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[填空题]Say goodbye to the world’s tropical glaciers and ice caps. Many will vanish within 20 years. When Lonnie Thompson visited Peru’s Quelccaya ice cap in 1977, he couldn’t help noticing a school-bus-size boulder that was upended by ice pushing against it. Thompson returned to the same spot last year, and the boulder was still there, but it was lying on its side. The ice that once supported the massive rock had retreated far into the distance, leaving behind a giant lake as it melted away.
Foe Thompson, a geologist with Ohio State University’s Byrd Polar Research Center, the rolled-back rock was an obvious sign of climate change in the Andes Mountains. "Observing that over 25 years personally really brings it home," he says. "Your don’t have to be a believer in global warming to see what’s happening."
41. Thawed ice caps in the tropics.
Quelccaya is the largest ice cap in the tropics, but it isn’t the only one that is melting, according to decades of research by Thompson’s te
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Melting Glaciers
Several glaciers in the Alps have already disappeared in as few as 40 year. In the Patagonian ice fields of Argentina, some glaciers have receded one and one-half kilometers in the last 13 years. In the Himalayan Mountains, glaciers are melting so fast that runoff sometimes floods the surrounding areas. Their fate is a preview of the future of other glaciers on Earth.
The shrinking of the world’s glaciers will have massive consequences for communities that depend on ice melt for their water. In the short-term, these consequences may appear beneficial. For example, extra water from glaciers means that hydroelectric dams will run at maximum power. In the long run, however, the melting of Earth’s glaciers could be catastrophic. Today’s extra hydroelectric power has been stolen from the future. Communities with ample power now may have none after the glaciers have melte
[简答题]The world’s tropical rainforests comprise some 6% of the Earth’s land area and contain more than half of all known life forms, or a conservative estimate of about 30 million species of plants and animals. 61)Some experts estimate there could be two or even three times as many species hidden within these complex and fast-disappearing ecosystems — scientists will probably never know for certain so vast is the amount of study required. Time is running out for biological research. 62)Commercial development is responsible for the loss of about 17 million hectares of virgin rainforest each year—a figure approximating 1% of what remains of the world’s rainforests.
The current devastation of once impenetrable rainforest is of particular concern because, although new tree growth may in time repopulate felled areas, the biologically diverse storehouse of flora and fauna is gone forever. 63)Losing this bountiful inheritance, which took millions of years to reach its present highl
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The world’s tropical rainforests comprise some 6% of the Earth’s land area and contain more than half of all known life forms, or a conservative estimate of about 30 million species of plants and animals. 61)Some experts estimate there could be two or even three times as many species hidden within these complex and fast- disappearing ecosystems — scientists will probably never know for certain so vast is the amount of study required Time is running out for biological research. 62)Commercial development is responsible for the loss of about 17 million hectares of virgin rainforest each year — a figure approximating 1% of what remains of the world’s rainforests.
The current devastation of once impenetrable rainforest is of particular concern because, although new tree growth may in time repopulate felled areas, the biologically diverse storehouse of flora and fauna is gone forever. 63)Losing this bountiful inheritance, which too
