Invasive Animal Species That Changed the World改变世界的入侵动物

Invasive animal species have a bad reputation—from tree-killing insects to rampaging wild pigs， they often crowd out native fauna and alter the environment they invade. Though through no fault of their own—they are almost always introduced to new areas by humans.

入侵动物的名声不好——从杀死树木的昆虫到横冲直撞的野猪，它们常常排挤本土动物，改变侵入之地的生态环境。然而，它们本身并没有错——几乎总是人类将它们引入新区域。

Often， invasive species proliferate rapidly because they lack natural predators that would keep their population in check. They range from tiny insects that harbor novel diseases to apex predators1 that can upend an entire food chain.

通常，由于没有可以控制其种群规模的天敌，入侵物种会迅速繁殖。它们可以是携带新型疾病的微小昆虫，也可以是能够颠覆整个食物链的顶级捕食者。

Learn more about invasive species that came to dominate new landscapes and changed the environment forever.

接下来，让我们详细了解几个入侵物种。它们主宰了新区域，而且彻底改变了当地的环境。

Earthworm

蚯蚓

Earthworms are considered one of the original invasive species. Given the ubiquity of earthworms， it only seems natural that they have existed underground across the world for millions of years. But in North America， native earthworms were largely wiped out by expanding glaciers during the Pleis-tocene2 ice age. Most of the earthworms in the United States， especially in northern states， are actually descended from species that arrived in America with the first European settlers.

蚯蚓被认为是最早的入侵物种之一。鉴于蚯蚓无处不在，它们在世界各地的地下生存了数百万年之久似乎是很自然的事。然而，北美的本土蚯蚓因更新世冰期的冰川扩张而基本灭绝。目前美国大多数蚯蚓，尤其是美国北方各州的蚯蚓，实际上是随同第一批欧洲殖民者抵达美洲的蚯蚓的后代。

While gardeners appreciate seeing earthworms in the soil， worms have had a mixed effect in North American forests. Studies have shown that invasive earthworms can reduce ground cover， allow invasive plants to thrive， and reduce populations of ground-nesting ovenbirds.

虽然园丁们很乐意在土壤中看到蚯蚓，但蚯蚓对北美森林的影响有好有坏。研究表明，入侵的蚯蚓会减少地被植物，促使入侵植物旺盛生长，还会减少在地面筑巢的灶巢鸟的数量。

Brown rat

褐家鼠

Rats have a long， devastating history as an invasive species. They were the first invasive species to arrive on Aus-tralia’s uninhabited Macquarie Island， soon after the island was discovered in the southern Pacific Ocean in 1810. The rats， along with introduced rabbits and cats， stripped the island of its natural vegetation and caused the extinction of two native bird species—the Macquarie Island parakeet and Macquarie Island rail.

褐家鼠作为入侵物种，有着悠久的入侵史，而且破坏力极强。1810年，人们发现了位于南太平洋的麦夸里岛。此后不久，褐家鼠成为第一个到达这座澳大利亚无人岛的入侵物种。褐家鼠与后来引入的猫和兔子糟蹋了岛上的自然植被，导致麦夸里岛的2种本土鸟——麦岛长尾小鹦鹉和麦岛红眼斑秧鸡灭绝。

In 2007， the Australian government pledged $24.6 million dollars to eradicate invasive species from the ecosystem by trapping， hunting， and monitoring. In 2014， they announced that the project was a success.

2007年，澳大利亚政府承诺拨款2460万澳元，通过诱捕、猎杀、监控等手段彻底消灭生态系统中的入侵物种。2014年，澳大利亚政府宣布该项目取得成功。

European starling

欧洲椋鸟

The European starling is native to Europe， Asia， and northern Africa but has been introduced to most of the world’s habitats， except for tropical rainforests. In the United States， starlings were introduced as part of a plan to fill the American landscape with all of the species referenced in works by Shakespeare.3 Starlings now exist in massive flocks that outcompete native species， steal nests from other birds， and damage crops.

欧洲椋鸟原产自欧洲、亚洲和北非，但放眼全世界，欧洲椋鸟已被引入除热带雨林外的大多数栖息地。美国曾有人计划让莎士比亚作品中提到的所有鸟类都能在美国境内随处可见，引入欧洲椋鸟便是这计划的一部分。如今，椋鸟在美国大规模群居，它们战胜了本土物种，窃取其他鸟类的巢穴，还破坏农作物。

Mountain pine beetle

山松甲虫

Mountain pine beetles are only about one-fourth of an inch long， but these invasive pests have had an enormous impact on pine forests. They bore under a tree’s bark， laying eggs and depositing a fungus that kills the tree. In the western United States and Canada， a 20-year outbreak that began in 1995 destroyed millions of acres of forest. The outbreak was particularly bad in British Columbia， where pine beetles killed nearly 30% of all forests. Scientists believed that this outbreak was particularly extensive because warmer winters due to climate change allow the beetles to expand their range.

山松甲虫的体长只有大约1/4英寸，但是这种入侵害虫对松林产生了巨大影响。它们在树皮下钻洞产卵，并在洞中储存一种可以杀死树木的真菌。自1995年起，美国西部和加拿大遭遇了长达20年的山松甲虫灾害，数百万英亩森林被摧毁。加拿大不列颠哥伦比亚省的受灾情况尤为严重，山松甲虫破坏了近30%的森林。科学家们认为，这场虫灾的波及范围之所以这么广，是因为气候变化导致的暖冬让甲虫的活动范围得以扩大。

Northern pacific seastar

北太平洋海星

The northern Pacific seastar is an invasive species in Australia. It is a vor-acious predator that feeds on mollusks， crabs， dead fish， and other seastars. Female seastars can produce 10 to 25 million eggs per year， leading to rapid population growth.

北太平洋海星是澳大利亚的入侵物种。它是一种贪婪的捕食性动物，以软体动物、螃蟹、死鱼和其他海星为食。雌性海星每年产卵多达1000万到2500万颗，导致其种群规模迅速扩大。

In Australia， it has contributed to the decline of the spotted handfish， a unique fish that “walks” on the seafloor using highly adapted fins. The spotted handfish is now considered critically endangered and is only found in the estuary of the Derwent River in Tasmania.

在澳大利亚，北太平洋海星入侵导致斑点疣躄的数量减少。斑点疣躄是一种独特的鱼，可借助自己适应性很高的鳍在海底“行走”。斑点疣躄目前处于极度濒危状态，只见于塔斯马尼亚岛德文特河的河口。

Wild pig

野猪

Wild pigs are one of the most prevalent invasive species in North America. They were brought to the Americas in the 1500s as domestic livestock. Escaped pigs soon turned into feral herds that live in the wild. In 2018， the population in the United States was estimated to be 6 million and growing， with feral pigs found in 35 states.