课程咨询

托福考试网 托福资料下载 托福资讯 0元讲座 水平测试

托福考试练习
新东方在线 > TOEFL > 托福听力 > 正文
托福培训

扫码免费领资料

内含托福全科备考资料

更有免费水平测试及备考规划

托福培训

扫码关注掌握一手留学资讯

回复XDF免费水平测试

录播精讲 直播课HOT

托福听力练习-科学美国人60秒:墨西哥湾死亡地带

2017-05-02 14:26:38来源：科学美国人60秒

点击查看>>科学美国人60秒音频：墨西哥湾死亡地带

　　科学美国人60秒听力练习：墨西哥湾死亡地带

　　科学美国人60秒英文文本

　　This is Scientific American — 60-Second Science. I'm Christopher Intagliata.

　　Every spring, the Mississippi River dumps tens of thousands of tons of nutrient runoff into the Gulf of Mexico. Add temperature, current and wind to that pollution, and you have the Western Hemisphere's largest stretch of oxygen-poor waters—a so-called "dead zone."

　　That dead zone hits the Gulf's famed—and financially important—brown shrimp fisheries. And it does two things: first, the low oxygen slows down the shrimps' growth.

　　"The other thing that happens is what I like to call the burning building effect." Martin Smith, an environmental economist at Duke University. "The shrimp try to avoid the low oxygen so they swim out of these areas of depleted oxygen. As a result they end up kind of aggregating on the edges. They kind of line up when they get outside the deoxygenated waters. And that's why I call it the burning building effect. If you're in a burning building you're running to get out of the fire, you don't keep running when you get outside, you stop and you take a breath."

　　Fishermen flock to where those shrimp "take a breath." And shrimp get caught earlier in the season. So combine these two effects—slower growth and earlier catches—and the result is a haul of more small shrimp, and fewer large and jumbo shrimp. Meaning the price on big shrimp temporarily goes up. Supply and demand, right?

　　Smith and his team studied that link—between the dead zone and a spike in large shrimp prices—using 20 years of shrimp pricing data. Their analysis is in the Proceedings of the National Academy of Sciences.

　　The brown shrimp fishery in the Gulf was once the most valuable in the U.S. Now, Smith says, we can measure the true cost of that nutrient runoff. "We can start to ask questions like, how much does the shrimp industry lose as a result of this problem, and how does that compare to what it would cost to control nutrient flows coming from food production upstream in the Mississippi watershed?" In other words—whether there might be some net economic benefit to keeping the water environmentally protected.

　　Thanks for listening for Scientific American — 60-Second Science Science. I'm Christopher Intagliata.

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人60秒

上一页 1 2 下一页

托福辅导

关注新东方在线托福

托福机经·Official题目练习

考前重点突破·听说读写海量资料

更多资料

关注新东方在线托福，
回复【XDF】获取大礼包

托福辅导
  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加】，回复对应关键字领取学习资料。
更多>>
更多内容

免费获取托福备考大礼包

微信扫描下方二维码 立即领取

托福辅导
更多>>
更多公益讲座>>
更多>>
更多资料
托福TPO 托福听力练习 托福口语练习 托福阅读练习 托福写作练习
我要
反馈 返回
首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10