如果這個世界沒有鯊魚

It's safe to say that most folks would be comfortable imagining a world without sharks. Whether you're a surfer who spends as much time scanning the waters for predators as looking for the next big rip curl or an ordinary beachgoer who's experienced the terror of sprinting to shore when a lifeguard goes heavy on the whistle, most of us would take to the seas with a little more ease knowing there aren't any hammerheads, blacktips or bull sharks patrolling the waters below. The truth is, however, that we need them more than we think.

可以說，一個沒有鯊魚的世界會讓大多數人感到舒服。無論你是一個花費大量時間在海上娛樂的沖浪愛好者還是一位嚴陣以待的救生員，當你知道水面下沒有任何錘頭鯊、黑鰭鯊或者牛鯊時，你可能會更加安心一點。但事實上，我們比我們想象的更需要鯊魚。

Sharks killed 10 people in 2013. Humans, on the other hand, cull the shark population by somewhere from 30 million to 70 million each year. The steady decline in sharks appears to be having a devastating effect on the aquatic ecosystem that could wind all the way up to your dinner plate. That's because a lack of sharks throws off the food chain that's been a way of life under the sea for hundreds of millions of years.

2013年，在全世界范圍內，鯊魚殺死了10人。但與此同時，人類每年殺戮的鯊魚數量從3000萬增加到了7000萬。鯊魚數量的穩(wěn)步下降會對水域生態(tài)系統(tǒng)造成毀滅性的影響，這種影響可能還會波及到你的晚餐。這一切都是因為鯊魚的缺席使得食物鏈失去了原本的作用，而這些食物鏈已經在海底存在了幾億年了。

Sharks are apex predators. That means the big ones are at the top of the seafood chain. They dine on smaller fish — like tuna — which in turn eat even smaller, bottom-feeding species — like scallops — that survive largely on algae. Without sharks to keep down the population, those algae-eaters are more likely to be swallowed up by their natural predators, who rise to the top of the chain with no one to hunt them. Absent the bottom-feeders, algae grow wild, damaging coral reefs and other vegetation, as well as clogging up fish gills and contaminating seafood and water .

鯊魚幾乎可以說是頂級的捕食者了，它們處在海洋食物鏈的頂端，它們以稍小一點的魚類為食，比如金槍魚。而金槍魚又反過來吃那些更小的海洋生物，比如扇貝。扇貝幾乎算是食物鏈的底層了，它們主要靠海藻生存。如果沒有鯊魚來控制金槍魚的種群數量，這些金槍魚就會爬到食物鏈的頂端，那些底層食藻動物的數量就會因為被大量捕食而減少。這樣一來，藻類就會瘋長，從而破壞珊瑚礁和其他植被。與此同時，這些失控的藻類也會堵塞魚鰓、污染海水。

An ocean free of sharks would also change the way that other marine life moves around. Shark prey would no longer be forced into remote areas less conducive to living and reproducing. That's because they wouldn't have to constantly be looking over their shoulders to see if they're on the lunch menu .

如果海洋里沒有了鯊魚，其它海洋生物的棲息地也會被改變。鯊魚的獵物們將不再被迫進入不利于生存和繁殖的偏遠地區(qū)，因為它們不再需要整天提心吊膽。

If that's not enough to convince you that sharks need to be here to stay, think about your own belly. Without sharks to help control the population underwater, midsize fish will be free to fatten themselves up on sea life that might otherwise make it to your plate. That's exactly what happened off the coast of North Carolina, where excess fishing of sharks decimated what were once thriving scallop, oyster and clam populations.

如果這些還不足以讓你相信我們確實需要鯊魚，想想你自己的晚餐。如果沒有鯊魚來幫助控制海洋里的人口，像金槍魚這樣的中型魚會在海洋中自由地增肥，最終它們會進入你的盤子。這正是北卡羅來納州沿海地區(qū)發(fā)生的事情，在那里，過度捕撈鯊魚使曾經繁榮的扇貝、牡蠣和蛤蜊種群大量死亡。