托福听力

🎧 听力原文

Listen to part of a lecture in an environmental science class. The professor is discussing the role of wetlands in flood control. "Now, many people think of wetlands as just swamps or marshes, and they assume they're useless, even dangerous, because they can be breeding grounds for mosquitoes. But actually, wetlands serve critical ecological functions, particularly in flood mitigation. When heavy rains occur, rivers overflow, and wetlands act like natural sponges. They temporarily store excess water, which slows down the flow and reduces the peak of the flood downstream. This is crucial because it gives communities more time to prepare. Moreover, wetlands also filter pollutants, because as water sits in the wetland, sediments and toxins settle out, improving water quality. Unfortunately, over the past century, many wetlands have been drained for agriculture and urban development. This has led to more severe flooding. For example, the 1993 Mississippi River flood was exacerbated by the loss of wetlands. So, restoring wetlands is not just about wildlife habitat, but also about protecting human populations."