Pollution effects on animal life

During the last decade of the twentieth century, the environmental problems predicted by environmental scientists decades prior began to be aggravated in a variety of ways. These included population explosion, food imbalances, inflation brought about by scarcity of energy resources, acid rain, toxic and hazardous wastes, water shortages, major soil erosion, the depletion of the ozone layer, and climate change. As a result of pollution, decreases in biodiversity and the extinction of both plant and animal species have accelerated. The burning and cutting of thousands of square miles of rainforest not only destroyed habitats for numerous animal species but also caused irreversible damage to ecosystems and climate. The recurring drought and famine in Africa became testimony to the negative effects of human activity. Concerned parties have warned that inaction will continue to severely threaten the well-being of both animals and humans. Further, they have warned that in order to take effective measures to reduce pollution and protect natural resources and the environment, people must first recognize these problems, as the ignorance and inaction of ordinary citizens will lead to disastrous consequences for both the environment and animal life.

Sources and Types of Pollution

Industrialization and the expansion of the human population have left relatively few places on earth undisturbed. In simple terms, human interference in natural ecosystems is the single most important source of pollution. First, heavy dependence on fossil fuels for energy, and on synthetic chemicals and materials, helped to dump millions of metric tons of nonnatural compounds and chemicals into the environment. Among such chemicals and compounds are fertilizers, insecticides, fungicides, and herbicides. Application of excess chemical fertilizers to soil hampers natural cycling of nutrients, depletes the soil’s own fertility, and destroys the habitat for thousands of small animals residing in the soil. Farm runoff carries priceless topsoil, expensive fertilizer, and animal manure into rivers and lakes, where these potential resources become pollutants. In the city, water pours from sidewalks, rooftops, and streets, picking up soot, silt, oil, heavy metals, and garbage. It races down gutters into storm sewers and often gushes into the nearest stream or river. Many of these chemicals also seep into the ground, contaminating groundwater.

Plants and factories manufacturing these chemical products are another source of pollutants and contamination. Burning fossil fuels releases greenhouse gases, carbon oxides, and methane. Coupled with deforestation in many regions of the world, carbon dioxide concentration in the atmosphere has steadily climbed, from 290 parts per million (ppm) in 1860 to more than 395 ppm in 2013, more than a 36 percent rise due to industrialization. That same year, atmospheric carbon dioxide surpassed 400 ppm for the first time in Earth's history. In 2017, the average concentration of carbon dioxide was 409 ppm. The National Oceanic and Atmospheric Administration (NOAA) reported in 2022 that this figure had reached 421 ppm, which represented a 50 percent increase over pre-industrial levels. Experts have asserted that the resultant global warming will have far-reaching effects on plants, animals, and humans in ways still not understood.

Acid rain, a result of overcharging the atmosphere with nitric oxides and sulfur dioxide (two gases also released by the burning of fossil fuels), has increased the acidity of soil and lakes to levels many organisms cannot survive. In 1991, the US National Acidic Precipitation Assessment Program reported that 5 percent of New England lakes were acidic, some to such levels that they were no longer able to support fish. This happens when much of the food web that sustains the fish is destroyed. Clams, snails, crayfish, and insect larvae die first, then amphibians, and finally fish. The detrimental effect is not limited to aquatic animals. The loss of insects and their larvae and small aquatic animals has contributed to a dramatic decline in the population of black ducks that feed on them. The result is a crystal-clear lake, beautiful but dead.

Another serious problem created by the chemical industry is ozone depletion. Chlorofluorocarbon (CFC) compounds contain chlorine, fluorine, and carbon. Since their development in the 1930s, these compounds were widely used as coolants in refrigerators and air conditioners, aerosol-spray propellants, agents for producing Styrofoam, and cleansers for electronic parts. These chemicals are very stable and for decades were considered to be safe. Their stability, however, turned out to be a real problem. In gaseous form, they rise into the atmosphere, where the high energy level of ultraviolet (UV) light breaks them down, releasing chlorine atoms, which in turn catalyzes the breakdown of ozone to oxygen gas. As a result of the decline of ozone and the depletion of the ozone layer, UV radiation rose by an average of 8 to 10 percent per decade between 1979 and 1992. This depletion of the ozone layer poses a threat to humans, animals, plants, and even microorganisms.

