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Question

Difficulty: HardEvaluating Causal Arguments and Alternative Explanations

Over a five-year period in a coastal agricultural district, local fruit orchards gradually replaced synthetic chemical pesticides with natural predatory insects to control pest populations. During the exact same period, nearby estuarine populations of a threatened wild salmon species increased by over 30 percent. Environmental analysts concluded that the reduction in synthetic pesticide runoff was the direct cause of the recovery in the wild salmon population.

Which of the following would it be most useful to establish in order to evaluate the validity of the environmental analysts' conclusion?

  1. Whether regional commercial fishing quotas for salmon were significantly reduced during the same five-year periodAnswer
  2. B
    Whether the natural predatory insects introduced to the orchards also feed on non-pest insect species
  3. C
    Whether synthetic chemical pesticides are more expensive per acre than acquiring and maintaining predatory insect stocks
  4. D
    Whether growing salmon populations cause a decline in the abundance of local aquatic crustaceans
  5. E
    Whether orchards in neighboring inland valleys that continued using synthetic pesticides experienced lower overall fruit yields

Answer

The correct option is the one inquiring whether regional commercial fishing quotas for salmon were significantly reduced during the same five-year period.
The argument concludes that reduced pesticide runoff caused the 30 percent increase in wild salmon based solely on the fact that both changes occurred over the same five-year period. To evaluate a causal argument of this structure, one must test for alternative explanations that could account for the observed increase in salmon. Finding out whether regional commercial fishing quotas for salmon were significantly tightened during this period provides critical information: if quotas were reduced, fewer salmon were caught, offering a direct alternative explanation for the population rise. If quotas remained unchanged, alternative causes are minimized, strengthening the analysts' conclusion.

Step-by-Step Solution

1
Deconstruct the core argument and identify premises and conclusion
Premise: Orchards replaced synthetic pesticides with natural predators. Premise: Salmon populations increased by 30% over the same 5-year period. Conclusion: The reduction in pesticide runoff directly caused the increase in wild salmon populations.
Understanding the precise causal leap from observed correlation (pesticide change + salmon increase) to cause is necessary to evaluate the argument.
2
Identify the central assumption and vulnerabilities of the causal claim
The author assumes that no other co-occurring factor (confounding variable or alternative explanation) was responsible for the increase in salmon numbers.
Causal claims based on co-occurring events are vulnerable to alternative explanations that occurred during the same timeframe.
3
Assess the answer choices for a factor that tests for alternative causes
Checking whether commercial fishing quotas were reduced tests an alternative cause. If quotas were significantly reduced, the salmon population increase may be due to reduced harvesting rather than cleaner water.
Evaluating a prominent alternative explanation directly determines whether the stated cause or an unstated external factor produced the observed effect.

Key Concept

Evaluating Causal Arguments via Confounding Variables / Alternative Explanations
Estimated Time:2m 0s
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Topics

Evaluating Causal Arguments and Alternative Explanations

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