文/鮑勃·施特勞斯 譯/莫昕 By Bob Strauss

The 10 Reasons Animals Go Extinct 動物滅絕的十個原因

文/鮑勃·施特勞斯 譯/莫昕 By Bob Strauss1

Why have so many animals gone extinct?

The earth teems with2teem with 富于；充滿。life: thousands of species of vertebrate3vertebrate脊椎動物。animals(mammals, reptiles, fish and birds);invertebrates (insects, crustaceans4crustacean 甲殼類、甲殼綱動物。, and protozoans5protozoan原生動物，一類單細胞真核生物，缺少真正細胞壁，細胞通常無色，具有運動能力，并吞噬營養(yǎng)。); trees, flowers, grasses and grains; and a bewildering array of bacteria, algae and other single-celled organisms, some inhabiting scaldinghot6scalding-hot滾燙的。deep-sea thermal vents7thermal vent海底熱泉。通常發(fā)現(xiàn)于火山活動頻發(fā)、大陸板塊移動的地區(qū)。. And yet, this rich profusion of flora and fauna88 flora and fauna動植物群。seems paltry9paltry無價值的，瑣碎的，微小的。compared to the ecosystems of the deep past: by most reckonings10reckoning計算，清算。, since the beginning of life on earth, a whopping11whopping巨大的，龐大的。99.9 percent of all species have gone extinct. Why?

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

為什么有這么多動物滅絕？

地球上充滿了各種生命：成千上萬種的脊椎動物（哺乳動物、爬行動物、魚、鳥）；無脊椎動物（昆蟲、甲殼類動物、原生動物）；樹、花、草和谷物；還有大量令人眼花繚亂的細菌、藻類和其他單細胞生物，其中一些存活在滾燙的深海海底熱泉里。然而，就算動植物種群如此豐富，與很久以前的生態(tài)系統(tǒng)相比，也似乎是微不足道的。大多數(shù)數(shù)據(jù)顯示，自地球有生命以來，所有物種中有99.9%已經(jīng)滅絕，這是一個巨大的數(shù)字。為什么會這樣？以下10點會讓你對這個問題有所了解。

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尤卡坦半島。島上的?？颂K魯伯隕石坑常被認為是造成白堊紀-第三紀滅絕事件的成因，并造成恐龍等生物的滅絕。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白堊紀-第三紀滅絕事件(縮寫為K-T滅絕），是地球歷史上的一次大規(guī)模物種滅絕事件，發(fā)生于中生代白堊紀與新生代第三紀之間。, but also the much more severe Permian-Triassic Extinction14二疊紀-三疊紀滅絕事件（簡稱P-Tr），是一個大規(guī)模物種滅絕事件，發(fā)生于古生代二疊紀與中生代三疊紀之間，距今大約2億5140萬年。—were caused by such impact events15impact event撞擊事件。在天文學上是指地球或其他行星和小行星、彗星等其他天體互相碰撞的事件。, and astronomers are constantly on the lookout16on the lookout注視著，警惕著。for comets or meteors that could spell17spell招致。the end of human civilization.

1.小行星撞擊

大多數(shù)人一聽到“滅絕”，想到的就是這個原因。這并非毫無根據(jù)，我們都知道，6500萬年前墨西哥尤卡坦半島的流星撞擊導致了恐龍的消失。地球上的許多次大規(guī)模滅絕——不僅是白堊紀-第三紀滅絕事件（K-T滅絕），還有更嚴重的二疊紀-三疊紀滅絕事件——很可能都是由此種撞擊造成的。天文學家們一直在警惕著可能會終結人類文明的彗星或流星。

2.氣候變化

即使沒有小行星或彗星造成的重大撞擊事件——這可能會將全球氣溫降低20-30華氏度，氣候變化對陸地動物也在產(chǎn)生持續(xù)不斷的威脅。只需看看約11,000年前的最近一次冰河時代末期便可知，當時各種巨型哺乳動物都無法適應快速變暖的氣溫（同時它們也遭受了食物缺乏和被早期人類掠食的噩運）。如今全球變暖對現(xiàn)代文明的長期威脅早已是人盡皆知！

