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1 .Today I'm going to talk about invasive species. Let me start by saying what an invasive species is and what it's not. Invasive species are any animal or plant that is introduced into an environment by humans, and which is then harmful to that environment.
今天我要讲的是入侵物种。首先，让我说明什么是入侵物种，什么不是。入侵物种是指由人类引入某个环境、并随后对该环境造成危害的任何动物或植物。
2 .It's important to be clear that not all introduced species are invasive. Many introduced - or non-native - species thrive in new areas without posing any threat.
有一点必须明确，并非所有引入的物种都是入侵性的。许多引入物种，或称非本地物种，在新区域繁衍生息，却不构成任何威胁。
3 .In some cases, invasive species have changed the natural world beyond recognition, so let's look at the different ways they can be problematic.
某些情况下，入侵物种已使自然世界变得面目全非，那么我们就来看看它们可能造成问题的几种不同方式。
4 .First of all, invasive species may eat native species, or sometimes they may bring a disease with them, which native species have never faced before and therefore have no defences against.
首先，入侵物种可能会捕食本地物种，有时也可能随自身携带一种疾病，而本地物种此前从未面对过这种疾病，因此毫无抵御能力。
5 .Often the invasive species breed very quickly - which further adds to the problem of native species losing their sources of food.
入侵物种往往繁殖极快，这进一步加剧了本地物种失去食物来源的问题。
6 .Species invasions are one of the biggest causes of damage in an ecosystem, actually putting its survival at risk.
物种入侵是导致生态系统遭受破坏的最大原因之一，事实上会危及其存亡。
7 .So, how do invasive species spread? Without a doubt, the biggest cause is human activity. This could be intentional, or it could be accidental, such as when people who've been on holiday in another country come back with, say, the seeds of plants on their clothes or shoes.
那么，入侵物种是如何传播的呢？毫无疑问，最大的原因是人类活动。这可能是蓄意的，也可能是无意的，比如在异国度完假的人，回来时衣物或鞋子上沾着植物的种子。
8 .Plants and animals, especially insects, arrive in or on the cargo of ships, and then escape into their new 'home'.
动植物，尤其是昆虫，会随船只的货物抵达或藏身其中，然后逃逸到它们的"新家"。
9 .But sometimes humans deliberately move animals and plants around the world, for example to use them to control pests on farms, or to be pets. This can go very wrong if those animals and plants move into wild settings and start breeding or begin growing in ways that one predicted.
但有时，人类会蓄意将动植物在世界范围内迁移，例如将其用于控制农场的害虫，或作为宠物饲养。然而，一旦这些动植物进入野生环境，开始以人们未曾预料的方式繁殖或生长，事情就可能变得极其糟糕。
10 .Let's now look at an example of an invasive species here in Australia: Rhinella marina is a species of toad that was deliberately introduced from Hawaii in 1935 as a form of biological control.
现在，让我们来看一个澳大利亚这里的入侵物种实例：海蟾蜍是一种蟾蜍，于1935年作为生物防治手段从夏威夷被蓄意引入。
11 .It was hoped that the toads would eat the grey-backed beetles responsible for destroying crops of sugar on many of the plantations. At first, just a handful of toads were released by scientists into Queensland, but this number soon grew as other states followed suit.
人们曾希望这种蟾蜍会捕食灰背甲虫，这种甲虫曾毁坏许多种植园里的甘蔗作物。起初，科学家仅在昆士兰州释放了少量蟾蜍，但随着其他州纷纷效仿，这一数字很快就增多了。
12 .Within two years, 62,000 young toads had been released into the wild. The toads did nothing to protect the plantations, but they did reproduce rapidly and could soon be found all over the northern half of the country.
不到两年时间，已有六万两千只幼蟾被释放到野外。这些蟾蜍对保护种植园毫无作用，反而迅速繁殖，很快便在整个国家的北半部随处可见。
13 .The toads are poisonous at every stage of their life cycle, and anything that eats them will die.
这种蟾蜍在其生命周期的每个阶段都带有毒性，任何吞食它们的动物都会死亡。
14 .My second example regarding invasive species is the United Kingdom. Actually, there are more than three-thousand invasive species there, including some that are extremely common.
我的第二个关于入侵物种的实例是英国。事实上，那里有超过三千种入侵物种，其中一些极其常见。
15 .Some invasive plants, such as Japanese knotweed, have had a devastating impact on parts of the UK. Gardeners in the nineteenth century considered it a beautiful ornamental plant - which it is, when it's kept under control - but it soon spread into the countryside and remains a problem even to this day as it's so hard to eradicate.
某些入侵植物，如日本虎杖，已对英国部分地区产生了毁灭性的影响。十九世纪的园丁曾视其为一种美丽的观赏植物，在加以控制的情况下也的确如此，但它很快就蔓延到郊野，直至今日仍是一个难题，因为它极难根除。
16 .Another invasive plant is rhododendrons, which can be found in UK parks and woodlands. Their introduction dates back to 1763, but they're now seen as harmful because they block out so much light that native wild flowers can't grow beneath them.
另一种入侵植物是杜鹃花，在英国的公园和林地中都能找到。它们的引入可追溯至1763年，但如今被视为有害植物，因为它们遮蔽了太多光线，导致本土野花无法在其下生长。
17 .And then there are grey squirrels, which are one invasive species almost everyone in the UK will have come across.
此外还有灰松鼠，这是几乎每个英国人都曾遇见过的一种入侵物种。
18 .They were brought to the UK from North America and introduced to private estates around the 1870s but are now found everywhere, from forests to city squares.
它们于19世纪70年代左右从北美被带到英国，引入私人庄园，如今却随处可见，从森林到城市广场不一而足。
19 .Grey squirrels have outcompeted the smaller, native red squirrels. They both eat the same food, and the grey squirrels carry a type of virus that is deadly to the red squirrels.
灰松鼠在竞争中胜过了体型较小的本土红松鼠。二者食物相同，而灰松鼠携带的一种病毒对红松鼠是致命的。
20 .Red squirrel populations have collapsed, and there are only a handful of sites left in the UK where they're found.
红松鼠的种群数量已急剧下降，英国境内尚存的栖息地也屈指可数。
21 .An important question for ecologists worldwide is, what can we do to tackle the problem of invasive species? The first step in controlling invasive species is learning about the behaviour of new species coming into the country.
对全世界的生态学家来说，一个重要的问题是，我们能做些什么来应对入侵物种的问题？控制入侵物种的第一步，是了解进入本国的新物种的习性。
22 .Monitoring is an important part of this, so that we can know if the new species begins to have a negative impact in its new environment.
监测是这项工作的重要组成部分，这样我们才能知晓新物种是否开始对其新环境产生负面影响。
23 .One effective way to keep track of invasive species is to create a database for the whole country. That way, all relevant authorities and agencies can share important information and take whatever action's needed.
追踪入侵物种的一个有效方法，是建立覆盖全国的数据库。如此一来，所有相关当局和机构就能共享重要信息，并采取一切必要行动。
24 .But the public also have a vital role to play in this process. They should be encouraged to photograph harmful species - because this helps with identification - and then to report when and where these were observed.
但公众在这一过程中也扮演着至关重要的角色。应鼓励他们为有害物种拍摄照片，因为这有助于物种鉴定，并随后报告观察到这些物种的时间和地点。
25 .But it's important to tell people not to destroy or even touch what they've found. Now, I'm going to move on to...
但重要的是，要告知人们不要破坏甚至触碰他们所发现的东西。现在，我要进入下一个部分……