In the 1930s, beetles2 with a sweet tooth gulped3 down a lot of sugarcane4 in Australia. Angry sugarcane farmers needed to do something quickly. Farmers in Hawaii gave them a tip: Cane toads5 like to munch6 on the beetles. Desperate Australian farmers imported a boxful of the fist-sized toads from Hawaii and let them loose 7.
Bad idea. Instead of chowing8 down on the beetles, cane toads gobbled9 anything they could swallow—pet food, garbage, honeybees, termites10, snails, and mice.
The toads multiplied11 , spreading across the northern coast of Australia. Today toads are such a problem that a member of the Australian government recently suggested that citizens use golf clubs to whack12 the warty13 amphibians14 !
Australia isn't the only country dealing with unwelcome animal guests. In the United States, hundreds of invasive species pose15 a threat to the environment.
The Aliens are coming
An invasive species is nonnative, or alien, to the ecosystem16. An ecosystem is a group of plants, animals, and other living organisms that live together in the same area. Although invasive species don't damage their own ecosystem, they can cause massive destruction when they invade another area.
For example, fingernail-sized zebra mussels17 hitchhiked18 from Russia to the Great Lakes in the water tanks of ships. When those ships landed in the United States, the zebra mussels began gobbling up food and oxygen, leaving nothing for other underwater creatures to eat.
They also irritated19 humans. Each year, a female zebra mussel can produce 30,000 to 1 million eggs. When those eggs hatch20, the mussels clog pipes that provide drinking water to houses and schools.
A beetle called the emerald ash borer21 arrived in the United States from China in wood packing material carried aboard cargo ships or airplanes.
The adult emerald ash borer nibbles22 on the leaves of the ash tree. The larvae23 of the beetle, however, cause far more damage by chomping24 through the inner bark25 of ash trees. The insects destroy the tunnels that allow water and nutrients26 to travel from the roots to the leaves. Emerald ash borers have killed 8 million to 10 million trees in Michigan, Ohio, and Indiana.
Another invasive species that is wreaking havoc27 is the snakehead28 fish.
Snakeheads arrived in the United States from Asia as exotic29 pets. When pet owners grew tired of the snakeheads, they threw the fish into nearby lakes and streams.
The snakehead fish now live in several states and can move over land from one body of water to another body. They dine greedily and can clear a pond of all its fish. The snakehead was recently spotted in a lake in Queens, N.Y., a part of New York City.
“The world has changed so much in the last 100 years,” Jodie A. Ellis, a scientist at Purdue University, told Senior Edition. “We are now able to share so many things with other countries, which is mostly a good thing. But there are costs, and one of those costs is the constant threat of invasive species.”
Why should we care?
In addition to destroying an ecosystem, the devastation30 caused by invasive species can be costly. In the United States, the damage caused by the peaky critters31 is roughly $137 million per year.
“Our natural ecosystems are the primary source of our food and drinking water,” Lisa Gould, a senior scientist at the Rhode Island Natural History Survey, told Senior Edition. “Ecosystems help keep our air clean. They give us medicines and materials for our industries. Without them, we could not exist for long.”
Battling the cane toad
Back in Australia, the government has devoted $1 million to combating that country's pesky toad problem. Scientists are researching what kind of poisons can kill the creature.
Wildlife officials are also setting up traps to catch the toads, which are now hitchhiking across Australia in the backs of cars and trucks.
“We cannot tolerate a situation where cane toads are getting a free ride across the continent,” says one Australian official.
What can you do?
Kids can do a lot of things to prevent alien plants and animals from invading our ecosystems. Robert J. Wiese, director of animal collections at the Fort Worth Zoo, says you should figure out which animals and plants belong in your community and which ones don't.
Most people don't know a lot about their natural surroundings. Wiese said. By the time a plant or an animal has invaded an ecosystem, it's too late. Wiese gives this advice:
● Use native plants in your garden.
●Don't release unwanted pets into the wild. That is especially a problem with tropical fish, which people often dump into waterways.
20世纪30年代，喜吃甜食的甲虫吞噬了澳大利亚的大片甘蔗。愤怒的蔗农必须迅速采取行动。此时夏威夷的农民给他们出了一个点子：蔗蟾喜食甲虫。绝望的澳洲农民从夏威夷进口了一箱拳头大小的蟾蜍，将它们投放到野外。
馊主意！这些蔗蟾非但没有吃掉甲虫，反而贪婪地吞食一切可食之物——宠物食品、垃圾、蜜蜂、白蚁、蜗牛以及老鼠。
蟾蜍迅速繁殖，扩散到整个澳大利亚北海岸。如今蟾蜍已成严重的公害，一名澳政府官员最近建议公民用高尔夫球棒消灭这些讨厌的两栖动物！
澳大利亚并非惟一忙于对付不受欢迎的外来动物的国家。在美国，数以百计的入侵物种对环境构成了威胁。
异类来犯
入侵物种对生态系统而言是非本土的或外来的。生态系统是指共同生活在同一地区的动物、植物和其它生物。虽然入侵物种并不破坏它们自己的生态系统，但当它们侵入另一个地区时却可能造成大规模的灾难。
例如，手指甲大小的斑纹贻贝就是从俄罗斯搭顺风船来到北美五大湖区的，水仓是它们的藏身之处。当船只抵达美国后，这些斑纹贻贝就开始贪婪地吞吃食物和氧气，不给其它水下生物留下任何吃的。
它们还招惹人类。每年，一只雌性斑纹贻贝能产3万到100万个卵，当它们孵化时，这些贻贝就会阻塞通往家庭和学校的饮用水管道。
一种叫白蜡树钻洞翠绿虫的甲虫从中国传入美国，传播途径是货船和飞机运载的木制包装材料。
成年白蜡树钻洞翠绿甲虫蚕食白蜡树的叶子。可是，该甲虫的幼虫能够啮穿白蜡树的里层树皮，从而导致更大的破坏。这些虫子足以摧毁把水和养料从树根输送到树叶的通道。白蜡树钻洞翠绿甲虫已经杀死了密西根州、俄亥俄州和印第安纳州的800万至1000万棵树。
另一种破坏性极强的物种是黑鱼。
黑鱼是作为外来宠物从亚洲引入美国的。当宠物的主人们厌倦了黑鱼之后，就把它们扔到附近的湖里或河川里。
黑鱼如今生活在美国的好几个州，还能从一片水域经陆地迁移到另一片水域。它们吃起来贪得无厌，能把一池塘的鱼吃个精光。最近在纽约市昆斯区的一个湖里发现了黑鱼。
“近一百年世界的变化太大了，”普渡大学的科学家朱迪·A·埃利斯对《读者文摘》高中版杂志说，“如今我们能够和其他国家分享许许多多的东西，这总的来说是一件好事。但也会付出一些代价，其中之一就是不断面临入侵物种的威胁。”
为何关注？
除了摧毁生态系统，入侵物种的破坏性还表现于巨额的经济损失。在美国，这些恼人的动物每年所造成的损失约为1.37亿美元。
“自然生态系统是我们的食物和饮用水的主要来源，”罗得岛自然历史考察协会的高级科学家莉萨·古尔德对《读者文摘》高中版杂志说，“生态系统有助于净化空气，为我们的各行各业提供良药和原料。如果没有生态系统，我们不可能长久生存。”
与蔗蟾作斗争
回到前文说的澳大利亚，澳政府已投入100万美元用于整治令该国头疼的蟾蜍问题。科学家们正研究用何种毒药可以杀死这种动物。
野生动植物官员也用陷阱捕捉这些蟾蜍，如今它们钻进小汽车或卡车的尾部在澳大利亚四处漫游。
“蔗蟾在澳洲大陆搭便车免费穿行，这种情况是我们所不能容忍的，”一名澳大利亚官员说。
你能做些什么？
孩子们可以通过做许多事情来阻止外来植物或动物入侵我们的生态系统。沃思堡动物园的动物收藏主管罗伯特·J·魏斯说，你们应该去了解哪些动植物属于你们的社区，哪些不属于。
大多数人对他们周围的自然环境并不十分了解，魏斯说，所以当某种植物或动物已经侵入一个生态系统的时候，为时已晚。魏斯提出如下建议：
*在你的花园使用本地植物。
*勿将不需要的宠物投入野外。热带鱼问题尤其突出，人们常常把它们扔弃到河道里。
1. alien adj. 相异的，外国（来）的
2. beetle n. 甲虫
3. gulp v. 狼吞虎咽
4. sugarcane n. 甘蔗
5. toad n. 蟾蜍
6. munch v. 用力嚼，大声嚼
7. let loose 释放
8. chow v. 吃
9. gobble v. 贪食，狼吞虎咽
10. termite n. 白蚁
11. multiply v. 繁殖
12. whack v. 猛击
13. warty adj. 似疣的，有肿瘤的
14. amphibian n. 两栖动物
15. pose v. 造成，引起
16. ecosystem n. 生态系统
17. zebra mussel 一种小型淡水贻贝
mussel n. 贻贝
18. hitchhike v. 搭便车旅行
19. irritate v. 激怒，惹恼
20. hatch v. 孵
21. emerald ash borer白蜡树钻洞翠绿甲虫 emerald adj. 翠绿色的，翡翠的 ash n. 白蜡树borer n. 钻蛀虫
22. nibble v. 轻咬，啃
23. larvae n. （lava的复数）幼虫
24. chomp v. 啮咬， 使劲咀嚼
25. bark n. 树皮
26. nutrient n. 营养品，滋养物
27. wreak havoc 造成大破坏
wreak v. 带来，引起
havoc n. 大破坏，浩劫
28. snakehead n. 黑鱼
29. exotic adj. 外来的，外国的
30. devastation n. 毁坏，破坏
31. pesky critters 恼人的动物
pesky adj. 麻烦的，讨厌的
critter n. 生物