AT THE top of Green Mountain, the central peak of Ascension Island, there is a small pond, dotted with lilies, shadowed to one side by the fronds of a pandan tree. It is the only open body of fresh water on the island—and for a thousand kilometres in any direction. Around Dew Pond grows a grove of towering bamboo, beyond which the trade winds blow incessantly from the south-east. Within the grove the air is still and damp.

在阿森松岛中部的绿峰山顶,有一口小池塘,池塘的一面被一颗露兜树的树冠所遮掩,池塘的水面上露出点点百合。这口小池塘是岛内唯一的一处露于地面的淡水,而且也是方圆一千公里内唯一的一处。这口露水池塘周围生长着一片高大的竹林,竹林的外层受到从东南方向刮来的信风一刻不停地吹打。但竹林内却不闻一丝风声,且空气潮湿。

Along the trailing ridge of the summit are fig trees, Cape yews and a garland of remarkably vigorous ginger. Below, on the mountain's lee side, trees and shrubs from all parts of the world spread down the hillside to a landscape of casuarina trees—ironwood, or she-oak—and thorny chaparral around its base. Even on the bleaker windward slope, grasses and sedges are dotted with Bermuda cedar and guava bushes. Above, the bamboo scratching at their bellies, are the clouds the trade winds bring; some days they cover the mountain top.

峰顶逶迤的山脊上散布着无花果树、好望角紫杉和一个盛开的生姜花环。在山顶下面的背风坡面上,可以看到来自世界各地的乔木和灌木自上而下一直延伸到山脚,山脚附近是一处由木麻黄属的各种常绿乔木所构成的景观,可以看到铁木、澳洲木麻黄和多刺的北美灌木丛。即使在寒风凛冽的迎风坡面上也生长着禾草与莎草,百慕大雪松和番石榴树丛则点缀其间。天空中是信风带来的朵朵云团,有些时候乌云会遮住整个山颠。信风驱赶着云团快速地移动着,而竹林就像在刮挠着云团的肚皮。

Once seen as too dry to be worth inhabiting, Ascension Island is becoming greener at an increasing rate. People are responsible. In part, their contribution was unwitting: the thorny mesquite that anchors a lot of the island's scrub was introduced for a landscaping project just 50 years ago. But the forest on the peak of Green Mountain represents a deliberate attempt to change the island's climate to make it more habitable. It is the centrepiece of a small but startling ecological transformation which is part experiment and part accident, part metaphor and part inspiration.

过去人们曾认为阿森松岛过于干燥,不适于植物生长,但现在植物却以越来越快的速度覆盖了这个岛屿。人类要为此负责。在某种程度上,人类对该岛绿化的贡献是在不知不觉中完成的。例如,多刺的牧豆树大大地减少了这个岛屿的水土流失,而在50年前人们只是为了一项景观工程而引进了这种植物。但绿峰生长的森林则代表了人们有意识地改变这个岛屿的气候,使之更适合人类居住的一种尝试。这是一个小规模但效果惊人的生态化改造最引人注目的地方,这个改造工程部分来自人类的试验,部分是出于巧合;部分只具象征意义,而部分却是对人类的一种鼓舞。

Ascension was discovered by the Portuguese in 1501. Just to the west of the mid-ocean ridge that separates South America's tectonic plate from Africa's, it is the top of a volcano which rises steeply from abyssal plains more than four kilometres below the surface of the ocean. The volcano made it above that surface only a million or so years ago, since when the island has grown to about 100 square kilometres. Before people arrived it was home to just a flightless bird, a land crab and no more than 30 species of plant, none as big as a bush. It was so barren and isolated that during the following three centuries of assiduous empire-building neither the Portuguese nor any other nation bothered to claim it. When Captain Cook passed by in 1775, Georg Forster—later to become renowned for his accounts of exploration—wrote it off as a "ruinous heap of rocks", drearier even than Tierra del Fuego and Easter Island. But Forster's naturalist father Johann saw something more promising:

阿森松岛是葡萄牙人于1501年发现的。它正好位于将南美板块与非洲板块分隔开的大洋中脊的西部,是一个火山锥露出水面的部分,这座火山锥从大洋表面下四千多米深的深海平原上陡峭地拔起。火山喷发使这座岛屿露出水面距今大概只有一万年左右,自那以后,这座岛屿生长到了大约100平方公里。在人类到达这座岛屿之前,它只是一种不会飞的鸟类、一种陆蟹和不超过30种植物的家园,所有植物的大小都不超过一丛灌木。阿森松岛孤悬于海外,又是如此的贫瘠,在随后的三个世纪内,尽管各大国忙于扩张疆土,但无论是葡萄牙还是其他国家都不屑于认领这个岛屿。当库克船长于1775年经过这个岛屿时,后来由于其探险经历而闻名的Georg Forster将它描绘成“一堆破败的石头”,甚至比火地岛和复活节岛都要单调和乏味。但福斯特的父亲,博学家约翰却认识到了该岛的某些价值。他写道:

