TOEFL Listening

🎧 Listening Transcript

Listen to part of a lecture in an environmental science class. The professor is discussing the role of wetlands in flood control. Professor: Today we're going to talk about wetlands, particularly their function in mitigating floods. Many people think of wetlands as wastelands, but they're actually vital ecosystems. Wetlands act like sponges. During heavy rainfall, they absorb excess water, slowing its flow into rivers and streams. This reduces the peak height of floods downstream. For example, in the Mississippi River basin, studies have shown that restoring just a fraction of the original wetlands could significantly lower flood levels in cities like St. Louis. The plants in wetlands also help by trapping sediment and pollutants, which improves water quality. However, over the past century, we've lost more than half of our original wetlands to development and agriculture. This loss has increased flood risks. So, conservation efforts are not just about protecting biodiversity—they're also a practical strategy for flood management. But note, wetlands are not a cure-all. In extreme events, like hundred-year floods, their capacity can be overwhelmed. Still, they're a valuable part of our natural defense system.