It's dinnertime but there's no food in the house, so you get in your car and drive to the grocery store. You walk the aisles browsing for something to buy. You pick up chicken and a pre-made salad, then return home to enjoy your meal. Consider the ways your seemingly simple trip to the market affected the environment.
Driving to and from the store contributed carbon dioxide to the atmosphere. The electricity required to light the store was powered by coal, the mining of which ravaged an Appalachian ecosystem. The salad ingredients were grown on a farm treated with pesticides that washed into local streams, poisoning fish and aquatic plants (which help keep the air clean). The chicken was grown on a massive factory farm a long distance away, where animal waste produced toxic levels of atmospheric methane. Getting the goods to the store required trucks, trains and more trucks -- all of which emitted carbon.
Even the smallest human actions initiate environmental change. How we heat our homes and power our electronics, how we get around, what we do with our garbage, where our food comes from -- all of these put a strain on the environment beyond what it's designed to support.
Taken at a societal level, human behavior changes the environment in dramatic ways. The Earth's temperature has increased by one degree Fahrenheit since 1975 [source: National Geographic]. The polar ice caps are shrinking at a rate of 9 percent a decade [source: National Resources Defense Council].
We hurt the environment in more ways than you could possibly imagine. Misguided construction, irrigation and mining can deface the natural landscape and disrupt important ecological processes. Aggressive fishing and hunting can deplete entire stocks of species. Human migration can introduce alien competitors to native food chains. Greed can lead to catastrophic accidents and laziness to environmentally destructive practices.
So what are the worst offenders? Here are the top 10.
10. Dam Follies
Sometimes public works projects don't work out so well for the public. Meant to generate clean energy, dam projects in China have ravaged their surroundings by flooding cities and environmental waste sites and increasing the risk of natural disasters.
The re-routed river has also greatly increased the risk of landslides along its banks, home to hundreds of thousands of people. It's estimated that another half-million people might be displaced by landslides along the Yangtze by the year 2020 [source: International Rivers]. And landslides choke rivers with silt, further depleting the ecosystem.
Scientists have recently linked dams to earthquakes. The Three Gorges reservoir is built atop two major fault lines, and hundreds of small tremors have occurred since it opened. Scientists have suggested that the catastrophic 2008 earthquake in Sichuan Province, which left 80,000 people dead, was exacerbated by water build-up at the Zipingpu Dam, less than half a mile from the earthquake's primary fault line. The phenomenon of dams causing earthquakes, known as reservoir-induced seismicity, is caused by water pressure building up underneath the reservoir, which in turn increases pressure in the rocks and acts to lubricate fault lines already under strain. An earthquake caused by Three Gorges Dam would present a humanitarian disaster of untold proportions.
"There are plenty of fish in the sea" might not be so true anymore. Mankind's appetite for seafood has emptied our oceans to such a degree that experts worry many species can't replenish themselves.
According to the World Wildlife Federation, the global fishing fleet is 2.5 times larger than what our oceans can support. More than half of the world's fisheries are already gone, and one-quarter are "overexploited, depleted or recovering from collapse." Ninety percent of the ocean's large fish -- tuna, swordfish, marlin, cod, halibut, skate and flounder -- have been fished out of their natural habitats. It's estimated that unless something changes, stocks of these fish will disappear by 2048 [source: Worm et al.].
Advances in fishing technology are the main culprit. Today's commercial fishing boats are basically floating factories equipped with fish-finding sonar. They drop massive nets the size of three football fields that can sweep up an entire school of fish in minutes. Once a commercial fishing boat stakes a claim on an area, it's estimated that the fish population will decline by 80 percent within 10 to 15 years [source: World Wildlife Federation].
8. Invasive Species
We've been moving species around the globe since the dawn of the Age of Exploration. While bringing your favorite pet or plant along may make a new place feel a bit more like home, it can also throw the natural balance out of order. Introducing invasive flora and fauna has proven to be one of the most damaging things mankind has done to the environment.