This barren island with very little trouble might be settled and made a very useful place of refreshment ... I am persuaded that if the common furze, which thrives so well on St Helena, were planted on this island, it would no doubt equally thrive here, and were these Furzes everywhere growing, grass and other plants would no doubt immediately grow between them ... The more the surface of the earth is covered with plants the more would they not only evaporate but even attract the moisture of the air ... after grass and water were more plentiful in the isle certainly many a tree would soon grow and thus afford fuel.

这个几乎不会给人带来麻烦的贫瘠小岛可能适于人类居住,可用作放松疗养之地……我相信,如果将在圣赫勒拿岛上生机勃勃的金雀花移植到这个岛上,毫无疑问它们也会在这里茁壮成长。如果岛上到处生长出金雀花,则草类和其他植物无疑将立即在它们之间生长出来。……岛屿表面覆盖的植物越多,它们蒸发出的水分就越多,甚至能够吸收空气中的水分……岛上的青草和水逐渐增多后,肯定很快就会生长出很多树木,从而为居住的人类提供了燃料。

Islands had a particular hold on the imaginations of explorers like Forster. It had long been widely held that the varieties of humankind reflected the action of different climates. In the late 18th century the opposite notion began to take hold among sailors, scientists and administrators: that humankind might itself act to change the climate, either for the worse or for the better, mainly through what it did or didn't do to trees. A decade after Cook and the Forsters, a French explorer, La Pérouse, visited Easter Island. Noting the island's "dreadful aridity" in the midst of an immense ocean, he blamed the ancestors of the island's inhabitants, who had cut down the trees.

岛屿特别能够激发福斯特一类探险家的想象力。人们长期以来就普遍认可这样的观点,即不同的人种反映了不同的气候作用。18世纪后期在水手、科学家和官员中有人开始持相反的观念:即人类本身的活动也可以改变气候。人类主要是通过破坏或保护树木的方式来影响气候的变化,可能产生好坏两种结果。在库克与福斯特登上复活节岛十年后,一名法国探险家拉彼鲁兹也考察了该岛。他注意到浩瀚的大洋中这个岛上“可怕的干旱”,他认为是该岛上居民的祖先们砍伐了岛上的树木而导致了这种气候。

Those imprudent ancestors have become symbols for mankind's short-sighted carelessness with his environment. As environmentalists began to preach the gospel of finite resources, and satellites sent home images of the Earth looking like a small island in a vast dark sea, the fate of Easter Island seemed like a fearful parable. In his jeremiad, "Collapse", Jared Diamond described Easter Island's story as "the closest approximation that we have to an ecological disaster unfolding in complete isolation".

复活节岛上不明智的先人已成为人类不珍视环境的短视行为的代名词。由于环保人士开始四处宣讲资源有限的道理,人造地球卫星也将地球就像一个黑暗大海中的小岛的照片发了回来,复活节岛的命运似乎成了一个可怕的圣经中的寓言故事。在他的长篇悲剧故事《崩溃》中,贾雷德?戴蒙德(Jared Diamond)将复活节岛的故事形容为“人类在经历了一场生态灾难后演变成完全孤立的一种最近似的状态”。

Yet it would be a mistake to place too much weight on this tale. The familiar story—deforestation leading to environmental degradation; subsequent population collapse, possibly including cannibalism; eventual endemic misery—has been revised in recent years. Some suggest that the Easter Islanders' fate was not purely self-inflicted: seed-eating rats, European slavers and climate change were in part responsible. And although apocalyptic stories have a power that brighter tales lack, mankind's record is more nuanced than the Easter Island story suggests. People have created fertile ecosystems as well as destroyed them. Ascension Island is a supreme example.

