英语听力：自然百科 秋日黄石公园 Autumn—17

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But just as Yellowstone reveals the complexity¹ of life, it also exposes its fragility. On its lofty ridges², there are signs that all is not well with the whitebark pine. From above, it looks like autumn colors have come to an evergreen³ world. 

 

But these trees are dying. Small eruptions⁴ of resin⁵ dot the trunk of the tree—evidence of an invasion. Tiny beetles⁶ are chewing through the tree’s outer defences. Once inside, they lay eggs that turn into larva that eat the tree. Each tree that is lost threatens all the animals that rely on its autumn bounty⁷. 

 

The only thing that can stop the beetles is extreme cold. But recently, the climate here has been getting warmer and warmer. No national park can protect against that.

 

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