Official 37 Passage 2

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Direct Species Translocation

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This is not the only example of a large-scale translocation that had positive results.

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  • It is becoming increasingly common for conservationists to move individual animals or entire species from one site to another. This may be either to establish a new population where a population of conspecifics (animals or plants belonging to the same species) has become extinct or to add individuals to an existing population. The former is termed reintroduction and the latter reinforcement. In both cases, wild individuals are captured in one location and translocated directly to another.



    Direct translocation has been used on a wide range of plants and animals and was carried out to maintain populations as a source of food long before conservation was a familiar term. The number of translocations carried out under the banner of conservation has increased rapidly, and this has led to criticism of the technique because of the lack of evaluation of its efficacy and because of its potential disadvantages. The nature of translocation ranges from highly organized and researched national or international programs to ad hoc releases of rescued animals by well-intentioned animal lovers. In a fragmented landscape where many populations and habitats are isolated from others, translocations can play an effective role in conservation strategies; they can increase the number of existing populations or increase the size, genetic diversity, and demographic balance of a small population, consequently increasing its chances of survival.



    Translocation clearly has a role in the recovery of species that have substantially declined and is the most likely method by which many sedentary species can recover all or part of their former range. However, against this is the potential for reinforcement translocations to spread disease from one population to another or to introduce deleterious or maladaptive genes to a population. Additionally, translocation of predators or competitors may have negative impacts on other species, resulting in an overall loss of diversity. Last but not least of these considerations is the effort and resources required in this type of action, which need to be justified by evidence of the likely benefits.



    Despite the large number of translocations that have taken place, there is surprisingly little evidence of the efficacy of such actions. This is partly because many translocations have not been strictly for conservation; neither have they been official nor legal, let alone scientific in their approach. Successful translocations inevitably get recorded and gain attention, whereas failures may never be recorded at all. This makes appraisal of the method very difficult. One key problem is a definition of success. Is translocation successful if the individuals survive the first week or a year, or do they need to reproduce for one or several generations? Whatever the answer, it is clear that a general framework is required to ensure that any translocation is justified, has a realistic chance of success, and will be properly monitored and evaluated for the benefit of future efforts.



    An example of apparent translocation success involves the threatened Seychelles warbler. This species was once confined to Cousin Island, one of the Seychelles islands, and reduced to 26 individuals. Careful habitat management increased this number to over 300 birds, but the single population remained vulnerable to local catastrophic events. The decision was taken to translocate individuals to two nearby islands to reduce this risk. The translocations took place in 1988 and 1990, and both have resulted in healthy breeding populations. A successful translocation exercise also appears to have been achieved with red howler monkeys in French Guiana. A howler population was translocated from a site due to be flooded for hydroelectric power generation. The release site was an area where local hunting had reduced the density of the resident howler population. Released troops of monkeys were kept under visual observation and followed by radio tracking of 16 females. Although the troops appeared to undergo initial problems, causing them to split up, all the tracked females settled into normal behavioral patterns.



    Unfortunately, the success stories are at least matched by accounts of failure. Reviewing translocation of amphibians and reptiles, researchers C.Kenneth Dodd and Richard A. Siegel concluded that most projects have not demonstrated success as conservation techniques and should not be advocated as though they were acceptable management and mitigation practices.


  • 越来越普遍地,环境保护主义者开始把动物或者整个物种从一个地方迁移到另一个地方。 这既可能是向某一族群(同种的动物或者植物)已经灭绝的地区输入新的族群,也可能是向一个现有生物族群引入新的个体。 前者的术语是物种再引入,后者的术语是物种再强化。 在这两种情况里,野生动物在一个地方被抓获,并且被直接传送到另一个地方。

    在环境保护成为人们所熟知的术语之前,直接物种迁移就已经被用于多种动植物,被用来作为食物来源来保持物种数量。 打着环境保护的名义的物种迁移数量急剧增加,这就导致了对于这种技术的批评,因为我们对其有效性缺乏评估,而且还因为它有潜在的不利之处。 实际上的物种迁移涉及到高度组织化和精细调查过的国内国际项目,也涉及到好心的动物爱好者对于动物的拯救与放生。 在一个碎片化的地貌上,不同的种群和栖息地是彼此隔绝的,这时候作为保护措施的物种迁移就起到了重要的作用;他们可以促进动物数量增长,帮助种群规模扩大,增加基因多样性,平衡小种群的数量,最终增加动物的存活率。

    物种迁移在经历过大量减少的物种中起到重要的帮助恢复作用,它还是可以帮助很多定居的物种完全或者部分恢复原有规模的最有效办法。 然而,反对这个看法的观点是,物种再强化式的迁移是可能把疾病从一个物种传到另一个物种的,或者向一个物种引入有害的或者适应不良的基因。 另外,捕食者或者竞争者的迁移也许会对别的物种产生不好的影响,导致多样性的整体减少。 这些考虑里,最后但同样重要的一点是,物种迁移所需要耗费的精力和资源仍然需要通过分析其可以带来的好处来确定合理性。

    尽管大量的物种迁移已经发生了,让人惊奇的是还没有什么证据来证明这些行动的功效。 这有一部分原因是因为很多物种迁移不是严格为了环境保护的;也不是官方的或者合法的,在实施过程中就不谈是否科学了。 成功的物种迁移不可避免地被记录下来,获得别人的关注,然而不成功的可能根本不会被记录下来。 这就使得评价这种行为非常困难。 一个关键的问题是,我们应该如何定义成功的物种迁移。 如果迁移过去的物种存活一周或者一年就算是成功了,还是需要它们繁衍上一代或多代才算成功?不论答案是什么,我们都需要一个总体的框架,来确保任意一次物种迁移都是正当的,它们实际上确实有可能成功,而且会被妥善监控并且评估其未来带来的好处。

    一个明显的物种迁移成功的例子是关于濒危的Seychelles warbler的。 这个物种一开始只生存于Seychelles Island群岛之一的Cousin Island,数量直降到26只。 小心的栖息地管理使其数量增加到超过300只,但是这个物种只存在于Cousin Island这一个地方导致其对于当地的灾害事件抵抗力极低。 人们决定,为了降低这个风险,把这种鸟迁移到另外两个岛屿上。 针对这种鸟的迁移发生于1988年和1990年,两次迁移都导致了鸟类数量的健康增长。 另一个成功的迁移活动发生在法国圭亚那地区的red howler monkey身上。 因为原栖息地被水力发电导致的洪水淹没,这种猴子被迁移到了别的地方。 释放地点是一个本地捕猎降低了这种猴子族群密度的地区。 猴子被释放以后一直在人们的观察之下,并且16只母猴被无线电追踪。 尽管释放猴群经历了最初的困难,导致族群的分解,所有被追踪的母猴最终找到了正常的行为模式。

    不幸的是,这些成功的案例背后,有同样数量巨大的失败案例。 研究者C. Kenneth Dodd和Richard A. Siegel在回顾了两栖动物和爬虫的迁移案例后,得出结论,大多数迁移项目并没有把成功阐释为保护措施的成功,尽管它们是可以接受的管理和减轻问题的实践,它们也不应该被提倡。
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    解析

    题型分类:句子插入题

    题干分析:待插入句this表示前文已提及相关信息,not the only example说这不是唯一的例子,前句提到的也是个同样功能的例子,也在说a large-scale translocation有着积极结果。


    选项分析:

    C选项前一句both have resulted in healthy breeding populations是成功的例子。

    C选项后一句A successful translocation exercise also,具体说明了被插入句的例子的具体内容。

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