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入侵物种是否该格杀勿论?

更新时间:2016-3-29 10:50:04 来源:纽约时报中文网 作者:佚名

Invasive Species Aren’t Always Unwanted
入侵物种是否该格杀勿论?

Invasive species are bad news, or so goes the conventional wisdom, encouraged by persistent warnings from biologists about the dangers of foreign animals and plants moving into new territories.

物种入侵是坏事,至少传统的看法是这样认为,而生物学家也不断警告外来动植物进入新地区的危害,进一步加固这一认识。

Conservation organizations bill alien species as the foremost threat to native wildlife. Cities rip out exotic trees and shrubs in favor of indigenous varieties. And governments spend millions on efforts to head off or eradicate biological invaders.

保育机构把外来物种列为原生物种的头号威胁。人们在城市里拔出外来的树和灌木,以保护土生土长的物种。政府耗费巨资用于根除生物入侵者。

“I think the dominant paradigm in the field is still a ‘when in doubt, kill them’ sort of attitude,” said Dov Sax, an associate professor of ecology and evolutionary biology at Brown University.

“我认为在这个领域的主导态度依然是‘有怀疑就杀死’,”布朗大学(Brown University)生态与进化生物学副教授多夫·萨克斯(Dov Sax)说。

But a growing number of scientists are challenging this view, arguing that not all invasive species are destructive; some, they contend, are even beneficial. The assumption that what hails from elsewhere is inherently bad, these researchers say, rests more on xenophobia than on science.

但是,越来越多的科学家开始挑战这一观念,提出并非所有入侵物种都是破坏性的;他们甚至认为其中有些是有益的。在这些研究者看来,假定外来物种本性有危害,更像是排外情绪,而不是以科学为依据。

“It’s almost a religious kind of belief, that things were put where they are by God and that that’s where they damn well ought to stay,” said Ken Thompson, an ecologist and retired senior lecturer at the University of Sheffield in England, who wrote the 2014 book “Where Do Camels Belong: Why Invasive Species Aren’t All Bad.”

“这几乎是一种宗教式的信仰:上帝把这些东西分别放在这些地方,那它们就该老老实实呆在那里,”英格兰谢菲尔德大学(University of Sheffield)生态学家、退休高级讲师肯·汤普森(Ken Thompson)说道。他在2014年出版了《骆驼属于哪里:为什么物种入侵不一定是坏事》(Where Do Camels Belong: Why Invasive Species Aren’t All Bad)一书。

“We’re actually moving plants and animals around the world all the time,” he said. “We have been for centuries.”

“其实我们一直都在把植物和动物满世界挪来挪去,”他说。“我们这么干已经有几个世纪了。”

Dr. Thompson and other scientists have called for a more nuanced approach to evaluating whether the presence of a species is harmful or beneficial. Eradicating most invasive species is virtually impossible in an era of globalization, they note. And as climate change pushes more species out of their home ranges and into new areas, the number of so-called invaders is likely to multiply exponentially.

汤普森等科学家一直在呼吁采取更细致的手段来评估一个物种的存在是利是弊。在全球化时代,根除大多数的入侵物种基本上是不可能的。随着气候变化将越来越多的物种赶出自己的故乡,前往新的地域,所谓入侵者的规模可能会出现指数增长。

Yet the notion that a species should not be judged on its origins is highly controversial, as Mark Davis, a biology professor at Macalester College in Minnesota, discovered when he and 18 other researchers submitted an article in 2011 saying just that in the journal Nature.

然而明尼苏达州玛卡莱斯特学院(Macalester College)的生物学教授马克·戴维斯(Mark Davis)说,物种不论出处的想法是极富争议的。2011年他和另外18位研究人员在《自然》(Nature)上发表论文陈述了这种观点后,立刻就感受到了这一点。

The response was immediate — and signed by 141 scientists, many of them specialists in the field known as invasion biology. Their approach, they said, was already sufficiently “nuanced,” thank you very much.

