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第一段
1 .OK, so we've been looking at how man-made changes in our environment can affect wildlife.
好了，我们一直在研究人类造成的环境改变是如何影响野生动物的。
2 .Now I'll discuss a particular example.
现在来讨论一个特别的例子。
3 .Let's take a look at mercury.
我们来看一下汞。
4 .Mercury's one of the 120 or so elements that make up all matter, and it has the symbol Hg.
汞是组成所有物质的120多种元素之一，它的符号是Hg.
5 .It's a shiny, silvery substance.
它是一种有光泽的、银色的物质。
6 .You may have seen it in old-fashioned thermometers,
你也许在老式的温度计中见过它，但由于其强烈毒性，现在用于家庭用途已不多。
7 .but it's not used much for domestic purposes now because it's highly toxic.
该句暂无译文！
第二段
1 .But the problem is that the amount of mercury in the environment's increasing.
但问题是环境中的汞含量在上升。
2 .The main reason for this is the power plants used to produce electricity.
该句暂无译文！
3 .The main source of energy that most of them use is still coal,
大多数发电厂的能量来源仍然是煤，
4 .and when it's burned it releases mercury into the atmosphere.
当煤燃烧时会释放汞到大气中。
5 .Some of this gets deposited into lakes and rivers,
有一些汞会沉淀到河湖中，
6 .and if it's ingested by a fish it's not excreted,
如果被鱼吸收而没有排泄出来，
7 .it stays in the fish's body and it enters the food chain.
就会残留在鱼体内，从而进入食物链。
8 .So it's been known for some time that birds which eat fish may be affected,
食鱼的鸟可能会受影响这一点为人所知已有一段时间，
9 .but what wasn't know until quite recently is that those that eat insects can also be affected.
但直到最近才为人知的是那些吃昆虫的鸟也会受到影响。
第三段
1 .So a woman called Claire Varian-Ramos is doing some research on how this is affecting birds.
一位叫做Claire Varian-Ramos正在研究这是如何影响鸟类的。
第四段
1 .And rather than looking at how many birds are actually killed by mercury poisoning,
她并没有看有多少鸟是汞中毒而亡的，
2 .she's looking for more subtle sub-effects.
而是研究更微妙的亚作用。
3 .And these may be to do with the behaviour of the birds.
这一切可能跟鸟类的行为
4 .or with the effect of mercury on the way their brain works,
或是汞对大脑工作的影响有关，
5 .so whether it leads to problems with memory, for example.
所以比如说它会不会导致记忆问题呢。
6 .And she's particularly focusing on the effects of mercury on bird song.
Varian-Ramos尤其关注汞对鸟类鸣叫的影响。
7 .Now, the process of song learning happens at a particular stage in the birds' development,
学习鸣叫的过程发生在鸟类成长中的一个特定阶段，
8 .and what you may not know is that a young bird seems to acquire this skill by listening to the songs produced by its father,
你们可能不知道的是幼鸟似乎是通过聆听其父亲的鸣叫习得这项技能的，
9 .rather than by any other bird.
而不是通过其他的鸟。
第五段
1 .And Varian-Ramos has already found in her research that if young male birds are exposed to mercury,
Varian-Ramos已经在其研究中发现如果幼年雄鸟暴露于汞中，
2 .if they eat food contaminated with mercury,
或是吃了受汞污染的食物，
3 .then the songs the produce aren't as complex as those produced by other birds.
那它们发出的鸣叫声就不有其他鸟发出的那样复杂。
4 .So quite low-level exposure to mercury is likely to have an impact on male birds in a natural situation,
所以在自然条件下，相当轻微地暴露于汞中可能对雄鸟产生影响，
5 .because it can mean that they're less attractive to female birds,
因为那可能意味着他们对雌鸟的吸引力较差，
6 .and so it can affect their chances of reproduction.
这就会影响到它们的繁殖机会。
第六段
1 .Now the way she's carrying out this research is worth thinking about.
Varian-Ramos进行这项研究的方法值得我们思考。
2 .She's using a mixture of studies using birds kept in laboratories,
通过对实验室养的鸟进行研究，并在野外进行户外研究，
3 .and studies carried out outdoors in the wild.
她所进行的是一项混合研究。
4 .The lab-based studies have the advantage that you don't get all the variables you would in a natural setting,
基于实验室的研究，其优点在于在自然环境中可能无法得到所有的变量，
5 .so the experimenter has a much higher level of control,
实验者因此有着更高程度的控制，
6 .and that means they can be more confident about their results in some ways.
这就意味着在某些方面他们能对自己的结果更加自信。
7 .And of course they don't have to worry about going out and finding the birds in order to observe them.
当然他们也不用担心得出去找鸟然后才能进行观察。
第七段
1 .So what are the implications here for humans?
那这对人类有什么启示呢？
2 .Well, because many birds are migratory,
因为很多鸟类是候鸟，
3 .they may be transporting mercury far from contaminated sites.
所以它们可能会将污染区域的汞带到很远的地方。
4 .For example, it's been found that ducks who'd been feeding at a contaminated site were later shot by hunters over a thousand kilometres away,
举例来说，曾经发现有在某个受污染区域觅食的鸭子 被千里之外的猎人射杀，
5 .and presumably eaten.
然后很有可能被吃掉。
6 .But these birds likely had mercury levels high enough to warrant concern for human consumption.
这些鸟体内的汞含量可能高至产生人类食用的担忧。
第八段
1 .In addition, going back to song learning by birds,
此外，回到鸟类学习鸣叫的事情上，
2 .we saw that this may be affected by mercury contamination.
我们看到这一过程可能会受到汞污染的影响。
3 .Well, we also know that in humans,
我们还知道
4 .mercury causes developmental delays in the acquisition of language,
汞会引起人类语言习得的发展延迟，
5 .and in fact this process is very similar in the brain regions it involves and even the genes that are involved.
事实上这一过程就其脑部控制区域而言跟鸟类学习鸣叫时用到的是相似的，甚至涉及到的基因也是相似的。
6 .But mercury contamination has other important implications for humans as well.
但是对人类而言汞污染还有其他严重的后果。
7 .It's now known that an unborn child can be affected if the food eaten by its mother contains high levels of mercury,
现在人们已知道未出世的婴儿会因其母亲食用了汞含量高的食物而受到影响，
8 .and these effects can be quite substantial.
而且这些影响可能是十分严重的。
第九段
1 .In the end, it comes down to whether more value is placed on human economic wellbeing or environmental wellbeing.
最终，问题还是回归到是要更重视人类的经济福祉，还是环境福祉。
2 .It's true there are new regulations for mercury emissions from power plants,
的确，现如今针对发电厂的汞排放有了新的规定，
3 .but these will need billions of dollars to implement,
但这些规定需要数以十亿计的美元来实施，
4 .and increase costs for everyone.
这会增加所有人的生活成本。
5 .Some argue that's too much to pay to protect wildlife.
有的人争论道为保护野生动物付出的代价太大了。
6 .But as we've seen, the issues go beyond that,
但正如我们所看到的，这一问题不止如此简单，
7 .and I think it's an issue we need to consider very carefully.
我认为我们需要非常认真地考虑这一问题。