Here is the text:
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, long-term data will not soon be forthcoming, and postponing environmental action while we wait for it may doom specie and ecosystems to extinction.
Now I apply the critical thinking line to this article.
1. The main purpose of this article is:
To refute the claims declared by some environmentalists.
2. The key question that the author is addressing is:
The difference between "declining population" and "endangered population".
3. The most important information in this article is:
The "endangered population" doesn't totally from "declining population".
4. The main inferences/conclusions in this article are:
Long-term data will not soon be available soon for taking measures to remedy the "crisis".
5. The key concept we need to understand in this article is:
a. The endangered population;
b. Population declines.
c. Differences in consequences between "endangered population" and "population declines"
By this concept, the author means:
a. The endangered populations do not result only from population declines.
b. Population declines have different consequences and they don't always lead to the extinction.
6. The main assumption underlying the author's thinking is:
The severe declines in the 1950s and 1960s might have generated the current crisis.
7a. If we take this line of reasoning seriously, the implications are:
Long-term data should be collected for making a sound decision on how to remedy the population "crisis".
7b. If we fail to take this line of reasoning seriously, the implications are:
8. The main point of view presented in this article is:
It is not so urgent as the environmentalists claimed to remedy the population declines.
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