Word: km
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Dates: during 2000-2000
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...benign. Dams and reservoirs permit unimaginable numbers of people to inhabit forbiddingly arid regions--as well as floodplains where cities would be washed away without upstream protection. Sacramento, Calif., for example, is dryer than North Africa, but the Sacramento River, on whose banks it sits, spread 30 miles (50 km) wide during the wettest California winter on record, in 1862, before dams and levees tamed the river. Dams produce more clean energy than nuclear reactors. Irrigation agriculture, largely dependent on reservoirs, grows 40% of the world's food on a much smaller fraction of its farmland...
...ecosystem's intricate, interdependent webs of life are hard to restore once they have become frayed. The U.S. is learning this lesson in its multibillion-dollar effort to halt the decline of the Everglades, the "river of grass" that once covered 4,500 sq. mi. (11,700 sq km) in Florida. Having spent much of this century channeling, damming and diverting Everglades water for urban and agricultural use, state and federal politicians have watched with growing alarm as these alterations threw the ecosystem into a tailspin. Wading-bird populations have plummeted; sport and commercial fish catches have fallen...
Until just a few decades ago, land was winning. By the time of the Louisiana Purchase, the Gulf had retreated some 60 miles (100 km) south of New Orleans. The Mississippi's immense burden of flaked-off topsoil (originating mainly from its big western tributary, the Missouri) overmatched the rising Gulf. The unrestrained river episodically changed course, laying new land from Biloxi to Houston. Over 7,000 years, the Mississippi River created a new piece of continent the size of New Jersey...
...just three or four decades, we had managed to reverse one of nature's most remarkable geomorphological phenomena. By the 1980s coastal Louisiana, instead of expanding in size, was disappearing under the Gulf at a rate of nearly 40 sq. mi. (100 sq km) a year. (The rate of land loss has declined somewhat since then; no one seems sure...
...space in the 1960s. Only in the past decade have they been made small enough to fit inside a car. The NECAR4, based on a Mercedes-Benz A-class compact sedan, accommodates five people plus luggage, reaches speeds of 90 m.p.h. (145 km/h) and goes about 280 miles (450 km) between fill-ups. "It's comparable," says Ferdinand Panik, head of DaimlerChrysler's Fuel Cell Project, "to the impact the microchip had on computer technology...