As technology improves, scientists are able to detect more pollutants, and at smaller concentrations, in Earth’s freshwater bodies.
Containing traces of contaminants ranging from birth control pills and sunscreen to pesticides and petroleum, our planet’s lakes, rivers,
streams, and groundwater are often a chemical cocktail. Beyond synthetic pollution, freshwater is also the end point for biological waste, in
Beyond synthetic pollution, freshwater is also the end point for biological waste, in the form of human sewage, animal ex-
crement, and rainwater runoff flavored by nutrient-rich fertilizers from yards and farms. These nutrients find their way through river sys-
tems into seas, sometimes creating coastal ocean zones void of oxygen—and therefore aquatic life—and making the connection between land
“Environmental pollution is an incurable disease.
Litter in the world’s oceans comes from many sources, including containers that fall off ships during storms, trash that washes off city streets into rivers that lead into the sea, and waste from landfills that blows into streams or directly into the ocean. Once in the ocean, this debris may degrade slowly and persist for years, traveling the currents, accumulating in large patches and washing up on beaches. Use of pesticides and fertilizers on farms has increased by 26-fold over the past 50 years, fueling increases in crop production globally. But there have been serious environmental consequences. Indiscriminate pesticide and fertilizer application may pollute nearby land and water, and chemicals may wash into nearby streams, waterways and groundwater when it rains. Pesticides can kill non-target organisms, including beneficial insects, soil bacteria and fish. Fertilizers are not directly toxic, but their presence can alter the nutrient system in freshwater and marine areas. This alteration can result in an explosive growth of algae due to excess nutrients. As a result, the water is depleted of dissolved oxygen, and fish and other aquatic life may be killed Air pollution brings to mind visions of smokestacks billowing black clouds into the sky, but this pollution comes in many forms. The burning of fossil fuels, in both energy plants and vehicles, releases massive amounts of carbon dioxide into the atmosphere, causing climate change. Industrial processes also emit particulate matter, such as sulfur dioxide, carbon monoxide and other noxious gases. Indoor areas can become polluted by emissions from smoking and cooking. Some of these chemicals, when released into the air, contribute to
smog and acid rain. Short term exposure to air pollution can irritate the eyes, nose and throat and cause upper respiratory infections, headaches, nausea and allergic reactions. Long-term exposures can lead to chronic respiratory disease, lung cancer, and heart disease. Long-term exposures also can lead to significant climatic changes that can have far reaching negative impacts on food, water and ecosystems. Artificial light and noise often drown out natural landscapes. In the Arctic, the sounds of oil and gas explorations are so loud that belugas, bowhead whales and other sea life have had difficulty feeding and breeding. Light pollution disrupts circadian rhythms for both humans and animals alike and may even contribute to the development of cancer. Light pollution also can impact sea turtles. Adult and hatchling sea turtles are drawn toward lights along the beach, thinking they are heading toward the moon. Coastal developments, therefore, are encouraged to turn off their lights or cover them at night In some cases wildlife populations have suffered severe losses or even faced extinction due to pollution. For example, the bald eagle, peregrine falcon, and brown pelican all nearly became extinct before scientists discovered that the synthetic chemical DDT was the cause of devastating reproductive failure in these species. Oil spills, such as the fouling of the coast of southern Alaska by the grounding of the Exxon Valdez, take an immediate toll on many species with the misfortune of living near such blunders. Toxic metals can kill adult members of wildlife populations and cause the production of deformed offspring, as seen at Kesterson Res-
ervoir in the San Joaquin Valley. Acid rain has caused hundreds of fish populations to disappear from lakes in the northeastern U.S. and Scandinavia. In this chapter each of these notorious instances of the impacts of pollution on wildlife are described. The chapter also provides a general discussion of the origins and effects of synthetic chemicals, oil spills, toxic metals, and acid rain. Pollution can be defined as the human alteration of chemical or physical characteristics of the environment to a degree that is harmful to living organisms. Some forms of pollution exert a destructive influence on wildlife by killing or impairing the health of individuals. Synthetic chemicals, oil, toxic metals, and acid rain are included in this category of toxic pollutants. Other forms of pollution affect wildlife in a more indirect manner by altering or destroying wildlife habitat. Examples include the obliteration of canyons, marshes, and grasslands with solid waste landfills; the destruction of the ozone layer by chlorofluorocarbons, which may lead to widespread damage due to the effects of excessive ultraviolet radiation on wildlife and their food sources; and carbon dioxide accumulation in the atmosphere, which may lead to global changes in climate and the distribution of wildlife habitats. Although both of these categories of pollutants pose significant threats to wildlife, this chapter focuses on toxic pollutants because of their specific effects on wildlife.
