The 10 Reasons Animals Go Extinct 动物灭绝的十个原因

文/鲍勃·施特劳斯 译/莫昕 By Bob Strauss

The 10 Reasons Animals Go Extinct 动物灭绝的十个原因

文/鲍勃·施特劳斯 译/莫昕 By Bob Strauss1

Why have so many animals gone extinct?

The earth teems with2teem with 富于；充满。life: thousands of species of vertebrate3vertebrate脊椎动物。animals(mammals, reptiles, fish and birds);invertebrates (insects, crustaceans4crustacean 甲壳类、甲壳纲动物。, and protozoans5protozoan原生动物，一类单细胞真核生物，缺少真正细胞壁，细胞通常无色，具有运动能力，并吞噬营养。); trees, flowers, grasses and grains; and a bewildering array of bacteria, algae and other single-celled organisms, some inhabiting scaldinghot6scalding-hot滚烫的。deep-sea thermal vents7thermal vent海底热泉。通常发现于火山活动频发、大陆板块移动的地区。. And yet, this rich profusion of flora and fauna88 flora and fauna动植物群。seems paltry9paltry无价值的，琐碎的，微小的。compared to the ecosystems of the deep past: by most reckonings10reckoning计算，清算。, since the beginning of life on earth, a whopping11whopping巨大的，庞大的。99.9 percent of all species have gone extinct. Why?

You can get some idea by perusing the following 10 points.

为什么有这么多动物灭绝？

地球上充满了各种生命：成千上万种的脊椎动物（哺乳动物、爬行动物、鱼、鸟）；无脊椎动物（昆虫、甲壳类动物、原生动物）；树、花、草和谷物；还有大量令人眼花缭乱的细菌、藻类和其他单细胞生物，其中一些存活在滚烫的深海海底热泉里。然而，就算动植物种群如此丰富，与很久以前的生态系统相比，也似乎是微不足道的。大多数数据显示，自地球有生命以来，所有物种中有99.9%已经灭绝，这是一个巨大的数字。为什么会这样？以下10点会让你对这个问题有所了解。

1. Asteroid strikes

This is the first thing most people associate with the word “extinction,”and not without reason, since we all know that a meteor impact on the Yucatan peninsula12尤卡坦半岛。岛上的希克苏鲁伯陨石坑常被认为是造成白垩纪-第三纪灭绝事件的成因，并造成恐龙等生物的灭绝。in Mexico caused the disappearance of the dinosaurs 65 million years ago. It’s likely that many of the earth’s mass extinctions—not only the K/T Extinction13白垩纪-第三纪灭绝事件(缩写为K-T灭绝），是地球历史上的一次大规模物种灭绝事件，发生于中生代白垩纪与新生代第三纪之间。, but also the much more severe Permian-Triassic Extinction14二叠纪-三叠纪灭绝事件（简称P-Tr），是一个大规模物种灭绝事件，发生于古生代二叠纪与中生代三叠纪之间，距今大约2亿5140万年。—were caused by such impact events15impact event撞击事件。在天文学上是指地球或其他行星和小行星、彗星等其他天体互相碰撞的事件。, and astronomers are constantly on the lookout16on the lookout注视着，警惕着。for comets or meteors that could spell17spell招致。the end of human civilization.

1.小行星撞击

大多数人一听到“灭绝”，想到的就是这个原因。这并非毫无根据，我们都知道，6500万年前墨西哥尤卡坦半岛的流星撞击导致了恐龙的消失。地球上的许多次大规模灭绝——不仅是白垩纪-第三纪灭绝事件（K-T灭绝），还有更严重的二叠纪-三叠纪灭绝事件——很可能都是由此种撞击造成的。天文学家们一直在警惕着可能会终结人类文明的彗星或流星。

2.气候变化

即使没有小行星或彗星造成的重大撞击事件——这可能会将全球气温降低20-30华氏度，气候变化对陆地动物也在产生持续不断的威胁。只需看看约11,000年前的最近一次冰河时代末期便可知，当时各种巨型哺乳动物都无法适应快速变暖的气温（同时它们也遭受了食物缺乏和被早期人类掠食的噩运）。如今全球变暖对现代文明的长期威胁早已是人尽皆知！

2. Climate change

Even in the absence of major asteroid or comet impacts—which can potentially lower worldwide temperatures by 20 or 30 degrees Fahrenheit—climate change poses a constant danger to terrestrial18terrestrial地球的，陆地的。animals. You need look no further than the end of the last Ice Age, about 11,000 years ago, when various megafaunamammals were unable to adapt to quickly warming temperatures (they also succumbed to19succumb to屈服于，死于。lack of food and predation by early humans). And we all know about the long-term threat global warming presents to modern civilization!