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，陸地的。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消滅，摧毀。a given species—the groundwork21groundwork基礎；根基。has to be laid first by starvation,loss of habitat,and/or lack of genetic diversity22genetic diversity遺傳多樣性。又稱為基因多樣性。同種個體間因為生活環(huán)境的不同，經(jīng)歷長時間的天擇、突變所產(chǎn)生的結果。遺傳多樣性越高，族群中可提供環(huán)境天擇的基因愈多，族群對于環(huán)境適應能力就愈強，有利于族群的生存及演化?！猼he introduction of a particularly lethal virus or bacterium at an inopportune moment can wreak havoc23wreak havoc肆虐；造成嚴重破壞。. Witness the crisis currently facing the world’s amphibians24amphibian兩棲動物。, which are falling prey to25fall prey to成為……的犧牲品；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

疾病成為某一物種滅絕的單一原因并不尋常，但某種特別致命的病毒或細菌的出現(xiàn)時機不當，可能會造成嚴重破壞。不過首先必須要有一定的基礎，如饑餓、棲息地喪失、遺傳多樣性缺乏等。且看目前世界上的兩棲動物所面臨的危機，這些兩棲動物正在成為壺菌病的犧牲品。這種真菌感染會使青蛙、蟾蜍和蠑螈的皮膚潰爛，并在幾周內致其死亡——更不用說在中世紀將歐洲人口減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搜尋糧草。, 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持續(xù)地。into the wild, these natural habitats diminish in scope—and their restricted and dwindling28dwindle減少，縮小。populations are more susceptible29susceptible易受……的影響。to the other extinction pressures listed in this article.

4.棲息地喪失

大多數(shù)動物都需要一定的領地以獲取食物，養(yǎng)育后代，并在必要時擴大種群數(shù)量。一只鳥可能滿足于一棵樹上的高枝，而大型食肉類哺乳動物（如孟加拉虎）的領地則以平方英里來計量。隨著人類活動范圍不斷向荒野擴張，這些自然棲息地的范圍會逐漸縮小，而其有限的、日益減少的種群更容易受到本文中列出的其他滅絕威脅因素的影響。

5.缺乏遺傳多樣性

一旦一個物種的數(shù)量開始減少，可選的異性總數(shù)也隨之減少，通常還伴隨著遺傳多樣性的缺乏。（這就是為什么和一個完全陌生的人結婚，會比和第一代堂/表親結婚更有利后代健康。因為在后一種情況下，可能會因“近親繁殖”而產(chǎn)生不良遺傳特征，如對致命疾病的易感性）。僅舉一個例子：由于棲息地急劇喪失，如今非洲獵豹的數(shù)量日益減少，遺傳多樣性異常低下，因此很可能無法適應下一次重大的環(huán)境破壞。

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近親繁殖，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彈性，適應性。to survive another major environmental disruption.

6. Better-adapted competition

Here’s where we risk succumbing to a dangerous tautology33tautology同義反復。: 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運動場，球場。.) 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.適者生存的競爭

說到這里，我們似乎犯了同義反復的錯誤。顧名思義，“適應性更佳的”種群總是勝過那些落后的種群，而我們常常在事后才知道到底什么才是良好的適應性?。ɡ纾瑳]有人會想到史前哺乳動物會比恐龍具有更好的適應性，直到白堊紀-第三紀滅絕事件改變了競爭的賽場。）通常需要數(shù)千年，有時甚至數(shù)百萬年的時間，才能確定哪個是“適應性更佳的”的物種。而事實上，絕大多數(shù)的動物都是以這種較為單調乏味的方式滅絕的。

