"Of all the First World countries, the United States is the most polluting nation on Earth" (Drexel University). Throughout history the Earth's climate has changed numerous times, adversely altering the livelihood of people, plants, and animals. Events occurred ranging from ice ages to long periods of warmth. "Beginning late in the 18th century, human activities associated with the Industrial Revolution have also changed the composition of the atmosphere and therefore very likely are influencing the Earth's climate" ("Climate Change"). Although some scientists declare that global warming occurs primarily as a result of natural factors, human factors impair the earth's environment at a greater level, such as pollution of the water, the land, and the atmosphere.
'Pollution is the action of environmental contamination with man-made waste' (Merriam-Webster). The world's water supply becomes polluted with approximately eight million tons of toxic waste each year. Even when the public attempts to become more eco-friendly, the earth still receives harm, which shows when McCully says,Dams, levees and reservoirs often make the problems they are designed to solve worse.
This is particularly true in the context of global warming which is making floods more severe and more common, meanwhile, the hype that hydropower dams are clean and green is undermined by the fact that they are responsible for a significant portion of global emissions of methane, the second most important greenhouse gas after carbon dioxide.
Petroleum contributes to water pollution in many ways. Petroleum pollutes the lakes, oceans, or rivers when an oil spill occurs. The Exxon Valdez proves a tragic example of this type of water pollution. The Exxon Valdez is often considered one of the most devastating man-made environmental disasters ever occurring at sea. The Valdez Sea in Alaska was a home for fish, seals, and sea otters. The Exxon ship spilled eleven...