文章当即引发反应——而且是141名科学家联署,其中许多是所谓“入侵生物学”领域的专家。他们说,他们的手段已经足够“细致”,不用你们费心。

“Most conservation biologists and ecologists do not oppose nonnative species per se,” wrote Daniel Simberloff, a professor of environmental science at the University of Tennessee, who led the group that wrote the rebuttal. He added that Dr. Davis and his colleagues had vastly played down the severe harm that alien species caused.

“多数保护生物学家和生态学家并不反对非原生物种本身,”田纳西大学(University of Tennessee)环境科学教授丹尼尔·西姆博洛夫(Daniel Simberloff)说。他是撰文反驳该论文的科学家群体的领导者。他还说,戴维斯和他的同事对外来物种的危害性轻描淡写。

But in the five years since that contentious exchange, the idea that invasive species should be assumed guilty until proven innocent has begun to wane, the shift prompted in part, Dr. Davis speculated, by concerns over the use of chemical pesticides and the disruption of landscapes caused by many eradication efforts.

然而在那场激烈的交锋过去五年后,入侵物种在证明无害前必须被假定有罪的想法开始出现动摇。戴维斯说,这种转变在一定程度上是源于化学杀虫剂的应用引发的担忧,以及许多根除物种的行动给土地造成的破坏。

Some alien species are undeniably harmful, a fact that neither Dr. Davis nor others who share his view dispute. The fungus that causes chestnut blight, for example, decimated thousands of trees and changed the American landscape in the early 1900s. The Zika virus is invading new regions, carried by infected mosquitoes that some say are being driven northward by warmer temperatures. The vampirelike lamprey, sneaking into the Great Lakes in the 19th century, gradually champed its way through the fish population.

有些外来物种无疑是有害的,无论是戴维斯,还是其他跟他有同样异议的人,都不否认这一事实。例如会导致栗树枯萎的真菌已经杀死了数千株树木,并在1900年代初改变了美国的风土景观。寨卡病毒正在侵入新的地区,有人说这是因为气温升高导致被感染的蚊子向北迁徙。吸血鬼般的七鳃鳗在19世纪潜入五大湖,逐步蚕食湖中的鱼群。

Islands and mountaintops are especially vulnerable to damage from invaders because their native species often evolved in isolation and lack natural defenses against predators or immunity to exotic diseases. The brown tree snake, accidentally transported to Guam, has virtually eliminated the bird population there.

岛屿和山顶格外容易受到入侵者的破坏,因为那里的原生物种往往是在隔绝环境下演化的,缺乏抗御掠食者的能力,或对外来疾病的免疫。被无意中带到关岛的棕树蛇导致那里的鸟类基本上灭绝。

But, Dr. Davis noted, “all species have negative impacts on something,” and the danger, he said, is often exaggerated.

但是戴维斯提出,“所有物种都会对某种东西有负面影响,”而他认为,这种危险往往被夸大了。

A study published Feb. 17 in the journal Biology Letters, for example, concluded that alien species “are the second most common threat associated with species that have gone completely extinct” since 1500 A.D.

例如《生物学通讯》(Biology Letters)在2月17日发表了一篇论文,结论是自公元前1500年至今,外来物种是“导致物种彻底灭绝的第二大威胁”。

But the study, Dr. Davis and other experts said, relies on subjective judgments about extinction and does not distinguish between island species — which are far more vulnerable — and land or ocean species.

然而戴维斯和其他专家说,该研究依赖的是关于物种灭绝的主观判断,没有将更容易受到伤害的岛屿物种和陆地、海洋物种区分开。

In some instances, nonnatives offer clear benefits. In California, for example, monarch butterflies prefer to spend their winters in the branches of the eucalyptus, an exotic tree transplanted to the state more than 150 years ago and viewed by some as an invasive fire hazard. In Spain, non-native crayfish serve as prey for migratory wetland birds, including some endangered species.

