Official 25 Set 2

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  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
置顶

Assisted Migration

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  • Q4
  • Q5
  • Q6
What is the main purpose of the lecture?
  • A. To explain the government's role in regulating assisted migration

  • B. To discuss ways in which plants and animals adapt to climate change

  • C. To discuss a controversial approach to conserving plant and animal species

  • D. To describe a recently discovered consequence of global warming

显示答案 正确答案: C

我的笔记 编辑笔记

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    NARRATOR:Listen to part of a lecture in a conservation biology class.

    FEMALE PROFESSOR:One consequence of global warming is extinction… there’s compelling evidence that global warming will be a significant driver of many plant and animal extinctions in this century.So, we’re considering various strategies to help some threatened species survive this unprecedented, this warming trend, which, as you know, is caused mainly by greenhouse gases produced by the burning of fossil fuels.Um, the most radical strategy being debated among conservation biologists is “assisted migration.”

    Assisted migration means picking up members of a species—or members of a group of interdependent species— and physically moving, or translocating them…

    …um, translocating threatened species to a cooler place, to higher latitudes or higher elevations, for example.

    [Backtracking]Now, migration’s a natural survival strategy.Over the past two million years, colder glacial periods have alternated with warmer interglacial periods, and so…um, in-in response to these gradual climatic swings, some species have shifted their ranges hundreds of kilometers.So, perhaps you’re wondering: Why not let nature take its course now?Well, we can’t.The main problem is today’s fragmented habitats.During previous interglacial periods, when glaciers retreated, they left behind open land in their wakes.Today, human development has paved over much of the natural world.

    Ecosystems are fragmented.Housing developments, highways, and cities have replaced or sliced through forests and prairies.There’re few corridors left for species to migrate through—without help.

    So, conservationists are trying to save as many species as possible.Now, assisted migration could become a viable part of our rescue strategy, but there are a number of uncertainties and risks.Without more research, we can’t predict if assisted migration will work for any given species.A translocated species could die out from lack of food, for example.At the other extreme, we might successfully translocate a species, but within five or ten years, that species could proliferate and become an invasive species.Like a nonnative plant that chokes out native plants by hogging the nutrients in the soil.Translocated animals can become invasive, too.It happened in Australia.The cane toad was introduced back in 1935 to control an insect pest that was destroying Australia’s sugarcane plantations.But the cane toad itself became a pest and has destroyed much of the wildlife on that continent.

    Also, many species are interdependent, intimately connected to one another, like animals that eat a certain plant, and that plant relies on a certain fungus to help it get nutrients from soil and on a certain insect for pollination.We’d probably have to translocate entire networks of species, and it’s hard to know where to draw the line.And, in addition to all that, it’s not even clear that assisted migration, or any migration for that matter, will help, at least for some species.Earth was already in one of its warm, interglacial periods when we started burning fossil fuels.And in the twenty-first century, global temperatures are expected to rise 2 to 6 degrees.That rate of heating’s far greater than during the last glacial retreat some 12,000 years ago.

    Um, whether to use assisted migration… this debate is mostly within the biology community right now.But the ultimate decision makers— in the United States at least— will be the government agencies that manage natural resources.Assisted migration really needs this level of oversight—and soon.Currently, there’s no public policy on using assisted migration to help species survive climate change.People aren’t even required to seek permits to move plants or invertebrate animals around, as long as they’re not classified as pests.In one case, a group of conservationists has already taken it upon itself to try, on their own, to save an endangered tree, the Florida torreya tree, through assisted migration.

    There’s only about a thousand individual Florida torreyas left, and global warming’s expected to significantly reduce or eliminate this tree’s habitat.So, this conservation group wants to translocate seedlings, Florida torreya seedlings, 500 kilometers north in order to expand the species’ range.The group believes that its effort is justified.[little skeptical, concerned]But I and many other biologists will be watching very closely how this maverick group makes out because, like I said, there could be unintended consequences.

