Scientists have long known that reefs are in peril, but a new study published today in the journal One Earth quantifies coral losses around the world. The in-depth analysis reveals half of coral reefs have been lost since the 1950s. Scientists say climate change, overfishing and pollution are decimating these fragile ecosystems and putting communities and livelihoods in jeopardy. Their study, which is among the most comprehensive assessment of reefs and their associated biodiversity to date, underscores the rapid pace of global coral collapse.

科学家们早就知道珊瑚礁处于危险之中，但今天发表在《One Earth》杂志上的一项新研究量化了全世界珊瑚礁的损失。深入的分析显示，自20世纪50年代以来，一半的珊瑚礁已经永远消失了。科学家说，气候变化、过度捕捞和海洋污染正在摧毁这些脆弱的生态系统，使它们处于危险之中。他们的研究是迄今为止对珊瑚礁及其相关生物多样性进行的最全面的评估之一，强调了全球珊瑚礁迅速崩溃的速度。

“Coral reefs have been in decline worldwide—I think that's pretty commonly accepted,” says Tyler Eddy, a research scientist at Memorial University of Newfoundland who co-authored the study. “We didn't necessarily know the magnitude of how much, when we looked on a global scale, that reefs had declined.”

“珊瑚礁在世界范围内呈下降趋势，我认为这是非常明显的，”加拿大纽芬兰纪念大学的研究科学家Tyler Eddy说，他共同参与撰写了这项研究。“从全球范围来看，我们不知道珊瑚礁减少了多少的确切数量。”

Coral reefs are biodiversity hotspots that provide habitat for fishes, protection for coastal communities and generate billions of dollars for fisheries and tourism. Part of the reason corals are dying is that they’re ultra-sensitive to changes in water temperature and acidity, says biologist Mary Hagedorn, who wasn’t involved in the study.

珊瑚礁是生物多样性的大集合，它为鱼类提供栖息地，保护沿海生态系统，并为渔业和旅游业创造数十亿美元的价值。生物学家Mary Hagedorn说，珊瑚死亡的部分原因是它们对水温和酸度的变化极为敏感。

“Corals have skeletons, which makes them seem like rocks,” says Hagedorn, but they are animals with symbiotic partners. Coral polyps rely on colorful algae, called zooxanthellae, which live in their tissue and produce food the corals need to survive. When the polyps are stressed by changes in light, water temperature or acidity, they break that symbiotic relationship and expel the algae in a process called bleaching. Corals have a short window to regain their symbiotic algae, but if corals are stressed for too long, their death is irreversible. “There is not a reef on earth that has not been touched by some aspect of this global and local threat,” says Hagedorn.

“珊瑚有骨骼组成，这使它们看起来像岩石，”哈格多恩说，但它们是有共生伙伴的动物。珊瑚虫依赖五颜六色的藻类，称为虫黄藻，它们生活在珊瑚虫的组织中，并产生珊瑚生存所需的食物。当珊瑚虫受到光照、水温或酸度变化的影响时，它们会打破这种共生关系，并通过一种称为珊瑚白化的过程将藻类排出体外。珊瑚恢复共生藻类的时间很短，但如果珊瑚承受的这种压力持续时间太长，它们的死亡是不可逆转的。她说：“地球上没有一个珊瑚礁未受到一定程度上的影响。”

Most coral assessments focus on specific regions or reefs, but Eddy and his colleagues from the University of British Columbia wanted to more complete assessment of coral losses. They used a combination of databases containing thousands of surveys of coral reef cover, marine biodiversity records and fisheries catch data to assess how each factor changed over time. They were particularly curious what dying corals meant for a reef’s “ecosystem services”—including providing habitat for diverse marine species, protecting the coast from storms and serving as a source of food and livelihood.

大多数珊瑚评估侧重于特定的区域或珊瑚礁群，但英属哥伦比亚大学的Eddy和他的同事希望更完整地评估珊瑚的损失。他们综合使用了包含数千项珊瑚礁覆盖调查、海洋生物多样性记录和渔获量数据的数据库来评估每个因素随时间的变化。他们特别好奇珊瑚礁的“生态系统”到底意味着什么——包括为各种海洋物种提供栖息地、保护海岸免受风暴侵袭以及作为渔民的食物和生计来源。

In addition to finding that half of living corals have died since the 1950s, researchers discovered that coral-reef-associated biodiversity dropped by 63 percent. Healthy reefs support thousands of different corals, fish and marine mammals, but bleached reefs lose their ability to support as many species. The scientists also found that catches of coral reef fishes peaked in 2002 and have been declining since then despite increasing fishing effort. And the study showed that the loss of coral species wasn’t equal across reefs—certain corals are proving more sensitive than others, leading some biologists to worry that some vulnerable coral species will be lost before they can be documented or preserved.

除了发现自20世纪50年代以来有一半的活珊瑚已经死亡外，研究人员还发现与珊瑚礁相关的生物多样性下降了63%。健康的珊瑚礁支撑着数千种不同的珊瑚、鱼类和海洋哺乳动物，但白化的珊瑚礁失去了支撑许多物种生态的能力。科学家们还发现，珊瑚礁附近鱼类的捕获量在2002年达到顶峰，尽管在此之前捕鱼数量不断增加，但此后一直在下降。这项研究表明，珊瑚物种的损失在整个珊瑚礁中并不平等。事实证明，某些珊瑚比其他珊瑚更为敏感，这导致一些生物学家担心，一些脆弱的珊瑚物种将在被发现或记录下来之前就消失了。

One challenge the team faced was finding detailed, accurate information about reef coverage in the 1950s. To deal with this limitation, they relied on coral cover estimates from their 2018 study on historical coral coverage. In the earlier work, the study authors asked more than one hundred scientists what they believed coral reef cover would have been at a given year based on existing evidence.

该团队面临的一个挑战是寻找1950年代珊瑚礁覆盖率的详细、准确信息。为了解决这一局限性，他们依靠2018年历史珊瑚覆盖率研究中的珊瑚覆盖率来试着估算。在研究早期，作者询问了100多位科学家，根据现有证据，他们由此来推断某一年珊瑚礁的覆盖率是多少。

The recent study didn’t assess what factors led to coral declines in recent decades, though overfishing and pollution from nearby land-based agriculture are common local stressors. Eddy and other coral experts agree the biggest threat to reefs is climate change, and note that the regions that contribute less to climate change often feel the worst impacts. Each year, the ocean absorbs around one-quarter of the carbon dioxide emitted from the burning of fossil fuels and becomes warmer, more acidic and less hospitable to corals.

最近的研究没有评估是什么因素导致了近几十年来珊瑚数量的下降，尽管过度捕捞和附近陆地农业的污染是当地常见的破坏源头。Eddy和其他珊瑚专家一致认为，珊瑚礁面临的最大威胁是气候变化，并指出，对气候变化本身产生影响较小的地区往往受到最严重的破坏。每年，海洋吸收化石燃料排放的二氧化碳的四分之一左右，并变得更温暖、更具酸性，对珊瑚也不那么友好。

“There are lots of strategies for saving coral reefs and for bringing down carbon emissions, and people often debate about what's most effective,” says Hicks. “What this study says is that it's even more vital that we act now, and that we act in all directions.”

Hicks说：“拯救珊瑚礁和减少碳排放有很多种办法，而人们常常在那争论什么办法最有效。”“这项研究表明，我们现在采取实实在在的行动更为重要，我们要全方位行动起来。