从某些案例看,非原生物种显然是有益的。比如在加利福尼亚,帝王蝶喜欢在桉树的枝杈上过冬。这种树是一种150多年前被移植到该州的外来树种,被一些人视为带来火灾隐患的入侵者。在西班牙,非原生的小龙虾成了迁徙性湿地鸟类的猎物,其中包括一些濒危物种。

And some notorious invaders can have positive effects. Western states have spent a fortune trying to eradicate the tamarisk tree, which many experts believe hogs more than its share of water and damages the habitat of native species.

有些恶名昭著的入侵者也产生正面影响。西部诸州花了很多钱消灭红荆树,许多专家认为这种树会抢占过多的水,破坏本地物种的栖息地。

But Julian D. Olden, an associate professor in the School of Aquatic and Fishery Sciences at the University of Washington, said tamarisks had been found to provide shelter for birds like the southwestern willow flycatcher. Some studies have also concluded that the tree’s water use is not significantly different from that of other tree species.

但华盛顿大学水生生物与渔业科学院(School of Aquatic and Fishery Sciences at the University of Washington)的助理教授朱利安·D·奥登(Julian D. Olden)说,可以看到红荆树成了西南柳鹟等鸟类的栖身之所。还有研究得出结论,认为这种树的用水和其他树种并没有太大差异。

The antipathy to foreign plants and wildlife is relatively recent. While the distinction between native and non-native species dates to the 18th century, the term “invasion” was first used in a 1958 book — “The Ecology of Invasions by Animals and Plants,” by Charles Elton — that drew on the militaristic vocabulary of the post-World War II era.

对外来植物和野生动物的排斥态度是最近才有的。原生与非原生的区分却可以追溯至18世纪,“入侵”这个词最早出现在一本1958年的书上,查尔斯·埃尔顿(Charles Elton)的《动植物入侵生态学》(The Ecology of Invasions by Animals and Plants)——采用了二战后时代的军事用语。

But the moniker did not achieve its full derogatory weight until the 1990s and early 2000s, when academic interest in the subject peaked and the number of papers on the subject generated by invasion biologists grew proportionately.

但这个称号直到1990年代和2000年代初才成为一个彻底的贬义词,当时这个课题是学界的大热门,入侵生物学家产出的论文急速增多。

To biologists like Dr. Simberloff, taking action to head off alien species early on makes sense, allowing governments to address threats before invaders take firm hold. Non-native species are far more likely to do harm than native plants and animals, he argued, adding that the debate was “a phony controversy.”

在西姆博洛夫等生物学家看来,对外来物种及时加以阻拦是有道理的,这样政府可以在入侵者扎根之前采取对策。他认为,非原生物种造成危害的可能性远高于原生物种,还说这场讨论只是“一个假惺惺的争议”。

Whether a species is viewed as native, however, often depends on when you arrived on the scene. Much of what Americans eat was originally imported: The horse, an icon of the American West, for example, was reintroduced by the Spanish thousands of years after the original North American horse became extinct. Several states list the honeybee as their state insect. But like many other state fish, insects and flowers, the bees are in fact immigrants.

然而,一个物种是否称得上原生,往往取决于你是什么时候到这里的。美国人吃的东西有很多是外来的:例如美国西部的象征——马,是北美原始马种灭绝几千年后,由西班牙人重新引入的。有几个州把蜜蜂列为它们的州虫。但和许多其他的州鱼、州虫、州花一样,蜜蜂也是外来的。

In at least one case, a species that was long extinct in its native range was treated as an interloper when it finally returned home.

有时一个物种在原生地域灭绝多年后再度回归,结果被当做闯入者对待。这种情况至少出现了一例。

Beavers were common in Britain until they were hunted to extinction centuries ago. But when a group of the toothy dam builders took up residence along the River Tay in western Scotland several years ago, local farmers and fishermen greeted the animals with hostility, saying they posed a threat to farmland and salmon runs and were potential carriers of disease.