3. Disease

While it’s unusual for disease alone to wipe out20wipe out消灭，摧毁。a given species—the groundwork21groundwork基础；根基。has to be laid first by starvation,loss of habitat,and/or lack of genetic diversity22genetic diversity遗传多样性。又称为基因多样性。同种个体间因为生活环境的不同，经历长时间的天择、突变所产生的结果。遗传多样性越高，族群中可提供环境天择的基因愈多，族群对于环境适应能力就愈强，有利于族群的生存及演化。—the introduction of a particularly lethal virus or bacterium at an inopportune moment can wreak havoc23wreak havoc肆虐；造成严重破坏。. Witness the crisis currently facing the world’s amphibians24amphibian两栖动物。, which are falling prey to25fall prey to成为……的牺牲品；深受……之害。chytridiomycosis, a fungal infection that ravages the skin of frogs, toads and salamanders and causes death within a few weeks—not to mention the Black Death that wiped out a third of Europe’s population during the Middle Ages.

3.疾病

疾病成为某一物种灭绝的单一原因并不寻常，但某种特别致命的病毒或细菌的出现时机不当，可能会造成严重破坏。不过首先必须要有一定的基础，如饥饿、栖息地丧失、遗传多样性缺乏等。且看目前世界上的两栖动物所面临的危机，这些两栖动物正在成为壶菌病的牺牲品。这种真菌感染会使青蛙、蟾蜍和蝾螈的皮肤溃烂，并在几周内致其死亡——更不用说在中世纪将欧洲人口减少了三分之一的黑死病。

4. Loss of habitat

Most animals require a certain amount of territory in which they can hunt and forage26forage搜寻粮草。, breed and raise their young, and (when necessary) expand their population. A single bird may be content with the high branch of a tree, while large predatory mammals(like Bengal Tigers) measure their domains in square miles. As human civilization expands relentlessly27relentlessly持续地。into the wild, these natural habitats diminish in scope—and their restricted and dwindling28dwindle减少，缩小。populations are more susceptible29susceptible易受……的影响。to the other extinction pressures listed in this article.

4.栖息地丧失

大多数动物都需要一定的领地以获取食物，养育后代，并在必要时扩大种群数量。一只鸟可能满足于一棵树上的高枝，而大型食肉类哺乳动物（如孟加拉虎）的领地则以平方英里来计量。随着人类活动范围不断向荒野扩张，这些自然栖息地的范围会逐渐缩小，而其有限的、日益减少的种群更容易受到本文中列出的其他灭绝威胁因素的影响。

5.缺乏遗传多样性

一旦一个物种的数量开始减少，可选的异性总数也随之减少，通常还伴随着遗传多样性的缺乏。（这就是为什么和一个完全陌生的人结婚，会比和第一代堂/表亲结婚更有利后代健康。因为在后一种情况下，可能会因“近亲繁殖”而产生不良遗传特征，如对致命疾病的易感性）。仅举一个例子：由于栖息地急剧丧失，如今非洲猎豹的数量日益减少，遗传多样性异常低下，因此很可能无法适应下一次重大的环境破坏。

5. Lack of genetic diversity

Once a species starts dwindling in numbers, there’s a smaller pool of available mates, and often a corresponding lack of genetic diversity.(This is the reason it’s much healthier to marry a complete stranger than your first cousin30first cousin第一代堂兄弟姐妹、表兄弟姐妹。, since otherwise you run the risk of “inbreeding31inbreed近亲繁殖，同系繁殖。” undesirable genetic traits, like susceptibility to fatal diseases.) To cite just one example:because of extreme habitat loss, today’s dwindling population of African cheetahs suffers from unusually low genetic diversity, and thus may lack the resiliency32resiliency弹性，适应性。to survive another major environmental disruption.

6. Better-adapted competition

Here’s where we risk succumbing to a dangerous tautology33tautology同义反复。: by definition,“better-adapted” populations always win out over those that lag behind34lag behind落后。, and we often don’t know exactly what the favorable adaptation was until after the event! (For instance, no one would have thought that prehistoric mammals were better adapted than dinosaurs, until the K/T Extinction changed the playing field35playing field运动场，球场。.) Usually, determining which is the “better adapted” species takes thousands, and sometimes millions,of years, but the fact is that the vast majority of animals have gone extinct in this comparatively unexciting way.

