Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to discuss a surprising factor in urban heat island effect. You might think that planting more trees is always beneficial, but recent research suggests that in some dry climates, trees can actually increase nighttime temperatures. How? Well, trees release moisture through transpiration, which cools the air during the day. However, at night, the canopy traps heat radiating from the ground and buildings, preventing it from escaping into the atmosphere. In humid regions, this trapping effect is offset by the cooling from transpiration, but in arid regions, where water is scarce, trees may not transpire much. Instead, their dense canopies act like a blanket, keeping the heat in. A study in Phoenix, Arizona, found that neighborhoods with more trees had higher nighttime temperatures than those with fewer trees. This doesn't mean we should stop planting trees, but it highlights the need for careful urban planning based on local climate conditions.
❓ Question What does the professor say about the effect of trees in dry climates?
A. Trees always cool the air by releasing moisture at night.
B. Trees can trap heat at night, raising temperatures in arid regions.
C. Trees have no effect on urban temperatures in dry areas.
D. Trees lower nighttime temperatures more effectively in dry climates than in humid ones.
✅ Correct Answer
Trees can trap heat at night, raising temperatures in arid regions.
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