In the United States, 400 of the 958 species listed as endangered under the Endangered Species Act are considered at risk because of competition with alien species [source: Pimentel, Zuniga and Morrison]. The Dodo bird is a good example. The Dodo went the way of the dino in part because cats, rats and pigs brought by European sailors to the Americas feasted on its nest and eggs. The wingless bird couldn't defend itself.
The problem of invasive species is most pronounced with non-vertebrate species. In the first half of the 20th century, a fungus from Asia wiped out more than 180 million acres (73 million hectares) of American chestnut trees. Blight such as this causes a domino effect: Ten moth species that depended on chestnut trees for survival became extinct as a result [source: Simberloff].
7. Coal Mining
The greatest risk to the environment presented by coal is climate change, but mining for the valuable resource endangers local ecosystems as well.
Market realities create grave risks to mountains in coal -- heavy regions, especially in the United States. Coal is a cheap source of energy - one megawatt of energy produced by coal costs $20 to $30, versus $45 to $60 for one megawatt of energy produced from natural gas [source: Moyers]. And one-quarter of the world's coal reserves are in the U.S.
Two of the most environmentally destructive forms of mining are mountain top removal and strip mining. In mountain-top removal mining, up to 1,000 feet (305 meters) might be shaved off the peak in order to scoop out the coal inside. The mountain is hollowed out as minerals are extracted. Strip mining is used when the coal is closer to the surface of the mountain. The top layers of the mountain face -- including trees and any creatures living in them -- are scraped away to extract valuable minerals.
Each practice lays waste to everything in its path. Vast swaths of old-growth forest are removed and dumped in nearby valleys. It's estimated that more than 300,000 acres (121,405 hectares) of hardwood forest in West Virginia have already been destroyed by mining [source: PBS]. By 2012, the Environmental Protection Agency estimates that an additional 2,000 square miles (5,180 square kilometers) of Appalachian forest will disappear through mountain top removal and strip mining [source: Goldenberg].
The question of what to do with the refuse compounds the environmental consequences. Usually the mining company simply dumps the rocks, trees and wildlife in a nearby valley. In West Virginia, Kentucky, Virginia and Tennessee, more than 1,000 miles (1,609 kilometers) of streams have been buried by strip mine refuse [source: PBS]. Not only does this destroy the natural ecosystem of the mountain and stream, it also dries up larger rivers and strangles ecosystems that feed on the higher-elevation streams. Industrial waste from the mine washes into river beds. In West Virginia, more than 75 percent of streams and rivers are polluted by mining and related industries [source: PBS].
6. Human Accidents
While most of the ways humans damage the environment occur over the course of years, some events can happen in an instant -- an instant with long-reaching consequences.
The 1989 Exxon Valdez spill in Prince William Sound, Alaska has had a lasting impact. Releasing almost 11 million gallons of crude oil into an otherwise unspoiled stretch of wilderness, the accident killed an estimated 250,000 seabirds, 2,800 sea otters, 300 harbor seals, 250 bald eagles, up to 22 killer whales and billions of salmon and herring eggs [source: Exxon Valdez Oil Spill Trustee Council]. At least two species, Pacific herring and pigeon guillemots, have not recovered from the disaster. As recently as 2006, scientists continued to find traces of oil on beaches around the Sound [source: Weise].
It's too soon to estimate the damage to wildlife caused by the BP oil spill in the Gulf of Mexico, but the scope of the disaster appears unmatched in American history. At its peak, 60,000 barrels of oil, or 2.5 million gallons (9.5 million liters), leaked into the Gulf every day -- the highest volume spill in American history. Most early estimates place the damage to wildlife below that of the Exxon Valdez because of the lesser density of local species in the Gulf compared to Prince William Sound. Regardless, there's no question that traces of the spill will be around for years to come.
America has long been considered the land of the automobile, so it should come as no surprise that one-fifth of all greenhouse gas emissions in the U.S. comes from cars. There are more than 232 million vehicles on the roads in this country -- only a tiny portion of which are electric-powered or hybrid. And an average American car consumes 600 gallons (2271 liters) of gasoline a year [source: Environmental Defense Fund].
