墨尔本PTE素材库——Beaver Dams Strengthened by Humans Help Fish Rebound

墨尔本PTE素材库——Beaver Dams Strengthened by Humans Help Fish Rebound

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这段Podcast讲解了为了获取皮毛，海狸鼠被过度猎杀，从而导致了当地鱼群数量的下降；同时由于环境的恶化，海狸鼠无法获取足够强度的木材来修建堤坝，而导致鱼群数量一直无法恢复。那么科学家们做出了怎样的努力来帮助海狸鼠们呢？

这就是你听完这段录音需要回答的问题啦！

澳大利亚语言学院整理的PTE素材库，旨在用最贴近PTE Official Question Criteria的材料，给大家提供一系列不同话题的PTE素材！让大家可以在平时练习听力、阅读、口语、写作，不至于陷入“题荒”的境地！

这段材料有大量的科学词汇，光用来累积词汇也是很好的。当然也可以用于练习Dictation和Re-tell Lecture，如果直接阅读Full Transcript的话也是一篇很好的阅读练习材料。

大家需要关注的关键信息是：

• What’s the relationship between beavers and local fishes?
• How are the scientists planning to help local beavers?

【Key Vocabulary】

flourish v. 繁荣，兴旺

timber n. 原木，木材

fur industry 皮草产业

salmon n. 鲑鱼，大马哈鱼

steelhead trout 红鳟鱼

beaver n. 海狸鼠

restoration n. 恢复，复位

empirical adj. 经验主义的，实证的

alter v. 改变

watershed n. 流域，分水岭，集水区

flimsy adj. 脆弱的，浅薄的，不周密的，容易损坏的

integrity  n. 完整

conventional adj. 传统的，常见的

Full Transcript

Fish flourished in creeks in which human engineers helped shore up beaver dams made weak by poor timber availability.

In the early 19th century the fur industry reached what was then known as the Oregon Territories. Lewis and Clark found massive numbers of Pacific salmon and steelhead trout there, swimming among the beaver dams scattered across the Columbia River Basin.

But in an effort to starve American interests, Canada’s Hudson’s Bay Company tried to create a “fur desert” by killing off as many fur-bearing animals as they could. As a result, beavers had all but disappeared from the area by the year 1900. And once the beavers and their dams were gone, fish populations dropped.

Today, steelhead trout numbers in the region continue to fall. But scientists and government agencies are working to restore their habitats.

“We’re looking for restoration approaches in these areas to recover ESA-listed species, but we really don’t know what works and what doesn’t.” Nick Bouwes of the environmental consulting firm Eco Logical Research and Utah State University.

He says that the U.S. spends a billion dollars each year to restore watersheds, but without any real empirical information to guide those efforts. So Bouwes and his team tested the idea that by helping beavers, they could help the fish.

Dams naturally alter the flow of streams, providing fish with a variety of suitable habitats. But the watersheds have become so degraded that there’s not enough woody vegetation available for the beavers to build strong dams. The flimsy ones they do build get washed away whenever there’s a big storm.

“The idea was, can we reinforce these dams so that they maintain their integrity during high flows, and can be maintained by beavers to capture that sediment, to reconnect that floodplain?”

For seven years, the researchers compared Bridge Creek, which had lots of artificially strengthened dams, to Murderer’s Creek, which had none. And in Bridge Creek, the fish flourished—despite the view held by some that beaver dams are bad for fish. The results are in the journal Scientific Reports. [Nicolaas Bouwes et al, Ecosystem experiment reveals benefits of natural and simulated beaver dams to a threatened population of steelhead (Oncorhynchus mykiss)]

“Beavers, they’re really good at making a mess of a system, and it’s that messiness that’s exactly what we’re looking for, by creating more complex fish habitat.”

And costing just $11,000 for each kilometer of stream, artificial dam reinforcements are much cheaper than conventional restoration methods—since the beavers do most of the work for us. And that is a dam good deal.

—Jason G. Goldman

(Source: http://www.scientificamerican.com/podcast/episode/beaver-dams-strengthened-by-humans-help-fish-rebound/)