7.入侵物種

雖然大多數(shù)生存競爭激烈而漫長，但有時候這種競爭發(fā)生得更快、更血腥，被其中一方占據(jù)了絕對優(yōu)勢。如果某種植物或動物無意中從一個生態(tài)系統(tǒng)被轉移到另一個生態(tài)系統(tǒng)（通常是由人類或動物宿主無意為之），該植物或動物可能會大量繁殖，導致當?shù)胤N群的滅絕。這就是為什么美國植物學家談野葛而色變。這種野草是在19世紀后期從日本引入的，現(xiàn)在正以每年15萬英畝的速度蔓延，擠占了當?shù)氐闹脖弧?/p>

7. Invasive species

While most struggles for survival transpire36transpire發(fā)生。over eons37eon永世；極長時期。, sometimes the contest is quicker, bloodier and more one-sided38one-sided一邊倒的，單方面的。. If a plant or animal from one ecosystem is inadvertently39inadvertently非故意地，無心地。transplanted40transplant移植，轉移。into another (usually by an unwitting41unwitting不知情的，無意的。human or an animal host), it can reproduce wildly, resulting in the extermination42extermination消滅，根絕。of the native population. That’s why American botanists wince43wince畏縮，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擠出，推開。indigenous vegetation.

8. Lack of food

Mass starvation is the quick, oneway, surefire45surefire一定成功的，不會有錯的。route to extinction—especially since hunger-weakened populations are much more prone to46prone to傾向于。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瘧疾。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

大饑荒是通向滅絕的確定無誤的快速單行道，尤其是因為饑餓導致種群體弱，更容易患病或被掠食，其對食物鏈的影響也可能是災難性的。例如，假設科學家找到一種方法來永久地消滅瘧疾，那就是消滅地球上的每只蚊子。乍看之下，這似乎對我們人類來說是個好消息，但是只要想想多米諾骨牌效應，所有以蚊子為食的生物（如蝙蝠和青蛙）都會滅絕，所有以蝙蝠和青蛙為食的動物也會滅絕，按此順序，食物鏈上的動物無一幸免！

9.污染

海洋動物對湖泊、海洋和河流中的有毒化學物質的痕跡可能非常敏感。以及由于工業(yè)污染引起的氧氣含量的急劇變化，也可能會使整個種群窒息而死。盡管并無資料表明單一的環(huán)境災難（如石油泄漏或水力壓裂工程）會使一整個物種滅絕，但是持續(xù)暴露在污染環(huán)境中，會使動植物更容易受到其他危險的影響，包括饑餓、棲息地喪失和疾病。

9. Pollution

Marine animals can be exquisitely48exquisitely敏銳地。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事實上，幾乎，實質上。unknown for a single environmental disaster (such as an oil spill or fracking51fracking水力壓裂，開采頁巖氣時所用的方法，用水壓將巖石層壓裂，從而釋放出其中的天然氣或石油。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事實上，幾乎，實質上。,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處于公眾注意的中心，出風頭。: hunting the starved, straggling53straggling掉隊的，脫離隊伍的。megafauna mammals of the last Ice Age, depleting54deplete耗盡，用盡。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.人類掠奪

人類占領地球僅有約5萬年的時間，所以將世界上大部分動物的滅絕歸咎于人類是不公平的。然而，不可否認的是，在人類獨領風騷的短暫時期里，造成了大量的生態(tài)破壞：在最近一個冰河時代，捕獵受餓離群的巨型哺乳動物；消滅了鯨魚和其他海洋哺乳動物的整個種群；幾乎在一夜之間使渡渡鳥和旅鴿滅絕。我們現(xiàn)在是否變得足夠明智，停止我們的魯莽行為？只有時間能給出答案。

1自由撰稿人，作家，致力于向普通讀者解釋科學概念和發(fā)現(xiàn)。該文選自網(wǎng)站thoughtco.com。

（譯者曾獲第五屆“《英語世界》杯”翻譯大賽優(yōu)秀獎）