“The environment will continue to deteriorate until pollution practices are abandoned.�
Water pollution is the contamination of natural water bodies by chemical, physical, radioactive or pathogenic microbial substances. Adverse alteration of water quality presently produces large scale illness and deaths, accounting for approximately 50 million deaths per year worldwide, most of these deaths occurring in Africa and Asia. In China, for example, about 75 percent of the population (or 1.1 billion people) are without access to unpolluted drinking water, according to China’s own standards. Widespread consequences of water pollution upon ecosystems include species mortality, biodiversity reduction and loss of ecosystem services. Some consider that water pollution may occur from natural causes such as sedimentation from severe rainfall events; however, natural causes, including volcanic eruptions and algae blooms from natural causes constitute a minute amount of the instances of world water pollution. The most problematic
ty (e.g. plastic bags, bottles). While these materials are not so harmful to human health as chemicals or pathogens, they comprise the majority of visual impact of water pollution. In the case of thermal pollution, these point source discharges typically affect the metabolism of aquatic fauna in adverse ways. Radioactive substances are really merely a special subclass of chemical pollutants, and by mass represent the smallest of the contributors to water pollution; however, their potential for harm allows recognition as a separate class. In fact, most discharge of radioactivity is not from the negligible escape from nuclear power plants, but rather arises from agricultural practices such as tobacco farming, where radioactive contamination of phosphate fertilizer is a common method of introduction of radioactive materials into the environment. Common pathogenic microbes introduced into natural water bodies are patho-
“We forget that the water cycle and the life cycle are one.” — Jacques Cousteau
The use of synthetic chemicals to control pests, principally insects, weeds, and fungi, became an integral part of agriculture and disease control after World War II. These chemicals were credited with providing an inexpensive means of increasing crop production, preventing spoilage of stored foods, and saving many millions of human lives by the prevention of certain insect-borne diseases. The history of DDTexternal link use in the U.S. is symbolic of the gradual development of an awareness of the ecological consequences of pesticide application. DDT was one of the most widely used pesticides in the postWar era. The first significant applications of DDT in the 1940s saved millions of human lives from malaria, typhus, and other deadly diseases. DDT was considered such an extraordinarily valuable substance that in 1948 the Nobel Prize in medicine was awarded to Paul Mueller, the Swiss chemist who discovered the compound’s insecticidal properties. By 1964, DDT was so broadly applied that annual production in the U.S. reached 90 million kilograms. By the late 1960s, however, wildlife biologists realized that DDT was producing disastrous side effects in wildlife species. In the 1970s most industrialized countries banned the use of DDT because of its unacceptable effects on wildlife and, ultimately, humans. DDT is classified as an “organochlorineexternal link” chemical, a descriptive label that reflects its chemical structure, consisting of a combination of carbon (organic molecules are defined as those comprised of at least some amount of carbon) and chlorine atoms. Other organochlorines that are important environmental pollutants include polychlorinated biphenyls (PCBsexternal link) and dioxinsexternal link. PCBs were used as insulators in the electrical industry until the environmental threat posed by their toxicity was realized in the mid-1970s. Dioxins are the most potent chemical carcinogens known, and are present in the environment largely as a byproduct of various industrial activities (e.g., bleaching of paper).