A single car emits 12,000 pounds -- that's right, pounds -- of carbon dioxide (or 5443 kilograms) every year in the form of exhaust [source: Environmental Defense Fund]. It would take 240 trees to offset that amount. In America, cars emit around the same amount of carbon dioxide as the country's coal-burning power plants. In 2004, U.S. cars and light trucks emitted 314 million metric tons (346 million tons) of carbon, which is one third of the nation's total carbon dioxide output. It would take a 50,000-mile-long (80,467-kilometer-long) coal train -- equal to 17 times the distance between New York and San Francisco -- to match the amount of carbon released into the environment by American cars every year. [source: Environmental Defense Fund].
Combustion in the car's engine produces fine particles of nitrogen oxides, hydrocarbons and sulfur dioxide. In high quantities, these chemicals interfere with the human respiratory system, causing coughing, choking and reduced lung capacity. Cars also generate carbon monoxide, a poisonous gas formed by combustion of fossil fuels that blocks the transport of oxygen to the brain, heart and other vital organs.
And then there's all the oil required to keep our cars moving. Drilling for oil has significant environmental consequences in its own right. Land-based drilling displaces local species and, in remote regions, requires that roads be built out of dense forest. Marine drilling and shipping not uncommonly results in spills like the BP Gulf of Mexico catastrophe -- there have been a dozen spills of more than 40 million gallons (151,416,471 liters) across the world since 1978. Dispersants used to mitigate the effects can also kill marine life.
4. Unsustainable Agriculture
One common trend emerges in all the ways mankind hurts the environment: We fail to plan for the future. Nowhere is this seen as much as in how we raise our food.
According to the U.S. Environmental Protection Agency, current farming practices are responsible for 70 percent of the pollution in the nation's rivers and streams. Runoff of chemicals, contaminated soil and animal waste from farms has polluted more than 173,000 miles (278,417 kilometers) of waterways [source: Horrigan et al.]. Chemical fertilizers and pesticides increase nitrogen levels and decrease oxygen in the water supply. Even before the BP Oil Spill, the Gulf of Mexico suffered a "dead zone" the size of New Jersey from industrial run-off from factories and farms along the Mississippi River.
Pesticides used to protect crops from predators endanger bird and insect populations. For example, the number of honeybee colonies on U.S. farmland dropped from 4.4 million in 1985 to less than 2 million in 1997 [source: Horrigan et al.]. Exposure to pesticides weakened the bees' immune systems, making them more vulnerable to natural enemies.
Large scale industrial agriculture also contributes to global warming. The vast majority of meat in the world comes from industrial farms. On any given farm, tens of thousands of livestock are concentrated in small areas for economy of scale. Factory farms emit harmful gases from unprocessed animal waste, including methane, which contributes to global warming. Livestock literally wade in pools of their own waste, which ravages the soil and nearby forests -- not to mention creating a ghastly odor.
There was a time, not that long ago, when the majority of the land on this planet -- almost half of the United States, three-quarters of Canada and nearly all of Europe -- was covered in forests. Today, the world's forests are disappearing before our eyes.
The United Nations estimates that more than 32 million acres (12,949,941 hectares) of forest are lost each year, including 14.8 million acres (5,989,348 hectares) of primary forest -- lands not occupied or affected by human beings [source: FAO]. Seventy percent of the planet's land animals and plants live in forests, and the loss of their homes threatens the existence of an untold number of species [source: National Geographic].
The problem is particularly acute in tropical forests, especially rainforests. Rainforests cover 7 percent of the Earth's land area and provide a home to half of all the species on the planet [source: Lindsey]. At the current rate of deforestation, scientists estimate that the world's rainforests could disappear in 100 years [source: National Geographic].
Deforestation contributes to global warming. Trees absorb greenhouse gases -- so fewer trees means larger amounts of greenhouse gases entering the atmosphere. They also help perpetuate the water cycle by returning water vapor to the atmosphere. Without trees, former forests can quickly become barren deserts, leading to more extreme temperature swings. When forests are burned down, carbon in the trees is released, contributing to global warming. Scientists estimate that Amazonian trees contain the equivalent of 10 years worth of greenhouse gases produced by humans [source: NASA].