Pollution in the form of plastic waste likewise harms marine habitats and wildlife, such as when marine animals eat or become tangled in such debris. Plastic waste makes up 60 to 80 percent of marine debris, and the demand for plastic bags, bottles, and containers is growing. According to the United Nations (UN), the global production of plastics reached 400 million tons in the early 2020s, a significant increase from 230 million tons a decade earlier. Of the plastic produced, 85 percent winds up in landfills, with only a small percentage—under 10 percent—recycled effectively. The UN further reported that as much as 200 million tons of plastic waste is found in the planet's oceans, much of which originates in rivers that span the globe.

Pollution Effects of Chemicals

The degradation of air, land, and water as a result of the release of chemical and biological wastes has wide-ranging effects on animals. On a large scale, pollution destroys habitats and leads to population crashes and even the extinction of species. Hazardous chemicals introduced into an environment sometime render it unfit for life, as in Love Canal, New York, and Times Beach, Missouri. At the individual level, pollution causes abnormalities in growth, development, and reproduction. Hazardous chemicals, introduced either intentionally (such as fertilizers, herbicides, and pesticides) or through neglect (such as industrial wastes), have a variety of detrimental, sometimes devastating effects on animals. They affect the metabolism, growth and development, reproduction, and average life span of many species.

In the 1940s, the new insecticide dichlorodiphenyltrichloroethane (DDT) was regarded as a miracle. It saved millions of lives in the tropics by killing the mosquitoes that spread deadly malaria, and it saved millions more lives by destroying insect pests that fed on crops, thus increasing crop yields. This miraculous pesticide, however, turned out to be a long-lasting nemesis to the environment and many species of wildlife. In the mid-1950s, the World Health Organization (WHO) used DDT on the island of Borneo to control malaria. DDT entered food webs through a caterpillar. Wasps that fed on the caterpillar were destroyed, and then gecko lizards that ate the poisoned insects accumulated high levels of DDT in their bodies. Both geckos and the village cats that ate the geckos died of DDT poisoning. As the cats died, the local rat population exploded. The village was then threatened with an outbreak of plague, carried by the uncontrolled rats. Meanwhile, in the United States, ecologists and wildlife biologists during the 1950s and 1960s witnessed a stunning decline in the populations of several predatory birds, especially fish eaters such as bald eagles, cormorants, ospreys, and brown pelicans. The population decline drove the brown pelican and bald eagle close to extinction. In 1973, the US Congress passed the Endangered Species Act, which banned the use of DDT, and the once-threatened species have since somewhat recovered.

Although DDT has been banned in much of the world, there has been a growing concern over the effects of a number of similar compounds known as xenoestrogens or environmental estrogens. These compounds interfere with normal sex-hormone functions by mimicking the effects of the hormone estrogen or enhancing estrogen’s potency. High levels of xenoestrogens, such as dioxin and polychlorinated biphenyls (PCBs), in the Great Lakes have led to a sharp decline in populations of river otters and a variety of fish-eating birds, including the newly returned bald eagles. These chemicals are also the cause of deformed offspring or eggs that never hatch. In 1980, a spill of dichlorodiphenyldichloroethylene (DDE), a common by-product of DDT, in Florida’s Lake Apopka led to a 90 percent drop in the birth rate of the lake’s alligators.

Effects of Air Pollution

Air pollution leads to acid rain and the greenhouse effect, as well as damage to the ozone layer. Acid rain falls in areas that are great distances from the source of the acids, destroying forests and lakes in sensitive regions and causing fish populations to dwindle or disappear entirely. Data collected from the Adirondack lakes and Nova Scotia rivers beginning in the 1980s indicated declines in acid-sensitive species. Similar results were obtained by analyzing fish population and water acidity in Maine, Massachusetts, Pennsylvania, and Vermont. The effects of acid rain on other animals are indirect, either through the dwindling fish population, thus eliminating a food source, or through stunted forest growth, thus disturbing other animals' habitats.

