Humans burn fuels, produce wastes, and use large amounts of fertilizers, pesticides, and other chemicals. These by-products of industrialization end up in the environment and are often harmful to living organisms. The condition of water-dwelling animals is in fact often a good measure of the condition of the environment; their demise suggests that something may be wrong in their habitat. Figure 5.…
Some 100,000 dams regulate America's rivers and creeks. Of the major rivers in the lower 48 states (those more than 600 miles in length), only the Yellowstone River still flows freely. In fact, University of Alabama ecologist Arthur Benke notes that it is difficult to find any river in the United States that hasn't been dammed or channeled. Dams epitomized progress, American ingenuit…
The Aral Sea is bounded by Uzbekistan and Kazakhstan, and was once the fourth-largest lake in the world. However, over the past 30 years, the lake has lost 60 percent of its water and shrunk to half its original area. This is due to the long practice of diverting water from the Amu-Darya and the Syr-Darya, two rivers that feed the lake, for irrigation and agriculture. With water loss, the lake has…
Worldwide, humans obtain 16 percent of their animal protein from fish. As the human population explodes, the fishing industry has tried to keep up with demand. Up to a certain point, fishermen are able to catch more fish without damaging the ecological balance. This is known as the maximum sustainable yield. Catches beyond the maximum sustainable yield represent overfishing. Overfishing removes fi…
Numerous aquatic ecosystems have been degraded by invasive species. The primary source of aquatic invasive species has traditionally been ship ballast water, which is generally picked up in one location and released in another. In San Francisco Bay alone, it is estimated that a new invasive species becomes established every 14 weeks through ballast water. Invasive species are also established thro…
Numerous aquatic species are endangered in the United States. In fact, Figure 5.12 shows that the biological groups with the greatest proportion of endangered species—freshwater mussels, crayfishes, amphibians, and freshwater fishes—are all aquatic. The U.S. also possesses some of the most diverse freshwater fauna in the world, including 29 percent of the world's freshwater mu…
The Lacey Act was originally passed in 1900 and is the oldest wildlife conservation law in the United States. The Lacey Act prohibits interstate and international trade in wildlife that has been collected or exported illegally. In 1999 the U.S. Fish and Wildlife Service processed 1,476 cases under the Lacey Act. These included illegal commerce in endangered species, illegal hunting, and illegal ha…
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