Baltimore, Maryland, has installed engineered structures along 71% of its shoreline to protect infrastructure from wave erosion and other hazards,...
GMAT Information and Ideas : (Ideas) Questions
Baltimore, Maryland, has installed engineered structures along 71% of its shoreline to protect infrastructure from wave erosion and other hazards, a practice known as shoreline hardening. To evaluate the responses of waterbirds to two types of hardening structures—riprap and bulkheads—Diann Prosser et al. surveyed waterbird communities consisting of the tundra swan, the great blue heron, and 62 other species at different sites in the Chesapeake Bay on the US East Coast. Utilizing the Index of Waterbird Community Integrity (IWCI), on which a high score corresponds to high community integrity, the researchers found that bulkheads are more strongly negatively correlated with waterbird community integrity than is riprap.
Which finding, if true, would most directly illustrate the researchers' finding?
The difference in average IWCI scores for waterbird communities at Stony and Old Road, two sites with a higher percentage of shoreline consisting of bulkheads than of riprap, was statistically insignificant.
Waterbird communities at Old Road, a site with a relatively high percentage of shoreline consisting of bulkheads, had lower average IWCI scores than did waterbird communities at Miles, a site with a relatively high percentage of shoreline consisting of riprap.
Waterbird communities at Curtis, a site with a high percentage of shoreline consisting of bulkheads and riprap, had lower average IWCI scores than did waterbird communities at Onancock, a site with a low percentage of shoreline consisting of bulkheads and riprap.
Waterbird communities at Curtis, a site with equal percentages of shoreline consisting of bulkheads and riprap, had higher average IWCI scores than did waterbird communities at Miles, a site with different percentages of shoreline consisting of bulkheads and riprap.
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Baltimore, Maryland, has installed engineered structures along 71% of its shoreline to protect infrastructure from wave erosion and other hazards, a practice known as shoreline hardening." |
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| "To evaluate the responses of waterbirds to two types of hardening structures—riprap and bulkheads—Diann Prosser et al. surveyed waterbird communities consisting of the tundra swan, the great blue heron, and 62 other species at different sites in the Chesapeake Bay on the US East Coast." |
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| "Utilizing the Index of Waterbird Community Integrity (IWCI), on which a high score corresponds to high community integrity, the researchers found that bulkheads are more strongly negatively correlated with waterbird community integrity than is riprap." |
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Part B: Provide Passage Architecture & Core Elements
Main Point: Research shows that bulkheads have a more negative impact on waterbird community integrity than riprap structures do.
Argument Flow: The passage establishes the context of shoreline hardening as a common practice, then describes a specific study that compared two types of hardening structures, and concludes with the finding that one type (bulkheads) is more harmful to waterbirds than the other (riprap).
Step 2: Interpret the Question Precisely
What's being asked? Which finding would most directly illustrate the researchers' conclusion that bulkheads are more negatively correlated with waterbird community integrity than riprap.
What type of answer do we need? A specific research finding or data comparison that demonstrates bulkheads having worse effects on waterbirds than riprap.
Any limiting keywords? "Most directly illustrate" - we need the clearest, most straightforward example of the research finding, not an indirect or partial illustration.
Step 3: Prethink the Answer
- The researchers found that bulkheads are MORE harmful to waterbird communities than riprap. So the right answer should show us a clear comparison where:
- A site with predominantly bulkheads has lower IWCI scores (worse community integrity) than a site with predominantly riprap
- OR data that directly demonstrates bulkheads causing more harm than riprap
- The comparison needs to be direct - bulkheads versus riprap, not mixed sites or sites with other variables that could confuse the relationship.
The difference in average IWCI scores for waterbird communities at Stony and Old Road, two sites with a higher percentage of shoreline consisting of bulkheads than of riprap, was statistically insignificant.
- Compares two sites that both have "higher percentage of bulkheads than riprap"
- Finds no significant difference between these two bulkhead-heavy sites
- Doesn't compare bulkheads to riprap at all - both sites are bulkhead-dominant
Waterbird communities at Old Road, a site with a relatively high percentage of shoreline consisting of bulkheads, had lower average IWCI scores than did waterbird communities at Miles, a site with a relatively high percentage of shoreline consisting of riprap.
- Directly compares Old Road (high bulkheads) to Miles (high riprap)
- Shows bulkhead site having lower IWCI scores than riprap site
- Perfectly illustrates the researchers' finding that bulkheads are more harmful than riprap
Waterbird communities at Curtis, a site with a high percentage of shoreline consisting of bulkheads and riprap, had lower average IWCI scores than did waterbird communities at Onancock, a site with a low percentage of shoreline consisting of bulkheads and riprap.
- Compares high hardening (Curtis: bulkheads AND riprap) to low hardening (Onancock: low bulkheads AND riprap)
- Both sites contain both types of structures
- Doesn't isolate the bulkhead vs riprap difference - could be due to total amount of hardening rather than type
Waterbird communities at Curtis, a site with equal percentages of shoreline consisting of bulkheads and riprap, had higher average IWCI scores than did waterbird communities at Miles, a site with different percentages of shoreline consisting of bulkheads and riprap.
- Compares equal percentages site to different percentages site
- Doesn't specify which site has more bulkheads vs riprap
- Shows the equal-percentages site performing better, which doesn't clearly support the finding