Nghe TOEFL

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Narrator: Listen to part of a lecture in an environmental science class. Professor: Today, we're discussing urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. This happens because concrete and asphalt absorb and re-emit heat more than natural landscapes do. Also, waste heat from vehicles and buildings adds to the effect. Now, one common solution is planting more trees, which provide shade and cool the air through evapotranspiration. However, trees alone aren't enough. A more effective approach is using green roofs—roofs covered with vegetation. These reduce heat absorption by the building itself and lower cooling costs. But there's a challenge: green roofs require careful maintenance and can be costly to install. Another idea is to use reflective materials on roofs and pavements, which bounce sunlight back into the atmosphere. This is cheaper and easier to implement. Yet, it doesn't address the root cause of heat generation. So, the best strategy is probably a combination of these methods, tailored to each city's specific needs.