新托福TPO 15综合写作详细解析：控制蔗蜍数量的方法

　　阅读材料：
　　The cane toad is a large (1.8 kg) amphibian species native to Central and South America. It was deliberately introduced to Australia in 1935 with the expectation that it would protect farmers’ crops by eating harmful insects. Unfortunately, the toad multiplied rapidly, and a large cane toad population now threatens small native animals that are not pest. Several measures have been proposed to stop the spread of the cane toad in Australia.
　　蔗蜍是一种原产于中南美洲的两栖动物，个头很大，重大1.8公斤。蔗蜍是在1935年由人工引进至澳大利亚的。因为它们可以吃害虫，所以希望借由它们保护农作物。不幸的是，蔗蜍繁殖迅速。而且，数量巨大的蔗蜍群体已经开始威胁一些对农业无害的小型本土生物。现在提出了几个解决蔗蜍在澳大利亚蔓延的方法。
　　One way to prevent the spread of the toad would be to build a national fence. A fence that blocks the advance of the toads will prevent them from moving into those parts of Australia that they have not yet colonized. This approach has been used before: a national fence was erected in the early part of the twentieth century to prevent the spread of rabbits, another animal species that was introduced in Australia from abroad and had a harmful impact on its native ecosystems.
　　第一个阻止蔗蜍蔓延的方法是建立一个全国范围的围栏。用围栏控制蔗蜍增长的方式是通过阻止它们迁徙实现的，这样它们就不会聚集到那些尚未被它们控制的地区了。这种方法以前就用过。在二十世界初期，澳大利亚就从用这种围栏阻止兔子的过度增长。兔子由澳大利亚从他国引进后，给当地的生态平衡造成了巨大的灾难。
　　Second, the toads could be captured and destroyed by volunteers. Cane toads can easily be caught in simple traps and can even be captured by hand. Young toads and cane toad eggs are even easier to gather and destroy, since they are restricted to the water. If the Australian government were to organize a campaign among Australian citizens to join forces to destroy the toads, the collective effort might stop the toad from spreading.
　　第二，可以招募志愿者抓蔗蜍。简单的陷阱就可以抓到蔗蜍，甚至徒手都可以抓到。至于蝌蚪和卵因为是生活在水里的，更是容易抓到和消灭。如果澳大利亚政府组织一个由澳大利亚公民参与的运动去消灭蔗蜍，那么可能会达到阻碍其蔓延的目的。
　　Third, researchers are developing a disease-causing virus to control the cane toad populations. This virus will be specially designed: although it will be able to infect a number of reptile and amphibian species, it will not harm most of the infected species; it will specifically harm only the cane toads. The virus will control the population of cane toads by preventing them from maturing and reproducing.
　　第三，研究人员正在研究一种用于控制蔗蜍数量的致病病毒。这种病毒是专门为控制蔗蜍研制的。尽管这种病毒也可以感染相当多数量的爬行动物和两栖动物，但是这种感染基本是无害的。它只会影响蔗蜍。这种病毒通过阻碍蔗蜍的蔗蜍的成熟和繁殖实现控制其数量的目的。
　　阅读部分需要提取的观点是：
　　- Main point: 提供了三个控制蔗蜍数量的方法
　　- Sub point 1: 建立全国范围性的围栏
　　- Sub point 2: 组织志愿者抓
　　- Sub point 3: 研制某种特殊病毒，阻碍蔗蜍的成熟和繁殖
　　听力材料：
　　The cane toad won’t be as easy to get rid of as the reading suggests. The measures proposed by the reading are likely either to be unsuccessful or to cause unwanted environmental damage.
　　蔗蜍不会像阅读部分说的那么容易出去的。阅读部分提供的观点不但是不会奏效，甚至会对环境造成损害。
　　First of all, a national fence probably won’t stop the spread of the toad. That’s because young toads and toad eggs are found in rivers and streams. No matter where the fence is located, at some point there will be rivers or steams flowing from one side to the other. These waterways will be able to carry the young toads and their eggs to the other side. Since it’s only necessary for a few young toads or eggs to get though the fence in order to establish population on the other side, the fence is unlikely to be effective.
　　首先，一个全国范围内的围栏不会阻止蔗蜍的蔓延。这是因为蝌蚪和蔗蜍卵是生活在河水和溪流中的。不管围栏怎么安排，总会有跨过河流和小溪的地方。在这些地方，流水可以越过围栏。蝌蚪和蔗蜍卵可以通过这些水流穿过围栏。只要有很小数量的蝌蚪和蔗蜍穿过围栏，它们就可以建立起一个种群。所以，这种围栏的方法是无效的。
　　Secondly, a massive group of volunteers could have success trapping and destroying toads. But it’s likely that these untrained volunteers would inadvertently destroy many of Australia’s native frogs some of which are endangered. It’s not always easy to tell the cane toad apart from native frogs especially when it’s young.
　　第二，人数众多的志愿者队伍的确可以抓住和消灭蔗蜍。但是这些没有经过训练的志愿者很可能会无意间杀死很多澳大利亚原产的青蛙，而其中的一些已经是濒危物种的。蔗蜍和澳大利亚原产青蛙并不容易区分，尤其是在它们都是幼体的时候。
　　Third, using the virus is a bad idea because it could have terrible consequences for cane toads in their original habitat in Central and South America. You might be wondering how can virus released in Australia cause harm in the Americas. Well, Australian reptiles and amphibians are often transported to other continents by researchers or pet collectors for example. Once the animals infected by the virus reach Central and South American, the virus will attack the native cane toads and devastate their populations. That would be an ecological disaster because in the Americans cane toads are a native species and a vital part of the ecosystem. So if they are eliminated the whole ecosystem will suffer.
　　第三，病毒可能会对蔗蜍原产的中南美洲的生态环境造成严重的破坏，所以使用病毒也是一个坏主意。你们可能很好奇为什么投放在澳大利亚的病毒会破换美洲的环境。恩，研究者或者宠物饲养者常常会被澳大利亚的爬行动物和两栖类动物带到其他的大洲。一旦感染此病毒的动物被带到了中南美洲，那么这种病毒就会感染当地的蔗蜍，使得其数量锐减。因为蔗蜍在美洲是原生物种，是生态系统的重要组成部分，所以其数量锐减将会是生态灾难。所以，如果蔗蜍灭绝了，那么美洲的生态系统也会受到破坏。
　　听力部分需要提取的观点是：
　　- Main point: 三个方法是无效甚至只有害的
　　- Sub point 1: 蔗蜍的蝌蚪和卵可以通过流水穿过围栏，方法无效
　　- Sub point 2: 尽管志愿者可以抓到蔗蜍，但是可能会错抓当地濒危的原产青蛙
　　- Sub point 3: 使用病毒可能会破坏蔗蜍原产地中南美洲的生态平衡