  • 旁白:请听来自保护生物学课堂的一段录音。

    教授:全球变暖带来的后果之一就是物种灭绝,有确凿证据表明全球变暖将成为本世纪动植物物种灭绝的重要驱动因素。因此我们在寻求各种方法来帮助濒危物种幸免于这次空前的全球暖化现象,众所周知,全球变暖是由燃烧化石燃料产生的温室气体造成的。饱受保护生物学家争议的一种激进的方法是“辅助迁移”。

    “辅助迁移”是指从某一物种或者相关联的几个物种中挑选样本群体人为将其迁移。

    比如,将其迁移到较冷、纬度或海拔较高的地区。

    物种迁徙是一种生存策略。在过去的一百万年间,冰期与间冰期交替,气候的冷暖也随之交替。因此,为了适应这种缓慢的气候波动,一些物种将其栖息范围拓宽至数百公里。你或许会想,那为什么不让动物顺其自然地迁徙呢?我们不能这样做。现在的主要问题是动物支离破碎的栖息地。过去在间冰期,冰川消融退去后会裸露出陆地。而今天人类的发展的足迹遍布整个自然界。

    生态系统不再是完整的整体,房屋、高速公路以及城市割裂了森林和草原。如今的物种已经无法在没有人类的帮助下自行寻找栖息地了。

    所以自然资源保护论者在努力尽可能多地拯救物种。现在,辅助迁移可以被看作拯救策略的一部分,但是其中也存在着一些不确定性因素和风险。要弄清楚辅助迁移是否适用于所有物种,我们还需要进行更深入的调查。一个被人为迁移的物种有可能会因缺少食物而灭绝。而另一种极端的情形则是物种被成功迁移,但是在五到十年内该物种迅速繁衍,成为对当地物种构成威胁的入侵物种。如同外来植物攫取土壤中的营养物质,由此扼杀当地植物那样。辅助迁移来的动物也可能会变为攻击性物种。这种情况在澳大利亚出现过。1935年为了除掉澳大利亚甘蔗种植园中的一种有害昆虫,蔗蟾蜍被引入。但是蔗蟾蜍却毁坏了大量的野生生物变成了那片土地上的害虫。

    另外,很多物种是相互依存的,彼此之间存在着紧密的联系,比如,一些动物靠吃某种特定的植物生存以及一些植物靠某种特定真菌帮助其从土壤中获得营养,靠一种特定的昆虫授粉。我们可能需要把它整个的食物链迁移过去,而且很难弄清楚我们要迁移的这个食物链是否完整。除了以上这些,我们甚至都不清楚辅助迁移或其他任何相同目的的迁移至少对某些物种来说是有帮助的。当我们开始燃烧化石燃料时,地球已经处于气候缓和的间冰期了。预计21世纪全球气温将上升2到6度。这样的升温速度远远超过了约12000年前的上一个间冰期。

    是否应该采用辅助迁移目前主要是生物学界争议的话题。但是最终的决策者将会是管理自然资源的政府机构,至少在美国是这样。辅助迁移的确需要来自这个层次的监管,而且是急需。目前政府尚未公布任何采用辅助迁移的方法帮助物种来度过这次全球变暖的危机的政策。人们甚至可以未经许可而迁移植物或无脊椎动物,只要它们未被归类为有害动植物。有一个案例就是,一群环境保护主义者决定采用辅助迁移的方法自行拯救濒临灭绝的树,佛罗里达州的榧树。

    目前存活的佛罗里达榧树只有1000株,且预计全球变暖会严重削减甚至毁灭其生长地。因此这个环境保护小组想要移植佛罗里达榧树的幼苗到其目前所在地以北500公里的土地上,以扩大其生长范围。这个小组认为这次行动是正义之举。但是我和其他生物学家会密切关注 这个特立独行的小组的成果如何,因为,正如我以上所说,辅助迁移可能会带来意想不到的后果。

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    题型分析:主旨题

    原文定位Now, assisted migration could become a viable part of our rescue strategy, but there are a number of uncertainties and risks. Without more research, we can't predict if Assisted Migration will work for any given species. A translocated species could die out from lack of food, for example. At the other extreme, we might successfully translocate the species, but within five or ten years that species could proliferate and become an invasive species.

    选项分析

    章前面一开始教授说到extinction,然后说到radical strategy   Assisted Migration进行了定义,随后分别详细介绍了viable and risk. 最后说会有意想不到的结果

    C选项即为文章核心关键词viable and risk的同义替换, 是对全文主旨最准确的概括

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