然而,将这个故事看的太重也可能会出现错误。一些人们耳熟能详的故事近几年来改头换面后又出笼了,如砍伐森林将导致环境退化,随后就是人口的锐减,甚至还可能出现人吃人的现象,总之最后的结局是特别地悲惨。一些人认为,复活节岛的命运不单纯是岛民自己造成的。吃种子的老鼠、欧洲的奴隶贩子和气候变化也要承担部分责任。虽然末日将临的故事比结局美好的故事更能使人猛醒,但人类迄今的活动记录与复活节岛故事的预示相比还是有着微妙的差别。人类既有毁灭生态系统的纪录,也有创造出丰富多彩的生态系统的事例。阿森松岛就是一个最好的例子。

A kaleidoscope of connections
形形色色的联系

Ascension's key advantage over Easter Island is that it is remote, but not entirely isolated. Once it was eventually settled, it remained connected to the rest of the world for all sorts of purposes and in a succession of different ways. Britain first took possession of it in 1815 lest it be used as a staging post to rescue Napoleon Bonaparte from exile in St Helena. Later it became a supply base for the navy's campaign against the slave trade; the steady warm air of the trade winds meant it also made a good sanatorium for sailors and freed slaves. For administrative purposes it was treated as a vessel, HMS Ascension, "sloop of war of the smaller class". Subsequently it provided succour to ships, both naval and merchant, that found themselves in distress. The fact that the island could supply magnificent turtles—they migrate from Brazil to lay eggs on, or in, the beaches—as a delicacy to the lords of the Admiralty probably helped justify its garrison, too.

阿森松岛与复活节岛相比,其主要优势在于虽然该岛地理位置偏僻,但与外界始终保持着一定的联系。自从有人在岛上定居之日起,出于各种目的,并以一连串不同的方式使这个岛屿与世界各地保持了联系。英国在1815年第一次占领了这个岛屿,以免有人利用该岛作为营救在圣赫勒拿岛流放的拿破仑的中转站。后来该岛成了英国海军反奴隶贸易战的后勤供应基地。信风带来的稳定的暖空气也使该岛成为了水手和被解救的奴隶们进行疗养恢复的好地方。为了管理方便,该岛被视作一艘军舰,编制为皇家海军“阿森松岛”号,属于“轻型单桅帆船战舰”。随后,该岛被用作向处于困境中的皇家海军军舰及商船提供救助。该岛还盛产上等海龟,这些海龟从巴西洄游到这个岛屿的海滩上产卵。海军大臣们对这种美味的嗜好可能有助于在该岛上保持驻军。

As the 19th century waned, steam and the Suez Canal meant that there was less and less call on Ascension for services to shipping. Then, in 1899, a telegraph cable connecting Britain to Cape Town came ashore amid the jagged rocks of Comfortless Cove. It was soon joined by cables from Sierra Leone, Buenos Aires and Rio de Janeiro. During the first world war radio receivers were strung over the lava like washing lines to provide communication with ships at sea.

伴随着19世纪的结束,蒸汽机和苏伊士运河相续出现,这意味着停靠阿森松岛进行补给和维修的船舶数量越来越少。然后,在1899年,一条连接不列颠岛与开普敦的电报电缆在礁石嶙峋的坎福特湾(Comfortless Cove)上岸。不久,来自塞拉利昂、布宜诺斯艾利斯和里约热内卢的电报电缆也都汇集到这里。在第一次世界大战期间,无线电天线就像晾衣绳一样布满了这座火山岩,这些天线为在海上航行的船舶提供通信联系架起了桥梁。

In 1922 the "stone frigate" HMS Ascension was decommissioned, and the island became in law a dependency of St Helena; in reality it became a fief of the Eastern Telegraph Company, which was subsequently absorbed by Cable & Wireless. Two decades later, it found itself part of a different connection—one that ran from the aircraft manufacturers of America to the North African and Mediterranean theatres of the second world war. American troops built an airstrip on the lava plains in the south of the island where the wide-awake terns nested; 20,000 fighters and bombers flew in from Brazil, refuelled and went on to Africa. Forty years after that, Ascension provided an air bridge when Britain fought for the Falkland Islands.

1922年,这艘“岩石护卫舰”,皇家海军“阿森松岛”号正式退役,而该岛在法律上成为了圣赫勒拿岛的属地,但实际上它成了东方电报公司(Eastern Telegraph Company)的采邑,这家公司后来被英国大东电报局(Cable & Wireless)合并。二十年后,阿森松岛又成了完全不相干的人走到了一起的地方。第二次世界大战中从美国的飞机制造厂逃跑出来的人以及逃避北非和地中海战火的人们在这里相聚。美国军队在该岛南部平整的熔岩上修建了一条飞机跑道,这里曾是机警的燕鸥的栖息地。先后有20000架战斗机和轰炸机从巴西飞来,在这里加满油后这些飞机又继续飞往非洲。四十年后,阿森松岛又为英国夺回福克兰群岛架起了一道空中桥梁。

These days it is a communications hub. Wires strung between two sets of tall towers transmit the BBC World Service's broadcasts to 85m listeners in Africa and beyond. Nearby, strange geometries of short-wave systems connect the British and American armed forces to ships and aircraft. Aerials that look a bit like fish-skeletons are used by the spooks at Britain's GCHQ, a strategic eavesdropping organisation. Dishes track space launches from Cape Kennedy and European space launches from French Guiana, and monitor tests of submarine-launched missiles.

眼下该岛被用作通信枢纽。两个高塔间垂挂着成串的线束,高塔将英国广播公司国际播音部的广播节目传递给非洲和更远一些地区的8500万听众。不远处,奇形怪状的短波系统天线连接着英国和美国军队的船舶与飞机。看起来像鱼骨架的天线其使用者是英国国家通信总局的情报人员,这是一个战略性的情报窃听机构。碟形天线被用于追踪从肯尼迪角及欧洲航天中心从法属圭亚那进行的宇航火箭发射,监测潜艇的导弹发射试验。

Not all the information that washes across Ascension is picked up by electromagnetic means. The Met Office station measures greenhouse gases. Seismometers listen out not just for earthquakes but also for illicit nuclear explosions. Infrasound monitors do the same job for the atmosphere, picking up the inaudible but remarkably persistent sound waves that circle the world when a bomb goes off. Offshore instruments near the American base listen out for the underwater sound of such blasts.

并非所有掠过阿森松岛的信息都用电磁截收设备进行捕获。英国国家气象局的监测站也监测温室气体的动态。地震检波器不仅要监测地震,也要监测非法的核爆炸。次声波监听仪的探测对象与地震波检波器相同,但捕捉的是大气中传播的人耳听不见的声波。如果一枚核弹爆炸,则会产生这种著名的等幅声波,这种声波会环绕地球进行传播。美军基地附近海岸上的仪器可以监听到到核爆炸在水下的传播声波。

Building a new Eden
建设一个新的伊甸园

In the mid-19th century one Joseph Hooker visited Ascension Island. He was the son of the director of Kew Gardens, a job he later took on himself. Hooker advised the Admiralty to plant trees over the top of the mountain, encourage brambles, aloes and briar rose in the ravines and establish acacia, casuarina and eucalyptus on the lower slopes. Shipments of plants from the Cape and from Kew started soon thereafter, drawing on the entire botanic inventory of empire. In four months of 1860, John Bell, the island's horticulturalist, is reported to have supervised the planting of some 27,000 trees and shrubs. Surveying the results 140 years later, a British ecologist, David Wilkinson, turned to science fiction for the appropriate metaphor. Like an alien planet rearranged for human life, he wrote, Ascension Island had been "terraformed".

19世纪中叶一个叫做约瑟夫?胡克(Joseph Hooker )的人造访了阿森松岛。他是英国皇家植物园主管的儿子,他后来也坐上了这个位置。胡克建议海军部在山顶植树,在山谷种荆棘、芦荟和石楠;在山坡低处让金合欢树、木麻黄和桉树扎下根来。此后不久,来自开普敦和英国皇家植物园的植物陆续运达该岛,散布于整个大英帝国的各色植物都汇集到这个小岛,使小岛为之一变。据报告称,在1860年的四个月内,岛上的园艺师约翰?贝尔( John Bell)就监督种植了约2.7万株乔木和灌木。一位英国生态学家大卫?威尔金森(David Wilkinson)在140年后考察了其成效,他转向科幻小说中去寻找恰当的比喻。他说,就如同重新改造一个外行星以使之适于人类生存一样,阿森松岛已经“仿地成形”了。

The chief aim was to provide more rain and soil for the farm that had been established when the garrison was founded. In this, the scheme proved a long-term failure: the farm is no more. With two flights from Britain and one flight from America every week as well as regular visits by the Royal Mail ship St Helena, it is now cheaper to import food than to grow it.

这场绿化的主要目的是为驻军上岛的时候起就成立的农场提供更多的降雨和土壤。在这点上,这项长期计划已被证明归于失败,农场已经不复存在了。每星期有两个航班从英国,一个航班从美国抵达该岛,而且有英国皇家邮轮“圣赫勒拿岛号”的定期造访,现在运进的食物比在岛上种植的更便宜。

Nor is it clear that the foresting of Green Mountain has increased rainfall. Precipitation varies on Ascension; in the years that Bell was expanding the plantings it was particularly heavy. Later it fell back and the farm, as well as some of the plantings, suffered. No one has documented any long-term trend in rainfall in response to the plantings, which is not surprising. The degree to which forests encourage rainfall is a matter of considerable debate. Those mechanisms that can plausibly be called into play at larger scales—such as the way that transpiration through leaves recycles water to the air, allowing the same moisture to fall as rain repeatedly—seem unlikely to apply on Ascension. The constant trade winds ensure that air passing over the mountain is back over the ocean in less than an hour.

绿峰的造林活动是否增加了降雨量也不十分清楚。阿森松岛的降雨量总是在变。在贝尔扩大林木种植的那几年,降雨量很大。后来降雨量减少了,因此农场倒闭了,岛上种植的一些植物也死亡了。没有人能够拿出有据可考的降雨量长期趋势分析报告,以证明该岛的降雨量与绿化有关,这并不奇怪。森林到底可以导致降雨量增加多少,在这一点上一直具有相当大的争议。那些有些道理的机制似乎在更大的空间尺度上能起作用,譬如通过叶片蒸腾到空气中的水份又以降雨的方式重新回归地面,如此形成了一种循环。但这种机制似乎不适用于阿森松岛。常年刮个不停的信风使经由该岛山顶上的空气在不到一个小时的时间内就又被刮到大洋上空。

In practice rainfall, like farming, is not much of a problem any more. The BBC, which has ended up producing most of Ascension's electricity because its transmitters are the biggest energy users, puts some of that power to work desalinating seawater. The American base has a desalination plant, too. Ascension could get by with no rain at all, if it had to. What the trees certainly do, though, is catch moisture directly from the clouds. As air climbs the mountain it cools, encouraging water vapour picked up from the warm ocean to condense. The trees provide copious surfaces on which that condensation—"occult precipitation", to ecologists—can take place. That is what provides the water for Dew Pond, for the moist air under the spreading yews and figs below it, and for the soil. The more trees, the more moisture, the more trees.

实际上,降雨与农作物的种植一样,都不再是岛上一个太大的问题了。英国广播公司最终成为阿森松岛上的发电大户,它发出的电量占岛上的绝大部分,原因是它的无线电发射机是岛上最大的耗电器。该公司将一部分电力用于海水淡化。美军基地也有一个海水淡化厂。如果必要的话,阿森松岛即使不降一滴雨也能过得下去。然而树木起到的作用是直接从云中捕获水分。空气爬上山坡就受到了冷却,使来自于温暖洋面的水蒸汽产生凝结。而山上的树木则提供了冷凝所需的大量的表面物质,用生态学家的话说,“玄妙的凝析现象”就这样产生了。这就是露池中水的来源,也是山下大片的紫杉和无花果树所需潮湿空气的来源,而且还湿润了土壤。树木越多,空气就越湿润,湿润的空气就促使更多的树生长出来。

This explains the success of the plantings on the mountain. It may also explain some of the greening that has swept down the mountain's south-eastern flank; water from higher up may be percolating through rock and soil. But not entirely. Stemson Stroud, the island's conservation officer, first arrived from St Helena to work at the Apollo tracking centre in 1967. He and others contend that the island's subsequent greening has been far more widespread than the slopes of Green Mountain.

这揭示了山上植树造林能够取得成功的机理。它也可以解释山的东南坡自上而下的绿化过程:生成于较高地势的水可以通过岩石和土壤渗流下来。但其机理人们还没有完全搞清楚。Stemson Stroud是岛上的自然保护官,他第一次来到该岛工作的时间是1967年。当时他从圣海伦娜岛来到该岛的阿波罗追踪中心工作。他和其他人都认为岛上后续出现的绿化区域已远远超出绿峰的斜坡范围。

The thorny mesquite is undoubtedly another factor. It was introduced to the island in the 1960s, when the BBC built a new village, Two Boats, for the people working on its World Service transmitters. Intended as decorative erosion-proofing the mesquite quickly took off, helped by the fact that its seeds pass happily through the digestive tracts of the island's small population of feral donkeys.

多刺的牧豆树无疑是另一个因素。这种植物是上世纪60年代引入该岛的,当时英国广播公司为在国际播音部发射台工作的员工建立了一个新的村庄:“两艘船”村。原本打算作为保护土壤的装饰性植物的牧豆树在岛上迅速繁衍起来,原因是它的种子可以通过岛上为数不多的野生毛驴的消化道而得到更好的传播。

Around Two Boats, which is near the foot of Green Mountain, the mesquite has teamed up with acacia, yellowboy (a shrub in the jacaranda family) and prickly-pear cactus to make thick scrub. It has also spread to the west and down to sea level. Mr Stroud and his colleagues spend a fair bit of time hacking it back and poisoning the stumps—and through them, they hope, the prodigiously deep roots—in order to preserve the lifeless volcanic splendour of at least some parts of the island. Goats, Mr Stroud speculates, might help them in their task. To hear a conservationist speak warmly of the notoriously omnivorous and disruptive goat is to get a sense of how potent a foe the mesquite has become.

“两艘船”距绿峰山脚不远,在村子周围牧豆树、合金欢树、yellowboy(一种紫薇科兰花楹属植物)与刺梨仙人掌一起组成了一片浓密的灌木林。牧豆树也传播到了岛的西边,向下一直抵达海平面的高度。斯特劳德先生和他的同事们正经是花了不少时间来砍倒这些牧豆树,然后在树桩上倒入毒药,他们希望毒药能够通过树桩流入深深扎入地下的树根部,以便至少在岛上部分地区保存下毫无生机的火山熔岩地貌的壮观景色。斯特劳德先生推测,山羊可能会帮助他们完成这一任务。他在听一位环保人士激烈地抨击山羊吃掉所有植被的臭名昭著的特性和对生态环境的破坏时,立即产生了一种灵感。啊哈,牧豆树啊,终于给你找到一个强大的敌人了。

But the greening is not just an invasion. Nor is it merely a result of increased soil moisture. Just look at Mountain Red Hill, an impressive cinder cone that lies south-west of Green Mountain. Contrary to its name, Mountain Red Hill is increasingly green, but not with mesquite, and not thanks to groundwater, unless it is a special type that flows uphill.

但该岛的绿化不仅是外来物种入侵的结果。也不仅仅是增加了土壤水分的原因。“红山”是一座令人印象深刻的火山灰渣堆积而成的锥状体山峰,坐落在绿峰的西南方向。让我们看看红山的变化吧。与它的名字唱反调的是,这座山峰变得越来越绿了。但这座山的绿化与牧豆树的入侵无关,与地下水也没有关系,除非这里的地下水与众不同,能够倒爬上山。

The green side of global warming
全球变暖也有其绿色的一面

One possibility, far from proved, is that Ascension is benefiting from global warming. Warmer seas impart more moisture to the winds blowing across them: more mists, more clouds, more condensation. Although the temperature on Ascension has not changed appreciably in the past 30 years, sea-surface temperatures upwind of it jumped by more than a degree in the 1980s before levelling off. This warming may be a natural variation; it may well not. Rainfall measured by the Met Office has not increased over 30 years; but its rain gauge, at the southern tip of the island, is in one of the drier spots.

虽然远未得到证实,但存在一种可能,就是阿森松岛正在受益于全球变暖的趋势。海洋变暖就能够蒸腾出更多的水份,风吹过海面带走了这些水汽,然后就形成了更多的云雾,云雾增多导致更多的水分凝析出来。虽然在过去的30年间阿森松岛上的温度并没有明显变化,但该岛上风向的洋面温度在上世纪80年代跃升了1度以上,在那之后洋面温度趋于稳定。洋面的变暖可能是自然变化,也很可能不是。英国国家气象局观测到的降雨量在30多年中没有增加,但其雨量计放置在岛的南端,而这里是该岛比较干燥的地点之一。

If there is more moisture in the air condensing as dew, you might expect to see the effects high up and to windward, on somewhere like Mountain Red Hill. If there's more rain, you might expect to see it in the lee of Green Mountain's central peak—and there is indeed a rainier strip, the locals say, stretching across the island from Two Boats to Comfortless Cove, a frequent source of teatime drizzle in the rainier months. It is along that strip that the mesquite and yellowboy grow most strikingly. If nearby ocean temperatures climb higher still, as climate projections would have them do, Ascension will probably become ever moister and greener. All those Victorian plantings mean that there are dormant seeds, both of plants that prospered and of those that didn't, all over the island, biding their time. Euan Nisbet, a Zimbabwean geologist and climate scientist, speculates that after a century or two of further warming the island may be green from top to toe.

如果空气中有更多的水分凝结成露珠,你就可能会在高处及迎风的地方看到其效果,红山就是这样一处地方。如果降雨量增多,你就可能会在绿峰中央山峰的背风处看到一条雨量增加的降雨带,那里也确有一条这样的雨带。据当地人说,从“两艘船”到坎福特湾,这条雨带横跨小岛。在降雨较多的月份,这条雨带经常会降下一顿饭工夫的蒙蒙细雨。正是沿着这条雨带,牧豆树和万寿菊生长的最为茂盛。按照气候预测的推断,如果附近的海水温度继续上升,阿森松岛很可能会变得更加潮湿,岛上的植被也会更加茂盛。维多利亚时代进行了如此大规模的种植,这意味着肯定还有许多处于休眠状态的植物种子遍布于全岛,这些种子有些曾繁茂一时,有些从未冒出过地面,但它们都在等待适当的生长时机。尤安?尼斯贝特(Euan Nisbet)是一名津巴布韦的地质学家及气候学家,据他推测,全球变暖的趋势延续一至两个世纪后,阿森松岛可能会实现彻底的绿化。

With plants in place and seed banks built up in the soil, such a greening might continue unassisted. It may, in time, have to. The fact that Ascension has always found new uses to replace old ones does not mean the trick can be carried on indefinitely. And the electromagnetic connectedness on which much of the island’s usefulness now rests allows it to get by with fewer and fewer inhabitants. Even on Ascension Island, which is about as far off shore as you can get, jobs can still go offshore; the contracting companies that run the island's many antennae are all looking to reduce their costs and their presence when possible. And since the crown allows no right of abode to anyone not working or dependent on a worker, nor the right to own private property, no jobs means no people.

随着植物在适宜之处的生长和种子在土壤中的积聚,这种绿化进程可能无需人类帮助就能进行下去。人类有时也许不得不插一把手。一种作用失去后,人们总是能为阿森松岛找到新的用途,但这并不意味这种状况可以永远进行下去。阿森松岛现今主要起到一种电磁桥梁的作用,这种状况使得即使岛上居民越来越少也能对付过去。阿森松岛即使远离大陆,孤悬于大洋之中,就业岗位仍然不断流失到岛外。负责岛上众多天线运行工作的承包公司都正在想方设法减少开支,而且只要可能的话就撤出这里。而且任何没有工作的人或依赖一个工人的人都不会获得官方许可的居留权,英国政府也不允许任何个人拥有该岛的土地所有权,没有了工作岗位就意味着该岛不再有人居住了。

If left to itself, Ascension would probably decline into dull, scrubby simplicity. Humans can help avoid that by creating the sort of balance that cannot evolve for itself on human timescales. To do so, though, is to make choices. Should the mesquite be allowed to kill the casuarina trees by drilling its roots deeper and depriving them of water, as in some places it seems to be doing? Which cinder cones should keep their bleak red beauty? What new elements should be introduced into the ecology in attempts to reinforce it? Would goats be OK? Would giraffes?

如果人类遗弃了这座岛屿,阿森松岛很可能退化成一座单调的,只有灌木丛生的荒岛。人类可以通过创建一种生态平衡系统来避免这种悲剧出现。以人类的时间尺度来计算这种平衡应该不会由于系统自身发生演变而被打破。然而这样做需要做出选择。牧豆树的根茎可以深深地扎入土壤之中,使麻黄树得不到水分而枯死,岛上的一些地方似乎已经在发生这样的事了。我们是否听之任之呢?岛上的火山锥是否还要保持其暗红色的凄凉之美?为了改善岛上的生态体系,到底该引入何种新成分?引入山羊妥当吗?引入长颈鹿又会如何?

Such questions are easier on Ascension, where the ecological canvas was almost empty to begin with, than in the other novel ecosystems that humans are, mostly by accident, setting up around the planet. Yet decisions must be made. In 2002 the island set about eradicating its population of feral cats. Introduced to control the rats that had arrived with sailors, they had instead chosen to prey on the vast colonies of sea birds that roosted on the lava plains, wiping them out. Every species on the island retreated to a small islet offshore, Boatswainbird Island, except for a few individuals that held on to the most inaccessible cliffs, and the phenomenally scrappy wide-awake terns that visit the southern plains to breed. With traps, poison and guns, over 500 cats were wiped out. The birds have started to return.

要回答类似这样的问题在阿森松岛更容易一些,与那些人类在这个星球表面其它地方新建立的生态系统(它们大多是人类在不经意间建立起来的)相比,阿森松岛的生态系统可以说是一张白纸。一张白纸好作画,如何动笔却难煞人啊。2002年,岛上开始着手消灭为数众多的野猫。引猫上岛是为了控制老鼠的数量,而这些老鼠是船员们无意中带来的。但这些猫不捕老鼠,却转而捕食海鸟。在该岛的熔岩平地上曾栖息着大群的海鸟,但野猫却把这里的海鸟都赶跑了。岛上的各种鸟类都转移到离岸不远的一个小岛,水手长鸟岛上了。仅剩下几种鸟类还坚守在人迹罕至的悬崖峭壁上,还有的就是非常吵闹而又机警的燕鸥,它们要短暂地飞到南部平地去孵化幼鸟。人们用陷阱、毒药和子弹消灭了500多只猫。鸟儿又开始回来了。

Not all indigenous species are so easily accommodated. The grasses, sedges and shrubs that have been brought to the island handily out-compete the native species, many of them ferns, that were making such a poor fist of greening the island before people came. This is hard to regret, seeing the result. What’s more, the new painting need not cover up all of the original, almost bare, canvas beneath. The creation of the new can, with care, make room for the conservation of the old.

