Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about an often-overlooked factor in climate change: the role of wetlands. Now, you might think of wetlands as just muddy, mosquito-infested areas, but they actually act as massive carbon sinks. When plants in wetlands die, they don't fully decompose because the soil is waterlogged and oxygen-poor. This means organic carbon gets trapped in the soil for centuries. In fact, wetlands store about 20 to 30 percent of the Earth's soil carbon, even though they cover only about 5 to 8 percent of the land surface. However, when we drain wetlands for agriculture or development, the oxygen enters the soil, and microbes rapidly break down that stored carbon, releasing carbon dioxide and methane into the atmosphere. This process can turn a carbon sink into a carbon source within just a few years. So, protecting and restoring wetlands is not just about wildlife habitat—it's a critical climate strategy. Any questions?
❓ Question What is the main point the professor makes about wetlands?
A. A) Wetlands are too muddy and mosquito-infested to be useful.
B. B) Wetlands store large amounts of carbon, but draining them releases greenhouse gases.
C. C) Wetlands cover most of the Earth's land surface and are the largest carbon sink.
D. D) Wetlands only affect climate change through methane emissions from mosquitoes.
✅ Correct Answer
B) Wetlands store large amounts of carbon, but draining them releases greenhouse gases.
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