外来物种和本地物种的区分是人为的。
Distinctions between exotic and native species are artificial.
你不能让时光倒流，消除所有外来物种或修复栖息地。
You can't roll back the clock and remove all exotics or fix habitats.
在美洲大陆上，外来物种是在第一次接触欧洲后引进的。
Across the American continents, exotic species are those introduced after the first European contact.
生态学家通常把外来物种定义为人们偶然或故意带到新地方的物种。
Ecologists generally define an alien species as one that people, accidentally or deliberately, carried to its new location.
在美国总共15万的物种中，有7000种外来物种，当中只有10%是入侵物种。
Of the 7,000 alien species in the United States—out of a total of 150,000 species—only about 10% are invasive.
在美国总共15万的物种中，有7000种外来物种，当中只有10%是入侵物种。
Of the 7,000 alien species in the United States—out of a total of 150,000 species—only about 10 percent are invasive.
一些科学家质疑这样的假设，即在自然生态系统中，外来物种的出现是绝对不会被接受的。
A number of scientists question the assumption that the presence of alien species can never be acceptable in a natural ecosystem.
我们正在做的另一件事是除掉生长在花园里的一些外来物种，并种回一些本地植物和树木。
The other thing we're doing is getting rid of some of the foreign species that are growing in the gardens and putting back some native plants and trees.
19世纪末，狗舌草被偶然引入新西兰，像许多入侵的外来物种一样，它很快就变成了一种有害生物。
Ragwort was accidentally introduced to New Zealand in the late nineteenth century and, like so many invading foreign species, quickly became a pest.
田纳西大学生态学和进化生物学教授唐·史密斯说：“只有一小部分外来物种会在新栖息地引发问题。”
"Only a small percentage of alien species cause problems in their new habitats," said Don Smith, professor of ecology and evolutionary biology at the University of Tennessee.
“只有一小部分外来物种会在它们的新栖息地引发问题。”田纳西大学生态学和进化生物学教授唐·史密斯说。
"Only a small percentage of alien species cause problems in their new habitats,'' said Don Smith, professor of ecology and evolutionary biology at the University of Tennessee.
生态学家警告说，外表可能具有欺骗性，而且这些外来物种中可能有许多是为人接受的，只是因为没有人记载过其有害影响。
Appearances can deceive, ecologists caution, and many of these exotics may be considered acceptable only because no one has documented their harmful effects.
对非外来物种的研究没有得到类似的结果，这使得研究人员推测鸟类的社会学习能力可能与哺乳动物的社会学习能力有根本性的区别。
Studies on nonalien species have not produced similar results, leading researchers to speculate that avian social learning may be fundamentally different from that of mammals.
然而，生态学家警告说，这些表象可能并不是真的；而且，这些外来物种中有许多可能被认为是可接受的，只是因为没有人记载过它们的有害影响。
Yet appearances can deceive, ecologists caution, and many of these exotics may be considered acceptable only because no one has documented their harmful effects.
当地的生态系统并不能应付这个外来物种。它正在摧毁我们的环境。
The ecosystem down there can't handle this non-native species. It's destroying the environment.
他们说把外来物种描绘成天生的坏物种是一种不科学的做法。
They say that portraying introduced species as inherently bad is an unscientific approach.
令人惊讶的是，本土物种的灭绝很少归因于外来物种的竞争。
Surprisingly few extinctions of indigenous species can be attributed to competition from introduced species.
默认情况下，没有外来物种的生态系统被认为是最自然的生态系统。
Ecosystems free of species defined as exotic are, by default, considered the most natural.
如紫色花的亚洲牡丹和草莓番石榴等外来物种，威胁着如无刺玫瑰和树蕨等脆弱的夏威夷本土物种。
Invaders such as purple-flowered Asian melastome and strawberry guava threaten delicate Hawaiian natives such as thornless roses and tree ferns.
本土物种和外来物种都有可能成为入侵物种，因此当它们开始失控时，我们必须对它们进行监视和控制。
Both native and exotic species can become invasive, and so they all have to be monitored and controlled when they begin to get out of hand.
外来物种包括日本紫菀和灌木忍冬。
Newcomers include Japanese knotweed and Amur bush honeysuckle.
外来物种的朋友：外来物种真的造成威胁么？
A Friend to Aliens: Are Invasive Species Really a Big Threat?
这些外来物种大多数都轻而易举地融入了所到之处的生态系统。
Most such aliens blend into the ecosystem in which they arrive without too much fuss.
大西洋货轮还在带入外来物种——目前的数量已经达到185种。
Atlantic freighters still bring in foreign species—there are now 185.
在过去25年里，海洋温度已经上升了1度，更多南部外来物种进入了北海水域。
Sea temperatures have risen by 1c in the past 25 years and more exotic southern species have entered North Sea waters.
海洋生物普查还指出了在世界上许多海洋生态系统中发现的所谓“外来物种”的影响。
The Census of Marine Life also points to the effect of so-called "alien species" being found in many of the world's Marine ecosystems.
栖息地的流失和碎化、生态系统的恶化以及外来物种的入侵才是最大的威胁。
Wildlife is threatened by the loss of land,fragmentation of habitats, deteriorating ecosystems and invasive foreignspecies.
报道提醒，直到十年前特意引进外来物种后，它们对区域生境的整体影响力才为人所知。
The full impact of an alien species on an area's habitat may not come to light until decades after its intentional introduction, a report has warned.
由于事实上不可能将这些外来物种彻底根除，因此重要的是南非应寻找控制它们滋生的办法。
Since it's virtually impossible to eradicate them, it's vital for the country to seek ways to bring the alien species under control.
这方面的一个经典案例就是金苹果蜗牛，即人们目前所称最具破坏力的侵入性外来物种之一。
One classic example is the Golden Apple snail - now cited as one of the most devastating invasive alien species.
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