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Question

Difficulty: HardWeakening Arguments

In 2021, the city of Eldervale implemented a comprehensive urban greening program, planting over 10,000 native trees across its central commercial district. Over the subsequent three years, reported air pollution levels in the district fell by 25 percent, and foot traffic to local businesses increased significantly. City officials concluded that the tree-planting initiative successfully improved the central district's environmental quality, thereby attracting more visitors and driving local economic vitality. Which of the following statements, if true, most seriously undermines the city officials' conclusion?

  1. Concurrent with the greening initiative, the city completed a major highway bypass that rerouted over 60 percent of heavy commercial vehicle traffic away from the central district.Answer
  2. B
    Surveys conducted during the three-year period revealed that visitors specifically cited the shaded aesthetic of the new trees as a primary reason for spending time downtown.
  3. C
    The annual maintenance and irrigation costs for the newly planted native trees exceeded initial municipal budget projections by nearly fifteen percent.
  4. D
    Similar tree-planting initiatives in neighboring cities with significantly different industrial profiles failed to yield measurable reductions in urban air pollution.
  5. E
    The city council had originally planned to pair the tree-planting program with an expansion of pedestrian-only zones, but that expansion was postponed indefinitely.

Answer

The statement noting that the city completed a major highway bypass rerouting heavy vehicle traffic away from the district most seriously weakens the argument.
The author concludes that planting trees caused the drop in air pollution and the increase in visitors. To weaken a causal argument, presenting an alternative factor that independently accounts for the observed effects is an effective strategy. If heavy vehicle traffic—a primary source of urban air pollution and pedestrian disruption—was rerouted away from the district at the exact same time, this bypass provides a compelling alternative explanation for both the 25 percent reduction in pollution and the increase in foot traffic.

Step-by-Step Solution

1
Identify the argument's premises and conclusion.
Premises: 10,000 trees were planted; subsequently, air pollution decreased by 25% and foot traffic increased. Conclusion: The tree-planting program caused the environmental improvement, which in turn attracted visitors.
Understanding the precise causal chain (Tree Planting → Better Air Quality & More Visitors) is essential before searching for a weakener.
2
Identify the logical vulnerability of the argument.
The argument assumes a correlation between two events implies a direct causal relationship, ignoring potential confounding variables or alternative explanations.
Causal claims based on observational changes over time are vulnerable to third-party factors that occurred during the same timeframe.
3
Evaluate the options to find an alternative cause or counter-evidence.
The opening of a major highway bypass rerouting 60% of heavy commercial traffic accounts for both the drop in air pollution and the improved pedestrian environment/foot traffic independent of the trees.
Demonstrating that another major factor directly caused the observed effects severs the assumed causal link between the tree planting and the outcome.

Key Concept

Alternative Explanations in Causal Arguments
Estimated Time:2m 0s
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Topics

Weakening Arguments

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