并非所有本地物种都是如此容易留住。人们带到岛上的禾草、莎草和灌木轻易地就打败了当地的物种,其中许多是蕨类植物。在人们来到这个岛上之前,岛上的原始植被可怜至极。看看现在岛上的一片绿意,人们很难为当初的选择而感到遗憾。此外要注意的是,人类在这个岛上绘制一幅新的生态画卷不必完全覆盖画布上原始的图案。尽管这幅原始图案几乎是空空如也,还是要留下来一点。如果小心慎重的话,在创建这幅新作的同时,人们也可以为保护旧的图案留下空间。

Restoring the balance
生态平衡重新恢复

Beneath the summit ridge on Green Mountain, on the lawns of a small garden, Mr Stroud nurtures indigenous plants. He discovered one fern only a couple of years ago—a species hidden for centuries. He plants the successes under a huge fig tree on the ridge. When they flourish he takes them further out into what on other islands would be the wild, but here is the artifice, returning occasionally to check up on them and take more seed. While he and his successors are here, those ferns and grasses will be safe from extinction. And a few are taking the initiative themselves. Xiphopteris ascensionis, a tiny endemic fern, had never seen a tree before the Victorian planters came. Now it lives in and on them, nestled in their moist bark, pioneering the epiphytic way of life familiar from ancient forests around the world and discovered afresh in their youngest cousin. Life, with helping hands, adapts.

绿峰山脊下有一个小花园,在花园的的草坪上斯特劳德先生培育着岛上的原生植物。他在两年前发现了一株蕨类植物,这种植物已经消失了几个世纪了。他在山脊上的一颗巨大的无花果树下成功地种活了这颗植物。当这种植物生长繁茂后,他又将其种子带到更远的地方种下。在其他岛屿上这种植物可能是野生的,但这里就只能是通过人工进行栽培。他偶尔还会回来查看这些植物,并采取更多的种子。只要他和他的继任者们留在这里,这些蕨类和草本植物就不会灭绝。甚至有几种植物正在主动行动。阿森松岛梳叶蕨(Xiphopteris ascensionis)是一种岛上特有的微型蕨类植物。在维多利亚时代的种植者们来到岛上之前,没有任何人见过这种植株。现在这种植物又回到了这里。他们依偎在其它树木潮湿的树皮下,以附生的方式生长。远古时代世界各地的森林里到处生长着这类植物,开创了这种生命形式的古老家族成员们会发现在他们最年轻的表亲身上,他们又获得了重生。这种植物借助于人类的帮助而适应了环境,他们生存了下来。

The lesson that Easter Island teaches humanity is bleak. Ascension Island's story has a more hopeful message. It shows that environments not remotely natural in their origins can become lovely to inhabit. People like Mr Stroud can and will act not just to preserve the environment but to improve it, making it more, not less, than it otherwise would be.

复活节岛的教训给人类上了一课,使我们尤感凄惶。而阿森松岛的故事传出了一个充满希望的信息。它表明,环境虽然不再是其遥远的自然状态,但仍然可以通过改造而适于人类居住,一样可以成为可爱的家园。如斯特劳德先生这类人可以,而且决心采取行动,他们不仅要保护环境,而且要改善环境,使之适于人类生存,而非反其道而行之。 更多信息请访问:http://www.24en.com/

Winding down the flank of the mountain, there is a graceful fluttering in the woods off to the side of the road. Free from the threat of cats, fairy terns have returned to the island—and forsaken their ancestral cliffs for a new life among the leaves and branches. They flash bright white and beautiful against the green.

沿着山侧蜿蜒的小道一路走下山坡,可以听到路旁的树林中传出鸟儿扑动翅膀的美妙声音。没有了猫的威胁,仙女般的燕鸥又返回到岛上。但不像其祖先那样栖息在峭壁上,她们在大树的枝叶间开始了自己的新生活。在绿叶的衬托下,这些白色的精灵显得格外美丽。