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找不到好的英语六级听力练习材料?绝对是你的不二选择。大家平时多用英语磨耳朵，时间长了英语六级听力绝对会有很大的提高。 英语六级听力练习：标准4.5 点击收听 If you want to protect endangered species in the wild, dont fence them in. An article in the journal Science says fencing can actually harm both animals and ecosystems. Scientists at the Zoological Society of London and the Wildlife Conservation Society say the use of fences to protect threatened species should be a last resort. Researcher Sarah Durant said, Fences by their nature will segregate habitats and that can actually be a real problem, particularly in drylands systems where wildlife often has to move quite large distances to access resources and water. So that in itself can be a problem. And then you have wide-ranging species, such as cheetah and wild dog, but also elephants as well, which need access to very large connected habitat for their survival. Fences are not very widespread right now in Africa. Durant said the biggest concentration is in South Africa. Theyre often used basically for territory protection. So people will own private land and they build fences around their private land to protect wildlife as a resource within those areas. However, she said theres concern more fences may be built, as human populations spread further into wildlife habitats. | 
