Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we’re going to talk about a surprising factor in climate change: the role of forests, not just as carbon sinks, but as sources of other greenhouse gases. Most of you know trees absorb carbon dioxide, but they also release volatile organic compounds, or VOCs, especially when temperatures rise. These VOCs can react with nitrogen oxides in the atmosphere to form ozone, a potent greenhouse gas. In fact, recent studies show that in some regions, the warming effect from these forest-emitted VOCs may offset a significant portion of the cooling effect from carbon dioxide absorption. This doesn’t mean we should stop planting trees—far from it. Forests are still vital for biodiversity and local climate regulation. But it does mean that climate models must account for these complex feedback loops. Understanding the net impact of forests requires looking at both the chemical and physical processes, and that’s what we’ll explore today.
❓ Question What is the main point the professor makes about forests?
A. A. Forests should not be planted because they emit harmful gases.
B. B. Forests only help cool the climate by absorbing carbon dioxide.
C. C. Forests can both absorb carbon dioxide and emit compounds that may warm the climate.
D. D. Climate models already perfectly account for all forest effects.
✅ Correct Answer
C. Forests can both absorb carbon dioxide and emit compounds that may warm the climate.
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