海狸曾经在英国很常见,但几个世纪前因捕猎而灭绝。然而在几年前,一群长着大门牙的“筑坝师傅”在苏格兰西部的泰河沿岸住了下来,却遭到当地农民和渔民的抵制,他们说这些动物对农田和鲑鱼迁徙是一个威胁,并且可能携带疾病。

Scottish Land and Estates, an organization representing landowners, insisted that the beavers’ centuries of absence from Britain nullified their resident status, the Independent reported in 2010.

《独立报》(Independent )在2010年报道,地主代理机构“苏格兰土地与地产”(Scottish Land and Estates)坚称,海狸已经有几个世纪没在英国出现,因此它们的居民身份已经失效。

“It’s just silly,” Dr. Thompson said, of the reaction to the Tay beavers. “I don’t think we would have ended up in this ridiculous situation if we hadn’t been so bombarded by propaganda about invasive species.”

“这也太傻了,”汤普森这样评价泰河海狸的遭遇。“如果不是整天被宣传入侵物种的危害,我觉得也不至于沦落到如此荒唐的地步。”

Often, he and others say, “invasion” is just another word for “change.” And the only thing that is certain is that more change is to come. Already, the flora and fauna of countries around the world are more homogeneous than they once were, as globalization has, accidentally or intentionally, moved exotic species from one place to another.

他和其他一些人说,“入侵”很多时候只是“改变”换个说法。唯一确定的是,接下来会有更多的改变。随着全球化或有意或无意地将异域物种带向别的地方,世界各国的动植物正日趋同质。

“From birds to plants to fish to mammals, there’s strong evidence that things are becoming more similar,” Dr. Olden said, likening the phenomenon to “the popping up of big-box retailers and the loss of mom-and-pop shops.”

“从鸟类到植物到鱼类到哺乳动物,有明显迹象表明大家正在变得越来越相似,”奥登说,他说这种现象跟“大商场涌现,夫妻档小店消失”是一回事。

As more species migrate, new quandaries are likely to arise. And as the human population increases, driving more animals and plants toward extinction, a species’ second home may be the only one it has.

随着更多的物种迁徙,新的窘境还会出现。而随着人口增长,越来越多的动物植物将走向灭绝,一个物种的第二家园,也许将是它们唯一的家园。

In a paper published last month in the journal Conservation Biology, two scientists in California, Michael P. Marchetti and Tag Engstrom, describe the “paradox” of species that are under threat in their native range but are viewed as invasive in other places they have settled.

在上月《保护生物学》(Conservation Biology)的一篇论文中,两位加州科学家迈克尔·P·马切蒂(Michael P. Marchetti)和泰格·英斯托罗姆(Tag Engstrom)描述了一种“诡局”,即一些物种在原生地域的生存受到威胁,但在它们选择的其他定居地又被当做入侵者。

They include the Monterey pine, endangered in California and Mexico but treated as a pest in Australia and New Zealand, and the Barbary sheep, endangered in Morocco and other countries but running rampant in the Canary Islands and elsewhere.

这其中包括了在加州和墨西哥濒危的蒙特雷松树,但在澳大利亚和新西兰又被视为一种有害植物,在摩洛哥等国濒危的蛮羊,却在加那利群岛等地泛滥成灾。

“This is a challenge,” Dr. Olden said. “If we identify a plant or animal that might not be able to respond to climate change, do we roll the dice and intentionally move that species northward, or up in elevation?”

“这是一个挑战,”奥登说。“如果我们认定一种植物或动物可能无法适应气候变化,我们要不要冒险,故意把它们往北方或高海拔地区转移?”

“We’re playing a little bit of ecological roulette here,” he added.

“我们这是在玩某种生态轮盘赌,”他接着说。

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