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「大自然的奧妙──看狼群如何改變河川」- How Wolves Change Rivers


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One of the most exciting scientific findings of the past half century has been the discovery of widespread trophic cascades. A trophic cascade is an ecological process which starts at the top of the food chain, and tumbles all the way down to the bottom. And the classic example is what happened in the Yellowstone National Park in the United States when wolves were reintroduced in 1995.
過去半個世紀中最令人興奮的科學發現之一就是大範圍營養瀑布效應的發現。營養瀑布是一個發生在食物鏈頂端,然後一路向下至底層的生態過程。而經典的例子是 1995 年美國黃石國家公園內狼群被重新引入時所發生的事。

Now, we all know that wolves kill various species of animals, but perhaps we're slightly less aware that they give life to many others. Before the wolves turned up, they'd been absent for 70 years, the numbers of deer, because there had been nothing to hunt them, had built up and built up in the Yellowstone Park. And despite efforts by humans to control them, they had managed to reduce much of the vegetation there to almost nothing. They had just grazed it away. But as soon as the wolves arrived, even though they were few in number, they started to have the most remarkable effects.
現在,我們都知道狼會獵殺許多不同種類的動物,但或許我們有些沒注意到牠們振興其他許多物種。在狼群到來前 (牠們已經缺席七十年了),鹿的數量 (因為沒有任何動物去獵食牠們) 在黃石公園內增加再增加。而儘管人類做了努力去控管牠們,牠們仍已將那兒的植被減少到幾乎空無一物。牠們就是把植物吃個精光。但狼群一抵達時--即便牠們的數量稀少--牠們就開始產生最不尋常的影響。

First, of course, they killed some of the deer, but that wasn't the major thing. Much more significantly, they radically changed the behavior of the deer. The deer started avoiding certain parts of the park, the places where they could be trapped most easily, particularly the valleys and the gorges, and immediately those places started to regenerate. In some areas, the height of the trees quintupled in just six years. Bare valley sides quickly became forests of aspen and willow and cottonwood, and as soon as that happened, the birds started moving in: the number of songbirds and migratory birds started to increase greatly. The number of beavers started to increase because beavers like to eat the trees.
首先,想當然爾,牠們殺死一些鹿,但那不是最重要的事。更加值得注意的事是,牠們急遽地改變了鹿的行為。鹿開始避開公園的特定區域 --牠們最容易被困住的地方--特別是溪谷及峽谷,而那些地方馬上開始恢復。在一些區域,樹的高度在僅僅六年內成長五倍。光禿禿的溪谷邊快速變成顫楊及柳樹和棉白楊的森林,那情形一發生,鳥兒就開始遷入:鳴禽和候鳥的數量開始大幅增加。海狸的數量開始增加,因為牠們喜歡吃樹。

And beavers, like wolves, are ecosystem engineers, they create niches for other species. And the dams they built in the rivers provided habitats for otters, and muskrats, and ducks, and fish, and reptiles, and amphibians. The wolves killed coyotes, and as a result of that, the number of rabbits and mice began to rise, which meant more hawks, more weasels, more foxes, more badgers. Ravens and bald eagles came down to feed on the carrion that the wolves had left. Bears fed on it too, and their population began to rise as well, partly also because there were more berries growing on the regenerating shrubs. And the bears reinforced the impact of the wolves by killing some of the calves of the deer.
而海狸--就像狼一樣--是生態系統的工程師,牠們創造利基給其他物種。牠們在河中築的水壩提供棲息地給水獺、麝鼠、鴨子、魚、爬蟲類、以及兩棲動物。狼群獵殺郊狼,而由於那樣,兔子及老鼠的數量開始增加,那就代表有更多隼、更多黃鼠狼、更多狐狸、更多獾。烏鴉和白頭鷹飛下來以狼吃剩的腐肉為食。熊也以此為食,而牠們的數量也開始增加,一部分是因為有更多的莓果生長在新生的灌木上。而熊因為獵殺一些幼鹿而增強了狼所造成的影響。

But here's where it gets really interesting, the wolves changed the behavior of the rivers. They began to meander less; there was less erosion; the channels narrowed; more pools formed more riffle sections, all of which were great for wildlife habitats. The rivers changed in response to the wolves. And the reason was that the regenerating forests stabilized the banks so that they collapsed less often, so the rivers became more fixed in their course.
但這是事情變得真正有趣的地方,狼群改變了河川的行為。它們開始較少蜿蜒;有較少的侵蝕作用;河床變窄;更多的湖泊形成更多的淺灘區段,這全都對野生動物棲息地很有益。河川改變以回應狼群。而原因是恢復的森林穩固河岸,因此它們較不常崩塌,所以河川在它們的路線上變得更穩定。

Similarly, by driving the deer out of some places, and the vegetation recovering on the valley sides, there was less soil erosion because the vegetation stabilized that as well. So the wolves, small in number, transformed not just the ecosystem of the Yellowstone National Park, this huge area of land, but also its physical geography.
相同地,由於將鹿從某些地方趕出去,以及溪谷邊植被的復甦,有較少的水土流失狀況產生,因為植被同樣穩固了溪流邊的土壤。所以數量稀少的狼群改變了不僅黃石國家公園--這廣大面積土地--的生態系統,還改變了它的自然地理。

  • 「出現、到來」- Turn Up

    Before the wolves turned up, they'd been absent for 70 years...
    在狼群到來前 (牠們已經缺席七十年了)...

  • 「對...的反應」- In Response To

    The rivers changed in response to the wolves.
    河川改變以回應狼群。

  • 「把...趕出去」- Drive Out

    Similarly, by driving the deer out of some places, and the vegetation recovering on the valley sides, there was less soil erosion...
    相同地,由於將鹿從某些地方趕出去,以及溪谷邊植被的復甦,有較少的水土流失狀況產生...

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