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.
Governments, for example, very often see fencing as a potential solution to addressing human-wildlife conflict. Its seen as a solution that appears more straightforward than it is in practice. Once you put a fence up, then you have to maintain it. And if you dont maintain it, you can end up with a situation where wildlife conflict could actually be higher than it was before.
Often, Durant said, local communities will actually breach such fences.
Very marginalized communities that have problems meeting their own household needs in terms of food and nutrition very often they will want to breach the fences to gain access to the wildlife. And also fence wire can be used to build snares and that can actually exacerbate a snaring problem.
She said many communities have developed strategies over the years to deal with marauding animals, such as elephants. Coping skills they might lose if fences are built around their communities, and then the fences are breached by one or more elephants. Whats more, fences can build resentment in communities against conservation efforts.
Besides that, the wildlife researcher said fences can affect predator-prey dynamics.
When you look at some of the densities of lions in fenced reserves what you find is that theyre actually kept at levels much higher than what the areas would be expected to support. So that suggests that its actually altering the predator-prey dynamics. And lions arent the only predators in ecosystems. Youve also got other predators such as spotted hyenas, wild dogs, she said.
Predators, such as cheetahs and wild dogs, need a lot of space.
They need areas in excess of 10,000 square kilometers, if youre going to support what we call viable and sustainable populations of these species. They need very wide areas of connected habitat. Elephants and wildebeests can need areas in excess of tens of thousands square kilometers, particularly where youve got migratory systems, such as you have in the Serengeti, where the wildebeests will range across areas in excess of 20,000 square kilometers, she said.
Durant said one well-known fencing disaster occurred in the Kalahari. The fence was a veterinary cordon barrier. It was designed to separate wildebeests from cattle and prevent disease from being transmitted to cattle herds. What happened, she said, was the collapse of the wildebeest migrations in that region.
Instead of spending a lot of money to build and maintain fences, she said, invest that money in alternative approaches. These include improved animal husbandry, community-based crop protection, insurance programs and sensitive use of land to help prevent human-wildlife conflict.
The authors of the article do say fences can be valuable resources in some cases. They cited the protection of birds in New Zealand against foreign species -- and safeguarding wolves and lynx in Scotland.
是好是坏 原来你一直都在
国外也有“苏享茂” 你能识破这些婚恋网站骗局吗?
完成联合国健康目标,新加坡、冰岛和瑞典走在最前面
国内英语资讯:China issues guideline on setting limits in territorial spatial planning
体坛英语资讯:Kenya, Cameroon to bid for continental Olympic volleyball qualifiers
车用乙醇汽油将在全国推广 2020年实现全覆盖
Pot luck 这个词和运气有关吗?
体坛英语资讯:Messi the star again as Barca beat Juventus
重温乔布斯最经典演讲: 求知若饥,虚心若愚
马来西亚宗教学校起火,至少24人丧生
国内英语资讯:Belt, Road Initiative an avenue to win-win global cooperation: Chinese official
川普将视察佛罗里达灾区
The Road I Walk 我走过的路
久坐党必备神器:健身单车站立式书桌
国内英语资讯:China Focus: UN conference ends with world commitment to stop desertification
研究发现 遇到危险时紧抓别人只是为了自保
Stiff upper lip?
体坛英语资讯:Urawa Reds beat Guangzhou Evergrande 2-0 in 1st leg of AFC Champions League
伊拉克南部连环袭击至少60人丧生
国内英语资讯:China, Brunei to boost ties
体坛英语资讯:Three-time world champion Liu Hong comes back stronger
久坐党必备神器:健身单车站立式书桌
iPhone X面部识别遭恶搞 防伴侣偷窥面罩问世
国际英语资讯:Suicide attack kills 3, injures 5 near cricket stadium in Kabul
国际英语资讯:Britain raises terror threat level to critical
On the fence?
国内英语资讯:China says human rights dialogue should be constructive, not shaming
国际英语资讯:Halimah Yacob swears in as Singapores first female president
1000美元iPhone将考验“果粉”忠诚度
苹果发布会推出十周年纪念版,价格逆天
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |