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学家，只需向某个潜水员请教一下，你就会明白珊瑚是多么重要。这种微小的水下生物在地球上的热带水域建造美丽而多彩的珊瑚礁。潜水员们向珊瑚蜂拥而去并非仅因其自身的美丽，而是因为珊瑚礁蕴藏着比其它水下世界更为丰富的生物多样性。25％以上的海洋物种是以珊瑚礁为栖息地的。毁掉珊瑚的话，珊瑚礁就不存在了——没有了珊瑚礁，整个生态系统就会崩塌。

不幸的是，上述这一幕似乎正要在地球上上演。据全球海洋物种评估委员会(GMSA) 周四在《科学》杂志上发表的一份全面调查报告显示，在700多种造礁珊瑚里有三分之一面临灭绝的威胁。而十年前，仅有2％的造礁珊瑚濒临灭绝。按照国际自然保护联盟（International Union for the Conservation of Nature）的标准——即该组织发布的一份濒危动物年度紧急名单——珊瑚是地球上最具灭绝威胁的动物。出现在劳德代尔堡（Fort Lauderdale）年度国际珊瑚讨论会上的这份评估结果，是在美国国家海洋和大气局（NOAA）宣布美国境内一半以上的珊瑚礁生态系统状况堪忧的一周以后出版的。“人类即将失去造礁珊瑚，”美国国家海洋和大气局的一位珊瑚礁专家威廉·普莱特说。

珊瑚的死亡原因多种多样，但它们都可归咎于同一个罪魁祸首：我们人类。过渡捕捞——尤其是使用炸药或毒药杀死整个鱼群的做法——对珊瑚造成直接性破坏，然而，受污染的农业活水几乎使珊瑚窒息而亡。从加勒比海到东南亚，迅速发展的沿海经济给脆弱的珊瑚造成更为严重的威胁。旅游业——尤其潜水——也可能会破坏珊瑚。和许多其它濒危物种一样，健康的珊瑚礁以及人类未开发的空间似乎没剩多少了。“人类的这些活动真是危害不浅，”珊瑚礁联盟的执行懂事布赖恩·休斯说。“在过去的35到50年间，在全球范围内人类已经失去了25％的珊瑚礁。总之，大家都清楚其中的原因。”

疾病是珊瑚死亡的另一个原因，曾发生过整个珊瑚群因突发疾病而死亡的事件。珊瑚患病的增加可能与气候变化引起的海水温度升高有关。全球变暖正是珊瑚生存的最大威胁。珊瑚与一种海藻有着共生关系，因为这种海藻通过光合作用为珊瑚提供营养和能量——还是我们所能想像出的珊瑚礁鲜艳色彩的来源。当珊瑚遭受温度升高时，它们就会将这种海藻驱走，结果珊瑚礁的骨骼就变成白色。这种现象叫做“漂泊”，而且被漂泊了的珊瑚会变得脆弱，并失去抵抗疾病的能力。大气中CO2浓度的增加也会加速海水的酸化，这会降低珊瑚形成珊瑚礁骨骼的能力。(在酸性的海水中，珊瑚礁会完全溶解。)“珊瑚似乎对CO2浓度的升高特别敏感，”《科学》杂志研究的主要作者兼全球海洋物种评估委员会主任肯特·卡彭特说。“如果海洋受到气候变化的影响，那么煤矿中的珊瑚会呈淡黄色。”

从某方面来说，珊瑚保护同其它濒危物种的保护方式一样。首先，我们必需减少对靠近海岸浅水区域的珊瑚栖息地的破坏活动。农业活水——已经致使墨西哥湾出现海洋“死区”，也使其它海岸受到严重污染——必需得到控制，人类往海水里投炸药或毒药的无意识破坏性渔业活动也同样要减少。最好的办法就是扩大海洋保护区域的范围——建造深海国家公园。现在布什政府值得信赖——通常在环境方面绝非如此。布什总统于2006年执政后，在夏威夷西南部创建了一个140，000平方英哩的海洋保护区，名为Papahanaumokuakea海洋国家公园。该海洋国家公园是美国境内最大的国家公园，它保护着美国境内10％的珊瑚浅水栖息地。要想控制人类活动对脆弱珊瑚的影响，这样的保护区还需扩大。

然而，人类如果不能制止气候变化，即使将整个海洋变成海洋公园，珊瑚还是会灭绝。随着海水温度 的不断升高，漂泊现象会越来越频发。根据《科学》杂志于去年底刊登的项研究显示，如果CO2的含量以现在的速度不断上升的话，珊瑚有可能会在2010年彻底灭绝。“如果人类不能解决CO2 含量升高的问题并加强保护珊瑚的措施，人类将会失去它们，”卡彭特说。珊瑚的暗淡前景提醒我们，如果放任气候变化不管的话，我们在上个世纪所做的一切保护野生动物的工作将付之东流。