(本文选自《经济学人》20201024期)
背景介绍：
围栏是世界各地最常见的一种人工建筑，人们建造围栏或是作为划定土地持有或政治区域的边界，或是用以控制家畜，或是用以保护公共安全和个人及公共资源，亦或是专门为保护濒危物种所设。长久以来，人们很少关注围栏对各种生物造成的影响，但绵延不绝的围栏已经成为动物难以逾越的一道屏障。
Fences are bad for wildlife
Where possible, they should be removed or redesigned
Earth’s longest artificial structure is usually said to be the Great Wall of China. Just how long that is is hard to say, for northern China actually has many walls, built at different times and not always interconnecting.
人们通常认为，世界上最长的人工建筑是中国的长城。很难说长城究竟有多长，因为在中国北方分布着许多修建于不同时期的城墙，并且它们往往不是相互连接的。
Earth’s second-longest artificial structure, though, is not a wall, but a fence. Its length is known exactly. It
stretches
for 5,614km across eastern Australia and is intended to stop the country’s native feral dogs, the dingoes, which live mainly to its north, from preying on sheep, which are farmed mainly to its south.
但说到世界上第二长的人造建筑，那就不是墙了，而是围栏，并且其长度是已知的。横跨澳大利亚东部的围栏全长5614公里，其修建的目的是为了阻隔生活在澳大利亚北部的野狗，它们会捕食人们饲养在澳大利亚南部的绵羊。
Australia’s dingo fence is remarkable. But it does not stand alone. Millions of kilometres of fences wrap the world,
outstripping
the collective length of its roads by something like a factor of ten. Some are intended to curb the movement of animals, some the movement of people, and some merely to mark the limits of territory, so that everyone knows who owns what.
澳大利亚的野狗围栏十分引人注目，但它们并不是孤立存在的。全世界有着数百万公里的围栏，其长度大约是全球公路总长度的十倍。有些围栏是为了限制动物活动，有些是为了限制人口流动，还有一些仅仅是为了划清领土界限，以便让每个人都知道各自的领地范围。
Even fences built for other purposes, though, often serve to constrain animals, too. For example, some ecologists worry that the barrier now being erected along the border between America and Mexico, to stop the movement of human migrants, will also disrupt movement of endangered large mammals such as the Sonoran pronghorn and the desert bighorn sheep.
但即便是为其他目的而修建的围栏也常常会对动物造成限制。例如，一些生态学家担心，目前在美国和墨西哥边境线上为阻止非法移民而修建的围栏也会阻碍濒危大型哺乳动物（例如索诺兰叉角羚和沙漠大角羊等）的迁徙。
Until recently, data like these on the effects of fences on wildlife have been
piecemeal
. That has changed with the publication, in Bioscience, of a report compiled by Alex McInturff of the University of California, Santa Barbara. Dr McInturff and his colleagues have attempted a comprehensive review of the scientific literature about fences and their environmental impact.
直到最近，有关围栏对野生动物影响的研究仅有些零散的数据。但加州大学圣巴巴拉分校的亚历克斯·迈克因塔夫在《生物科学》杂志上发表的一份报告使得情况有所改变。迈克因塔夫和他的同事们试图全面梳理有关围栏及其对环境影响的科学文献。
One discovery they have made is that more than half of published fence research focuses on just five countries—America, Australia, Botswana, China and South Africa—with America alone making up over a fifth. A second is that only a third of these studies examined the impact of fences on anything other than the target species involved, meaning the animals explicitly intended to be kept in or out.
他们首先发现，超过一半已发表的有关围栏的研究仅集中在五个国家（美国、澳大利亚、博茨瓦纳、中国和南非），仅美国就占了五分之一以上。其次，仅有三分之一的研究就围栏对目标动物（这些动物是人们明确打算关在围栏里或围栏外的）以外物种的影响进行了调查。
Non-target species, however, are often those that have their fortunes most drastically reshaped by the appearance of poles and wire. Australian fences intended to keep out dingoes and other pests are also barriers to long-necked turtles, which travel great distances over land when moving between nesting sites.
然而，非目标物种的命运往往会因电线杆或电丝网的出现而被彻底改变。澳大利亚用于阻隔野狗和其他害虫的围栏也成了长颈龟的障碍，它们会在陆地上长途跋涉，以往来于各筑巢地点。
In Botswana veterinary fences erected to spare cattle from wildlife-borne disease result in serious interference with wildebeest migrations. Fencing intended to protect the Qinghai-Tibet railway, in China, has similarly affected the migration routes of Tibetan antelope.
在博茨瓦纳，为防止家畜感染野生动物传播的疾病而竖起的兽医围栏严重干扰了角马的迁徙。在中国，为保护青藏铁路而修建的围栏也同样影响了藏羚羊的迁徙路线。
Pangolins curl up into a ball when endangered, in order to protect their soft underbellies. This is generally a wise move, but not when it causes them to embrace the wire of an electrified fence. Pronghorn tend to crawl under fences rather than jump over them, leading to hair loss that can increase the risk of hypothermia. And so on.
濒临灭绝的穿山甲在遇到危险时会缩成一团，以保护它们柔软的腹部。这本是一个明智的举措，但当触碰到电丝网时，缩成一团就不太明智了。叉角羚喜欢钻钻过过围栏，而非跃过围栏，这会导致毛发的脱落，使其更有可能面临体温过低的风险。诸如此类的例子还有很多。
Not every creature fares badly. Hawks in Montana gladly perch on newly erected livestock fencing to prey on small herbivores, while fence-dwelling spiders in South Africa
outperform
their tree-based cousins when it comes to catching insects.
围栏并不是对每一种生物都那么糟糕。在蒙大拿州，老鹰欢喜地栖息在新竖起的牲畜围栏上，捕食着小型食草动物；而在南非，围栏上的蜘蛛比树上的蜘蛛更容易捕捉到昆虫。
Often, though, the winners are creatures that cause trouble for existing ecosystems. Excluding dingoes from large parts of Australia has allowed invasive red foxes to multiply, free from attack by what is, since the extinction of the thylacine, the country’s top predator. Native rodents have suffered as a result. Some have been brought to the brink of extinction.
然而，受益者往往是那些不利于现有生态系统的生物。在澳大利亚大部分地区，由于顶级捕食者袋狼的灭绝，以及野狗被围栏阻挡在外，外来物种红狐得以免受攻击，从而大量繁殖。结果导致当地啮齿类动物深受其害，有些物种甚至已经濒临灭绝。
And fences erected around Tawharanui, a reserve in New Zealand, have successfully excluded many undesirable large mammals that threaten the indigenous birdlife, but also keep out predators of house mice, an egg-eating alien whose numbers continued to rise.
新西兰在塔瓦瓦努伊保护区周围建起的围栏成功阻挡了许多对当地鸟类构成威胁的不受欢迎的大型哺乳动物，但也阻挡了家鼠的捕食者，从而导致这种以鸡蛋为食的外来物种得以大量繁殖。
(红色标注词为重难点词汇)
本文翻译：Vinnie
校核：Vinnie
编辑：Vinnie
说起世界上最长的人工建筑，人们通常认为是中国的万里长城。而说到第二长的人工建筑，那或许就是在全世界随处可见的围栏了。有人估算，全世界围栏加起来的长度是全球公路总长的十倍。围栏确实在经济、政治等方面起到了重要的作用，但我们也同样应该考虑它们会对野生动物造成怎样的伤害。
重难点词汇：
stretch
