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第1段
1 .<-NARRATOR:->Now listen to part of a lecture on the topic you just read about.
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第2段
1 .<-FEMALE PROFESSOR:->Actually, fires are a natural part of the ecological cycle, and their role is not just destructive, but also creative.
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2 .That’s why the “let it burn” policy is fundamentally a good one, even if it sometimes causes fires on the scale of the 1988 Yellowstone fire.
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3 .Let’s look at what happened after the ’88 fire.
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第3段
1 .First, vegetation. As you might imagine, scorched areas were in time colonized by new plants.
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2 .As a matter of fact, the plant life in Yellowstone became more diverse, because the fire created an opportunity for certain plants that could not grow otherwise.
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3 .For example: areas where the trees had been destroyed by the fire could now be taken over by smaller plants that needed open, unshaded space to grow.
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4 .And another example: seeds of certain plant species won’t germinate unless they’re exposed to very high levels of heat, so those plants started appearing after the fire as well.
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第4段
1 .It’s a similar story with the animals. Not only did their populations recover, but the fire also created new opportunities.
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2 .For instance, the small plants that replaced trees after the fire created an ideal habitat for certain small animals like rabbits or hares;
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3 .and when the rabbits and hares started thriving, so did some predators that depended on them for food.
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4 .So, certain food chains actually became stronger after the fire than they were before.
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第5段
1 .And last, fires like the ’88 Yellowstone fire would be a problem for tourism if they happened every year;
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2 .but they don’t. It was a very unusual combination of factors that year—low rainfall, unusually strong winds, accumulation of dry undergrowth—that caused the fire to be so massive.
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3 .This combination has not occurred since—and Yellowstone as not seen such fires since 1988.
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4 .Visitors came back to the park the next year and each year after that.
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