Kestrel Bay Tree-Planting Study
Read this passage: 'In 2019, the city of Kestrel Bay planted 4,000 trees along its eastern arterial roads. A follow-up study found that surface temperatures on tree-lined blocks were 2.8°C lower than on bare blocks at 3 p.m. in July. The authors noted that the eastern blocks also received 40 minutes more afternoon shade and that the trees were irrigated during their first two summers. Maintenance costs averaged $18 per tree per year. The city council has proposed extending the program to 12,000 trees, citing the temperature finding.' A student writes: 'The study proves that planting trees will lower temperatures by 2.8°C anywhere in the city.' The instructor asks the class to separate what the passage states from what it merely suggests, and to evaluate the council's use of the evidence.
1. Identify two specific overstatements in the student's sentence and explain what the passage actually supports.
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'Proves' and 'anywhere in the city' are the overstatements. The passage reports an observational comparison: tree-lined blocks were 2.8°C cooler than bare blocks at 3 p.m. in July. That is a correlation recorded at one time of day, in one month, on eastern arterial roads. The passage also notes two confounds, extra afternoon shade and irrigation during the first two summers, so the temperature difference cannot be attributed to trees alone. 'Proves' claims certainty a single follow-up study cannot provide, and 'anywhere' universalizes beyond the sampled blocks. A defensible paraphrase: 'On the studied eastern blocks, surface temperatures were 2.8°C lower at 3 p.m. in July, though irrigation and shade may have contributed.'
2. The council cites the temperature finding to justify expanding to 12,000 trees. What is the strongest version of the council's argument, and what evidence would make it stronger?
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Strongest version: the observed association is large enough and plausible enough to justify a pilot expansion with evaluation, not a certainty claim. The council can argue that 2.8°C is meaningful for heat exposure and that the mechanism (shade, evapotranspiration) is well established. To strengthen: compare matched streets with and without trees while holding irrigation constant; measure air temperature and human heat stress, not only surface temperature; track effects across seasons and years; and report cost per degree or per health outcome. The current $18 per tree per year is a maintenance figure, not a full cost-benefit analysis. The council should also avoid saying the study 'shows trees cause' cooling.
3. What does the phrase 'citing the temperature finding' imply about the council's reasoning?
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It implies selective use of the evidence. The passage contains at least four relevant items: the 2.8°C difference, the extra shade, the irrigation, and the maintenance cost. The council cites one and omits the others. That is not automatically dishonest, since a proposal often highlights its strongest point, but it is a rhetorical choice worth naming. A careful reader should ask whether the omitted details change the conclusion: irrigation and shade are plausible alternative explanations, and cost affects whether expansion is worthwhile. The phrase therefore signals that the council is making an advocacy case, not a neutral summary. Evaluating it means asking what a full accounting would include.