Points of View: The Three Gorges Dam

China’s Yangtze River is the third longest river in the world after the Nile and the Amazon. The Yangtze River flows through the Three Gorges region of central China, which is famous for its natural beauty and historical sites. For thousands of years, the area’s sheer cliffs have inspired paintings and poems. This idyllic region seems like the sort of place that would be protected as a park or reserve. But in fact, it is the site for the Three Gorges Dam—the largest hydroelectric dam project in the world. Now that the dam is fully operational, the Yangtze River forms a reservoir that is 595 km (370 mi) long—as long as Lake Superior. In other words, the reservoir is about as long as the distance between Los Angeles and San Francisco!

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Making a Difference: Dr. E. O. Wilson: Champion of Biodiversity

Dr. E.O. Wilson

Dr. Wilson with one of his favorite subjects—ants.

Dr. Edward Osborne Wilson deserves some of the credit for the fact that this book includes a chapter called “Biodiversity.” Just a few decades ago, the word biodiversity was used by few scientists and wasn’t found in many dictionaries. Dr. Wilson has helped make the concept and value of biodiversity widely recognized, through his extensive research, publishing, organizing, and social advocacy.

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Society and the Environment: Lost Populations: What Happened?

Easter Island stone figure

These large stone figures found on Easter Island were made by a civilization that has disappeared.

At various points in human history, entire populations have disappeared and left mysterious remains such as the Egyptian pyramids and the Anasazi pueblos in the southwestern United States. Why did these people and their civilizations disappear? Archeologists sometimes find evidence that environmental destruction was one of the reasons the populations disappeared.

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Society and the Environment: Conserving Top Predators


Successful reintroduction of wild wolves in the American West has led to significant changes in the ecosystem.

Return of Wolves
By the early 1900s wolves had been virtually eliminated from most of their native range in the United States. They were hunted vigorously because they killed livestock. In Yellowstone National Park, wolves were hunted to extinction.

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Society and the Environment: Hurricane Katrina and New Orleans

New Orleans

Over 80 percent of New Orleans was submerged by floodwater when Hurricane Katrina struck in August, 2005.

The city of New Orleans was built on the Mississippi River Delta, about 160 kilometers upriver from the Gulf of Mexico. This city is vulnerable to flooding from the Mississippi River, Lake Pontchartrain to the north, and heavy rainfall from tropical storms. In addition, hurricanes that pass over the coast can create storm surges—waves up to 9 meters.

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Making a Difference: A Little Piece of Cajun Prairie

collecting seed

Charles Allen is shown here collecting seeds from a compass plant at a Cajun prairie remnant. The leaves of the compass plant face east to catch the sun.

Cajun prairie is a distinct grassland, named for the settlers who lived there. It once covered more than 2.5 million acres of southwest Louisiana. Today, only about 100 acres of Cajun prairie remain. If the work of two biologists and many volunteers pays off, however, a little piece of Cajun prairie will always exist in Louisiana.

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Society and the Environment: Changing Seas

catching fish

Overfishing from higher trophic levels means commercial fishers must harvest from lower trophic levels to meet demand.

Most of the food we eat comes from agriculture and farming, but we also rely on the fishing industry. About 15% of the animal protein consumed in the world comes from fish and other marine and aquatic organisms. But many fish species have been overharvested. The swordfish and cod fisheries of the North Atlantic and the salmon fishery off the northwestern coast of the United States are examples of depleted fisheries. In many parts of the world, sharks are disappearing rapidly because of the demand for shark fin soup. Some fisheries now contain so few fish that harvesting them is not economical. And the size of some of the harvested fish that remain are now smaller because they don’t survive long enough to grow.

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Making a Difference: Butterfly Ecologist

Dr. Alfonso Alonso

Dr. Alfonso Alonso examines a monarch as part of his efforts to understand its ecology.

Imagine millions of butterflies swirling through the air like autumn leaves, clinging in tightly packed masses to tree trunks and branches, and covering low-lying forest vegetation like a luxurious, moving carpet. According to butterfly ecologist Alfonso Alonso, this is quite a sight to see.

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Society and the Environment: Ocean Currents

rubber duckie

A shipment of rubber ducks lost at sea helped scientists study ocean current movements.

Ocean currents are important in transporting heat, water, nutrients, pollutants, and organisms around the world. Even though they are important, ocean currents have been hard to study. Scientists used to drop labeled bottles in the oceans in different places and then recorded where they were picked up. Now, oceanographers attach transmitters to drifters. These transmitters send their position to satellites overhead, providing scientists with information that is helpful in a variety of ways, from protecting endangered species to making important decisions with far-reaching effects.

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Society and the Environment: Bats and Bridges

Congress Avenue bridge bats

Mexican free-tailed bats leave their roost under the Congress Avenue Bridge in Austin, Texas, to hunt for insects.

A large colony of Mexican free-tailed bats lives under the Congress Avenue Bridge in Austin, Texas. These bats eat millions of insects a night, so they are welcome neighbors. Communities around the country and around the world have learned of the bats and have asked Austin for help in building bat-friendly bridges. But all that the people of Austin knew was that the bats appeared after the Congress Avenue Bridge was rebuilt in the 1980s. What attracted the bats? The people of Austin had to do a little research.

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