The effect of climate change on the animal kingdom is a serious and complex issue that has caused significant challenges for animals in the early twenty-first century. As global temperature rises, ice caps in polar regions and glaciers melt, ocean waters expand in response to atmospheric warming, and the sea level elevates. The expected sea-level rise will flood coastal cities and coastal wetlands. These threatened ecosystems are habitats and breeding grounds for numerous species of birds, fish, shrimp, and crabs whose populations could be severely diminished. The Florida Everglades will virtually disappear if the sea level rises two feet. The impact of global warming on forests could be profound. The distribution of tree species is exquisitely sensitive to average annual temperature, and small changes could dramatically alter the extent and species composition of forests, and thus the population distribution of animals. A rise may make temperatures unsuitable for some species, hence reducing biodiversity. Additionally, more intense storms and extreme conditions like droughts and flooding caused by climate change can destroy animal habitats and help spread invasive species.

The effect of the depleted ozone layer on animals is yet to be fully understood. It is known that the high energy level of ultraviolet (UV) radiation can damage biological molecules, including the genetic material deoxyribonucleic acid (DNA), causing mutation. In small quantities, UV light helps the skin of humans and many animals produce vitamin D and causes tanning. However, in large doses, UV light causes sunburn and premature aging of skin, skin cancer, and cataracts, a condition in which the lens of the eye becomes cloudy. Due to UV radiation’s ability to penetrate, even animals covered by hair and thick fur cannot escape from these detrimental effects. UV damage caused by depleted ozone has cost US farmers billions of dollars annually in reduced crop yields.

Possible Remedies

The various types of pollution all have serious effects on the plant and animal species that share this planet. Experts have warned that it is all too easy to document the impacts of pollution on human health and ignore its effects on the rest of the living world, and that any possible remedies to alleviate these problems should start with education at both an individual and global level.

Synthetic chemical pollutants that are poisoning both people and wildlife could be largely eliminated without disrupting the economy, as reported in a study published in 2000 by the Worldwatch Institute, a Washington, DC–based environmental organization. The report presented strong evidence from three sectors that are major sources of these pollutants—paper manufacturing, pesticides, and polyvinyl chloride (PVC) plastics—to show that nontoxic options are available at competitive prices. Agricultural pollution can be mitigated, significantly reduced, or virtually eliminated through the use of proper regulation and economic incentives. Farmers from Indonesia to Kenya have begun learning how to use less of various chemicals while boosting yields. In 1998, all farmers in China’s Yunnan Province eliminated their use of fungicides while doubling rice yields by planting more diverse varieties of the grain.

Other efforts have led to positive changes. In 1989, the US government established the Acid Rain Program in an effort to reduce sulfur dioxide and nitrogen oxide emissions. By 2007, emissions of sulfur dioxide had been reduced by 40 percent. Also in 1989, the Montreal Protocol went into effect; this international treaty, which calls for the complete elimination of CFCs, went on to become universally ratified by all parties of the UN. Governments continued to enact legislation and work together to reduce pollution into the 2010s and 2020s. The Paris Agreement was adopted at the UN Climate Change Conference in late 2015 and went into effect a year later. The international treaty sought to limit global warming by reducing greenhouse gas emissions. In 2022, an intergovernmental planning committee of the UN drafted a resolution to address plastic pollution globally. In the US, lawmakers passed the Inflation Reduction Act in 2022, which included stipulations for tackling climate pollution to improve conditions for people and animals across the country. These included grants to help reduce greenhouse gases such as methane emissions.

Many have argued that the question is not whether it is possible to alleviate pollution of the environment; rather, it is whether we realize the urgency and are willing to sacrifice to do it. As a result, they have called for better approaches to be taken to preserve the environment and biodiversity for the common well-being of generations to come.

Principal Terms

acid rain: rainfall containing nitric or sulfuric acid, caused by the release of nitrogen oxide or sulfur dioxide into the air

chemical pollutants: harmful chemicals manufactured and released into the environment, where they frequently contaminate ecosystems

chlorofluorocarbons (CFCs): a group of very stable compounds used widely since their development in 1928 that, once risen into the stratosphere, cause ozone depletion

greenhouse effect: the process by which certain gases, such as carbon dioxide and methane, trap sunlight energy in the atmosphere as heat, resulting in global warming as more gases are released to the atmosphere by human activities

ozone layer: the ozone-enriched layer of the upper atmosphere that filters out some of the sun’s ultraviolet radiation, which causes skin and other types of cancer

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