Poverty is a root cause of deforestation -- most tropical forests are in Third World countries -- as are policies to encourage economic development in undeveloped areas. Loggers and farmers drive deforestation. In most cases, a subsistence farmer, crowded into pioneer lands by overpopulation, will cut down trees for a farm plot.
The farmer typically burns the trees and vegetation to create a fertilizing layer of ash. This is called slash-and-burn farming. The risks of erosion and flooding are increased. Soil nutrients are lost, and in a few years, the land often proves unable to support the very crops for which the trees were cut down [source: Lindsey].
2. Global Warming
The average surface temperature of the Earth has increased by 1.4 degrees Fahrenheit (0.8 degrees Celsius) in the last 130 years, and by 1 F (0.56 C) since 1975 [source: National Geographic]. Global ice caps are melting at an alarming rate - since 1979, more than 20 percent of the global ice cap has disappeared. Sea levels are rising, causing flooding and, according to a bevy of scientists, influencing catastrophic natural disasters around the globe.
Global warming is caused by the greenhouse effect, in which certain gases trap heat from the sun in the atmosphere. Since 1990, yearly emissions of greenhouse gases have gone up by about 6 billion metric tons (6.61 billion tons) worldwide, an increase of more than 20 percent [source: National Geographic].
The gas most responsible for global warming is carbon dioxide, which accounts for 82 percent of all greenhouse gases in the United States [source: Energy Information Administration]. Carbon dioxide is produced through combustion of fossil fuels, mostly in cars and coal-powered factories. In 2005, global atmospheric concentrations of the gas were 35 percent higher than they were before the Industrial Revolution [source: Environmental Protection Agency]. America's transportation and industrial sectors each account for around 30 percent of the country's greenhouse gas emissions [source: Pew Climate].
Global warming could lead to natural disasters, large-scale food and water shortages and devastating outcomes for wildlife. According to the Intergovernmental Panel on Climate Change, the sea level could rise between 7 and 23 inches (17.8 and 58.4 centimeters) by the end of the century. Rises of just 4 inches (0.9 meters) of sea level, and much of the world's population lives near coastal areas. More than a million species face extinction from disappearing habitat, changing ecosystems and acid rain.
Overpopulation "is the elephant in the room that nobody wants to talk about," says Dr. John Guillebaud, professor of family planning and reproductive health at University College in London. "Unless we reduce the human population humanely through family planning, nature will do it for us through violence, epidemics or starvation." [source: Guardian]
The world's population has grown from 3 billion to 6.7 billion in the past 40 years. Seventy-five million people -- the equivalent of the population of Germany -- are added to the planet every year, or more than 200,000 people every day [source: peopleandplanet.net]. The Earth's population is projected to exceed 9 billion by the year 2050.
In that same time period, the population of the U.S. grew from 200 million to more than 303 million. By 2050, it's projected to be 420 million.
More people means more waste, more demand for food, more production of consumer goods, more need for electricity, cars and everything. In other words, all the factors that contribute to global warming will be exacerbated.
Increased demand for food will force farmers and fishermen to exploit already-fragile ecosystems. Forests will be cleared as cities and suburbs expand, and to make room for more farmland. Strains on endangered species will increase. In rapidly developing countries such as China and India, increasing energy demands are expected to accelerate carbon emissions. In short, more people means more problems.
For more on environmental issues, visit the links on the following page.
