科学美国人60秒:Beaver Dams Strengthened by Humans Help Fish Rebound

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.

19世纪初期，皮毛生产行业在俄勒冈州兴起，以生产海狸皮毛闻名。在哥伦比亚河盆地的海狸水坝游泳时，Lewis和Clark在这儿发现了大量的太平洋鲑鱼和和虹鳟鳟鱼。

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.

但为了争夺美国利益，加拿大哈德逊湾公司试图通过尽可能的杀死更多皮毛动物，来创建一个“皮毛沙漠”，结果到1900年，海狸消失殆尽。并且一旦海狸和它们建造的水坝都消失了，鱼类的数量将会下降。

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

如今，该地区虹鳟的数量继续下降。但科学家和政府机构正在共同努力修复它们的栖息地。

"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.

“在这些地区，我们正在寻找修复方法，以恢复这些物种。但我们真的不知道什么方法可行，什么方法不可行。”环境咨询公司生态逻辑研究和犹他州立大学的Nick Bouwes表示。

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.

他表示每年美国花十亿美元来修复流域，但没有任何实际经验来指导这些工作。因此 Bouwes和他的团队对通过帮助海狸，进而帮助鱼类的设想进行了验证。大坝自然改变了源源溪流，从而为鱼类提供各种合适的栖息地。但水域的恶化使得没有足够的木本植物供海狸用来建造坚固的水坝。每当有大风暴时，它们所建造的脆弱的水坝就会被冲走。

"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?"

“当时的想法是，我们是否可以加固这些海狸坝，这样有洪流时就可以保存它们的完整性，并且是否海狸可以对其进行维护，截留沉积物，使其与河漫滩重新连接起来。”

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)]

七年来，研究人员们将两者进行了对比，前者拥有许多人为加固的大坝，而后者一座也没有。在Bridge Creek，鱼类生长繁荣——尽管一些人所持的观点为：海狸建造的水坝对鱼类有害。该项研究结果发表在《科学》杂志上。

"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."

“海狸，它们真的很擅长把一个系统弄得一团糟。并且，这些混乱正是我们所寻找的。通过创建更复杂的鱼类的栖息地。”

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.

并且，每公里溪流整治仅需花费11,000 美元，人工加固大坝比传统修复方法更加便宜。因为海狸为我们做了大部分的工作。并且这是一个非常好的交易。

—Jason G. Goldman

Jason G. Goldman报道。