VOA慢速英语--研究称到2050年，非本土物种将急剧增加

Researchers are predicting that the number of non-native species will rise by about 36 percent worldwide by 2050.

Non-native, or alien species, are plants or animals that humans have moved around the world to places where they are not naturally found. Sometimes the introduction of an alien species to an area is accidental. Sometimes, it is done on purpose.

Research shows the movement of plants and animals rose across the planet over the last century as human trade and travel opened up new worldwide pathways.

A new study predicts such movements are likely to continue, with the largest increases expected to be big insects, birds and small creatures such as mollusks and crustaceans¹.

Researchers are calling for more rules and better observation methods to help reduce the spread of alien species.

The findings were recently reported in the publication Global Change Biology.

Scientists involved in the study say more than 35,000 alien species had been identified in the most recent report on the subject in 2005. Some of the species can go on to become invasive, meaning they spread quickly in undesirable² and harmful ways.

The study suggests alien species introductions will increase on every world continent. But the largest increases are predicted to be in Europe. The researchers estimate such species will increase 64 percent across Europe by around 2050.

Hanno Seebens is an ecologist at Germany's Senckenberg Biodiversity and Climate Research Centre. He was the lead writer of the study. "Together with climate change and land use change, invasive alien species are posing one of the greatest threats to biodiversity," Seebens said.

He added that a species can only arrive in a new area when human activity connects different areas. "When we extended our trade networks, we connected more and more (areas), which allowed more and more species to come."

The researchers developed a mathematical model to predict alien species introductions for each continent between 2005 and 2050. The model was based on past records of alien species introductions, as well as estimates of species that could end up becoming invasive if current movements continue.

Cascade³ Sorte is a professor of ecology and evolutionary⁴ biology at the University of California Irvine. She was not part of the research. "We know that a certain proportion of alien species will be problematic, so the more of them that there are, the higher the likelihood that we'll have problems," she said.

Sorte described the latest predictions as "shocking" because even with the past rises in alien species, "there's even a possibility that things can get worse."

However, Hanno Seebens said it is possible the number of species could fall in the future based on continued rising movements. "We may just run out of species to be transported, because at some point, all species may have been transported already," he said.

Words in This Story

species – n. a group of animals or plants that are similar and can produce young animals or plants

pose - v. to cause a problem

biodiversity – n. the existence of many different kinds of plants and animals in an environment

allow – v. to permit

evolution – n. a gradual process of change and development

proportion – adj. a part of a total number or amount

1 crustaceans   

n.甲壳纲动物（如蟹、龙虾）( crustacean的名词复数 )

参考例句：

• These crustaceans provide a valuable food source for some fish. 这些甲壳纲动物是某些鱼类重要的食物来源。 来自《简明英汉词典》
• When the tide ebbs it's a rock pool inhabited by crustaceans. 退潮时，它便成为甲壳动物居住的岩石区潮水潭。 来自辞典例句

2 undesirable   

adj.不受欢迎的，不良的，不合意的，讨厌的；n.不受欢迎的人，不良分子

参考例句：

• They are the undesirable elements among the employees.他们是雇员中的不良分子。
• Certain chemicals can induce undesirable changes in the nervous system.有些化学物质能在神经系统中引起不良变化。

3 cascade   

n.小瀑布，喷流；层叠；vi.成瀑布落下

参考例句：

• She watched the magnificent waterfall cascade down the mountainside.她看着壮观的瀑布从山坡上倾泻而下。
• Her hair fell over her shoulders in a cascade of curls.她的卷发像瀑布一样垂在肩上。

4 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。