Lots More Information
- Importance of Biodiversity Puzzles
- Fact or Fiction: Living Off the Grid Quiz
- Renewing the Grid Pictures
- Top 10 Natural Building Materials
- 10 Sustainable Buildings
- Environmental Defense Fund, "Cars by the Numbers." March 20, 2007. (Accessed online August 22, 2010.) http://www.edf.org/article.cfm?ContentID=6083
- U.S. Environmental Protection Agency, "Carbon Dioxide." March 2010. (Accessed online August 22, 2010.) http://www.epa.gov/climatechange/emissions/co2.html
- Goldenberg, Suzanne, "US Scientists Demand Government Ban on Mountaintop Mining." Guardian UK. January 7, 2010. (Accessed online August 21, 2010.) http://www.guardian.co.uk/environment/2010/jan/07/us-scientists-mountaintop-mining
- Horrigan, Leo, Robert S. Lawrence, and Polly Walker, "How Sustainable Agriculture Can Address the Environmental and Human Health Harms of Industrial Agriculture." Environmental Health Perspectives, Volume 110, Number 5. May 2002. http://ehp.niehs.nih.gov/members/2002/110p445-456horrigan/horrigan-full.html
- Independent Lens, "Razing Appalachia." (Accessed online August 22, 2010.) http://www.pbs.org/independentlens/razingappalachia/mtop.html
- Intergovernmental Panel on Climate Change, "IPCC Fourth Assessment Report: Climate Change 2007." 2007. (Accessed online August 24, 2010.) http://www.ipcc.ch/publications_and_data/publications_and_data_reports.htm#1
- International Rivers, "Three Gorges Dam." (Accessed online August 22, 2010). http://www.internationalrivers.org/china/three-gorges-dam
- International Rivers, "China's Three Gorges Dam: A Model of the Past," November 2009. (Accessed online August 22, 2010.) http://www.internationalrivers.org/files/3Gorges_FINAL.pdf
- Lindsey, Rebecca, "Tropical Deforestation." NASA Earth Observatory. March 30, 2007. (Accessed online August 20, 2010.) http://earthobservatory.nasa.gov/Features/Deforestation/
- Moyers, Bill, "The Cost of Coal." August 2, 2002. (Accessed online August 22, 2010.) http://www.pbs.org/now/science/coal.html
- NASA Earth Observatory, "Climate Impacts." (Accessed online August 22, 2010.) http://earthobservatory.nasa.gov/Features/Deforestation/deforestation_update2.php
- National Geographic, "Deforestation." (Accessed online August 21, 2010.) http://environment.nationalgeographic.com/environment/global-warming/deforestation-overview.html
- National Geographic, "Causes of Global Warming." (Accessed online August 21, 2010.) http://environment.nationalgeographic.com/environment/global-warming/gw-causes/
- National Resources Defense Council, "Global Warming Puts the Arctic on Thin Ice." November 22, 2005. (Accessed online August 24, 2010). http://www.nrdc.org/globalwarming/qthinice.asp
- Peopleandplanet.net, "Population and Human Development - The Key Connections." June 21, 2009. (Accessed online August 20, 2010.) http://www.peopleandplanet.net/doc.php%3Fid=199§ion=2.html
- Pimentel, David, Rodolfo Zuniga, and Doug Morrison, "Update on the Environmental and Economic Costs Associated with Alien-Invasive Species in the United States."
- Ecological Economics. 2004. http://ipm.ifas.ufl.edu/pdf/EconomicCosts_invasives.pdf
- Simberloff, Daniel, "Introduced Species: The Threat to Biodiversity & What Can Be Done." Action BioScience. December 2000. (Accessed online August 21, 2010.) http://www.actionbioscience.org/biodiversity/simberloff.html
- U.S. Energy Information Administration, "Greenhouse Gases, Climate Change, and Energy." (Accessed online August 22, 2010.) http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html
- Worm, Boris, Edward B. Barbier, Nicola Beaumont, J. Emmett Duffy, Carl Folke, Benjamin S. Halpern, Jeremy B. C. Jackson, Heike K. Lotze, Fiorenza Micheli, Stephen R. Palumbi, Enric Sala, Kimberley A. Selkoe, John J. Stachowicz, Reg Watson. "Impacts of Biodiversity Loss on Ocean Ecosystem Services." Science. November 2006.
- Volume 314. Number 5800. www.sciencemag.org/cgi/content/abstract/314/5800/787