You don't have to be a marine biologist to understand the importance of corals — just ask any diver. The tiny underwater creatures are the architects of the beautiful, electric-colored coral reefs that lie in shallow tropical waters around the world. Divers swarm to them not merely for their intrinsic beauty, but because the reefs play host to a wealth of biodiversity unlike anywhere else in the underwater world. Coral reefs are home to more than 25% of total marine species. Take out the corals, and there are no reefs — remove the reefs, and entire ecosystems collapse.

Unfortunately, that's exactly what appears to be happening around the world. According to a comprehensive survey by the Global Marine Species Assessment (GMSA) published Thursday in Science, one-third of the more than 700 species of reef-building corals are threatened with extinction. Compare that to a decade ago, when only 2% of corals were endangered. Using criteria established by the International Union for the Conservation of Nature — a group that publishes an annual Red List of threatened animals — that makes corals the most endangered species on the Earth. The assessment's results, presented at the annual International Coral Reef Symposium in Fort Lauderdale, come just a week after the National Oceanic and Atmospheric Administration (NOAA) announced that more than half of the coral reef ecosystems in U.S. territory are in fair or poor condition. "We're losing the coral in the coral reef," said William Platt, a coral reef expert with NOAA.

The causes of the coral's demise are manifold, but they all come back to one culprit: us. Overfishing — especially the kind that uses dynamite or poison to kill whole schools of fish — destroys the coral directly, while polluted runoff from agriculture simply chokes them. Development in booming coastal economies from the Caribbean to Southeast Asia further threaten the delicate reefs. Tourism — in the form of diving and snorkeling — can also cause damage. As with so many other endangered species around the world, there doesn't seem to be enough space for healthy coral reefs and unchecked human development. "It's just a litany of bad actions," says Brian Huse, the executive director of the Coral Reef Alliance. "Over the past 35 to 50 years, we've lost 25% of our reefs worldwide. Put it altogether, and you can see why."

Disease plays a role as well, with whole coral colonies wiped out by sudden sickness. That rise in illness may be linked to warmer sea temperatures, which is caused by climate change. And it's global warming that poses the most serious threat to the survival of coral. Corals have a symbiotic relationship with a kind of algae that provide nutrients and energy through photosynthesis — not to mention the vivid colors we associate with coral reefs. When corals are stressed by rising temperatures, the algae are expelled by the coral, turning the reefs bone white. That's a "bleaching event," and bleached coral are left weakened and defenseless against disease. Increased carbon dioxide concentrations in the atmosphere also lead to more acidic seas, which impairs the ability of corals to form their skeletal reefs. (In acidic water, the reefs simply dissolve.) "Corals appear to be particularly sensitive to the buildup of CO2," says Kent Carpenter, the lead author of the Science study and the director of GMSA. "The corals will be the canary in the coal mine in terms of the effect climate change will have on our oceans."

In one way, protecting the coral is not that different from protecting any endangered species. First, we need to cut back on activities that ruin their habitat, the shallow waters close to our coast. Agricultural runoff — already responsible for the oceanic "dead zones" seen in the Gulf of Mexico and other heavily built up coasts — has to be curtailed, as does the senselessly destructive fishing practices that have us tossing dynamite or poison into the waters. One of the best strategies is to expand the range of territory protected by marine reserves — national parks of the deep. And here the Bush Administration — usually anything but environmental — deserves real credit. With a stroke of a pen in 2006, President George W. Bush created the Papahanaumokuakea Marine National Monument, a 140,000 sq. mi. protected area northwest of Hawaii. Larger than every other national park in the U.S. combined, the monument protects 10% of the shallow coral reef habitat in U.S. territory. These kind of reserves need to be expanded, to limit the influence of human activity on delicate corals.

But we could make the entire ocean into a marine park and still lose the coral, if we can't stop climate change. As temperatures rise in the ocean, bleaching events will become more and more common. According to a study published in Science late last year, if CO2 levels continue rising unabated, by 2100 coral could be utterly extinct. "If we can't contain the CO2 problem and enact strong coral reef conservation measures, we will lose them," says Carpenter. The depressing fate of the coral could be a reminder that climate change has the power to undo all the work of wildlife conservation over the past century — if we let it.

