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(xué)家，只需向某個(gè)潛水員請(qǐng)教一下，你就會(huì)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?yàn)樯汉鹘柑N(yùn)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(gè)生態(tài)系統(tǒng)就會(huì)崩塌。

不幸的是，上述這一幕似乎正要在地球上上演。據(jù)全球海洋物種評(píng)估委員會(huì)(GMSA) 周四在《科學(xué)》雜志上發(fā)表的一份全面調(diào)查報(bào)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(hù)聯(lián)盟（International Union for the Conservation of Nature）的標(biāo)準(zhǔn)——即該組織發(fā)布的一份瀕危動(dòng)物年度緊急名單——珊瑚是地球上最具滅絕威脅的動(dòng)物。出現(xiàn)在勞德代爾堡（Fort Lauderdale）年度國際珊瑚討論會(huì)上的這份評(píng)估結(jié)果，是在美國國家海洋和大氣局（NOAA）宣布美國境內(nèi)一半以上的珊瑚礁生態(tài)系統(tǒng)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(gè)罪魁禍?zhǔn)祝何覀內(nèi)祟悺＿^渡捕撈——尤其是使用炸藥或毒藥殺死整個(gè)魚群的做法——對(duì)珊瑚造成直接性破壞，然而，受污染的農(nóng)業(yè)活水幾乎使珊瑚窒息而亡。從加勒比海到東南亞，迅速發(fā)展的沿海經(jīng)濟(jì)給脆弱的珊瑚造成更為嚴(yán)重的威脅。旅游業(yè)——尤其潛水——也可能會(huì)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(fā)的空間似乎沒剩多少了。“人類的這些活動(dòng)真是危害不淺，”珊瑚礁聯(lián)盟的執(zhí)行懂事布賴恩·休斯說。“在過去的35到50年間，在全球范圍內(nèi)人類已經(jīng)失去了25％的珊瑚礁�？傊�，大家都清楚其中的原因。”

疾病是珊瑚死亡的另一個(gè)原因，曾發(fā)生過整個(gè)珊瑚群因突發(fā)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(guān)。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(guān)系，因?yàn)檫@種海藻通過光合作用為珊瑚提供營(yíng)養(yǎng)和能量——還是我們所能想像出的珊瑚礁鮮艷色彩的來源。當(dāng)珊瑚遭受溫度升高時(shí)，它們就會(huì)將這種海藻驅(qū)走，結(jié)果珊瑚礁的骨骼就變成白色。這種現(xiàn)象叫做“漂泊”，而且被漂泊了的珊瑚會(huì)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(huì)加速海水的酸化，這會(huì)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(huì)完全溶解。)“珊瑚似乎對(duì)CO2濃度的升高特別敏感，”《科學(xué)》雜志研究的主要作者兼全球海洋物種評(píng)估委員會(huì)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(huì)呈淡黃色。”

從某方面來說，珊瑚保護(hù)同其它瀕危物種的保護(hù)方式一樣。首先，我們必需減少對(duì)靠近海岸淺水區(qū)域的珊瑚棲息地的破壞活動(dòng)。農(nóng)業(yè)活水——已經(jīng)致使墨西哥灣出現(xiàn)海洋“死區(qū)”，也使其它海岸受到嚴(yán)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(shí)破壞性漁業(yè)活動(dòng)也同樣要減少。最好的辦法就是擴(kuò)大海洋保護(hù)區(qū)域的范圍——建造深海國家公園。現(xiàn)在布什政府值得信賴——通常在環(huán)境方面絕非如此。布什總統(tǒng)于2006年執(zhí)政后，在夏威夷西南部創(chuàng)建了一個(gè)140，000平方英哩的海洋保護(hù)區(qū)，名為Papahanaumokuakea海洋國家公園。該海洋國家公園是美國境內(nèi)最大的國家公園，它保護(hù)著美國境內(nèi)10％的珊瑚淺水棲息地。要想控制人類活動(dòng)對(duì)脆弱珊瑚的影響，這樣的保護(hù)區(qū)還需擴(kuò)大。

然而，人類如果不能制止氣候變化，即使將整個(gè)海洋變成海洋公園，珊瑚還是會(huì)滅絕。隨著海水溫度 的不斷升高，漂泊現(xiàn)象會(huì)越來越頻發(fā)。根據(jù)《科學(xué)》雜志于去年底刊登的項(xiàng)研究顯示，如果CO2的含量以現(xiàn)在的速度不斷上升的話，珊瑚有可能會(huì)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(qiáng)保護(hù)珊瑚的措施，人類將會(huì)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?cè)谏蟼�(gè)世紀(jì)所做的一切保護(hù)野生動(dòng)物的工作將付之東流。