Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're talking about urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. This happens because materials like concrete and asphalt absorb and re-emit heat more than natural landscapes. Also, waste heat from vehicles and buildings adds to the effect. But there's a lesser-known factor: the loss of trees. Trees provide shade and release moisture through transpiration, which cools the air. When we remove trees for development, we lose that cooling effect. One study in Phoenix found that neighborhoods with dense tree cover were up to 5 degrees Celsius cooler than nearby treeless areas. So, city planners are now considering 'green infrastructure'—like planting more trees and creating green roofs—to combat this. However, some argue that trees require water, which is scarce in arid regions. But researchers point out that the water used is often offset by the energy saved from reduced air conditioning use. So, the net benefit is still positive.
❓ Question What is the lecture mainly about?
A. A. The causes and potential solutions to urban heat islands
B. B. The water consumption of trees in arid climates
C. C. A comparison of Phoenix with other cities
D. D. The history of green infrastructure
✅ Correct Answer
A. The causes and potential solutions to urban heat islands
TOEFL Listening Tips
Skim the questions first to predict the content
Watch for signal words in lectures and conversations (however, actually, in fact)
For main idea questions, focus on the beginning; for detail questions, focus on examples and data
For attitude questions, pay attention to the speaker's tone and word choice
Take notes on keywords; don't try to write down every word
