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Important vocabulary word: an·thro·po·gen·ic (adjective)
1. Caused by humans: anthropogenic degradation of the environment.
This course guide will introduce you to a variety of resources for selecting a topic and for doing research on your human impact research project. Use the APA Citation Help area of this guide for assistance on citing your sources.
Cane Toads were introduced to Australia with the aim of controlling a sugar cane pest, but they over-multiplied and became a serious problem in the Australian ecosystem. You will be viewing the humorous but also serious documentary, Cane Toads: The Conquest this semester. See the Videos page on this guide.
"Top Ten Ways Man is Destroying the Environment" by Matt Schwarzfeld. Originally posted on the Discovery.com's Curiosity Blog.
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. 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.
Top ten list of the worst offenders:
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.
2. Global Warming
Global warming is caused by the greenhouse effect, in which certain gases trap heat from the sun in the atmosphere. 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.
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. 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 (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 (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.
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 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 (Horrigan, et. al). Exposure to pesticides weakened the bees' immune systems, making them more vulnerable to natural enemies.
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 (Environmental Defense Fund).
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 (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.
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, 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.
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.
"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 Foundation, 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 technolgoy 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 ( World Wildlife Foundation).
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 and landslides choke rivers with silt, further depleting the ecosystem (International Rivers website).
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.
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