildlife and deplete the delicate balance of the ozone layer. We can take a long, low bow for playing a weighty part in the internal and external deformities and deaths of amphibians and reptiles.One dumb move from mankind, one giant backlash for biodiversity.