6.适者生存的竞争

说到这里，我们似乎犯了同义反复的错误。顾名思义，“适应性更佳的”种群总是胜过那些落后的种群，而我们常常在事后才知道到底什么才是良好的适应性！（例如，没有人会想到史前哺乳动物会比恐龙具有更好的适应性，直到白垩纪-第三纪灭绝事件改变了竞争的赛场。）通常需要数千年，有时甚至数百万年的时间，才能确定哪个是“适应性更佳的”的物种。而事实上，绝大多数的动物都是以这种较为单调乏味的方式灭绝的。

7.入侵物种

虽然大多数生存竞争激烈而漫长，但有时候这种竞争发生得更快、更血腥，被其中一方占据了绝对优势。如果某种植物或动物无意中从一个生态系统被转移到另一个生态系统（通常是由人类或动物宿主无意为之），该植物或动物可能会大量繁殖，导致当地种群的灭绝。这就是为什么美国植物学家谈野葛而色变。这种野草是在19世纪后期从日本引入的，现在正以每年15万英亩的速度蔓延，挤占了当地的植被。

7. Invasive species

While most struggles for survival transpire36transpire发生。over eons37eon永世；极长时期。, sometimes the contest is quicker, bloodier and more one-sided38one-sided一边倒的，单方面的。. If a plant or animal from one ecosystem is inadvertently39inadvertently非故意地，无心地。transplanted40transplant移植，转移。into another (usually by an unwitting41unwitting不知情的，无意的。human or an animal host), it can reproduce wildly, resulting in the extermination42extermination消灭，根绝。of the native population. That’s why American botanists wince43wince畏缩，退避。at the mention of kudzu, a weed that was brought here from Japan in the late 19th century and is now spreading at the rate of 150,000 acres per year, crowding out44crowd out挤出，推开。indigenous vegetation.

8. Lack of food

Mass starvation is the quick, oneway, surefire45surefire一定成功的，不会有错的。route to extinction—especially since hunger-weakened populations are much more prone to46prone to倾向于。disease and predation—and the effect on the food chain can be disastrous. For example, imagine that scientists find a way to permanently eliminate malaria47malaria疟疾。by exterminating every mosquito on the face of the earth. At first glance,that may seem like good news for us humans, but just think of the domino effect as all the creatures that feed on mosquitoes (like bats and frogs) go extinct, and all the animals that feed on bats and frogs, and so on down the food chain!

8.食物缺乏

大饥荒是通向灭绝的确定无误的快速单行道，尤其是因为饥饿导致种群体弱，更容易患病或被掠食，其对食物链的影响也可能是灾难性的。例如，假设科学家找到一种方法来永久地消灭疟疾，那就是消灭地球上的每只蚊子。乍看之下，这似乎对我们人类来说是个好消息，但是只要想想多米诺骨牌效应，所有以蚊子为食的生物（如蝙蝠和青蛙）都会灭绝，所有以蝙蝠和青蛙为食的动物也会灭绝，按此顺序，食物链上的动物无一幸免！

9.污染

海洋动物对湖泊、海洋和河流中的有毒化学物质的痕迹可能非常敏感。以及由于工业污染引起的氧气含量的急剧变化，也可能会使整个种群窒息而死。尽管并无资料表明单一的环境灾难（如石油泄漏或水力压裂工程）会使一整个物种灭绝，但是持续暴露在污染环境中，会使动植物更容易受到其他危险的影响，包括饥饿、栖息地丧失和疾病。

9. Pollution

Marine animals can be exquisitely48exquisitely敏锐地。sensitive to traces of toxic chemicals in lakes, oceans and rivers—and drastic changes in oxygen levels, caused by industrial pollution, can suffocate49suffocate使窒息。entire populations. While it’s virtually50virtually事实上，几乎，实质上。unknown for a single environmental disaster (such as an oil spill or fracking51fracking水力压裂，开采页岩气时所用的方法，用水压将岩石层压裂，从而释放出其中的天然气或石油。project) to render an entire species extinct, constant exposure to pollution can render plants and animals more susceptible to the other dangers,including starvation, loss of habitat and disease.

10. Human predation

Humans have only occupied the earth for the last50virtually事实上，几乎，实质上。,000 or so years, so it’s unfair to blame the bulk of the world’s extinctions on Homo sapiens. There’s no denying, though, that we’ve wreaked plenty of ecological havoc during our brief time in the spotlight52in the spotlight处于公众注意的中心，出风头。: hunting the starved, straggling53straggling掉队的，脱离队伍的。megafauna mammals of the last Ice Age, depleting54deplete耗尽，用尽。entire populations of whales and other marine mammals, and eliminating the Dodo Bird and the Passenger Pigeon virtually overnight. Are we wise enough now to cease our reckless behavior?Only time will tell.

10.人类掠夺

人类占领地球仅有约5万年的时间，所以将世界上大部分动物的灭绝归咎于人类是不公平的。然而，不可否认的是，在人类独领风骚的短暂时期里，造成了大量的生态破坏：在最近一个冰河时代，捕猎受饿离群的巨型哺乳动物；消灭了鲸鱼和其他海洋哺乳动物的整个种群；几乎在一夜之间使渡渡鸟和旅鸽灭绝。我们现在是否变得足够明智，停止我们的鲁莽行为？只有时间能给出答案。

1自由撰稿人，作家，致力于向普通读者解释科学概念和发现。该文选自网站thoughtco.com。

（译者曾获第五届“《英语世界》杯”翻译大赛优秀奖）