即使你不是海洋生物學家，只需向某個潛水員請教一下，你就會明白珊瑚是多么重要。這種微小的水下生物在地球上的熱帶水域建造美麗而多彩的珊瑚礁。潛水員們向珊瑚蜂擁而去并非僅因其自身的美麗，而是因為珊瑚礁蘊藏著比其它水下世界更為豐富的生物多樣性。25％以上的海洋物種是以珊瑚礁為棲息地的。毀掉珊瑚的話，珊瑚礁就不存在了——沒有了珊瑚礁，整個生態系統就會崩塌。

不幸的是，上述這一幕似乎正要在地球上上演。據全球海洋物種評估委員會(GMSA) 周四在《科學》雜志上發表的一份全面調查報告顯示，在700多種造礁珊瑚里有三分之一面臨滅絕的威脅。而十年前，僅有2％的造礁珊瑚瀕臨滅絕。按照國際自然保護聯盟（International Union for the Conservation of Nature）的標準——即該組織發布的一份瀕危動物年度緊急名單——珊瑚是地球上最具滅絕威脅的動物。出現在勞德代爾堡（Fort Lauderdale）年度國際珊瑚討論會上的這份評估結果，是在美國國家海洋和大氣局（NOAA）宣布美國境內一半以上的珊瑚礁生態系統狀況堪憂的一周以后出版的。“人類即將失去造礁珊瑚，”美國國家海洋和大氣局的一位珊瑚礁專家威廉·普萊特說。

珊瑚的死亡原因多種多樣，但它們都可歸咎于同一個罪魁禍首：我們人類。過渡捕撈——尤其是使用炸藥或毒藥殺死整個魚群的做法——對珊瑚造成直接性破壞，然而，受污染的農業活水幾乎使珊瑚窒息而亡。從加勒比海到東南亞，迅速發展的沿海經濟給脆弱的珊瑚造成更為嚴重的威脅。旅游業——尤其潛水——也可能會破壞珊瑚。和許多其它瀕危物種一樣，健康的珊瑚礁以及人類未開發的空間似乎沒剩多少了。“人類的這些活動真是危害不淺，”珊瑚礁聯盟的執行懂事布賴恩·休斯說。“在過去的35到50年間，在全球范圍內人類已經失去了25％的珊瑚礁。總之，大家都清楚其中的原因。”

疾病是珊瑚死亡的另一個原因，曾發生過整個珊瑚群因突發疾病而死亡的事件。珊瑚患病的增加可能與氣候變化引起的海水溫度升高有關。全球變暖正是珊瑚生存的最大威脅。珊瑚與一種海藻有著共生關系，因為這種海藻通過光合作用為珊瑚提供營養和能量——還是我們所能想像出的珊瑚礁鮮艷色彩的來源。當珊瑚遭受溫度升高時，它們就會將這種海藻驅走，結果珊瑚礁的骨骼就變成白色。這種現象叫做“漂泊”，而且被漂泊了的珊瑚會變得脆弱，并失去抵抗疾病的能力。大氣中CO2濃度的增加也會加速海水的酸化，這會降低珊瑚形成珊瑚礁骨骼的能力。(在酸性的海水中，珊瑚礁會完全溶解。)“珊瑚似乎對CO2濃度的升高特別敏感，”《科學》雜志研究的主要作者兼全球海洋物種評估委員會主任肯特·卡彭特說。“如果海洋受到氣候變化的影響，那么煤礦中的珊瑚會呈淡黃色。”

從某方面來說，珊瑚保護同其它瀕危物種的保護方式一樣。首先，我們必需減少對靠近海岸淺水區域的珊瑚棲息地的破壞活動。農業活水——已經致使墨西哥灣出現海洋“死區”，也使其它海岸受到嚴重污染——必需得到控制，人類往海水里投炸藥或毒藥的無意識破壞性漁業活動也同樣要減少。最好的辦法就是擴大海洋保護區域的范圍——建造深海國家公園。現在布什政府值得信賴——通常在環境方面絕非如此。布什總統于2006年執政后，在夏威夷西南部創建了一個140，000平方英哩的海洋保護區，名為Papahanaumokuakea海洋國家公園。該海洋國家公園是美國境內最大的國家公園，它保護著美國境內10％的珊瑚淺水棲息地。要想控制人類活動對脆弱珊瑚的影響，這樣的保護區還需擴大。

然而，人類如果不能制止氣候變化，即使將整個海洋變成海洋公園，珊瑚還是會滅絕。隨著海水溫度 的不斷升高，漂泊現象會越來越頻發。根據《科學》雜志于去年底刊登的項研究顯示，如果CO2的含量以現在的速度不斷上升的話，珊瑚有可能會在2010年徹底滅絕。“如果人類不能解決CO2 含量升高的問題并加強保護珊瑚的措施，人類將會失去它們，”卡彭特說。珊瑚的暗淡前景提醒我們，如果放任氣候變化不管的話，我們在上個世紀所做的一切保護野生動物的工作將付之東流。