托福听力

🎧 听力原文

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're talking about urban heat islands. As you know, cities tend to be warmer than surrounding rural areas. This is mainly because concrete and asphalt absorb and retain heat during the day and release it slowly at night. But there are ways to mitigate this effect. One effective method is increasing vegetation, like planting trees on streets and creating green roofs. Trees provide shade and also cool the air through evapotranspiration, a process where water evaporates from leaves. Another approach is using reflective materials on rooftops and pavements. These light-colored surfaces reflect more sunlight instead of absorbing it. However, there's a trade-off. Reflective roofs might reduce heating costs in summer, but in winter they could increase heating needs because they reflect sunlight that could otherwise warm buildings. So, city planners must consider the local climate. In warmer regions, reflective surfaces are clearly beneficial, but in cooler climates, a balance is needed.