There are recent reports of apparently drastic declines in amphibian populations and of extinctions of a number of the world’s endangered amphibian species. These declines, if real, may be signs of a general trend toward extinction, and many environmentalists have claimed that immediate environmental action is necessary to remedy this “amphibian crisis,” which, in
their view, is an indicator of general and catastrophic environmental degradation due to human activity.
To evaluate these claims, it is useful to make a preliminary distinction that is far too often ignored. A declining population should not be confused with an endangered one. An endangered population is always rare, almost always small, and, by definition, under constant threat of extinction even without a proximate cause in human activities. Its disappearance, however unfortunate, should come as no great surprise. Moreover, chance events—which may indicate nothing about the direction of trends in population size—may lead to its extinction. The probability of extinction due to such random factors depends on the population size and is independent of the prevailing direction of change in that size.
For biologists, population declines are potentially more worrisome than extinctions. Persistent declines, especially in large populations, indicate a changed ecological context. Even here, distinctions must again be made among declines that are only apparent (in the sense that they are part of habitual cycles or of normal fluctuations), declines that take a population to some lower but still acceptable level, and those that threaten extinction (e.g., by taking the number of individuals below the minimum viable population). Anecdotal reports of population decreases cannot distinguish among these possibilities, and some amphibian populations have shown strong fluctuations in the past.
It is indisputably true that there is simply not enough long-term scientific data on amphibian populations to enable researchers to identify real declines in amphibian populations. Many fairly common amphibian species declared all but extinct after severe declines in the 1950s and 1960s have subsequently recovered, and so might the apparently declining populations that have generated the current appearance of an amphibian crisis. Unfortunately, longterm data will not soon be forthcoming, and postponing environmental action while we wait for it may doom species and whole ecosystems to extinction.
It can be inferred from the passage that the author believes which of the following to be true of the environmentalists mentioned in highlight lines ?
定位：第一段中，关于environmentalists有2点，如果数量的减少是灭绝的信号，那么1 环保措施很重要 2 这个现象时由人类活动引起的
作者对1的态度在第4段，对 2 的态度在第2段
A They have wrongly chosen to focus on anecdotal reports rather than on the long-term data that are currently available concerning amphibians.
原文相反：第四段开头，there is simply not enough long-term scientific data,是对第三段结尾 anecdotal reports的回应，支持观点。没有涉及到wrongly chosen to focus on anecdotal reports
B Their recommendations are flawed because their research focuses too narrowly on a single category of animal species.
无涉及too narrowly on a single category of animal species.
C Their certainty that population declines in general are caused by environmental degradation is not warranted.
D They have drawn premature conclusions concerning a crisis in amphibian populations from recent reports of declines.
对应第二段：A declining population should not be confused with an endangered one.
E They have overestimated the effects of chance events on trends in amphibian populations.
0 0 回复 2019-10-14 17:07:37
0 0 回复 2019-10-16 23:27:00
due to human activity， not environmental degradation
an indicator ≠ caused by
想请教一下C错在哪里。 C的意思是说，环境学家认为数量的下降是由于环境恶化导致，这是不大对的 根据作者的意图，应该是反对the dicline, is an indicator of general and catastrophic environmental degradation due to human activity的，不是应该和C的意思相一致吗？ 谢谢！
0 0 回复 2017-08-29 11:17:42
0 0 回复 2018-08-18 15:03:24
我觉得可能是说 population in general 错了
1 0 回复 2019-02-16 04:51:24