[ti:Study: Non-Native Species to Rise Sharply by 2050] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]Researchers are predicting that the number of non-native species [00:06.36]will rise by about 36 percent worldwide by 2050. [00:14.72]Non-native, or alien species, are plants or animals [00:20.72]that humans have moved around the world [00:23.88]to places where they are not naturally found. [00:28.80]Sometimes the introduction of an alien species [00:33.08]to an area is accidental. [00:37.08]Sometimes, it is done on purpose. [00:41.60]Research shows the movement of plants and animals [00:46.52]rose across the planet over the last century as human trade [00:52.80]and travel opened up new worldwide pathways. [00:59.00]A new study predicts such movements are likely to continue, [01:04.00]with the largest increases expected to be big insects, [01:09.88]birds and small creatures such as mollusks and crustaceans. [01:17.76]Researchers are calling for more rules [01:21.52]and better observation methods [01:24.16]to help reduce the spread of alien species. [01:29.88]The findings were recently reported [01:32.80]in the publication Global Change Biology. [01:38.08]Scientists involved in the study [01:41.20]say more than 35,000 alien species had been identified [01:47.56]in the most recent report on the subject in 2005. [01:53.40]Some of the species can go on to become invasive, [01:58.56]meaning they spread quickly in undesirable and harmful ways. [02:05.68]The study suggests alien species introductions [02:10.04]will increase on every world continent. [02:14.80]But the largest increases are predicted to be in Europe. [02:20.72]The researchers estimate such species will increase [02:25.48]64 percent across Europe by around 2050. [02:32.44]Hanno Seebens is an ecologist [02:35.68]at Germany's Senckenberg Biodiversity [02:39.48]and Climate Research Centre. [02:43.20]He was the lead writer of the study. [02:46.84]"Together with climate change and land use change, [02:51.48]invasive alien species are posing [02:55.20]one of the greatest threats to biodiversity," Seebens said. [03:01.52]He added that a species can only arrive in a new area [03:06.44]when human activity connects different areas. [03:10.84]"When we extended our trade networks, [03:14.64]we connected more and more (areas), [03:17.56]which allowed more and more species to come." [03:22.60]The researchers developed a mathematical model [03:26.32]to predict alien species introductions [03:29.88]for each continent between 2005 and 2050. [03:35.96]The model was based on past records of alien species introductions, [03:41.92]as well as estimates of species that could end up [03:46.48]becoming invasive if current movements continue. [03:52.24]Cascade Sorte is a professor of ecology and evolutionary biology [03:58.76]at the University of California Irvine. [04:02.24]She was not part of the research. [04:06.52]"We know that a certain proportion [04:09.16]of alien species will be problematic, [04:12.72]so the more of them that there are, [04:15.48]the higher the likelihood that we'll have problems," she said. [04:21.64]Sorte described the latest predictions as "shocking" [04:26.28]because even with the past rises in alien species, [04:30.88]"there's even a possibility that things can get worse." [04:36.20]However, Hanno Seebens said it is possible [04:40.64]the number of species could fall in the future [04:44.20]based on continued rising movements. [04:48.52]"We may just run out of species to be transported, [04:52.88]because at some point, all species [04:56.12]may have been transported already," he said. [05:00.20]I'm Bryan Lynn. 更多听力请访问51VOA.COM